September 4, 2003

Hortiscope

Ronald C. Smith, Horticulturist
NDSU Extension Service

Q: Could you please tell me a safe distance to plant a lilac bush from the foundation of my house? I would like to avoid future problems with larger, older roots. (E-mail reference)

A: People worry too much about roots and foundations. Plant it about 12 feet or more from the foundation if you are really worried.

Q: I have two mature lilac bushes that don't bloom in the spring. Is there anything I can do to encourage new blooms? (E-mail reference)

A: Try cutting some of the roots with a sharp edged spade in four or five places around the plant; avoid lawn fertilizers around the root zone and don't prune. If this doesn't work then they are probably in too much shade so you would need to move them to a sunnier spot. If that doesn't work, then give up and get some new ones.

Q: There is a row of huge pine trees that are planted along the perimeter of a cemetery. They are planning to prune the bottom of these trees 5 to 6 feet up. Will pruning harm the trees? The surrounding homeowners are concerned that this would be the wrong thing to do to these beautiful trees. (Vermillion, S.D.)

A: It will not hurt the trees in the least. What the homeowners are complaining about is the destruction of the natural shape and beauty of these majestic spruce trees. If they pose a security or safety problem and pruning will rectify the problem, then I would point that out to the homeowners and go ahead and prune them.

Q: Is it possible that elm tree sap, when mixed with water, can spoil and cause an awful stink? I returned home after two days to notice an awful smell coming from the curb. I noticed some standing water along the curb. It wasn’t very much but it extended down the block. At first I thought someone dumped their RV waste because the smell sort of resembled it. The next day I went out with a garden hose and leaf blower to push the waste (note: the water had a white scum on it) to the sewer drain at the end of the block. A neighbor's friend stopped by and said it was sap causing the stink. The sap this year was heavy. I've only been in this home for two years so I'm a rookie when it comes to these things. I called my dad and he thought perhaps a sewer line broke but there's no water coming up and the grass along the curb is bone dry. Any thoughts? (Moorhead, Minn.)

A: Sap doesn't necessarily need water to stink. If you look carefully up into the canopy, you might see a canker where "bleeding" sap could be coming from to form a puddle of the stinky stuff. That is the result of some internal rot. The stinky stuff is called "slime flux."

You might want to contact an International Society of Arboriculture certified arborist to see if something can be done to re route the stinky stuff or remove the cankered branch. The usual summertime sap drippings coming from mature trees is usually the result of aphids feeding on the foliage and the sap passing through their bodies as "honeydew" that get all over sidewalks, cars and streets. During dry periods that normally occur this time of year, the tree leaves bleeding sap through microscopic openings on the leaf edges exacerbate the problem. Try and avoid parking your car under such trees as it damages the finish.

Q: Can I purchase lythrum in North Dakota or is it considered a noxious weed? I think it makes a very beautiful plant in a perennial garden but I know most states have outlawed it. If the state doesn't allow it, can I purchase it somewhere else or is there a comparable plant I could grow instead? I have tried lavender but it will not come back. (Tioga, N.D.)

A: By law, you cannot purchase or own lythrum. You can use liatris (prairie gayfeather) in much the same way that you use lythrum. It is completely legal, readily available and hardy for our environment.

Q: This year our tomato plants are drying up starting from the bottom around the center and then moving up. They are getting plenty of water and we even gave them Miracle-Gro. The plants aren't very big. They do have tomatoes and some are nice sized. Any idea what could be drying them up or what we can do? (Selby, S.D.)

A: It is tomato blight time again in the Upper Midwest! Our wonderfully variable regional weather has set the stage for tomato blight diseases. There are four diseases that fall into this general category, each with distinct symptoms and caused by different fungi. Based on your description, I would guess that yours is early blight. It attacks the older foliage and slowly works its way up the vine. Secondary damage to the fruit is manifested by sunscald from foliage loss.

Avoid overhead watering or using mulch. Use only clean seed and don’t plant in the same location each year. Spraying with fungicides at this time will do little good and only contaminate the environment with unnecessary pesticide. Be sure to clean the garden of all litter this fall and turn the soil over before the snow flies if you have a chance.

Q: I have a very mature cottonwood tree (70 feet) in my backyard. Since it provides shade, I'd like to keep it as healthy as possible. There are two very large roots that I would like to cut since they are near a concrete patio. One has broken through the surface and the other is a couple of inches down. Will cutting these roots hurt the tree? (E-mail reference)

A: I cannot answer that question without seeing the tree and checking it out. I would advise getting a hold of an International Society of Arboriculture certified arborist to check the tree over before you make such an arbitrary decision. You don't want to cut something out that will result in an imbalance that could cause it to fall during the next storm.

Q: I have snow on the mountain under two trees. Both areas are browning and it looks like it's dying. Previously you said a leaf fungus causes the problem. What causes it and is there anything that I can do to avoid it in the future? We laid sod this year so we've been watering quite a bit. Could it be getting too much water? We started out the season with the fullest, nicest stand that we ever had so it's very discouraging. Will it come back again next year if we treat it with a fungicide? (E-mail reference)

A: The watering would do it. Mow it off for now and pick up all the clippings. Next spring, as the new growth is opening up, spray with a fungicide like Ortho's Multi Purpose Fungicide. Because this is a preventative application, you should get good control as long as you don't water like you did this year. Monitor the planting to be sure something doesn't get started again. If it does, reapply the fungicide.

Q: I have a large border of marigolds that are shriveling up and dying. I'm not sure if it's too much water, not enough water, heat, or bugs. I can't see any bugs. The leaves start getting pale while the veins stay a little greener but eventually the whole plant dries up. (Fargo, N.D.)

A: It could be any number of things, including those that you mentioned, but it sounds like a white mold fungus. The best thing you can do right now is pull up the infected plants, roots and all, and dispose of them.

Q: I have a very old juneberry tree whose leaves are turning yellowish brown and falling off. The tree is almost bare and it is only mid-August. Also, the trunk is a little greenish in color. I’m hoping you can tell me if this tree is diseased or dying. (E-mail reference)

A: Obviously so but I cannot tell you what could be doing it from your description. Since it is in the same family as the apple, I suspect it might have a leaf spot or scab disease that commonly afflicts apples. About all you can do at this point is clean up all fallen litter and starting next spring, spray the shrub with lime sulfur while still dormant. Follow up with a spraying of Bordeaux mixture after leafing out is complete. That may stop the development of the disease.

Q: We have an old jade plant that was given to us. It's about 2 feet high and 1 1/2 feet wide. We repotted it last year into a fairly large pot. It seemed to be doing fine but in the last six months or so it started losing whole branches and drops leaves often. The branches or parts of the branches crack off even without being touched. We water it a few times a month. Should we water it really well once a month, removing any standing water? I don’t think we give it enough water even though we do it twice a month. (E-mail reference)

A: Jade plants need more sunlight than most folks give them. If you can, gradually move the plant to where it will get more direct sunlight. I have seen jades grow as high as the second floor when they were getting incoming radiation from a skylight. I have never seen a jade drop leaves or branches if it was getting a good dose of direct sunlight. Allow the soil to dry between waterings in the summer but go back to your once a month watering during the winter months. Also, don't forget to fertilize during active periods of growth in the spring and summer.

Q: I'm not a plant expert, but want to do a favor for my in laws. They want to move a 30-year-old grapevine so they can take it with them this fall. Is there a way to transplant it or part of it from rootstock? Should they use cuttings and try to root them? (E-mail reference)

A: You would need dynamite to get it out of the ground so save your back and take cuttings. They root easily and your in laws can then have several plants to harvest. Perhaps they will share the bounty with you, their favorite son in law!

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