January 3, 2002

Hortiscope

Ronald C. Smith, Horticulturist
NDSU Extension Service

Q: One of my dad’s trees has started to crack in the crotch of the tree. He was wondering if he should cut the branch that is making the crack worse or if he should tie something around it to keep the crack from getting any bigger. The tree has slanted to one side so for it to grow straight again I thought he should cut the branch off. I just wanted a second opinion. ( Fargo, N.D.)

A: Thanks for a good question. The answer depends on a number of things: The age, species, and size of the branches in question; whether or not the tree will be badly misshapen as a result of the cut you want to make and whether or not the tree's branches are at a location in the structure of the tree that would allow cabling or bracing. Whatever the choice, something needs to be done so there is no further damage to the tree. If your inclination is to cut off one of the offending branches, I trust your aesthetic judgement and ability to make the proper cut. Whatever you do, don't "tie" anything around any branches or a girdling effect will make everything worse.

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 a hibiscus plant that needs pruning. How much can I take off without killing the plant? It's about 4 feet tall, has blossomed twice while on the patio and twice inside, but it's pretty large and is obstructing the view of the TV. (E-mail reference)

A: The hibiscus can be cut back to suit your needs. They are generally vigorous plants and will produce new growth shortly, although not in the robust manner that is experienced in spring and summer seasons.

Q: Is Christmas cactus poisonous to pets, specifically cats? We recently purchased a Christmas cactus plant and our cats are attempting to eat it. I know that Poinsettia is poisonous to cats. (E-mail reference)

A: Poisonous, no; good to eat, also no. I would still keep the cats away from the plant, as there might be some residue from pesticide applications that could make them sick. I suggest visiting a local pet store and purchasing some grass seed or some grass that has already sprouted. That they can eat, but it acts as a purgative on them in most cases, so be prepared to clean something up!

Q: I have a large rubber plant (about 3 feet tall) and am concerned about its future. My mother had the plant in her care for four years while I was in college and it did quite well with nice full branches. Now the plant continues to grow upward but loses all of its leaves downward. It also continues to grow plenty of offshoots that do quite well. The plant has never been repotted and I noticed the soil is getting a little low in the pot. I don't water often (every couple of weeks), after an overwatering mishap about six months ago. Could this still be the result of overwatering? Or lack of sunlight, as it gets little of that? (Moorhead, Minn.)

A: The plant is reacting to a stressful event, either something recent or the watering mishap you mentioned. I advise repotting it and cutting the "pole" stem back to encourage a flush of new growth. Once the rubber plant drops its leaves, it has been my experience that they never come back again. It would be a very good idea to repot it, then practice consistent watering--not overwatering--but allow the top to dry before watering completely again, to the point that it leaches into the saucer the container is sitting in. These plants are also sensitive to drafts, either hot or cold, so be sure to place them far enough away from a window that they are not affected by any cold air coming off of it. Once in a location where they are doing all right, it is a good idea to let them remain there, as moving them elsewhere often causes defoliation.

Q: I am writing for a lady who has a couple of questions. She bought an avocado from the local grocery store and started an avocado tree that she has been growing inside. It is now 4 feet tall. She wants to know what to do to get it to produce fruit, and would it grow outside in our climate? She has no knowledge of the variety, because it was just a fruit bought over the counter. Can she produce a banana tree from the seeds in the bananas at the grocery store? I guess I am a little confused by this question, and maybe just a couple banana facts could clear this up for her. (Mohall, N.D.)

A: What great questions! Thanks for sending them on to me. The avocado is not a tree for our climate; it grows in Southern California. Up here, it can be grown a few years as a novelty houseplant, nothing more. When it starts to get ungainly is the time to dump it and begin again.

Bananas do not produce seeds, as they are reproduced asexually via a process known as parthenocarpy, and the resulting fruit is known as a berry. Banana plants are very rhizomatous plants, producing what are called "pseudostems" that the fruit is actually produced upon. In essence, the plants are sterile, so no seed is formed, but a semblance of seeds may be observed when one cuts a banana in cross-section, as the fruits develop from the ovaries of female flowers, leaving numerous black dots where the ovules on the axile placentas aborted. They cannot be excised and they will not germinate.

Q: Do you or any of your readers know how to get rid of white flies on house plants organically?

If not organically, is there a systemic chemical you put in the soil so they can eat themselves to death? (Brookings, S.D.)

A: Use insecticidal soap solution as a dip on the houseplants that you can treat that way. If you cannot dip a plant, use the soap as a spray. It is organically approved and insects cannot build resistance to it like they can with the inorganic chemicals. Another material is known as Neem, derived from the tree of the same name. It is found in "Schultz's Expert Fungicide 3" which acts as an insecticide and miticide as well as a fungicide. This works very well in providing control.

Another way (not organically approved) is to use a no-pest strip. Put the houseplants in a large plastic trash bag along with the strip and tie it shut for 24 hours. That usually does the trick for good. I would use this as a backup where you cannot get satisfactory control with the insecticidal soap or the Neem. Good luck! They are terrible pests. It used to be that when they got into tomato greenhouses the only way you could control them was to strip everything out of the house and let it lay cropless for a season through heat and cold, as well as an insecticide treatment.

Q: I have an opportunity to get a holly tree about 8 feet tall now from my parents’ yard in Maryland. Will it survive in South Dakota? My mother loves it and hates to leave them all behind when they move out to the Dakotas to live with us. This one is the smallest in her yard because it volunteered where it didn’t belong. It has to be removed anyway, so will it make it if I mulch it, fertilize it or do what ever it needs? I know nothing about holly tree care although I do have a green thumb when it comes to gardening. (New Underwood, S.D.)

A: I don't advise it. Hollies are mostly broadleaf evergreens (there are a couple of deciduous species) which do not fare well in our prairie environment. I am afraid your efforts would all be for naught, as there is essentially nothing right for it to survive: minimum temperatures are too low, the soil pH is wrong, and the exposure, along with the wide swings we get in temperature, would likely kill it. However, if it has to be moved anyway, what do you have to lose? Give it a shot. Spray it with Wilt-Pruf first, dig as much of the root ball as you can handle, plant it in modified soil, rich in organic matter like peat moss, and fertilize with acid-forming material that is specific for holly and azalea plants.

Do you have a gardening or houseplant question? Write to Hortiscope, Box 5051, NDSU Extension Service, Fargo, ND 58105 or e-mail to Ron Smith at ronsmith@ndsuext.nodak.edu. Note to e-mail correspondents: please identify your location (city and state) for most accurate recommendations.

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Source: Ron Smith, (701) 231-8161, ronsmith@ndsuext.nodak.edu
Editor: Gary Moran, (701) 231-7865, gmoran@ndsuext.nodak.edu