Questions on: Cactus

Ron Smith, Horticulturist, NDSU Extension Service

Q: I have a cactus that belonged to my mother. I have no idea how old it is, but it has to be at least 25 to 30. It is very woody at the base, not extremely filled out and somewhat leggy. During the last year, it has become very limp and some of the leaves are a poinsettia pink. I repotted it for the first time in probably five years. I may have jumped to too large a pot. Will that be a problem? It is not looking any healthier. What should I do? I hate to loose it because my mother passed away this year. I am attempting to start another plant, but it has not shown any growth. (e-mail reference)

A: For information, go to I don't know what else to tell you except to keep trying to get something rooted from one of the fronds.

Q: I saw your question-and-answer page on the Web while trying to find an answer to a question. I got a cactus as a gift and it was looking great. However, for the past few months, it has been growing a lot. The new growth is a much brighter green than the original growth and it doesn't have sharp thorns, just stubby, soft thorns. Should I be worried? (e-mail reference)

A: Don't be worried. The original foliage developed under different environmental conditions (most likely a greenhouse with full access to sunlight) than that of your home location. The new growth is reflecting that environmental change.

Q: I have a question about the three cactus plants I purchased. I believe they are different types. Two of the plants are growing green roots off the top. They resemble roots on a potato, but are bright green. Is this some sort of fungus? (e-mail reference)

A: These are aerial roots and likely are from a Christmas cactus species. Go to my Web site on cactus at for some self-education on the species.

Q: (This is the response to my answer about the Thanksgiving cactus.) Thank you so much for your prompt reply. I did not realize that these plants had a life span. What happens at the end of their life? Do they get too large to hold themselves up? Would it help to prune it (I have never done this before)? I will take your advice and make some cuttings. Where should I make the cut and how big a plant area should it be? (e-mail source)
A: Mother Nature never planned for houseplants to exist genetically. When we move plants from their natural environment into an artificial one, the whole ball game changes. For example, your Thanksgiving cactus is an epiphyte, which means that it is found in association with other plants or on rocks. It clings to its support with aerial roots and gets nourishment from the atmosphere (tropical jungles of Brazil) or from the tree crevices in which it lodges. When the leaves get too ungainly, they can break off and lodge in another spot on the same or another tree and then send out very small roots and aerial roots to get a new life established. What’s sold in the commercial trade are hybrids that growers have developed for flowering characteristics. The success of this plant as a houseplant depends on the owner having the ability to approximate rainforest conditions. That is not completely true because I have seen some very beautiful Schlumbergera spp. plants thriving in anything but tropical forest conditions. Apparently the hybridizing results in far more adaptable plants for the indoors. The death of a plant occurs when one of the growth factors is eliminated, such as light, water or nutrients, or when an herbivore decides to have it for lunch or a pathogen takes up residency. Pruning would not hurt the mother plant and would assure perpetuation should anything happen to the original beauty that you have grown so fond of. Take stem cuttings consisting of two or three pads as spring comes around. Allow the ends to dry for a day, then plant in a moist, pasteurized, high-organic potting soil. Keep the plant in the shade or out of direct sunlight until new growth appears.

Q: I live in Michigan and have a Thanksgiving cactus that is roughly 5 years old. It was a cutting from my mom's plant that was 20 to 25 years old at the time of the cutting. The plant seems very happy and healthy. It blooms at Thanksgiving, Christmas and around Easter. I can't count the number of blooms I get, but I would say close to 100 each time. I transplant it every year or two into a bigger pot because it has grown quite large. The last time I transplanted it was more than a year ago. I typically water it once or twice a month. More in the summer months as it dries out. I recently decided to determine if my plant was a true Christmas cactus or something else. I discovered that my plant is a Thanksgiving cactus because of its pointed leaves. I was disturbed to read a post about root rot and that someone mentioned that their plant was looking woody and wilted. I’ve noticed that the base stems are getting woody and hard. I thought this a normal part of my plant maturing, but after reading the other post, I am concerned it could be a sign of root rot. I have no other signs that the plant is having any health problems. It is continuing to grow and there are many shoots and leaves forming. The new leaf growth tends to have a purplish color, but as the leaves mature, they change to a deeper green. One thing that I may have done wrong is use the wrong type of soil. Would it be best for me to repot to a larger pot with the right soil mix or just use fresh mix into this same pot? If I repot, how can I determine if my plant has root rot? If so, what should I do? (e-mail reference)

A: Interesting story and thanks for relating it to me. Basically, you have nothing to worry about. The plant is really indifferent to the potting soil, as long it is pasteurized and drains decently. The woody character of the stem base is an indication of the maturity of the plant, since the stem appears to be firm and everything else is growing satisfactorily. You are close to the end of what is considered a normal life span for this species (please don't bury me with letters or phone calls about having had the same Christmas or Easter cactus much longer). I would advise you to take some leaf cuttings and root them this year. Do this about the time you repot in late summer or early spring. Otherwise, keep on doing what you have been because you obviously have discovered the secret to success with this species!

Q: I have had a cactus in my office for more than six years. White spots formed on it about 18 months ago. I think that if I do not do something soon, the problem will kill the plant. I have two other cactus plants with similar issues. I think the problem started when I repotted the plants with new soil that was supposed to be especially for cactus plants. (e-mail reference)

A: The problem is scale or mealybugs. I strongly suggest that you get to a garden supply store and obtain some systemic insecticide that can control these pests. The bugs eventually will kill your plant if they continue to go unchecked. In the future, make sure that the soil you use for repotting is sterilized or pasteurized. If you can't find any, do it yourself in the microwave.

Q: I was searching for an answer about my cactus plant. Someone gave it to me last year. It was about an inch tall. It has grown to a height of 3 inches and it has eight little baby plants. Should I remove the baby plants or leave them alone? (e-mail reference)

A: If you enjoy the cluster, let them stay for now. If not, then transplant them. At some point, you will have to do so to allow them to develop normally.

Q: I have some questions regarding crown of thorns and mammilaria pilcayensis. My crown of thorns is growing wonderfully and getting new leaves, but not blooming. I fertilized it recently and it sits at a west window. The mammilaria also is at the west window. It is growing, but not blooming. I water them every two weeks with a special fertilizer for cacti. What can I do to make them bloom? (e-mail reference)

A: Both will bloom in good time, so be patient. Don't overwater and don't add fertilizer until you see new growth or right after they’ve flowered.

Q: Can you tell me what the white substance is inside of a cactus? Someone I know has tasted it (probably not the smartest thing to do). About a half hour later, their tongue was burning. (e-mail reference)

A: It is a type of latex, which is a skin irritant. You are correct, it’s not a good idea to go around tasting things one doesn't know anything about.

Q: My boyfriend brought me a plant-your-own-cactus novelty kit from Las Vegas for my birthday. There are two plants in the kit. I would feel awful if they died. One plant is tall and thin with white hair wisps coming out of the top. The other plant has a cluster of three short, round trunks with aggressive-looking spines that are brown at the tip. One of the round trunks started to turn red and the spines are drooping. This condition is slowly spreading to the rest of the cluster. It appears one of the roots has grown out of the soil, but the pot should be more than large enough. I'm not sure if it is normal, but there is some white fuzz at the juncture of all the spines. (e-mail reference)

A: You have a very thoughtful boyfriend, so I understand your desire to keep the plants alive. I'll try my best to help you. The cactus with the wispy white hair is known as the old man cactus, Cephalocereus senilis. The purpose of the wisps is to help shield the plant from the severe desert sun. The other plant sounds like it is a prickly pear cactus, genus Opuntia spp. There are many species and cultivars of this one, so it is difficult to determine which one he got for you. The prickly pear cactus may have a mealy bug infestation that is slowly killing the plant. Cut out the one pod that has totally collapsed because it probably won’t survive. With the others, dip some cotton swabs in rubbing alcohol and then dab it on these characters, rubbing them off if possible. If this task is too daunting, go to a local garden center and get some houseplant spray for insects. The Schulz and Safer companies offer this product. Don’t be surprised if you lose this plant because an infestation this heavy can be very destructive, even on tough cactus plants.

Q: I left my cactus plant next to the wood burner one night. The side that was next to the burner has turned yellow and dark brown. Can I save the plant by cutting off these parts? The main stem is not affected. (e-mail reference)

A: You didn't identify what kind of cactus you have, but that makes little difference. Go ahead and cut out the damaged part back to undamaged tissue. It should callous over and seal the wound over a reasonable period.

Q: What is pasteurized soil? I bought new soil specific for cacti, but it doesn't specify that the soil is pasteurized. (e-mail reference)

A: If the bag doesn't say the media inside is pasteurized, then it probably isn't. If you want to be on the safe side, moisten the soil you intend to use and nuke it the microwave for about four minutes in an open sandwich bag.

Q: I have cactus houseplants for the first time. I know that if in doubt, do not water, but I must water some time. How do I know when to water and how much? If some leaves fall off, does that mean I’m overwatering, underwatering or is that normal? I have had my plants for about three weeks and have watered once. One plant is losing leaves. (e-mail reference)

A: Since there are as many cacti as there are Smiths (almost!), I suggest you go to the Web site and roam through all the cactus care tips based on the species you have.

Q: I replanted a 10-year-old cactus. Now, its body is 60 percent black and fading fast. Should I repot it with just the “good” part? I think I overwatered and used the wrong soil. Is there a Miracle-Gro for cactus? (e-mail reference)

A: Try cutting off the nondecayed top and allow it to “cure” for a couple of days before planting it to see if you can get roots to form from the cutting. There is no Miracle-Gro for cactus.

Q: I would like to know some facts about the water status of a cactus. I don’t know the name of the cactus, but it has hanging, flat stems. My colleague thinks the plant is overwatered, so that’s why the tips of the stems are soft and part of the stem close to the roots above the soil (the oldest part) turned brown. I remember studying biology in high school that water makes plant cells turgid, so when the stems are soft it means the plant needs water. Am I right? (e-mail reference)

A: The right amount of water makes plant cells turgid, so too much water over a long period can cause rot, which is reflected in the softness you describe.

Q: What type of root does a prickly pear cactus have? Is it a taproot or a fibrous root? I am doing a school project on the prickly pear, but can’t find any information on the type of root it has. Thank you for your time. (e-mail reference)

A: Cactuses have extremely long roots to reach out through sandy, rocky soil. The roots grow close to the soil surface to collect moisture from the occasional rains that come into their environment. This makes them fibrous roots. Because they are succulents, cactuses store most of their water in the aerial part of the plant. Their thick rind and needlelike spines prevent water loss.

Q: I thought I had bookmarked the Web site you wrote about in your cactus column regarding propagation techniques. Apparently, I thought wrongly. Could you please send me the address for the site? I found it extremely interesting and there are several ideas I would like to explore. (e-mail reference)

A: No problem. The information is available on the Web at . Thanks for the interest!

Q: I read your material about cactus plants with great interest. Since my plant has gently scalloped edges, I am assuming it is an Easter variety. I purchased it several years ago. It is healthy, but has never bloomed. Here is my dilemma. About three months ago, I moved it to a little greenhouse. The plants in the greenhouse get 18 hours of light a day. The cactus went through a huge growth spurt. It has a lot of new leaf growth and little four-sided growths that look like new stems. Considering that I have subjected the plant to an artificial summer, can I soon put it back in a room where it will continue to get at least 12 1/2 hours of light through the rest of spring and summer and then cover it to force buds for Thanksgiving? (e-mail reference)

A: If you want it to flower by next Thanksgiving, there is no “sin” in making it do so. It sounds like a beautiful plant, so even if it doesn’t flower by Thanksgiving, it certainly would be a handsome devil to look at and you could contemplate it flowering for you by Easter.

Q: My cactus has some light brown spots on it (almost like scales). If I rub them with my fingernail, they come off and what’s underneath is paler compared with the rest of the plant. I don’t know what kind of cactus it is (sorry). Would you have any idea what this is and how I can treat it? (e-mail reference)

A: It probably is scale. There are crawler stages and adult stages. What you are seeing is the adult stage with the protective covering. You might want to get some horticultural oil and Q-tips. Dip the end of the Q-tip in the oil and dab it on the individual adults. Be sure to hit them all. This oil kills by eliminating the insect’s air supply.

Q: I have a mature partridge cactus that has snapped off at the roots (the pot was knocked over). I have tried to get the plant to reroot using growth hormone, but it has started to rot at the base. Any idea how I can save this plant? It still has maintained its turgidity and looks quite healthy everywhere else! (e-mail reference)

A: Try making a fresh cut and allow it to “cure” for a few days before attempting to root it in a sandy/peat medium. Keep it barely moist. This may work for you, I hope. It often does with other cacti.

Q: My cat knocked over my cactus plant, knocking off the top. The plant now has mold on top.

It has been a couple of months since then and the mold is spreading. I’d like to save it if I can because it’s probably more than 60 years old! (e-mail reference)

A: The top breaking off is unusual, unless you have been keeping it too moist or the air is too humid. Are you sure it isn’t callus growth? That is the usual pattern when something like this happens. If you are sure it is fungus growth, all you can do is make a fresh cut back to where there is no mold. Dust the surface with a locally purchased fungicide, such as a Bordeaux mixture.

Q: I have had a barrel cactus for a couple of years. Recently it started to turn brown at the base. A beige, shrunken (dead or dying) section is on one side. It sits in a southern window and I water sparingly once a week. Can you help me save my cactus? (e-mail reference)

A: Watering once a week is too much. Take a cutting and try to root it. To do this, cut off a part of the stem where there is no rot. The cutting should be about 3 inches in length. Allow it to cure for a day and then try to root it. It should root in two to three months.

Q: My co-worker has a cactus plant on her desk. We noticed a little red bump growing out of one of the creases surrounded by a lot of fuzzy, white stuff. We poked at the bump and it popped off. It looks like a little red berry. She says now there are several of these little red balls on her cactus. What are they? (e-mail reference)

A: For shame! You knocked off a cactus apple. There must have been a flower there that was ignored or just forgotten. In Arizona, New Mexico, Southern California, etc., where cacti grow, it is common to see these apples form. They can be harvested and made into jellies or juice. Let those that are on the plant ripen and fall off naturally. Fix a nice treat, but be careful of those little leaf modifications that remind us, often painfully, that they are cacti!

Q: I have several cacti that have a white, fuzzy and sticky substance at the juncture of the needles and the main body of the cactus. (e-mail reference)

A: It could be cottony cushion scale. Take a Q-Tip, dip it in rubbing alcohol and wipe it on these characters to see if you can get rid of them. Then spray the cacti with Fungicide 3. It is an insecticide, fungicide and miticide. It is a neem product, so it will be safe to use indoors on most houseplants. Prior to using it, check the label to be sure your plants are not excluded. This general spray will cover any crawler stage (juvenile) that has not yet settled into making the cottony covering to protect it.

Q: A week ago I was helping my aunt plant a cactus plant. I accidentally grabbed the cactus and tiny spores got into my hand. I tried to pull them out, but some broke off in my hand and are still there. What can I do to get them out and are the spores poisonous? (e-mail reference)

A: They are not poisonous, so stop worrying. Go to a dermatologist at your earliest convenience to get the spine pieces removed. Often times they just fester out on their own without medical attention.

Q: I have a Christmas cactus that bloomed very nicely twice a year. It was always located in a south window. Last year, after the Easter blossoms fell off, I had to transplant it. It was too tall for its pot, so I transplanted it into a bigger pot. It is growing nicely but there were only two blossoms on it for Christmas and none for Easter. I have been giving it fertilizer. (Gackle, N.D.) 

A: Be patient. The plant needs to get a little pot-bound to help it bloom. This fall, around the end of September, start covering the plant. Cover it at 5 p.m. and uncover it at 7 a.m. You should see plenty of flower buds developing after six to eight weeks.

Q: My girlfriend bought a new house so I moved her very large euphorbia cactus. It looked fine when I left but when she came to check on it five hours later, it was dead. Is this possible? (E-mail reference)

A: Isn't it amazing how easily we can get into trouble with the women in our lives? It could only be possible if the plant was moved, without protection, when the temperatures were too low.  You might offer to purchase a replacement along with a box of her favorite chocolates and a note of apology. Hope that works!

Q: I have a small fish hook barrel cactus that seems to have some kind of mold or fungus. The area around the top is white and fuzzy-looking but has now spread over the rest of the plant. I've moved it away from my other plants to protect them. Is there anything I can do to help my plant? (E-mail reference)

A: It could be just a superficial mold such as powdery mildew that was picked up from close association with your other plants. I think you have done the best thing by moving it away from the other plants. Do not water the plant for the time being to see if the problem will clear up on its own. That is the best advice I can give you at this point based on the information I have. If you send me a photo I might be able to make a better recommendation.

Q: Why does a cactus not have leaves? (E-mail reference)

A: Most cacti are lacking in traditional leaves because of the environment they evolved in. Their adaptation is one of survival by storing water as long as possible when it is available through an extensive root system that is very efficient at absorbing water from the soil when it rains. In a typical leaf there is a large amount of water loss through the stomatal openings that are found throughout all leaf surfaces. The cacti have adapted by being leafless and growing spines but not thorns. Thorns are stem modifications and spines are leaf modifications. Spines on cacti do not carry on photosynthesis, but the stems do. Note their green color. Spines provide a microclimate for the cacti by shading the rounded or ribbed stem from the blazing sun of the desert where they dwell. Spines also play a somewhat protective role for certain animal species in the desert, giving shelter to some from predators, while others can consume cactus parts that are covered with spines with no ill effects. They certainly are a deterrent to we humans who might absent mindedly stroke, steal, or smell the flowers that occasionally bloom on them. Interestingly, the cacti species that are in full exposure to desert sun have a denser covering of spines than those same species that may be growing in canyons or the shade of large boulders.

Q: My 3-year-old cactus has tiny webs at the ends of the stems. I don't see any insects and the plant, in general, is healthy looking and making new sprouts. I hope my problem isn't spider mites. I don't want to infest my other plants near it. (E-mail reference)

A: Well, you might want to take back your thanks in advance because it sounds like you do have spider mites. Place a clean white piece of paper under some of the leaves and tap them lightly. You have spider mites if the specs that fall move around. Misting and a dose of insecticidal soap will take care of them so don't worry.

Q: My sister calls her cactus a Thanksgiving cactus because it blossoms at this time of the year. It has developed a bark-like appearance at the base of the stems and seems to be wilting. Any suggestions to get it back to health? (E-mail reference)

A: Her problem is likely caused by rot developing at the base of the plant on in the roots. The best thing she can do is take some cuttings and root them. They root easily and that way she would be perpetuating the same plant which is important to many people.

Q: I have several plants that have been outside all summer in pots and would like to them in for the winter. Do I have to do anything special? I planted them in Miracle-Gro potting soil this spring. Some are cactus that I have already sprayed with insecticidal soap but still have some cobwebs on them. Can I cut a mandevilla vine down and try to keep it over winter? How does one start lantana? I have many beautiful ones and would like to try and root some for next year as they are about $3.50 each. Do they come from cuttings or seeds? (Minot, N.D.)

A: I would suggest repotting anything that has summered outdoors whether or not you repotted prior to setting the plants out. You can use the same potting soil brand or anything that is available with similar qualities. Spiders will be wiped out by the insecticidal soap but the webbing will not. With the Mandevilla vine, go ahead and give it a try. Make sure you have plenty of light. Lantana's can be started easily

Q: My grandmother's Christmas cactus is in my living room. Right now it doesn't look good. It has long stems and baby leaves. Do I need to repot it? What type of soil do I use? I fear it will not survive and would be crushed if it dies. Please help me since this cactus is very sentimental to me! (E-mail reference)

A: It sounds like repotting is in order. Do you have it in a bright enough location? They need bright, indirect light. I would suggest propagating it from cuttings, if you can, to help assure its survival.

Q: I read that if, at the first part of October, you feed your Christmas cactus a solution of two tablespoons castrol oil and one-half cup lukewarm water it would bloom before or at Christmas time. Is there any truth to this? I don't want to kill my plant as it came from a clipping of a cactus that was brought over from England over 125 years ago. I also must be the only one from North Dakota that can't get zucchini to grow. They bloom, produce a few squash, and the rest of the blooms either fall off or don't produce. They are in an easterly direction, where it gets early morning sun and plenty of water from the roof of a building when it rains. I also water often.

A: The Christmas cactus will come into flower when its need for short day length has been satisfied. I have never heard of using castrol oil and advise against it. You must be the only one I've ever known that can't grow zucchini! It may be the rainwater from the roof, otherwise, I don't know!

Q: I purchased a Christmas cactus at Christmas and would like some basic information on how to care for it (when to fertilize, how much sun, east, south etc.) so that it will bloom again. I have been pretty much leaving it alone, only watering maybe once a month. (Fargo, N.D.)

A: This plant is daylength sensitive - at least it is supposed to be! What this means, is that it sets the flower buds in the fall of the year with shortening daylight hours. This means that you need to give it more than 12 hours of continuous darkness starting at the end of September to have it flowering around the holidays. Once the buds become visible, daylength is no longer critical.

East facings are generally best; fertilize during active growth periods, and don't over water. Following all of this may get the plant to bloom, but I have known people who have done nothing along these lines and the plant blooms beautifully right on schedule!

Q: Can you give me any insight on why Christmas cactus leaves may turn pink? ( Mandan, N.D.)

A: No, I can’t, unless you have it in front of or near an air conditioner vent that blows cool air and the plant is losing chlorophyll and the anthocyanin (red-pink pigment) is being expressed.

Q: I have two Christmas/Easter cacti . When they bloomed I took the blooms and cross pollinated then. Now I have seeds pods forming. My question is, do I wait for the pod to fall off or do I wait for it to dry on the plant or do I open it and sprinkle them onto potting soil? (E-mail reference)

A: Wait for the pods to dry on the plant, then excise the seed and plant.

Q: My Christmas cactus is wilting and has not bloomed this year. Any advice on caring for this type of plant and correcting the wilt problem would be greatly appreciated. (E-mail reference)

A: Wilting is not good for the Christmas cactus. I suggest trying to propagate it with some cuttings, selecting the firmest leaves you can find.

Q: I have a beautiful large Christmas cactus. The problem is the branches are quite big, rotten, and breaking off. I would like to know why this is happening. I have the plant in a self watering pot. I water it weekly. (Jamestown, N.D.)

A: You are most likely having root rot problems, along with some type of leaf decay. If you can find some healthy leaf tissue, snip it off and root in a sand/peat mixture after allowing the cutting to dry for two to three hours. That is probably your best bet for perpetuating this plant.

Q: I bought two Christmas cactus that were both blooming, but now about three weeks later the new buds that appear dry up and fall off. I have had approximately 20 buds fall off. The plants are in my kitchen, by the window that faces south. The instructions say to keep the soil moist, but I have heard to water them sparingly. I would appreciate any advice (Glyndon, Minn.)

A: Keep the soil evenly moist, and do not let a draft from the window hit the plants. A cold draft could cause bud abortion. Simply move it back from the window a bit. Generally a kitchen is a good place because of the heat and humidity the place generates.

Q: I have two beautiful Christmas cactus getting ready to bloom. What is a good watering schedule or when can I tell when they need watering? (E-mail reference)

A: Whatever you do, keep the soil mixture continuously moist, continuing the same pattern you have been following up to this point until after the flowering period. If you alter it too much now, the blossoms are likely to abort and you would end up with no show. Do not allow the pot to stand in water after watering. Pour off the excess. After flowering, moderate your watering to just moisten the soil mixture throughout, allowing the top inch to dry before watering again.

Q: I have a question regarding a Thanksgiving cactus. My wife has had one for 14 years and now it’s very droopy with very little vigor. We don't know if it will bloom this year. Is there anything you suggest? We repotted it a few years ago in good soil and compost. I promised her you would have an answer. (St. Paul, Minn.)

A: Boy, are you a brave man, promising your wife that I will deliver the goods. The pressure is too much! Here is what I suggest. Repot immediately in a very porous, peat-based mixture, to which you add very coarse sand or perlite in a free-draining pot. This should be done every year after the plant flowers. I suspect that the present soil mixture is water-logged, eliminating the necessary air the roots need to carry on respiration. Another possibility is the plant may have been exposed to too much direct sunlight over the summer. This is a jungle cactus, not a desert one, so it is a sub-canopy species in the natural environment. Filtered sunlight is the most it should ever receive. You might try watering (after repotting) with distilled or at least bottled drinking water that isn't too hard. These cacti do not do well on very hard water. Also, you might try misting the foliage with distilled water during the heating season to keep the humidity up around the plant. I hope something here helps. If it doesn't, it is likely due to a root rot disease that has set in. If that is the case, you will end up discarding the plant.

Q: I have two different Christmas cactus, one has a narrower leaf than the other. I have them in a north window, but neither one blooms for me. I had them repotted this summer at a greenhouse. Would you please tell me how to care for them and what am I doing wrong? (Breckenridge, Minn.)

A: The Christmas cactus is a jungle sub-canopy species that is never exposed to full sunlight. The flower buds form at this time of year with the restricted light of shortening autumn days. However, we mess up the cycle by turning on the lights when it get dark! So, cover the plants with a black or otherwise light-proof cloth, giving them short days of less than 12 hours. I suggest playing it safe and giving them just 10 hours of light and 14 hours of darkness. Cover at 5 p.m. and uncover at 7 a.m. Continue until flower buds are evident.

Q: I have a mixture of potting soil, scoria and river sand as a cactus mix. I got this yellow looking fungus which grew throughout my entire collection. It ends up with large yellow mushrooms coming out of the bottom of the pots. I repotted most of my plants with a new mix. Now I see the fungus is also growing in the new pots. It is almost impossible for me to repot my plants, and I would lose a lot of my larger plants if they went through another transplant. Is it possible to treat the soil with some sort of fungicide? I have tried the general fungus treatments and they have had no effect. (E-mail reference)

A: If I understand your concerns correctly, the fungus is growing in the soil and containers, not the plants per se. If that is the case, don’t you have much to worry about, as what you are seeing is a saprophyte that is growing in a part of your media that is not sterile or pasteurized. Other than aesthetics, it should pose no threat to your plants. When you do get around to repotting, I suggest using media components that have been heat pasteurized or sterilized. You containers need to be sanitized as well. Soak them overnight in a 10 percent solution of chlorine bleach to kill any spores and allow to sun dry completely.

Q: I have a Christmas cactus that is just blooming. Should the spent blooms be removed? Will it help the rest of the blooms develop?

A: The flowers can be removed once they are spent. This saves energy in making seed, allowing more to be put into the blooming, which we all appreciate.

Q: When we were in New Mexico last winter, I collected some Cholla cactus cuttings, thinking I could grow them as a house plant here. They didn't root, but the yellow ends of the cuttings released seeds when they dried up. Do you have any information on what conditions are needed to get these seeds to sprout? (E-mail reference)

A: About that specific cactus, no, but for cacti in general here is what is needed, and I don't see why it wouldn't work for your Cholla as well. Free the seeds of any pulpy material surrounding them. This may cause the seed to not germinate. They need light to germinate. Indoors, use fluorescent light, for eight hours continuously, with the soil temperature warmed into the upper 70s. They also need moisture at this stage, so keep them continually moist via misting. If nothing emerges in 10 to14 days, then either the seed is not viable, or they need another special treatment. This procedure works for about 90 percent of the cacti that I know of. If this doesn't work, then I'd suggest contacting the extension horticulturist at University of New Mexico in Las Cruces.

Q: I have a Thanksgiving cactus and it bloomed, but now it looks limp. Is it because I overwatered it? I also have a Christmas cactus that is blooming now, but some of the buds have fallen off. What is causing this? (Springfield, S.D.)

A: Cold or hot drafts can cause buds to drop. Overwatering can cause a root rot to develop which results in the limp appearance you are seeing in your plants. Back off on the watering, and your plants may recover if the problem hasn’t gone too far.Q: I have a Christmas cactus that looks like it is dying. It blossomed at Christmas time and usually again around Easter. It is quite old. Can it be revived? What is causing it to droop? It is in a south window and has been doing quite well there until now. What can I do for it? (Wheaton, Minn.)

Q: I was researching some websites to find out more about my Christmas cactus plant, and everything is still confusing. All I want to know is this: how often should I water it and can I plant it in regular soil? Also, how much water should I give it? I know it depends on the size of the pot; I have a medium pot. (E-mail reference)

A: There are two periods of critical watering; during the active growing period, and during the rest period. Through the end of January, water normally- that is completely wetting the growing medium, never allowing it to completely dry. Then, through February and March, get the plant into a cooler location and water infrequently and moderately -- enough to get the medium wetted, but allow the top 1 to 2 inches of the medium to dry before rewatering. As spring approaches in April (actually the noticeably longer days), increase the watering frequency as before, keeping the potting mixture continuously moist, but not standing in water. As for the soil, because of their high requirements for water most of the time, the Christmas cactus should never become waterlogged, hence the need for a coarse media that is peat-based, with the addition of coarse sand or perlite in a 3:1 ratio. For every part of the "normal" potting soil, add three parts of the coarse material. Ideally, these plants should be repotted every year after flowering. In spite of all of this information on "requirements" for normal growth, I know lots of folks who pay no attention to this kind of information and grow beautiful plants!

Q: This is in response to the inquirer who asked about the saguaro cacti. Here is some information I recently discovered while in Arizona. A saguaro growing from a seed will grow only 4 inches in the first 10 years. It takes 50 years for a cactus to reach 10 feet. After 18 feet--and 60 years--it will begin to grow an arm. So the reader will not see much change from year to year in the saguaro cactus. (Fargo, N.D., e-mail)

A: Now that I have read what you said, part of that information comes back from when I was living in Arizona some 15 years ago. Thanks for the refresher!

Q: My praying hands plant has brown spots on the edge of its leaves. What could it be from? I don't water my plants unless they feel dry when I feel the top of the soil. The Christmas cactus is doing really good and blossoming along with the rest of my plants. (Carrington, N.D.)

A: The prayer plant (Maranta spp.) is sensitive to being underwatered. While such treatment is good for Christmas cacti, it causes problems with this species. Unlike many (if not most) houseplants, the soil should be kept moist at all times--do not allow it to dry out.

Other possible causes of brown leaf spots could be dry air or too much direct light. Mist the foliage often with distilled water, and keep in mind that the sunlight intensity and duration is on the increase now, so exposure that wouldn't cause harm two or three months ago could be the culprit now. Be sure to remove any badly affected leaves.

Q: I would like to know why my cactus plant doesn't bloom. I have had it since last year. Also, how often should I water cactus plants and where is the best place to keep them? (LaMoure, N.D.)

A: You likely need an extra dose of patience more than anything else. They need the sunniest spot in your house during winter, and to be kept moist from spring through summer. In the fall, allow to dry and water only enough to keep the plants from shriveling; carry on with this procedure through the winter months.

Q: Everybody wants to know how to get a Christmas cactus to bloom. I have no problem. My cactus is setting beside the television by an east window. The Venetian blinds are shut, and lace curtains are over the window. It sets there year-round. I do nothing but water it.

It bloomed for Halloween last fall and hasn't stopped blooming since. For Halloween it had 89 full blossoms plus 12 buds that didn't open. About two weeks after all the blossoms had dried up, it got two more full blooms, and a couple of weeks after that it got two more full blooms. As the last one was drying up I noticed that it already has 14 buds again. I call this my miracle plant. (Jamestown, N.D.)

A: Thanks for sharing the success you had with your Christmas cactus. I just have to share this information with the readers.

Q: I received a Christmas cactus as a gift. How do I take care of it? (Selby, S.D.)

A: Basically, it should be treated like a poinsettia that you are attempting to re-bloom: Short days starting at the end of September (less than 12 hours), a reduction in watering and keep it in a cool location. That should do it! Once the flower buds are obvious, short days are no longer needed.

Q: Help! My Christmas cactus is limp. I've tried watering and not watering it, and nothing seems to make any difference. Any ideas? Maybe I should toss it. (Gettysburg, S.D., e-mail)

A: Unfortunately, when the plant does not respond to either regime, then it is either root rot or a vascular disease of some sort. Toss it and start anew.

Q. My problem lies with a cactus. Its size is getting to be a hindrance and it seems to grow best when placed outside during the spring and summer months. Is there some way to maintain this plant at a given size? Is there any way to straighten out crooked leaves? Also, could you recommend a book on cacti that might answer more questions as they arise? (Forman, N.D.)

A. There are dozens of cacti species that you could be making reference to, so I cannot accurately advise you. As far as books on this genera, I suggest a visit to a bookstore and do some browsing. I do not have any specific books on cacti, so I am unable to make a recommendation.

As far as the crooked leaves go, why not let them add character to the plant? Assuming you rescued this plant from the desert Southwest, I'd encourage you to continue summering it outdoors.

Q. Please let me know the name and care of the cactus. It's about 5 feet tall and at the bottom it's starting to get brown and crusty. (Amherst, S.D.)

A. Your plant sample is an Epiphyllum sp., but which species, I cannot tell. In general, these cacti need direct sunlight, dry soil, no fertilizer in winter, and cool conditions during winter months. If the plant is starting to decline, I suggest taking cuttings like you sent me, to root and perpetuate the plant.

Q. Enclosed please find leaves from two of my cacti. I have nine cacti of various sizes. One or more is always blooming. Although I've read quite a few articles on cactus, I've never read why one goes limp and looks as though it's dying. This has happened before, but the plant has come back healthy. They do get more hours of darkness than light. Also, I try to water on a consistent basis (not every week) and do fertilize once a month. Also I do need to transplant some of the smaller ones. What is the best mixture of soil to use? Thanks for all the information you provide. Your column is very helpful. (Moorhead, Minn.)

A. Many plants have a very distinct rest or dormant period and various Christmas cacti are included in that category.

You are approximately providing the right care for your plants. They like plenty of light, but not direct summer suns. They generally flower when the days are naturally short; when flower buds form, mist often and fertilize weekly with a dilute (about ½ normal strength) solution. The plants generally enter their resting period coming into summer when watering should be greatly reduced; and repot with equal parts of sand, loamy soil and peatmoss. Commercial mixes are available.

Q: I was given a Christmas Cactus that has probably been in the same pot for 30 years. It just had two blooms on it. Any advice on when and how to repot it would
be helpful.

Also I started my dahlias indoors and they have really taken off. Should I cut them back? Some are 10 to 12 inches tall with lots of leaves. (Sheyenne, N.D., e-mail)

A: Thirty years in the same pot! That has to be a record. Typically, this type of cactus is potted after flowering is completed, which it should be now. It
would also benefit from a summering outdoors in a shady location.

As for the dahlias, yes, cut them back somewhat, and move them out doors during the day when the temperature is 50 F or higher to begin slowing
them down and acclimatizing them.

Q: Will it hurt to transplant my Christmas cactus? It has a few buds on it, and one is a pretty good size where you can see the color of the flower, but it has a way to
go before it opens up. Should I transplant it into fresh soil? I have been told not to repot it because it won't flower again. Is this true?

I also would like to get a banana tree again. Is it too early to get one yet? (Carrington, N.D.)

A: Go ahead and repot it--now is the time, and yes, use fresh soil. You might also want to summer it outdoors as well. Locate it in a shady spot and be
sure to bring it in well ahead of the first fall frost. Don't worry. It will bloom again for you!

As long as you are not planning to place it outside, it is not too early to get a banana tree.

Q: I have had two Christmas cacti and both have been doing really well, until lately. Someone told me that I have been watering too much so I cut back, but the cacti
still have not improved. What is wrong with them? (McIntosh, Minn.)

A: Most likely, the overwatering (a common problem) caused some root rot or vascular disease to develop. Once either one is established the plants
are history. Sorry for the bad news. Start over with new plants, and the next time you get the urge to water, wait at least another day.

Q: I have a trumpeter vine or butterfly vine. It grows slowly and I can not get it to blossom. It is 3 years old. What am I doing wrong with it? Also, I have not
repotted my Christmas cactus for five years, and I am wondering if it is time. (Morris, Minn., e-mail)

A: I suspect you are being too good to your vine. Try root pruning it a little to stimulate flower production. Simply drive a straight-edge spade into the
soil a few feet away from the vine to sever some of the roots. Avoid fertilizing at all. If it still fails to flower next year, then it is likely in too shady a

Concerning your question on the Christmas cactus, if it has been five years since the last repotting, I would say that repotting it in the next nominal-size
container would be a good idea. Summer it outdoors--not in direct sunlight--and it should produce an abundance of blooms for you this winter.

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