Boxwood Leaves Turning Brown

Mark75 · Fri Dec 23, 2011 1:55 pm

I have ab 30 japonica boxwoods in a hedge that are turning a lite to medium to brown color. They don't appear to be dieing as on close examination of the leaves they are still moist, fleshy and alive. The brown color is primary and is mixed with some dark green. The extreme edges of the leaves are yellow. From a distance the plants look completely dead and brown. The condition is spreading from plant to plant (about 22 plants currently effected). I am in Sunset zone 18 which can get as low as the low 20's high teens about 2-4 nights/year on average. We have had about 7 - 10 days of upper to mid 20's nights already this winter.

Is this a dormant phase of the plant or could something else be the cause.

bullthistle · Fri Dec 23, 2011 4:22 pm

All plants shed their leaves, evergreen as well as deciduous, however what you are talking about is a problem. You didn't say how long they were planted and if it was recently I suggest you go back and tamp down the soil, because air pockets will kill plants fast, but if not then moisture and wind/sun is playing a bad tune and the only thing to suggest is to wrap the plants in burlap.

Mark75 · Fri Dec 23, 2011 4:46 pm

You bring up a good point. We planted 15 boxwood about 3 years ago. This summer we filled in with 15 new plants (very healthy plants) due to too great a distance between the original 15. The new plants started showing signs of going brown first followed by the older plants.

We get what I would consider normal shifts in weather (typical for SoCal. One day it is raining and in the 40's the next it is 75 degrees and sunny, the next it is blowing at 55mph from dry Santa Ana winds. It has been a fairly typical fall/winter. So I'm hesitant to point to the weather as the cause. The older plants went through 3 years of the same weather without issues.

The strangest part about this probem is the plant are not dieing. The seem otherwise healthy. New growth continues and is the normal boxwood green color - at least until overtaken by the brown color.

bullthistle · Sat Dec 24, 2011 10:16 am

Check and find out if there is something to do with blight or a fungus. Cooperative extension or similar or a college with a horticluture program. If both plantings are infected now that would be the issue not what I initially suggested.

WildcatNurseryman · Mon Feb 20, 2012 4:55 pm

Phytophthora Root Rot is a disease that we experience fairly often here in KY. Root-Feeding Nematodes also cause quite a bit of damage, especially where drainage is an issue. I like to keep my boxwoods a little on the dry side as a result, and a once-a-season root drench of systemic insecticide keeps the carriers at bay.

cynthia_h · Mon Feb 20, 2012 11:37 pm

Phytophthora has been reported in California; it's a scourge in vineyards. Some rootstocks from California, though, are resistant to it and were used in the 19th century to replenish French vineyards after a truly disastrous wave of Phytophthora destroyed a large fraction of them.

OTOH, I have never (so far, knock on wood) heard of root-knot nematodes in California. This is only one reason why the California Dept. of Food & Ag. is so diligent about asking people what kinds of plants they're bringing into the state.

Composts containing lobster, shrimp, and other crustacean "ingredients" have been found to be effective vs. root-knot nematodes. See [url=https://www.helpfulgardener.com/forum/viewtopic.php?p=67356]this page[/url] (page 2 of a 3-page thread) for more info about chitin's role in bringing nematodes down.

Cynthia H.
Sunset Zone 17, USDA Zone 9