Digger Spade, MG Plant Detective
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| Heather, Calluna vulgaris. Source |
The client came in with a sample. The question, “What’s wrong with my heather?” The answer was obvious, no research needed:
“It’s dead.”
When you can break off brittle twigs there is little doubt.
But the next question, not so easy:
“What killed it?”
The client told us that the heather was planted at least five years ago, had grown well and flowered every year. It had seemed OK last summer but now most of the plant was dead, though part still had leaves and flowers. Several other heathers had similar but lesser damage.
Interestingly, in hikes around the neighborhood we had noticed quite a few heathers with similar symptoms, though couldn’t be sure about their condition last year.
Heathers are generally pretty healthy but they are subject to a few diseases. Root and crown rots caused by Pythium species, Phytophthora cinnamoni and Armillaria root rot might be a factor. The client described the site as a fairly steep slope very well drained, which would argue against the phytophthora options. Armillaria also seemed unlikely, but could be checked for by looking under the bark for fungal plaques at soil level or below.
So what is left? November 2014 might be the cause. We had several days of dry, unusually cold and breezy weather early in the month. The cold killed quite a few perennial plants that were still growing because of the pleasant fall weather that preceded it. Even seedling red cedar were killed this winter. The leaves on many trees froze before they could senesce, turned brown and dried up before dropping. This scenario has played out for several years now and plant damage has sometimes been extensive. If November weather killed the heather, we can expect so see more examples as the spring unfolds. Even plants that are typically hardy here can be caught with their sap up, and if that freezes there can be lots of cell damage. The same kind of damage that can kill plants in pots when their roots freeze.
So we told the client how to check for what we thought was the unlikely possibility of a root or fungal disease and to cut back into plant to see if there is healthy tissue in the larger stems. If he pulled up a plant we asked him to bring it in so we could check the condition of roots and main stems. Unfortunately, heathers don’t seem to grow back from heavy pruning so removing and replacing the severely affected plants may be the only solution. Then, knowing whether diseases were a problem is important so that something other than heather can be planted.
Resources
Phytophthora Root Rot
WSU Hortsense
http://hortsense.cahnrs.wsu.edu/Search/MainMenuWithFactSheet.aspx?CategoryId=12&ProblemId=4005
Armillaria Root Rot
WSU Hortsense
http://hortsense.cahnrs.wsu.edu/Search/MainMenuWithFactSheet.aspx?CategoryId=12&ProblemId=4000