What to do about Hawthorn tree with leaf spotting and general defoliation

Asked August 24, 2016, 5:39 PM EDT

Hi OSU - we have a couple of old Hawthorn trees in the back yard that are showing a lot of leaf spotting, defoliation, and other plant material (algae, lichens?) growing on the leaf stems. Is there some spray or other techniques we can use to get them healthy again? When might we apply spray? What about pruning? Thanks!

Polk County Oregon

1 Response

Hawthorns commonly have a leaf spot which often leads to early leaf drop. The best time to treat leaf infections varies according to the causal organism and the normal progression of the disease. Some diseases are best managed with a spray as the leaves begin to unfurl in spring, while other infections start later in the season. It’s too late this year to spray. In any event, your tree is of a size that requires equipment generally unavailable to home gardeners.

The recent several years of less than normal rainfall are also contributing to tree problems, including early leaf loss. Then, too, the excessive heat during 2015 further stressed trees. Contrary to popular opinion, most landscape trees should be irrigated deeply at least monthly through our dry season.

Unfortunately, some stressed trees have passed the point of no return.

Determining what to do for your tree would be best served by an on-site evaluation by several Certified Arborists. We suggest Certified Arborists because they must pass an exam and must also acquire continuing education hours. To locate such persons, go to www.treesaregood.org where you can search with your zip code.

Lichens and mosses are common here in the northwest on woody plants. Their presence indicates good quality air.