What is ailing my asclepias
Hello. I have two types of asclepias in my garden - tuberosa and incarnata. Both are showing signs of disease. Both are in a raised garden bed that was built as a lasagna bed with some cardboard and straw at the bottom and soil and leafgro on top. All plants have hardwood mulch around them. Most plants had several cups of sand mixed with soil at planting time. All plants were purchased in the spring from nurseries. The tuberosa species were damaged by deer early on and then appeared to have stunted growth. Both types have yellow leaves starting from the bottom and going up and some stems appear black. What can i do to save them? Thank you.
Montgomery County Maryland
Based on your description and photos it sounds like the soil conditions are a bit rich for these plants and the soil may be holding too much moisture. Check the drainage. There is also too much mulch around the base of the stems. Make sure mulch is no thicker than several inches and keep away from the base of the plants. These plants usually do not have serious pest or disease issues.
Tuberosa - grows well on sunny slopes with excellent drainage. They like well drained dry soils. https://extension.umd.edu/hgic/topics/butterfly-weed-milkweed
Incarnata - This plant can tolerate more moisture. Black stems - check for sucking insects like aphids which can exude a honeydew as they feed which fosters the
growth of a black sooty mold or just poor growing conditions https://plants.ces.ncsu.edu/plants/asclepias-incarnata/
Thank you so much for your advice. I will move mulch away from the stems. I am observing orange aphids on one of the incarnata plants and i will attempt to remove them. I think you are right about water issues. Sonetimes less is more.
You are welcome.
Here is some information on oleander aphids on the asclepias https://extension.umd.edu/hgic/topics/aphids-got-your-milkweeds