By Carol T. Bradford
Dear Carol: We have tons of arborvitae trees around our in-ground pool. There are three trees that have had to be replaced three times in the same area. There must be something wrong with the soil in that area. What do you think could be wrong and what can we do about it? Where can we have our soil tested? — L.W., via e-mail.
Dear L.W.: I would say you are getting a clear message that arborvitae don’t want to grow in that particular spot. The possible reasons are almost infinite in number, and it would be prohibitively expensive to test for them. There’s only one solution in any case, which is to dig out the soil in the area and replace it. Most roots are in the top foot of soil, so if you dig down two feet you’ll probably be OK.
You may learn a great deal when you dig. The issue is more likely to be a physical or structural problem with the soil than a chemical one having to do with soil fertility or contamination. Especially when there has been construction nearby, like that pool. What builders do is almost unimaginable sometimes. It all gets covered with a layer of “topsoil” and graded, and no problems are apparent until plants try to grow.
I’ve found blacktop, chunks of concrete and rocks the size of a dining room table just below the surface. Hardpan, a layer of compacted subsoil that can develop, will prevent soil drainage and stunt or drown plants. A worst case scenario would be that somebody dumped a persistent herbicide or oily sludge and contaminated the soil. Or perhaps emptied a sack of lime so that the pH is so alkaline nothing can grow. Chlorine is toxic to plants; if they are being exposed to pool chemicals that could be a concern.
Arborvitae (northern white cedar, Thuja occidentalis) are native to this area. They are relatively fast growing for evergreens, inexpensive to propagate and easy to transplant, so they are seen everywhere. Deer love them, and unfortunately the trees do not recover well from browsing, or any misguided pruning, for that matter. Snow and ice can cause branches to break. This can be prevented by siting the trees properly — not under the eaves — and by protecting with A frames or wrapping with burlap or twine.
There are many cultivated varieties available, different shapes, sizes and growth rates. The species turn brownish in the winter and several of the cultivars have been selected because they maintain their green color all year. Michael Dirr recommends ‘Emerald’ (aka ‘Smaragd’), ‘Techny’ and ‘Nigra’ for Northern gardens.
Cornell University has outsourced routine soil testing to Dairy One. Contact them at Dairy One, 730 Warren Road, Ithaca, NY, 14850. It’s Web site is http://www.dairyone.com/ and its telephone numbers are 800-496-3344 or 607-257-1272.
Syracusan Carol T. Bradford writes about gardening for Stars and on Saturday in The Post-Standard. Send questions to her at firstname.lastname@example.org or in c/o Stars, P.O. Box 4915, Syracuse, NY 13221.