Grumpy loves flowering dogwoods. He thinks that anybody who can grow them and doesn't has a serious developmental flaw. But sometimes your beautiful dogwood suddenly doesn't look so pretty anymore. Here are 4 common problems and what to do about them.
Problem #1 -- Scorched Leaves
Description: One day, your dogwood looks as happy as a Wall Street banker trading on inside information. The next, the leaves turn whitish tan, especially around the edges, and start dropping. This usually happens in mid- to late summer.
Cause: Dogwood has shallow roots and doesn't like long periods of hot, dry weather. If it dries out even for a single day, the outermost leaves will scorch and stay that way or drop. If this isn't severe, the tree will recover.
Solution: Put down several inches of mulch around the base of the tree (not touching the trunk). The mulch will cool the soil and help it retain moisture. Check the leaves regularly during hot, dry spells. If you see wilting leaves in morning, water the tree immediately and thoroughly.
Problem #2 -- Leaf Spots
Description: Small, brownish purple spots with tan centers dot the leaves. This most often occurs to dogwoods growing under tall trees following a spell of rainy weather in summer. Diseased leaves dry and hang on through winter. Cankers forming on the twigs can eventually girdle and kill branches or the entire tree.
Cause: Spot anthracnose is a fungal disease that targets dogwoods. It spreads via water splashing the spores from leaf to leaf. It's more of a problem for understory trees than trees growing out in the open.
Solution: Remove and diseased branches and leaves and throw them out with the trash. Spray healthy spring flowers and foliage according to label directions with Daconil. Repeat as soon as you see any spots appear on leaves. Also plant resistant dogwood selections, such as 'Appalachian Spring.'
Problem #3 -- Powdery Mildew
Description: A whitish film spreads on leaves. Affected leaves may shrivel and drop.
Cause: Powdery mildew is a fungus. There are lots of different kinds of mildew that attack lots of different plants. This particular mildew likes dogwoods. I find it generally shows up later in the growing season, usually on the newest leaves, but I have seen it in early summer too. Like spot anthracnose, it prefers trees growing in groups under tall trees. It also likes cool, rainy weather.
Solution: If it shows up in late summer, let it go. It won't do enough damage to hurt the tree. If it appears in early summer, consider spraying according to label directions with neem oil, horticultural oil, or Natria Disease Control.
Problem #4 -- No Blooms Like These
Description -- Your dogwood grows just fine with lots of healthy, green leaves. Just no blooms.
Causes: The most common causes for dogwood not blooming are: not enough sun (tree grows in shade, but won't bloom well there); tree dried out in summer and didn't set flower buds; tree is too young to bloom; instead of being a named selection like 'Cherokee Brave' (above), tree is labeled just "white" or "pink" and could bloom heavily or hardly at all.
Solutions: Give flowering dogwood at least a half-day of sun with light shade in the afternoon. Water tree during summer droughts. Buy named selections chosen for their outstanding displays rather than unnamed trees that could do anything.