What is wrong with these moonbeam coryopsis? #415150 - Ask Extension

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What is wrong with these moonbeam coryopsis? #415150

Asked July 18, 2017, 1:54 PM EDT

Based on a landscape plan provided by a local nursery, this is the 3rd year I've planted and tried to grow moonbeam coreopsis in my front yard bed. After last year's failure, I asked another local nursery about planting info for these specimens and learned that I had possibly water them too much. This year we planted them in late April and watered them very little to get them established. They did well for a while, but now look as they have the last 3 times years - brown and dying or dead. Any description I've seen of these plants indicates the conditions of this bed are fine for coreopsis and you can see that the caryopteris, sedum, and rudbeckia are all doing well here. What is your diagnosis? I'm pretty much ready to give up on these pretty plants and try something else...

Frederick County Maryland

Expert Response

In general plants can decline if underwatered or overwatered. If plants are overwatered and the soil drains poorly, plants can be susceptible to disease issues.

 Based on your photos it looks like the plants did not receive enough water to establish themselves. These plants are drought tolerant but only after the root systems become established. They are not drought tolerant  in the first year of planting.

Check the soil moisture of new plants at least once a week up until the ground freezes. Soil that is moist to the touch is fine. You may need to probe with a screwdriver. Make sure mulch is no thicker than several inches and keep away from the base of the stems. See our website for care of perennials http://extension.umd.edu/hgic/flowers/maintenance-annuals-and-perennials

At this point, prune dead plant material and water up until the plants dieback for the winter. Look for new growth next spring.  You can decide if you want to add additional plants or replace with a new species.

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