Coneflowers wilting and dying - Ask Extension
The plants have been in this garden for 3 years, installed by a local nursery. It is the second season for me to own the property. There were no sign...
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Coneflowers wilting and dying #874859
Asked June 26, 2024, 5:48 PM EDT
The plants have been in this garden for 3 years, installed by a local nursery. It is the second season for me to own the property. There were no signs of this last year. The garden has black under laymen’s for weed prevention, with large river rock on the surface. The soil can be excessively moist during the spring/fall if we have excessive rain, although it is typically dry during the summer. The coneflowers are 27-34 inches tall. I have 15 of these coneflowers, 7 which are showing potential disease. One which has completely died - the roots appeared black and this particular plant was in the wettest location of the garden this spring.
Anne Arundel County Maryland
Expert Response
A stone mulch with a landscape fabric/weed barrier underlayer may be exacerbating the soil moisture or dryness issues, since it hampers letting the soil "breathe" to air-out when wet and absorb moisture when rainy. Stone retains heat, affecting the cooling ability of damp soil to minimize plant stress, and the radiated heat overnight can also stress plants that prefer to cool off to metabolically "rest." The underlayer also interferes with the recommended method of monitoring plants for watering needs. Ideally, you should feel the soil about five inches deep next to the roots, and when it becomes somewhat dry to the touch, water thoroughly. (If damp when checked to that depth, watering is probably not needed.) Additionally, the fabric's reduction of airflow and evaporation may mean that it is creating an environment more conducive to certain diseases, like Southern Blight, which becomes prevalent once it becomes hot.
The coneflower symptoms look primarily like drought stress, though overlapping conditions are possible. Isolated stems that are dead or dying might be blighted, have a stem borer (insects that are not a serious threat to the plant's overall health), or were physically damaged by winds or wildlife kinking or breaking a stem. Those should be trimmed back to their base.
Try to feel the soil around five inches down and give each plant around a gallon of water if it's not damp at that depth. Most of Maryland experienced prolonged drought last year, and we have again entered drought or near-drought status for most of the state so far this year.
The plant that died and had dark roots might have succumbed to root rot if it was in a location that stayed more consistently damp. If that area skews wet, consider moving any remaining coneflowers to another location and instead using species that prefer or tolerate damp soils. Coneflowers are native to prairie conditions, in soils that drain well. While they are drought-tolerant, they do have their limits of tolerance, and once wilting in dry weather, need watering to avoid root damage and a possible lapse in flowering that will be caused by that stress. Wilting can occur when plant roots are too wet as well, but this is why the soil check is a good way to avoid making assumptions about above-ground symptoms before deciding when to water.
Miri
The coneflower symptoms look primarily like drought stress, though overlapping conditions are possible. Isolated stems that are dead or dying might be blighted, have a stem borer (insects that are not a serious threat to the plant's overall health), or were physically damaged by winds or wildlife kinking or breaking a stem. Those should be trimmed back to their base.
Try to feel the soil around five inches down and give each plant around a gallon of water if it's not damp at that depth. Most of Maryland experienced prolonged drought last year, and we have again entered drought or near-drought status for most of the state so far this year.
The plant that died and had dark roots might have succumbed to root rot if it was in a location that stayed more consistently damp. If that area skews wet, consider moving any remaining coneflowers to another location and instead using species that prefer or tolerate damp soils. Coneflowers are native to prairie conditions, in soils that drain well. While they are drought-tolerant, they do have their limits of tolerance, and once wilting in dry weather, need watering to avoid root damage and a possible lapse in flowering that will be caused by that stress. Wilting can occur when plant roots are too wet as well, but this is why the soil check is a good way to avoid making assumptions about above-ground symptoms before deciding when to water.
Miri
