What's happening to Aaron's Beard (hypericum calycinum)

Asked July 26, 2020, 2:00 PM EDT

It looks like this plant is not doing well. It's about a year in the ground, full sun. Is this a fungus? pest infestation? Should I treat or ignore?? I don't seem to see any buds and so far it has not bloomed. Anything to keep it healthy would be appreciated. Thanks.

Montgomery County Maryland

1 Response

The symptoms look like those of a fungus called rust, which Hypericum can contract. Rust fungi are quite common, though different types have different host plants; in this case, it's a rust which doesn't require an alternate hose to complete its life cycle. Fungicide treatment is typically not effective, and even when useful, is not curative. At best, a fungicide may prevent spread of infection if used early enough in the season next year; the label must list rust as a controlled pathogen and follow its directions regarding frequency of re-application. Ideally, fungicides should not be sprayed while plants are in flower in case they have damaging effects on pollinators.

For now, all you can do is to clean up infected tissue and discard it. Since the plant is not yet budded/blooming you probably won't miss much if you cut it back entirely and wait for it to re-sprout. Avoid getting the leaves wet from sprinkler use or water early enough in the morning (as needed, since Hypericum tolerate drought well) that the leaves can dry by nightfall.

Hypericum should be in bloom by now if in full sun, so we're not certain why this plant isn't at least budded. Perhaps environmental stress (drought, high heat) or the incidence of rust has diverted the plant's resources. Hypericum tend to be tough once established, so hopefully it will finish settling-in this year and perform better next year. We do not see signs of pests or any other diseases.