Help with emerald green arborvitae
In May I purchased 10 bare-root arborvitae trees. I have what seems to be a heavy, compact clay soil. I watered the roots prior to planting and I mixed in a moisture control miracle grow potting soil in with the clay soil to help with drainage. 7 of these trees are planted along my fence line, 4 of the trees are thriving while the other 3 are turning a brown/yellowish/pale green color (the other 3 are in pots, 1 thriving and 2 died). I’m trying to figure out what I can do to save these trees. From what I can tell, there are no pests that would be causing the damage. So how do I determine what is causing discoloration to these trees in terms of over/underwatering or transplant shock? I have noticed that with the three discolored trees, the branches still seem very stiff... the branches still appear to be in an upright position while the 4 other trees appear to be nice and full and the branches have almost relaxes. Should I pull up these 3 trees and try to fix the soil? Thank you so much for any help!!
Erie County New York
Hello, and thank you for contacting us about your arborvitae. My apologies for the delay in responding to you but I wanted to consult with a horticulturalist on the west coast where these trees are generally grown.
It seems that most of the large nurseries and box stores purchase their stock from British Columbia, Washington, or Oregon. These trees are genetically predisposed to do better in the climate of the pacific northwest. They get significantly more precipitation, especially in the winter, and are accustomed to cooler summer temperatures. Trees that are locally grown, especially native species, would probably fare much better in your climate.
I have seen many Emerald cedars dry out and often die when they are grown in the east or mid-west. They should receive 1 to 2 inches of water each week (including rain), applied in a long, slow drip. Drip irrigation or a sprinkler set to trickle is the best way to be sure that the water perks down to the root level rather than running off.
The trees also should be mulched. Apply about 3 inches of woodchips over the entire root zone, being careful to keep the mulch several inches away from the trunk of the trees. Compost may be applied on the surface of the soil under the mulch.
We do not advise amending the soil when planting trees. Use only the native soil. Amendments change the texture of the soil in the planting hole, so water and the roots do not move out into the surrounding soil. Also, from your photo, it looks as though the tree on the left may be below grade. The trunk flare (where the bark meets the crown) should be at, or a bit above soil level to avoid potentially rotting the bark which can lead to disease problems.
In answer to your question, yes, you probably should consider digging the trees up if you feel you placed an excess of soil amendments into the planting holes, or if the trees sit too deep. This is not the best time to transplant because of the heat and dryness; however, if the health of the trees is declining anyway, it might be good to do this now. Just make sure the roots are kept moist, not wet.
Shortly after writing to you, I came across this article which provides some good information about newly planted trees.
The article mentions over-watering, which may also be a factor in your situation. When you dig up your trees, do take a good look at the roots to make sure they look healthy and are not rotting from too much water sitting in the planting hole. While the roots should not dry out, they will die if the water does not drain properly.
Lynne Marie S.