HG: Homegrown Column january 17, 2009

I have two beautiful flowering crab apple trees in my front yard that produce a lot of crab apples. The apples stay on one of the trees until spring, which the returning robins feed on. 
The other tree drops the apples in November and requires many hours of cleanup using my shop vac. I usually get about 40 gallons of apples for the trash. I have attempted to spray the blossoms in the early spring, but that doesn’t seem to work very well.  If I leave the apples on the lawn can I expect damage to the lawn?
— Jerry

You can see damage sometimes by leaving the crab apples on the lawn.

Sometimes they can get so thick that they shade out the grass beneath, but mostly the problem is that as they decompose, they can produce chemical compounds (such as alcohols) that are antagonistic to plant growth.

What I’ve seen is that the lawn starts to get thin and patchy. I haven’t seen this problem on woody plants growing beneath crab apples. I don’t know why that is. Maybe they’re a bit tougher than the lawn or perhaps because they have deeper roots to avoid these compounds.

Anyway, I’d try to get most of the crab apples off the lawn if you can. You don’t need to get them all, but try to get most of them.

We have what may be a potential problem with the root system of a Russian olive tree. The tree is approximately 16 years old, 18 feet high, with its drip line 8 to 10 feet from the tree trunk. We recently discovered that our domestic water line is on the edge of the tree’s present drip line. The water line is plastic tubing. Do you foresee potential damage to our water line from the tree root system?
If we were to cut down the tree at ground level and use brush killer on any new growth, would the tree root system continue to grow and still become a potential hazard to our water line?  
Thank you for your assistance.
— Linda

I suppose there’s a chance of trouble, but I’d be surprised if the roots of the tree gave your water line any problems.

The biggest reason for that is that the water line is set deeper than the roots of the tree will grow. Studies of root growth indicate that 99 percent of all roots are located in the top 36 inches of soil, and I think that locally it is even a bit shallower.

Most of these studies were done in the Midwest where the soils are better than ours (better
drained and better aerated) and our heavy clays tend to push roots shallower.

In a “typical” root system, the roots are often a bit deeper right beneath the trunk, but as you get farther from the tree, the roots tend to grow out horizontally 12 to 18 inches below ground level.

Because your water line is at least 4 feet deep to avoid frost, I don’t think you have anything to worry about.

I have seen rare instances where roots have constricted plastic pipe, but it is almost always polyethylene pipe (the flexible black stuff).

The type of pipe that’s usually used today for water service is PVC (the rigid white plastic pipe), and it’s much stronger and durable than polyethylene pipe. Plus, the only times I’ve seen constriction is in sprinkler systems, where the pipe is only buried 8 to 12 inches deep.

If you absolutely don’t want any chance of problems, then killing the tree will take care of things.

I’d cut the tree off and then treat the stump with Fertilome Brush and Stump Killer. It contains an herbicide called Triclopyr that is spread systemically through the roots, killing them.

Just be sure it is applied to a fresh cut so it can be absorbed and taken down to kill all the roots. One trick is to drill some 3/4-inch holes down a couple inches into the trunk. Drill them in a circle just inside the bark. You can then fill the holes with the Stump Killer to do the job. 

Dennis Hill is the nursery manager at Bookcliff Gardens, online at http://www.bookcliffgardens.com. Send questions to Bookcliff Gardens, 755 26 Road, Grand Junction 81506; or e-mail .(JavaScript must be enabled to view this email address).


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