My bee balm has a lot of leaves that are turning yellow or brown and it’s definitely dying in the centre. Any ideas why?
It sounds like you have two separate problems.
For starters, bee balm is prone to powdery mildew which can sometimes appear as an obvious snowy powder on the leaves of the plant. At other times, it can be quite subtle and you have to squint to really see it. Left untreated, powdery mildew will eventually cause the leaves to yellow, turn brown and just generally look awful.
For this reason, bee balm is usually planted in full sun locations with lots of air circulation. This tends to improve the mildew situation although rarely does it eliminate it.
Planting resistant varieties is the better answer to the problem.
Other than that, all you can really do is treat the mildew on your bee balm as you would on any other perennial and that includes picking off affected plant parts as soon as you notice the problem. Some gardeners like to knock the white powder off the leaves with a stream of water early in the morning once or twice a week (powdery mildew is temperature activated, not moisture activated) and that seems to help with nasty cases.
The second problem you have is that your bee balm is dying back in the centre and that has nothing to do with the mildew. Bee balm spreads out horizontally from the roots to form new plants right next to the old ones. However, each individual bee balm plant is not long lived and the oldest ones, which are located at the centre of the clump, start dying off while the younger, outer plants continue to thrive.
The result is a nasty dead patch smack in the middle of the clump.
The solution to the problem is to dig up the clump, separate out the dead centre, then divide the remaining clump into separate plants before replanting them.
Every few years, you’ll need to repeat the process as the centres of your new clumps also start dying back. There is no way around this since it’s the nature of this particular plant to form clumps that die from the centre out, but as long as you’re vigilant, your bee balm will continue to look nice.
If you have any questions or comments, please send them to me at vanessa@gardenmuse.ca.
Originally published in the Creston Valley Advance on August 19, 2010.
