2001-05-09 (April 9, 2001)

Subject:  Cereus hildmannianus
Jesse Zanger – USA

You look like you are the perfect outfit to answer my question! It may sound quite familiar to you but I am sure you are aware of the unique way these peculiar, beautiful plants effect people and I want to make sure mine grows just right.

Over the past weekend, on a visit to the New York Botanical Gardens, I spotted one of the strangest and most beautiful plants I have ever seen in my life.  It was a Cereus hildmannianus v.  monstrose, fully grown and totally breathtaking.  Just today I jumped on the internet in a search for one, and to my surprise was able to purchase one.  It should be slightly over a foot long when I receive it. 

I live in a studio apartment in New York City.  I have a southern exposure, meaning that my apartment windowsill gets direct sunlight from about 11-4 in the winter, and longer in the summer.  The difficulty is that my windowsill also houses my radiator beneath it (which is quite hot in wintertime) though obviously not a factor in the summer. 

I intend to make a commitment to this plant’s care and well being.  After seeing what it can grow into it I would like to nurture it for as long as I can, though I do not intend to let it get very big until I move into a bigger space. 

What is the best way to care for my plant? How often should I water it and how much? Does it like food? Will the heat of the radiator present a significant problem for it in winter? Please help!!
I can’t wait to own it, and for it to grow in it’s uniquely wavy way.


Yes I know how succulents affect people.  There is no cure! Cereus hildmannianus is a tree-like cactus growing to 5 m and more high and often freely branching.  Flowers will be over 20 cm large and white.  The plant is from Brazil. 

Ideally this cactus needs full sun all day long year round.  It is really not suitable as a plant to grow in the home.  It is better grown in a greenhouse with the brightest light possible on rainy days and full sun on sunny days so that all this light reaches all parts of the plant.  The quite hot radiator in winter isn’t ideal either.  I always like to ask myself …  how would I feel in such and such a situation.  If I would not be comfortable standing next to a hot heater — neither will my plant.  This cactus needs some warmth through winter months but should also be allowed to rest at that time with cooler temperatures than it has in hot summer months.  During winter when days are shorter and temperatures cooler less watering is needed than in summer …  which also encourages a period of rest.  If the “quite hot” heater is on it will continually dry out the soil and the roots and force you to water it more than it needs at that time.  Excess heat can kill the roots and so can overwatering so you can’t win growing the plant near the heater.  Depending on how hot the heater is it could damage the skin of the plant too.  In summer water the soil thoroughly (soil must be very loose and well draining) and then don’t water again until the soil has almost dried out. 

As said above, much less water is needed in winter months when days are short and the plant is not in full growth.Feed every month or so with any good houseplant fertilizer diluted to 1/4 strength. 

Subject:  Aloe barbadensis (Aloe vera)

My aloe has grown out of the space I put her in when I first got her.  I’ve given her a larger pot to grow in and now I need a larger space to put her in.  Her seat infront of the window is getting to small for her.  I read in one of my books that some type of aloe like allot of light and others do not, but they did not specify which types of aloe those were.  I have a new place for my aloe vera plant but it is no longer infront of the window.  More specifically, it is between my door and my window…it would get no direct sunlight.  What I want to know is will the plant be OK with this.  Will I kill it with sun deprivation if I put it there.  Some of my other succulents, like one of my aeoniums, nearly died with direct light, I had to keep it away from the windows.  Is aloe barbadensis like that?


The question is how much light is there for the plant between your door and the window.  The Aloe will do well without full sun but needs the brightest light possible without direct sun.  If your aeonium nearly died it was not because of too much light.  Unless you suddenly put the plant into full sun after it was used to no full sun.  Transition to brighter light needs a slow transfer over a period of a few weeks.  Aeoniums won’t flower if they are not getting enough light.

Subject:  Kalanchoe daigremontiana
John Oyston – Canada

As a kid I used to grow a succulent which had a serrated leaf.  Little baby plants would form on the leaves, drop to the floor and grow.  I have no idea what it was called – I thought it was a tear drop plant, but so far have been unable to find any such plant.  Any ideas? I would love to show my kids one!


The name of that plant is Kalanchoe daigremontiana. 

Subject:  Nopalxochia phyllanthoides
Sandy Munn – USA

What can you tell me about Nopalxochia phyllanthoides? I “inherited” my mother’s plant, which I had never seen bloom until about 5 or 6 years ago.  Then it bloomed two years in a row.  And, now again, nothing.


You have a lovely plant there with beautiful flowers.  As you probably know this is an epiphytic plant and should be treated similar to an Epiphyllum.  Soil should be on the acid side (add some peat to your soil mix).  The plant will flower better if somewhat pot bound.  If the pot is too big the plant spends its energy into growing the green stems at the expense of flowers.  It will flower better if allowed in winter to have short days – the same number of hours of light as occurs outdoors with no artificial lighting such as in the house. 

This plant needs shading from full sun but still very bright light, warmth year round and never to be allowed to go totally dry although less water is needed in winter months. 

Feed in spring and summer with a dilute solution of houseplant fertilizer (1/4 strength). 

Subject: Fungus
C.  Coluccio – USA

I’ve enjoyed reading the different articles in your website and was hoping to find a similar problem to mine.  I have a 10 year old, 5 sided, approx.  15′ tall cactus that has a white powder forming all over.  Is this a fungus? What can I do to save it??

It has been kept indoors for the past few years due to the height it’s grown.  Luckly we have a high ceiling and the window it is in front of is facing the south.  I used to take it outside in the summer months but as I mentioned it’s not possible any more.  I know it should be transplanted into a bigger pot……could that be the problem?? What type of fungicide would you recommend for indoor use?? Thank you in advance for your help


Mildew does not usually hit plants grown in the house.  But if you had put it outside in summer it’s possible.  If this is an all-over white powdery substance it is mildew.  If it is clumps of white fuzz here and there – it may be mealy bugs although this type of cactus is rarely pestered by mealy bugs.  I think a fungal spray is your best bet but you know it’s not healthy to use any pesticides/fungicide products in the house.  I can’t even recommend Safer’s natural products because many have found that these burn the skin of cacti over time.  I haven’t a clue what fungicidal products are sold in your area.

You’d have to ask your local garden supply store what they recommend, telling them it is for use in the house.  Do not go for any of the Safer’s products though for the reason mentioned above. 
One other thing you can try …  is to mix a couple of tablespoons of liquid bleach in a bucket of water (not more than that), mix it in well and soak a sponge and wet down the plant with it.  The bleach should kill the mildew without harming the plant if you use just a little. 

You asked about the pot and repotting.  More than likely the plant needs fresh soil if it has not been repotted for a few years.  The size of the plant makes this near to impossible though.  What you should do is remove several inches of soil from the top of the pot and try to mix in as best you can some fresh soil mix. 

Let me know how you make out.

C.  Coluccio – USA

Thank you for your advice – so far so good!! I did as you said, I put 1tbl.  Of bleach to 1 gallon of water and put the solution in a spray bottle and started at the top and sprayed my way down.  Then I removed about 5 inches of soil around the cactus and replaced it with new soil.  No sign of mildew after 1 week. 

Thank you again,


It’s so nice to have a follow-up like this to know how you made out with the advice.  I’m pleased the bleach and water worked for you.  Thanks for letting us now. 

Subject: Desert Rose
H.  Kindsfater – USA

I planted nine Adenium obesum seeds, five small and four large.  The four large seeds sprouted in 6 days, the five small ones haven’t done anything yet. 

The seedlings are now four days old.  The seed hulls are still attatched to the plants that came up, should I remove them or let nature take care of it?


I had exactly the same problem when I sowed seeds of that plant.  The hulls are stubborn little guys – they seem to stick like cement. 

Eventually I had to carefully remove the hulls by hand but four days is too soon to do that.  I’d wait at least a month and if they don’t let go, remove them as carefully as you can.  That gives them time to strengthen a little with less likelihood of stems breaking when you remove them. 

Subject: Enlarging trunks
Kyle Brown

I took a cutting of an Ipomoea albivenia specimen and rooted it.  The trunk is not quite one quarter-inch in diameter.  Are there any fertilizers that I can use on it to encourage the trunk to enlarge? I also have a rather large specimen of Raphionacme flanaganii that has slow growth.  When it grows leaves it doesn’t produce the normal size leaves.  They stay very small.  My other caudiciforms are also experiencing slow growth.  Do you have any suggestion?


Fertilizers will do nothing to encourage trunks of plants to enlarge.  If you feed the plants too much and force the plants to grow faster than they normally should, to get the bigger trunk, you will only weaken the plants in the long run. 

Cuttings of most caudiciforms will root to make new plants but in most cases the new plants will not have the same enlarged base as the original plant. 

If your caudiciforms are not growing well and leaves don’t look the right size, consider your growing conditions.  Are the plants getting enough light and warmth year round …  the right amount of water and fertilizer in the growing season? Stunted plants are usually not getting as much light as they need.  You might also check the roots to make sure there are no problems there.  Is your soil well draining so that the soil dries out within a reasonable length of time? Roots sitting in constantly wet soil will begin to drown and die off …  the plant above suffers as a result. 

Feed your plants in spring and summer with 1/4 strength houseplant fertilizer, preferably with trace elements.  Don’t feed them in winter.

Subject: Cacti in a bowl
Ladyebonystar – USA

I was looking for a site for information on cacti and came across your site.  I must say that I was truly impressed with the preciseness of your answers and really was incited to go purchase more cacti! (smile)!

My question is as follows:

I just purchase a small arrangement of cacti from Home Depot and am inquiring about the best care method for them.  I’m new to this and will describe them the best I can: 1) 3″ 7-sided columnar cactus; 2) 1-1/2″ Bright Red 9-sided round cacti that has been grafted onto a 3-sided cacti stock.  3) 1″ 18-sided round cactus; and 4) a 2-1/2″ light green columnar-like 8-sided specimen with about 21 smaller like baby shoots. 

My second question is that the red cactus and the light green cactus have what seems to be babies.  Can I/should I pulls them off and try to replant?

Your advice is truly appreciated and thanks for your question forum!


Thanks so much for your nice comments but I bet you are just using me as an excuse to go buy more plants.  As I say on our main page – if you fall in love with succulents, one is never enough!

The problem with cacti together in a bowl is that often not all in the bowl need the same care.  And eventually as these grow you will need to pot them up separately …  especially the columnar types. 
Columnar cacti of this small size need to be in the brightest light possible and while small should not be put in full sun …  but eventually as they grow, most will need to be moved a little at a time into full sun.  By full sun I always mean sun all day long – not just an hour or two in morning or afternoon. 
The bright red cactus is no doubt a Gymnocalycium and these do not like full sun.  They prefer a shaded position.  The stock it is grafted on is probably Hylocereus which, by the way, needs warmth year round.  The Hylocereus may produce side shoots.  Remove these if they appear otherwise the goodness of the stock will go into the new shoots instead of to the scion (Gymnocalycium) which it is feeding.  You can dry these cuts and pot up to make new grafting stocks.

The pups or offsets or babies of the red cactus can be removed (severed cleaning at the point where it joins the mother plant) and grafted on to another stock.  There is no point trying to root these to make new plants because there is no chlorophyl in these pink/red scions and they won’t grow on their own roots even if they had roots.  They are only kept alive by the stock onto which they are grafted. 
“”””” 2-1/2″ light green columnar-like 8-sided specimen with about 21 smaller like baby shoots.”””””
I haven’t a clue what this might be but I do know it is probably not a columnar cactus as columnars need to be much larger and older than that to produce offsets or branches.

You have a choice with babies (or offsets).  You can either sever them cleanly from the mother plant at the join.  Or you can leave them on the plant.  If you sever them off at the join, then take another small cut to increase the size of the rooting area.  Let this dry and harden over and sit on a pot of mix and in a few weeks roots will form and you have new plants.  Drying takes anywhere from a week to several weeks depending on the size of the cut and how warm the weather is.  I repeat though.  There is no point doing that with pups from the red cactus.  If these are removed they MUST be grafted.

Make sure your soil is very well draining if you pot these into separate pots.  In spring and summer water the bowl (or individual pots) THOROUGHLY and wait until the soil is almost dried out before THOROUGHLY watering again.  Many lose their plants from over watering but just as many lose plants because they are afraid to give them too much water.

If you think you are getting seriously interested about growing cacti and succulents, it is far better to order named plants so you can find out what each plant needs.  There are many on line dealer catalogs now with pictures to help you choose which plants you’d like to grow. 

Subject: Fading old man
Dave Sage

I have what I believe is called an old man cactus.  I’ve had it since it was about 3 feet tall about eight years ago.  It is now about 5 feet tall.  It has been, over the last couple of years, turning pale, away from it’s previous darkish green color to a more pale green/yellow color.  It is still growing slowly and appears happy.  It resides in a west bay window (the only one I have large enough) and receives direct sun from about 2pm to 5pm in the summer.  I recently moved it to a slightly bigger pot from it’s previous (I believe) 12 inch pot.  I water it about once every 2 weeks, perhaps not enough but about 3-4 cups but not watered through.  I rarely fertilise it except for something commercial called “cactus juice” but then rarely. 

Like I say it has been treated this way since I’ve owned it and it has grown very nicely, it’s just turning pale.  Any advice would be appreciated. 


I don’t have good news for you.  Your cactus is one which needs as much all day sunshine as it can get year round.  When a plant that needs that much sun doesn’t get it, over a period of time the condition of the plant deteriorates even though it may still put on some growth.  This is really not a cactus that is happy growing in the home. 

A large cactus in a large pot should be in really well draining soil so that the soil dries out within a reasonable amount of time.  When watered in spring and summer it should be watered thoroughly so that all the soil in the pot is moist.  Then you wait until it has almost dried out before watering again.  Too little water is not going to reach all the roots that need to take up the moisture.  If some roots don’t get any moisture they will eventually dry out and die off.  Watering cacti is not a matter of giving it a drink every two or three weeks – but only when the soil has almost dried out. 

Put a flat stone on top of the soil in the pot.  When you raise the stone, so long as there is a spot of moisture there you know it doesn’t need watering.  If the spot is dry under the stone, water thoroughly again.  Trouble at the roots is another cause of a cactus changing color and going pale or yellowish.  So you have two problems with this one.  1) It is not getting enough light (sun).  2) It is not getting enough water and at the right times. 

If you are able to move the plant outside in spring (when the weather warms up) and leave it there all summer, that should help but don’t suddenly move it into sunshine.  The move should be gradual to a brighter and brighter location over a period of several weeks.  You could then bring it inside for the winter when you reduce watering considerably for the winter months. 

With regard to fertilizer, cacti prefer a balanced fertilizer with trace elements, low in nitrogen.  Any good houesplant fertilizer with trace elements can be used if you remember to dilute it to 1/4 strength recommended on the label for other house plants.  I would not feed your plant, however, until you can improve it’s growing conditions and see some improvement in its color. 

It is never a good idea to feed a sick plant. 

If the plant was healthy and you just repotted it into a fresh, nutritious mix, it wouldn’t need extra feeding for several months.  There is nothing wrong with cactus juice but I feel that cacti and succulents (all plants for that matter) are better off with a more balanced feeding of nutrients and trace elements – especially columnar, tall growing types which eat up the goodness from the soil rather quickly and need something to replace the nutrients in that spent soil. 

Let me know how you make out.

Subject: Jade Plant Problem
Dorie Godfrey

I don’t know if you answer individual questions, but I am having trouble with my three jade plants that are about 15 years old.  With the advice of local jade enthusiasts, I have ascertained that the jades have a systemic fungus, caused by a very damp summer.  I have repotted, totally cleaned with water the entire plants (twice), and removed all leaves with even the slightest sign of fungus.  The plants look much better, but the “spots” keep appearing on the leaves.  It starts with a black/brown spots with powdery white on the spots.  It is not an insect, I’ve looked with a magnifying glass and nothing moves and there are no webs.  A sytemic fungicide has been recommended but no one here knows what is a safe fungicide for jades.  Can you help?


What you need is a “contact” spray – a regular fungicide spray to spray the entire plant and leaves (top and under) and stems.  That should cure your problem.  A systemic won’t do any good.  You need the spray to make contact with the affected parts.  You may have to do it again in a couple of weeks but maybe not. 

Subject: Are greenhouses good for succulents?

I am thinking about building my own greenhouse.  I am in Missouri.  Would succulents be possible? Can you give me any tips, suggestions or whatnots?


A greenhouse is an ideal place to grow cacti and other succulents …  if you can provide some heat in the winter or bring the plants in to the house over winter …  or grow only cold hardy plants. 

A greenhouse needs to be in a sunny location so plants get the best light year round.  There are some succulents that need shading from the sun and for those you will need shadecloth on the roof of the greenhouse – either partly or entirely depending on which plants you grow. 

Ventilation in a greenhouse is very important.  Heat rises to the top so some sort of opening at the top to let heat escape is a real necessity.  Openings on the sides are needed to ensure good air circulation.  From experience, a very small greenhouse builds up tremendous heat and cooks the plants so don’t make your greenhouse too small.  Another reason for not too small is that before you know it you will run out of space!!

If you have any other questions, let me know.

Subject: Pruning
Betty Gabe

When is the best time to prune and at what joint would you cut.  Thanks in advance for any information you can give me. 


I could not reply by e-mail because my message was returned as address unknown. 

If you want to tidy up the shape of the plant or reduce it in size, you can cut the joints wherever you please although don’t do too much chopping at one time or you might stress the plant. 

If you want to propagate more plants from the cuttings …  schlumbergeras are easy to propagate from stem cuttings at any time in spring or summer.  Remove a section of stem consisting of two or three joined segments, allow to dry for a few hours and push the bottom segment into a 3 inch pot of potting mixture as recommended above.  Insert the segment just deep enough to support the cutting.  Several cuttings may be inserted around the edge of a larger pot.  Treat the cuttings as mature plants.  They should start into growth within about four weeks. 

Subject: Euphorbia latex
Rich Kriegel – USA

I have two small Euphorbias (ferox and obesa).  How toxic are they? My mother has also kept for years a E.Trigona.  Can you tell me where that one ranks on the toxicity scale? She has taken numerous cuttings off it and I’ve seen the sap come out, but she hasn’t suffered anything from being exposed to it as far as I know. 


Euphorbia obesa is one of the less toxic ones although the latex can still can be an irritant. 

Euphorbia ferox is said to be virulently poisonous.

Euphorbia trigona said to be moderately toxic.

The reactions one has to the toxic latex in euphorbias often depends on the individual.  Whereas one person may be badly affected by getting some latex on the hands, etc., another may have no problems at all.  However, whether you are a person who reacts strongly or not, if you get any of it into your eyes by rubbing your eyes when it’s been on your hands – serious damage including blindness can result even by plants thought to be mildly toxic. 

Subject: Aloe dominella or Aloe inyangensis
Rich Kriegel – USA

I was wondering if you have or know of pictures of Aloe dominella or Aloe inyangensis known as grass aloes.  They sound very interesting. 


Sorry I can’t find pictures of these anywhere.  Maybe others can help with this one. 

Subject: Cactus Seedlings
Alain Beaufays – Belgium

I’m real beginnner.  Would you tell me what I have to do with my new hatched cactus.  Three weeks ago, I found out at home a pack of cactus seeds (I don’t know what species, but I guess common ones for tourists) I bought last summer in Canarias.  I put them in earth (I mean inside in a pot, because I’m living in Belgium where right now it’s pretty cold outside), and I can see now a lot of very small plants about 5 mm.  Since the begining I watered them a lot and put a plastic bag around to not let the earth getting to dry.  Well, what to do now ? Have I to remove the plastic bag and let the earth getting dry because the pot is close to the window to get light but near a radiator?

In fact could you please tell me how long does need a cactus a wet environment at the begining of it’s live. 


Seedlings of all succulent plants should not be allowed to totally dry out for the first year.  When using the plastic bag method, you should not have to add more water for many months.  The soil needs to be moist, not soaking wet.  You can open the bag occasionally to allow air to circulate and then close it up again.  Keep the seedlings in a bright, warm location – not in full sunshine.  When the seedlings fill the pot and begin to clump up, open the bag more often so they get used to the air until finally they are out of the bag all the time.  Transplant to small pots – carefully, keeping in mind the roots are very delicate and easily broken at this point. 

Plants from a mixed bag of seeds may or may not require sunshine later on.  It is best to keep them in a very bright location out of direct sun until you know what the plants are.  Give the seedlings an occasional feeding with a good houseplant fertilizer – diluted to 1/4 strength. 

Subject: ID and transplanting
Renee Brown – USA

We have a three-sided cactus, with spines on the ends of the sides.  It grows new babies of the sides.  It’s about 6ft tall and seems to be top heavy.  We think it needs transplanting.  We’ve had it for almost four years with no transplanting.  How deep do we transplant, with what mixture.  Can you help us identify it?


I’m sorry but from your description it’s impossible to tell you the identity of the plant.  It could be a cactus (with spines) and it could be a Euphorbia (with thorns that look like spines).  If you could send me a picture it would help a lot. 

Are the spines growing out of what look like little cushions of hair on the plant – or straight out of the skin of the plant? If cushions the plant is a cactus.  If no cushions it is not a cactus. 

Whatever it is, when transplanting, never plant deeper in the new soil mix than the plant is in it’s current container.  If the plant is very heavy, it might be safer to simply remove a few inches of the soil on top and replace it with a fresh soil mix.  Of course it is always better to pot into a bigger pot with totally fresh mix after you shake off some of the old soil off the roots.  If you decide to transplant, I suggest for a tall plant you tie it with soft ties to a sturdy piece of wood the length of the plant.  That way you can handle it without touching the plant itself and stabbing yourself with the spines/thorns. 

Soil should be very well draining.  Half good potting soil and half coarse sand or grit works well.  After transplanting don’t water the plant for two or three weeks to give any injured roots a chance to heal.

Subject: Joshua Tree Seedlings
Mike Melchiore – USA

I just seeded Joshua tree seeds.  After 10 days I got growth.  It’s been about 2 months and I need some information on how to care for them.  How much water and what type of soil and food.  They are about 3 in.  tall.  Three of them in the same pot about 2 1/2 in.  pot.  Please give some information on them. 


More than one plant has this same common name but I suspect from the fast growth of your seedlings this is Yucca brevifolia. 

Seedlings should not be allowed to totally dry out for the first year.  Don’t drown them either.  A mix of half houseplant soil and half coarse sand or grit is fine.  The water needs to run through and out the pot leaving the soil moist but not soaking wet all the time. 

Keep them in a warm, very bright place but not full sun for the first year.  Filtered sun is okay.  Transplant them to their own pots when they look uncomfortable in the current pot.  That should be soon if you are growing yuccas. 

Feed monthly with any houseplant fertilizer (preferably with trace elements) – diluted in water to 1/4 strength.

Subject: A Problem Agave americana
Andrew Michalski – USA

First off, I enjoy your website very much and have found some very useful info, especially in this section. 


1.Can you identify this plant? I think it is an agave americana but I can’t find any close-up pictures online to be sure. 

2.The plant is developing some brown spots on its lower leaves.  (plant003.jpg) This leaf was cut from the plant when we transplanted it to a larger pot.  The lower leaves were developing “folds” in them and were dying off.  But just as quickly, new ones were growing on top. 

3.When we removed it from the old pot, it had a tubular root that wound it’s way down the outside of the pot.  I guess that it was around 3-4 feet long.  What should I do with this root? (We put it in the new pot as best we could without damaging it) A small section of a different identical root (about 18″ long) broke off.  I’m letting it dry (heal) for a few days, then I hope to transplant it. 

4.We also have numerous offsets that were removed from the big plant, over the past few months, and need some expert advice on caring for the small plants.  Any advice would be appreciated. 

At this moment, the plant is in a south facing vestibule of our office.  It is hot during the day when the sun is out (even in the dead of winter), we water occasionally, but I think it may be overwatered by overambitious help. 

Picture #4 (plant004.jpg) is of an offset of the larger one and I included it in the hopes it will help in identification.  This one is in a North facing room but seems to be doing well.  I think you can see an offset or two in the picture.


I’m pleased to hear you enjoy our website and especially that you find useful information here.  I hope I can help with this problem.  Let’s try. 

The plant in the picture you sent does appear to be Agave americana.  It looks healthy enough but the growth habit doesn’t seem quite right.  The leaves seem to have elongated somewhat which might be weak growth often caused by lack of enough light.  See photo attached of normal growth habit of this plant.  Ideally agaves prefer an all day sunny location with maximum light all around the plant – and tons of fresh air. 

Small Agave offsets on the other hand do better in bright light without direct sun until they are big enough to be gradually moved to a full sun position.  In nature the small plants are protected from full sun by surrounding vegetation and of course by shading from the large leaves of the mother plant. 
A North window is definitely not a good place for any Agave, large or small. 

If your office is hot year round this could be one cause of drying out of the leaves.  These plants need lots of fresh air year round and enjoy a drier, cooler period in winter than they have in summer months.  Are lights left on 24 hours a day in your office? This too can affect plants which eventually lose their sense of when they should grow and when they should rest.  This can be stressful and lead to all sorts of problems. 

It is not easy to water agaves without getting some water on the leaves.  I had the brown spots problem on my plants for a long time and solved it by watering in the pot saucer and letting the plant soak up the water from the bottom.  One would ask – well then how come agaves don’t react to rain like that? I don’t know.  I suspect it has something to do with the tap water we use to water our plants. 

Leaves at the bottom that fold and dry up as new leaves appear on top is not uncommon.  It does happen naturally but you should not lose more than one or two lower leaves a year. 

Long roots can be cut off without damage to the plant and may, if you plant them, produce shoots of new plants.  It is a lot faster to pot up the offsets though than to wait for the possibility the root will produce shoots. 

This is a reeeely large growing plant that will always have a fast growing very large root system.  Eventually the rosette can grow to 10 to 14 ft across!! Leaves eventually to 8 ft.  long!!

This plant should be repotted every year into a bigger pot.  If you reach a maximum pot size and don’t want to put it in a larger pot, then you will have no choice but to cut the root system down slicing off about one third of the roots.  If you do that allow the roots to dry out for a few days before potting up in a fresh soil mix.  The problem is that the root system that is left will have become so thick and dense there is little if any room left for soil from which the plant receives nutrients. 

All this leads me to say Agave americana is not the ideal plant for an office.  It needs a large greenhouse with maximum light and fresh air where there is enough space to keep increasing the size of the pot to accommodate the huge roots and amount of soil it needs from which to get proper nutrients.  Or it needs to be planted out of doors in suitable climates. 

With regard to watering, in spring and summer agaves need a good soaking each time the soil has almost dried out.  Less water is needed during the short days in winter when the plant should be having a rest and daylight hours are reduced.  Agaves are extra sensitive to waterlogging.  A good soak with a longer period between waterings is far wiser than a little water every day. 

Agaves also like a nutrient rich soil.  They should be fed with every watering in spring and summer with a good houseplant soil with trace elements – mixed at 1/4 strength.

Subject: Aloe/Agave propagation
Ann Cooper – USA

Hello, lovely website.  Is it possible to grow aloe plants from leaves of mature plants? The same with agave.  Any information on how to do this best?


Thanks for the compliment. 

You can propagate aloes from leaves, also from runners and head cuttings.  Not all that easy though.  Some more difficult (tree type species) than others.  Plants are usually propagated from head cuttings from tree like and shrubby species which often take a year or more to root.  Very easy to grow from seed.  Agaves are propagated from seeds, offsets or runners. 

Dry the cuttings thoroughly until a hard callous forms and then insert in soil not too far down. 
Leave it alone and don’t water it for a few weeks.  Then put a little water in the pot saucer so some moisture creeps into the soil.  Good Luck. 

Subject: Kalanchoe daigremontiana

I have a succulent that is very unusual.  It’s leaves are teardrop shaped and are jagged.  at the points of each jagged edge, there are ‘baby plants’ with the root intact.  Eventually they fall off to form new plants.  Could you please help me in identifying this plant? Thanks so much!!!


This sounds very much like Kalanchoe daigremontiana

Subject: Mealy Bug Infestation
Sheila Hale – Canada

My Christmas Cactus (and most of my other houseplants) are infested with mealy bugs.  I have been working away for well over a year now with insecticidal soaps and other treatments with no luck.  I actually have several cacti infected including Christmas, Thanksgiving and Orchid varieties. 

I need to know if there is any type of systemic insecticide which is safe to use on them.  My main Christmas Cactus is huge and over 60 years old.  It is just too big and heavy to try and lift and handle for many of the preferred less drastic treatments.(My boston ferns are too large and dense as well). 
Any suggestions for a systemic would be appreciated. 


No systemics are really safe to use and for sure you should not use them on plants in the house.  The smell is horrific and the fumes very unhealthy.  Systemics should only be applied to plants outside or in the greenhouse where there can be maximum ventilation.  Isotox is the systemic I use when I have to.  It gives excellent results.  Latox is another equally effective product.

Subject: Sick Euphorbia
Mark Ozaki – USA

I have an African Sure Euphorbia I recently purchased from a nursery.  Much of the cactus was a light brown color when I purchased it.  White sap oozes from almost all of the aerioles (or whatever the spots where the spines grow are called).  Two parts of the cactus have produced new, healthy growth.  Since I have other cacti, I am concerned whether other cacti (non-euphorbias) may contract this condition.  Can this cactus be saved? If it can’t be saved, should I just lop off the newer growth and try to root that? Thanks. 


Since you recently purchased the plant, I advise you to return it and either get your money back or ask for a substitute plant that is healthy.  From your description the plant is in big trouble and trying to save it will more than likely be a waste of your time.  You can lop of the newer growth and try to root that but if most of the plant has turned brown ,the problem causing that has likely gone through the entire plant.  If so the cuttings will have the problem too and die before they root. 

I have never heard of the white sap of euphorbias oozing out of the plant without the plant being nicked or injured in some way.  Unless of course the plant is in such bad shape the skin is so thin the sap is oozing out of it.  This white latex should be treated with caution.  Don’t get it in your eyes or on your hands.  It can cause irritation to the skin and in some cases blindness if it gets into the eyes.  If you get it on your hands don’t rub your eyes either! Some euphorbias have latex that is much more toxic than others. 

A Euphorbia is not a cactus.  It is one of the ‘other’ succulents.  All cactus are succulents but not all succulents are cacti!! Very sorry I couldn’t help you save this plant but I do urge you again to return it. 

Subject: Help with Identification
Denise Smith – USA

I am hoping that you can help me identify a plant I inherited from my mother.  I believe it to be a succulent, and it’s not doing well.  I want to save this plant before it’s too late.  It is a deep green color with white dots on the leaves.  It sort of looks like clusters of very small aloe plants.  Many of the clusters have just dried up.  Any help you could give me to identify this plant so I can save it would be appreciated.  Thank you!


I tried to send this answer to you via e-mail but it came back to me undelivered. 

The description could be that of a Haworthia.  Haworthias do not like to be grown in sunlight.  This is one possible reason parts are drying up.  It may also need re-potting into fresh soil that is very well draining.  If the soil is old the plant is not getting enough nutrients.  If you could tell me more about its growing conditions maybe I could make other suggestions. 

Subject: Monanthes, Stapelia culture
Karen Sternberg – USA

1.  Last weekend I admired & was gifted with a Monanthes.  Did some internet reading on it, seems to be a crassula (tho’ reminds me more of a sedum).  Am wondering about culture please. 

2.  Recently got a tiny charming stapeliad, not 3 inches high, was blooming when I bought it.  Bloomed again a month later, let rest a month, turned it out to check roots, was totally potbound, after re-potting bit larger got flush of new growth & some flower buds.  It seems very happy.  Anything else I should do for it? Am unclear about how much to water, so am just giving it once a week (in terra cotta pot).


Monanthes is a genus native to the Canary Islands, Madeira and Morocco.  Monanthes is in the family Crassulaceae.  They are small, clump-forming plants with fleshy leaves crowded into rosettes at the ends of the branches.  They produce star-like flowers in late spring to early summer in colors of pink, yellow oro white. 

These are fairly hardy plants and need little more than frost protection in winter.  They are cultivated like crassulas, require shade in summer and cool conditions in winter. 

You must be doing the right things for your Stapelia since it has bloomed for you. 

Watering is not a matter of watering every week or two weeks – it is a matter of watering when the plant needs it.  Succulents only need more water when the soil has almost dried out. 

Stapelias are very prone to the black death, a dangerous fungus showing up as black spots.  This disease is encouraged by poor light, cool temperatures and high atmospheric humidity and over-watering.  Watch for it in winter months especially.  The affected parts must be immediately cut off and burned since the fungus can spread rapidly to the rest of the plant. 

These are shallow rooted plants and should be put in shallow pots, not deep ones.

Trevor Wood

In your advice to Karen Steenberg you state that stapeliads are shallow rooting.  In fact many will readily grow roots that are longer than than the above-ground height of the plant.  I have had good results from giving these plants plenty of depth for their roots.  A well-draining but deep pot lets the top layer of potting mix dry out to reduce the risk of fungal attack on the stem of the plant while keeping enough moisture down at the growing tips of the roots to prevent root death and consequent dehydration.  Having to produce new roots each growing season delays the growth of new stems and hastens the death of the old.  The natural die-back of part or whole stems is a frequent source of rot-attack so anything to increase new growth and extend the life of the old is good.  Take pre-emptive action by pruning back any yellowing stems or stem sections.  In winter the more heat you can provide, the better their chances of survival.  Some species will take a light frost but most need to be kept above 10C and others will need warmer still.  Humidity can be tolerated in winter if warmth is maintained.  As less moisture is lost to evaporation watering can be less frequent.  This reduces the risk of over-watering which is ultimately worse than under-watering.  I personally water the sensitive ones with a teaspoon.


Thanks, Trevor.  We often learn more from shared growing experiences with our plants than we do from books.  My answer to Karen was short and perhaps vague.  I should have explained why these plants are better planted in shallower/wider rather than deeper/narrower pots and that is because most of these plants are creepers.  They need room to expand with new branches which develop from the main shoot.  In turn other branches develop from the main shoot of those new branches.  They need room to develop in the pot and take root.  The roots of these are not dependent on the roots of the main shoot but take up moisture independently. 

Subject: Cactus graft in trouble
Terry Hill – USA

I have a Moon Cactus (grafted).  Unfortunately, all of my cacti were without light for a week (they were out of the windowsill due to extreme cold) and they started doing poorly until I bought a plant light.  The only one that hasn’t perked up is the Moon Cactus.  The pink graft looks mostly reddish-brown and shriveled, except at the very top of the graft and the bottom, that’s a healthy pink.  How I keep it going and growing until the whole graft is bright pink again?


Your moon cactus is a Gymnocalycium – to be precise Gymnocalycium mihanovichii var friedrichii (isn’t that a mouthful?)

It sounds like your Gymno (short form we use to avoid repeating the long name) is starting to rot.  If plants are next to a window there’s a certain amount of moisture there as well as cold and many succulents won’t do well in that atmosphere.  So that combined with no lack of light for a week has probably caused the problem. 

You can cut off the pink part on top but you would have to graft it on to another cactus because it won’t live without being attached to a green cactus from which it gets its chlorophyll. 

You can cut off the brown part to the pink part on the bottom and hope the cut will dry well and not deteriorate further – leaving a piece of the pink Gymno on the green cactus (which is called the stock) and if it survives it will later in spring or summer begin to produce little Gymnos which you can either leave as is or take off and graft on other cacti. 

This is a very bad time of year to attempt grafting.  It needs to be done in very warm weather. 
It may also be that what has affected the shrivelled part has gone all through the plant in which case it’s lost and you can’t save it. 

Sorry about that but look at it this way.  You will have to go out and buy a nice new plant.

Subject: New Cactus Bed
Nazim Mokhnachi – France

I’m planning to make a cactus bed on a terrace.  It would be about 4 feet long and two feet 3 inches wide, against a white wall in full sun.  My question is how deep does it have to be if I want to grow some tall columnar cacti? (about one meter high) Because even if I lay three layers of bricks, it will never be as deep as in the ground.  So I’m wondering how deep cacti roots go down in the ground.  I live in France in a Mediterranean climate.  Many Opuntias and Agaves around, but Agaves don’t flower, even though they grow huge.  Do I stand good chances? Is this a good way to grow cactus or would they be better off in separate pots?

Thanks in advance for your good advice which I already had the occasion to use.


Cacti roots can grow quite far down into the soil when they are grown in pots.  However, when they are planted in free root run such as the cactus bed you plan, the roots tend to go sideways just under the soil rather than deeper down into the soil although some roots will reach further down into the soil as they run out of room/nutrients near the surface.  Cacti most often grow in nature in areas where rainfall is very limited so the roots stay closer to the surface to take advantage of what little moisture is available.

A bed 4 feet long and 2 feet wide will not comfortably accommodate too many columnar cacti because you need a good spacing between them so air can circulate and so that if one or more produces branches, there is room for that growth without it growing into the other plants.  To avoid plants growing into each other you also need to stagger the plants and not plant them in line one beside the other. 
As to the depth you need, you have to keep in mind there must be sufficient depth for enough space for a good root system to form to support the increasing size of the plants which can become very heavy as they grow.  I would not try to grow columnar cacti or large growing opuntias in less than a depth of about 8 inches of soil.

Pots are an advantage if you think you will ever have to move the plants.  And they are an advantage if you want to grow plants which require somewhat different care or which have their growth period at different times.  If you water one in growth you are watering the other not in growth and that as you can appreciate is not a good thing.  So choose your plants wisely for the new bed. 

I have personally grown cacti both in pots and in beds and have found that columnar cacti and large growing opuntias grow and flower better when planted in free root run beds. 

You will be tempted to fill in the space between the columnar cacti with other smaller plants.  If you do, try not to use highly succulent plants or those which are very tricky as to watering such as Ariocarpus – because when you water the large plants, the little ones will be sitting in wet soil too long and have a tendency to rot. 

If you want to give me the names of the plants you choose I’ll try to give you advice on whether it is a good idea to grow them together in the same container. 

Agaves often need to be very large and quite old before they flower.  Why the large ones you mention never flower I’m afraid I have no idea.  If you could tell me their names I could do a little research for you on that question. 

Keep in touch and let me know how you make out.

Subject: Haworthia crest
Don Baker – USA

I have a crested euphorbia that I got when it was only about an in tall.  It has developed into a huge plant (for my collection) of apporx.  12″ and is scraping the bottom of the shelf above it. 
Any suggestions on what I can do to either trim it back or how to start a new plant?


To reduce the height of your crest you’d have to slice a piece off the top and ruin the look of the plant in the process.  If you did that it would probably force the plant to produce new growth which could be removed and rooted to start new plants.  It would be better to put it on the top shelf where it has more head room. 

To start new plants you’d be better to slice off a piece of the crest where it doesn’t show too much, on the lower sides of the plant, dry carefully and pot up and hope they will root. 
Many euphorbias take a long time to root and crests are often most difficult of all to root.  The best time to do this is in late spring and summer when weather is warm. 

Subject: Sedum multiceps
Nancy – USA

My problem is with a Sedum multiceps in particular, but I seem to have the same trouble with all my sedum; they do well for awhile, then seem to wane almost to the point of death, then recover slightly, and on and on.  This little ‘mini joshua tree’ is beginning to get a wilty look to the tips of its ?branches?.  I’m afraid it is headed in the same direction as its brethren.  Are there some seasonal care rules for this species? I generally keep my succulents/cactus cool and dry in the winter (in a glasshouse – kept above freezing with an electric heater if necessary, which it has been this winter!).  What can I do to encourage this little guy to flourish?


Sedums need fertile, well-drained soil and plenty of moisture during the summer.  They should have full sun and lots of fresh air.  Most do better if given a few months outside of the greenhouse in a sunny position during warm months of the year. 

Sedum multiceps is from Algeria so it would not enjoy a very cold greenhouse in winter.  A minimum temp of 50F is best..  If your greenhouse is colder than that, this could be the reason why the plant is not looking perky.  If kept at this temp in winter less watering is needed than in spring and summer – just enough every so often to keep the roots from totally drying out and dying.

Norma Lewis – USA

Sedum multiceps goes dormant during the summer months, it will look like it is about to die, I then put it in the shade.  During the winter months it will take temperatures down into the high 20 to 30 without dying.  This is also a good time to take the cuttings. 

The questions and answers above were rescued from the Wayback Machine of April 9, 2001.