How to Care for Arborvitae— The Tall Screening Tree

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Question. We planted eight large (8 foot tall) arborvitae in a row along our property line last spring. In September we noticed that one had brown leaves near the top. I pruned off those leaves and made sure the tree was adequately watered for a few days until the rains came. In October the rest of the trees turned a golden-brown from the inside out and we lost them all. Is there something we should have done to promote their well-being?

---Helyn in Lansdale, PA

Answer. Yes—any new tree needs to have the heck watered out of it the first year in the ground. If you wait until you see trouble, it's way too late. If it isn't going to rain immediately after planting, let a hose drip at the base of each tree for 24 hours (use a soaker hose for multiple trees) and repeat deep soakings at least twice a week for several hours at a pop any week you don't get rain.

It also sounds like you may have crowded them. It's better to plant so-called 'screening trees' in staggered, triangular grids than to try and jam them into a tight straight line.

Question. I planted nine emerald arborvitae last spring and kept them watered well throughout the summer. They look healthy from a distance, but if I get close and peek into their trunks, some of the greenery is turning a little...oh, not brown but gold. Is this normal? I want to make sure they're ok. We planted them correctly—not too deep, in a nice wide hole.

---Annmarie in Chesterfield, NJ

Answer. Whenever someone assures me they did something {quote} "correctly", I see the Red Cross rushing in with chocolate and lawyers for the poor plants. So let's review 'correct tree planting'.

Remove all wrappings from balled and burlaped trees. You may be told to leave the burlap on, to bury the burlap with the tree (perhaps to hide evidence linking you to the murder), etc., etc. The people telling you to do those things are wrong, wrong, wrong!

As you note, you should dig a wide hole, but not a deep one; you want the root flare to be exposed above ground. If the planted tree looks like a lollipop, take it out and plant it higher. Refill the hole with your lousy native soil. Surrounding the roots with an island of nice perfect loose stuff is like putting a big-screen TV into your child's bedroom after college. You need to force both of those kinds of organisms to make their way out into the world instead of making it easy for them to linger much too close to home.

If the tree needs to be staked its first year (which arborvitae and the similar Leyland cypress often do), do so very carefully and gently; don't let any of the material dig into the bark and get rid of that support the first day possible.

READ COMPLETE ANSWER Mulch the surface with an inch or two of nice black, yard-waste compost—not wood, bark or root mulch; not peat moss, sawdust, or other bad ideas. A compost mulch will prevent weeds as well or better than the same amount of wood. Don't let the mulch (or ground cover or ivy or anything else) touch the trunk of the tree. Begin six inches away from the trunk and take the mulch out as far as you can.

Unlike wood mulches, compost mulch will also feed the tree perfectly (wood mulches may actually steal food from the tree.). A fresh mulch of compost can be applied every year. If you use a gentle organic fertilizer to feed the tree, go light; and just feed the tree this way for the first few years. And no 'tree spikes' or other chemical fertilizers—ever!

Do all those things and minor discoloration—which is fairly common and can come from sunscald or windburn—should repair itself.

Question. Mike: I'm getting conflicting information on when to prune my arborvitae. Their 15' to 20' height is starting to shade part of my garden. What time of year is good to trim about four feet from the tops? Correct me if I'm wrong but I believe you said to prune in the spring. Thanks,

---Tom in Bristol, PA

Answer. Consider yourself corrected, Tom. If you were talking about gently trimming the sides a bit to do something like keep a walkway in play, Spring would be the time. But take a good look at the top of those puppies. See how they come to a point—like my head? If you lop off those pointy tops the trees will look like Hades for awhile and then die—which will be a relief, because until they expire their wretchedness will be a constant reminder of your 'excellent idea'.

Plant shade loving things in the affected garden area and build some new raised beds out into the sun.

Question. I have an emerald arborvitae that is doing poorly. I planted two of them about three years ago on each side of my front steps. Although both are the same height (4-5 ft), one is going gangbusters and the other has a lot of "dead zones" in it. I believe the problem was poor drainage, which I have corrected with modifications to my downspouts. Should I try to save the weak arborvitae or just replace it? I can still purchase one of similar height that would match the healthy one.

---Delma in Eastern Coastal North Carolina

Answer. Small areas that brown out during brutal summers or harsh winters are often naturally replaced with healthy green tissue when the plant recovers. But large brown areas will likely be ugly forever. And one thing these trees (and most trees, and most plants) cannot tolerate is constantly soggy soil.

So yes, snag that replacement. But don't plant it if your summer has already reached "dogs under the porch" weather. Either get the nursery to keep it healthy for you until Fall, or take it home, keep it well watered in dappled sun and plant it in the Fall.

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