December 4, 2003

Hortiscope

Ronald C. Smith, Horticulturist
NDSU Extension Service

Q: We have lots of native cottonwoods growing in our area. We dug up four of them and planted them in our yard. How far should they be from the house so the roots won't be a problem with the foundation? Is the cotton the tree drops a problem? (Watford City, N.D.)

A: The roots will only be a problem with the foundation if there are cracks in it. Otherwise, you have nothing to worry about. I have received hundreds of letters over the 18 years I have been writing this column complaining about the cotton and wanting to know how to eliminate it. Cut them down has always been my answer. I have yet to receive one letter that says the writer loves the falling cotton!

Q: My fifth grade son has been assigned an elementary science project. He wants to do something with plants. We were wondering if germination techniques would be a good topic. Do you have any suggestions on experiments he could do with plants? (E-mail reference)

A: Some plant seeds need light for germination while others need darkness. He could take chamomile seed and sprinkle it on a flat of sterilized or pasteurized soil and take the same species of seed and bury it 1/4 to 1/2 inch into the soil. Place a fluorescent lamp with one cool white and one warm white bulb in the holder and suspend it about 12 inches above the flat. Keep the surface moist by misting. The uncovered seed should germinate well ahead of the covered seed. He could take any seed such as corn, beans or grass and sprinkle 10 seeds on three petri dishes with paper coffee filters in them that are saturated with some type of water. He could use distilled water, tap water and one molar solution of sodium chloride (table salt). To make a molar solution of sodium, take the atomic weight of the two elements of sodium and chlorine (23 + 35.5 = 58.5 grams). Take that figure, 58.5 grams or about 2 ounces and add it to one liter of water, which he can then add to the third petri dish. The sequence of germination should be distilled water, tap water and then the one molar solution of sodium chloride unless the tap water is very high in salts. Another possibility is to get a hold of an easy-to-root plant like coleus, forsythia or willow. Make six cuttings six inches long. Stick three in the sand with the top of the cutting facing up. Put the other three in the sand with the tops in the sand. You will need to keep them misted on a regular basis or at least keep the humidity high by placing them in a terrarium. In about four weeks the three normally planted cuttings will leaf-out and root. The others will do the same except they will be demonstrating what is called geotropism. The leaf tissue will be bending upward while the root tissue will be bending toward the earth. This is an example of negative geotropism, while the other is an example of positive geotropism. That should give him plenty of choices. Good luck!

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: I own three Christmas cacti; two are the color of the picture I sent you. I've had two of them for three and a half years. They have been doing great and I usually get three bloom explosions a year. About a year and a half ago, I took the one cactus, while it was blooming, and pollinated it with the cactus in the picture. It worked and I got two fruits, which I’ve had for about a year and a half. They don't look like they are ready to fall off any time soon. Should I pluck the fruit and plant it or should I leave the fruit on and let nature take its course? I bought a pale white and pink cactus a month ago and I tried the same thing with it. I think I might have a fruit developing on it but it’s too early to tell. (E-mail reference)

A: If the fruit has remained the same for the last year and a half, I would harvest one of them and cut it open to see if any seed has developed. If so, spread the seeds on a sheet of paper to dry for a day or two. Then put the seeds on damp sand and cover with some type of clear wrap to see if it germinates. Give them a maximum of 60 days. I am not sure what the requirements are for germination and can't find anything in my references. If nothing germinates after 60 days then the seed was not ripe. If there is no seed, then the pollination was not complete and fertilization did not take place. Propagation is normally asexually by way of tip cuttings, which root easily. If you do have seed, and the plants you crossed had different flower colors, it is very likely that the new ones will also be multi colored.

Q: I have a dwarf apple and grapes that were planted last spring. I read one should buy a "whip" but I also read whips are not available. Do I make my apple sapling into one? It's fairly symmetrical at the moment and hasn't been pruned at all since planting. (E-mail reference)

A: "Whip" or espalier is two dimensional pruning meaning height and width but very little in depth. Before new growth begins this spring, cut it back to make the shortest branches possible with those you presently have. Leave at least one bud that will grow at vertically or horizontally but not out toward you. As new growth begins, keep it pruned back to encourage the "espalier" or two dimensional growth. You will need to get some holdfasts to keep them against the wall or fence. As the tree matures, you will be able to walk right up to it and harvest the apples that are growing on the "wall." There is, of course, a lot more to this than the four simple steps I've outlined. I suggest a visit to a good bookstore.

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: Rich Mattern, (701) 231-6136, richard.mattern@ndsu.nodak.edu