August 22, 2002

Hortiscope

Ronald C. Smith, Horticulturist
NDSU Extension Service

Q: Is it possible to add something to the water in my rain barrels to prevent mosquitos from hatching out yet won't harm my plants? I considered the BT "doughnuts" they sell for ponds, but they are hard to find. I have put a couple goldfish in there in the past, but during dry spells the water gets too low and murky. With West Nile virus present in our area, I need to do something, but with the drought it is hard not to save every drop of rain that falls. Any ideas? (Howard S.D.)

A: In a rain barrel, a couple of tablespoons of vegetable cooking oil will do, and will not hurt your plants. The oil will float on the water's surface and suffocate the mosquito larvae. If that idea does not appeal, go to the nursery or garden supply store and see if they have a "summer horticulture oil." About the same thing and as effective.

Q: Over the winter piles of snow gather in certain spots on the lawn. In the spring these snow piles turn to ice until everything melts. Consequently, these spots remain bare during the summer. The surrounding grass will not spread over onto them. Sowing grass seed onto them does not help either. What is wrong and what can I do about it? (Mina, S.D.)

A: These areas are usually surface "sumps" where, when it rains or snows, the moisture collects and causes havoc with growing grass. If you can, core aerate, and bring in some fresh topsoil to spread lightly over the area. Then spread the seed, working it into the upper 1/4 inch of soil.

In spreading the soil, try to slope or grade it in such a way that water or snow will not collect and turn into ice, but run off or percolate into the soil below.

Q: I have three beautiful blue spruces. I noticed that the needles are starting to fall off, and when we looked closer there are cocoons hanging all over the tree and these worm-like insects are using the needles to make their cocoons. We sprayed Sevin a few times but they keep spreading. It started on one tree and now it’s on all of them. I removed one of the cocoons and placed it in a bowl with holes in the lid to see what exactly these things become. Is there something else we should be doing? And can these kill the trees? (E-mail reference)

A: It has been quite some time since anyone has written me about bagworms. I was beginning to think they might have become extinct......no such luck! Anyway, if there are just a few that you can reach, cut them off and dump them into kerosine or into a campfire, and do so at your earliest convenience. If there are too many, spray the tree with an insecticide like malathion, which will control them as they continue to feed. Pupation of this species takes place in early September, and several days later the adult winged males emerge and mate with the wingless females at the lower tip of the case or bag they are carrying. The male dies, and after the female deposits her eggs in the old pupal case, she also dies. The eggs overwinter, and new larvae emerge the following spring to take up where their parents left off, building a new bag out of silk and the foliage they are consuming.

Q: Last year my parents moved in to a new house which has a large oak tree. It appears to have been two tree trunks growing out of a large main tree trunk. One tree trunk has died and left a gapping hole in the remaining trunk. The hole faces upward, fills with water, and continually gets a variety of ants and bugs in it. They really want to save the tree. It appears healthy everywhere else. The bark seems to be repairing itself and the leaves look very healthy. What would be the best way to prevent any further infestations and repair the hole? (E-mail reference)

A: A certified professional arborist will know what to do. The arborist will clean out the cavity, check the heartwood for soundness and fill in the cavity with a material that will help the bark to grow over it. This is not something that you want to do yourself, I assure you. Besides, the heartwood check is an absolute necessity from what you tell me, as a tree can look very sound and healthy but be rotten in the core, with very little structural strength. The procedure is not expensive, and the knowledge (one way or the other) is worth it!

Q: I have some calla lilies that are going to seed, and I would like to attempt to grow some more from seeds. What is the best method to accomplish this? (E-mail reference)

A: Unless you are a very competent grower, with a cool greenhouse at your disposal, this is not an undertaking to take lightly. It requires a lengthy process that is complicated and must be carried out under carefully controlled conditions. You are far better off propagating them via division of the rhizomes, or detachment of the offsets that develop under the main rhizome. The best time to carry this out is in the fall, dividing the rhizome into several pieces, making sure that each one has a healthy growing point. Then carefully place each rhizome just under the dampened potting soil mixture into a 6-inch pot, taking care that it is placed in a horizontal position and to not damage the growing point.

Q: I obtained a jade plant from a friend of mine when he moved out of state. I have had it since August of 2001 and it has done well. I repotted it about six months ago because it needed a better pot. I now have it in a heavy pot. In the last few days it has started leaning almost completely over so I decided it needed to be replanted and added more dirt to make it more stable. When I pulled the plant up, I felt a snap and all I saw at the bottom was a small mushy end. I went ahead and put it into the dirt and stabilized it as much as I could. I have no idea how to repot or anything about plants. I am afraid I might have killed it. This plant means so much to me. Can you please tell me what I need to do to save it? (E-mail reference)

A: The best thing you can do is take some 4-inch cuttings from the plant and root them; individual leaves will also root. I doubt that you can save the entire plant at this stage, but if you saved propagules from the mother plant, that would be the same thing basically. If you will forward me your mailing address, I will send you a circular on home propagation techniques that should help you get some new plants established.

Q: One of my neighbors tore down their garage and in the process removed three beautiful 7-foot green emerald arborvitae bushes, and I snagged them up. Some of the roots were a little damaged but all in all they looked really good, and still do. That was about five days ago. I planted them in peat moss, mulch and good soil, and so far, so good. I just wanted to know if I should do anything special, like some Miracle-Gro or fertilizer spikes. (E-mail reference)

A: Good snagging! I would suggest a shot of Miracle-Gro right now. Forget the fertilizer spikes, they are a poor investment and do more harm than good for the trees. This fall, prior to freeze-up, I suggest a spraying of Wilt-Pruf to keep them from desiccating over the winter. Their roots are limited somewhat as to the amount of moisture they can take up, so don't let them go into the winter dry. Don't overdo the watering either, just keep them from drying out.

Q: When is a good time to transplant raspberries? Would now be a good time? (E-mail reference)

A: No, not now. Early spring before new growth breaks, or this fall when they go dormant from frosts.

Q: I have a grape arbor in the back yard which produces very well and is now growing along the fence. This vine is now about five years old and I have never pruned it. Should I do so, and if so how far back should I prune it? (Fargo, N.D.)

A: Good grief - never pruned in five years? I am surprised it has not taken over your house! The time to prune a grapevine is in the early spring before new growth begins, and in your case, I don't think it would make any difference how far back you pruned it, it would shoot up again with rampant growth!

Q: For three years, I have planted potatoes in three different spots. Each time they grow well but are all covered with warts. We like new spuds with skins on, but I can't bring myself to serve them without peeling. Is something lacking in our soil? This is all new ground that we acquired by tilling up part of the lawn. (Tower City, N.D.)

A: It sounds like you are being plagued by potato scab, an organism that is found in the soil and causes one of the most serious diseases of potato. I suggest trying some of the resistant cultivars such as Goldrush, Katahdin, Kennebec, Red Norland, Red Pontiac, Russet Norkotah, or Superior, which is a white potato.

Q: I am growing purple coneflower in my yard for ornamental purposes and I found there’s an Echinacea Angustifolia and an Echinacea Purpurea. What are the differences between them? Does one flower more prolific? Which is native to North Dakota? (West Fargo, N.D.)

A: There are some nine species of Echinacea in North America. The E. angustifolia is the native; the E. purpurea is the showier of the two, getting a little taller, and is considered more ornamental. Both have medicinal properties and are currently under study at NDSU by yours truly, along with E. pallida, for medicinal constituents. Once established, Echinacea will reseed itself, spreading nicely among other perennials or prairie plantings. The E. purpurea is growing beautifully in my prairie garden at home with no problems, but in our research plots it appears to be vulnerable to aster yellows.

Q: I ate a peach yesterday and the pit was partially opened. For the first time I noticed there were seeds inside and so I bit one to see what it tasted like. It tasted very almondy to me and have a nice soft nut like texture. Are these seeds edible and if so, why can't I find any commercial reference to them? (E-mail reference)

A: Not a good idea! You are fortunate to be alive. All parts of the peach, plum, and cherry are poisonous, with the stone kernels containing the highest concentration of cyanide, at 164 mg/100 grams. While no human deaths have been reported, hogs and cattle have succumbed to eating fallen peaches pit and all. Now you know why they are not for sale on the market.

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