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A Dogwood Dilemma

Q. A while back, Elaine from Washington State wrote: "On a recent show you addressed maple tree wilt. I'm wondering if this disease or something similar can also affect Dogwoods. We planted a memorial Dogwood tree to honor my dad after he passed and it is not doing well, and we are desperate to save it. It previously flowered nicely but this past year it did not. The lower branches have died. Much appreciation for any help you can provide!"

A. The maple tree wilt we discussed was a form of verticillium, the pathogen that kills tomatoes if they are planted in the same spot year after year.

Slight digression, as this is a great time of year to discuss tomato rotation. The problem occurs when a soil-borne wilt named verticillium interacts with the roots of tomatoes (other plants as well, but it's much more pronounced in tomatoes). There's no problem the first year a tomato is planted in a certain patch of ground. If tomatoes are planted in that same spot the following year, there may be a little yellowing of the lower leaves, but the harvest should not be affected. Use that same spot again a third year and the yellowing will begin earlier, progress faster and could affect the harvest. A fourth year generally leads to an early death.

So plan now for a two to three year rotation of your tomatoes. Good news: After a patch of ground has remained tomato-free for a few years it's safe to use that spot again.

But you don't have verticillium; in fact, most sources speculate that dogwoods are naturally resistant to this condition. Unfortunately, they are prone to many other problems, especially anthracnose, a very nasty actor.

You don't specify which part of Washington State in which you reside, which makes a big difference. The West Coast of the state is notoriously damp and wet; the kind of weather that makes it difficult to keep dogwoods healthy, as they don't like being wet. (Damp conditions are ideal for the spread of many diseases, with anthracnose at the top of the list.) A sub-species known as the Pacific Coast dogwood has the best chance of survival there.

Years ago, listeners in Spokane informed me that they are NOT Seattle! In fact, the East side of the State, where Spokane is located, is surprisingly dry. Excellent climate for dogwoods as long as their roots are kept well-watered during dry times.

There are over 50 varieties of dogwood, but the two main types for our purposes here are the Eastern dogwood, which is native from Canada down to Florida and west to the Rockies; and the Pacific dogwood, which is clustered around a relatively small area of the Pacific Northwest. If you do live near the Coast, a non-Pacific dogwood would not be your best choice. And when a dogwood has problems in its proper region, it's probably not salvageable.

That's why I always beg people not to plant a tree or shrub in memory of a loved one; instead install a park bench in their honor, or an archway or a gazebo or similar structure. If it has to be a plant, go to your State Extension Service's website and research which plants in your specific region are long-lived, disease-resistant, and 'bulletproof'.

(There are varieties of dogwood that have shown resistance to anthracnose, but the Pacific strain is not one of them, so in this case even going native could have worked against you.)

To quote the Davey Tree Care Company: "Anthracnose attacks twigs, branches, trunks, and leaves of dogwoods in cool, wet weather. Tan, blotchy leaf spots are early signs of infection. The disease can cause dead leaves and twigs that remain attached to the tree. If the disease reaches the main trunk, it can kill the tree." I'll add that one sure sign of anthracnose would be grey and rumpled looking leaves remaining on the tree over winter.

Dead or diseased twigs, branches and leaves should be pruned out over winter. Then rake away any prunings or other debris under the tree and put it in the trash. Do not compost it.

Dogwoods also need to be planted where the tree will receive morning sun and afternoon shade. They dislike intense all-day sun as much as they dislike having wet leaves. Their very shallow roots require supplemental watering during extended periods of dry weather, especially during their first few years.

To prevent disease, prune crowded trees in the Spring, after the flowers fade, to maximize internal airflow. Airflow is the enemy of disease! (But, like all things that make dogwoods contradictory, this opens the tree up to attack by boring insects; dogwoods also bleed sap heavily.)

Wild dogwoods seem to do just fine, but I have long felt that intentionally planted ones can be extremely difficult to care for. Although it's easy to emphasize the problems caused by excessive moisture, lack of tolerance to drought may be their biggest enemy. They MUST be watered during dry times.

My suggestion here is to prevent future heartache. Cut down the tree, pull out the roots, clean up the soil surface, cover it with compost and plant a tree that's recommended by your State Extension System in a different place.

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