Hortiscope

Ron Smith, Extension Horticulturist
North Dakota State University

Q: How many different kinds of spider plants are there? I know of two. If there are more, what are they and do you know how to find them? (E-mail reference, Leesburg, Va.)

A: There are three "spider plants" that I am aware of: the houseplant spider plant -- Chlorophytum comosum, the outdoor hardy annual -- Cleome hasslerana and the "spiderwort." which in American lingo means spider plant. The botanical name of this one is Tradescantia virginica. This doesn't mean that there are not more known by this common name in local regions of the country, but having lived in many places in my life, I cannot recall any more than these three right now. All of them should be available in garden supply stores -- a florist for the Chlorophytum and a nursery or garden center for the Cleome and Tradescantia.

Q: We had a crabapple tree that we dug out last spring. We dug down approx. 4 feet to get as many roots as possible. We are experiencing little suckers that are sprouting up as far away as 20 feet from where the tree base was. We are using Roundup on each individual little varmint that sprouts. Is there a secret way to eliminate these sprouts without having to continually address each individually? (E-mail reference, Glenrock, Wyo.)

A: The answer is simple. Use a broadleaf herbicide like Trimec and apply it like you are trying to control dandelions, plantain, or similar weeds (everybody's lawn has them!). You will incidentally kill off those suckers that are coming up from the old root system without hurting the grass.

Q: I have an iris bed that has become infested with dandelions, some growing in between the rhizomes so they can’t be dug out. Is there any spray that I might use that won’t harm the iris? (Dent, Minn.)

A: I know of no herbicide that will selectively take out dandelions in an iris bed. Best thing to do is dig everything up and re-set the iris in clean soil.

Q: How do you start a black walnut tree? I have two black walnuts from a tree and they are starting to turn dark. (Greenbush, Minn.)

A: If you can crack the outer husk with a hammer, do so, and plant the nuts where you want a tree to come up. Set them down about 6 inches in the soil. If the seeds are viable, germination will take place next spring. If you haven’t already discovered, wear gloves when handling walnut fruits as they do an excellent job of blackening one’s hands -- for a long time!

Q: I have questions about the yellow-brown look to some of our trees and shrubs. The maple trees turn yellow in early summer, then brownish and the leaves fall of by mid summer. Our Potentilla also does, and our rose bushes have this mid-summer. We cannot tell if insects attack the roses, but the flowering almond bushes definitely have bug attacks, if not both fungus and insect damage. How do we tell whether to spray for insects or fungus or both and when and how often do we spray? Nothing seems to help. (Wheatland, N.D.)

A: If such diagnosis were easy, I, along with thousands of other horticulturists and plant professionals would be out of a job! Here is what I’d suggest without knowing the source of your plant problems: 

1. Clean up all fallen leaves this autumn.
2. Spray next spring with a lime-sulfur and dormant-oil combo. That will take care of all overwintering insects and disease spores.
3. Apply a protective spray of Bordeaux mixture on your plants after the leaves have elongated. Apply systemic insecticide like Orthene to non-edible plants where insect damage is suspected.
4. Monitor the plant material for initial signs of trouble. If these steps don’t improve things, then you’ve got real problems!

Q: I have this plant that has long runners, but some of the leaves are turning yellow with black spots. Why? (Enderlin, N.D.)

A: Your plant is known as Maranta leuconeura massangeana or Prayer plant. The likely cause of leaf discoloration could be a nutrient deficiency, not enough light, roots in poor condition, and under watering. The black spots are most likely a fungal disease. I suggest repotting in a freely-draining container with a high humus potting soil. An African violet-type soil would be a good choice. Pick off all affected leaves, water with high quality (low salt) water, keeping the soil continuously moist but not water-logged. Fertilize once a month in summer, once every two months in winter.

Q: Please let me know how to take care of my peace lily. The one I have has rusty looking ends on its leaves, and I have been fertilizing it once a month keeping the soil moist all the time. (Hosmer, S.D.)

A: This is usually an indication of excessive salts in either the soil or water. I suggest backing off on the fertilization for the next month, and watering with either 100 percent distilled water or cutting your current water source by 50 percent with distilled water. This will not correct the leaves with the fried tips but should result in new growth that is free of it.

Q: I have a bougainvillea that has been in the same pot for about four years. It grew really well this year, but still no flowers. What do I do with it this winter to get it to flower next year? (Faulkton, S.D.)

A: The same thing you did the past four winters! Just kidding of course, but you can cut it back hard and bring it indoors well ahead of the first frost. Place it in a south-facing window and provide supplemental lighting to give it at least 14 hours of continuous light.

Q: I purchased eight arborvitae trees a year ago last spring. These trees were about 4 feet tall. What I noticed shortly after the landscaper planted them was that the root ball was exposed to about 4 to 6 inches on most of the trees. I have lost three of them so far, and when I complained to the landscaper he claimed there is nothing wrong with the root ball being exposed. Common sense tells me that the roots would dry out and the tree would die. What do you think? When a new tree is planted should the entire rootball be below the soil? (E-mail reference, Chicago, Ill.)

A: Your common sense is correct. B&B (balled and burlaped) trees and shrubs are dug from a nursery where the roots are not exposed. The top of the rootball is the top of the root system, and should be planted at grade level -- certainly not above it, and not below it. I don't know the value of what you had planted, but it should be worth a small claims court action. Document everything as carefully as possible -- take photographs, seek a consulting arborist or horticulturist, and if necessary, a lawyer. Arborvitaes are usually crowbar tough, bread and butter plants to use in the landscape, usually with no problems. A loss of almost 40 percent of the plant material is not acceptable in a landscape job. Something wasn't done right.

Q: I bought a hardy hibiscus plant on sale at the end of a season four years ago (it was more dead than alive) and planted it in the south side of our vegetable garden. Every year it dies back to dead stalks in the winter, I cut these completely off in May, then it comes back with a vengeance in the late summer. Blossoms are about 6 to 7 inches across. Each year the same pattern, except the plant is now huge beyond belief. (Over 7 feet tall and at least as wide, many blossoms, but getting gangly.) My question is, can I divide it into more, smaller plants? How? When? I really don't want to hurt it, yet it seems I can't just let it keep coming back bigger and bigger like this. (E-mail reference, Michigan)

A: Hibiscus are not divided but are propagated by softwood cuttings in early summer. Don't worry about cutting the plant back. Do so each spring, as hard as necessary to your satisfaction to keep it in bounds. Pruning back to two or three buds will yield large flowers.

Q: I am looking for an ornamental tree to plant in my landscape (full sun) that will only get to about 20 to 25 feet tall. I had thought of a mountain ash but my research shows it is susceptible to fire blight. (I really like the looks of this tree but don't want a headache.) I have also thought of maybe a crabapple, but they have a lot of suckers, don't they? (E-mail reference, Glyndon, Minn.)

A: One of my favorite trees is the Amur maple. It meets your height requirements, has a beautiful fall color, and is virtually disease and problem free. Another very similar tree is the Tatarian maple. They are so similar, in fact, that they often cross breed naturally resulting in seedlings that have characteristics of both species. Be sure to get a named cultivar of either of these trees. I don't think you can go wrong with either one!

Q: I have had two different garden phlox that I have tried in five different spots (full sun) over the past 10 years and still have not had any luck in getting it to bloom. I have tried Miracle Grow and thinning the stems. (E-mail reference, Lisbon, N.D.)

A: I really don't know unless there are some cultural gaps you are missing. Watering -- phlox need to be consistently moist. The old theory of "keep the feet wet, the clothing dry" refers keeping the roots moist but the water off the foliage. Mulching -- all phlox respond well to an organic mulch such as peat moss, compost, or pine needles. Mulch helps control the weeds and keeps the soil moist. Fertilizer -- use a 10-10-10 at time of planting and sprinkle around the plants as new growth emerges in the spring. I would think that your Miracle-Gro would take care of that need. Other than these basic suggestions, I have nothing else to offer you as to why the phlox will not flower.

Q: Can I winter my ivy geranium? It has been outside and I potted it. I only have a north and west window for sun. (E-mail reference)

A: Yes, you can winter your geranium indoors as a potted plant. Use the west window and provide supplemental lighting if possible, with a Gro-Lux bulb. Set it back a little from the window to cut down on a direct cold draft coming from it in the winter.

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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.

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