Josie from Boston, MA writes:
This summer my lavender plants have gotten this black film on the bottom branches and are starting to look sick. What could be happening? Can lavenders get moldy?
Yes, and in fact this is much more common and worrisome than heat or dry spells. Lavender can handle hot and even very humid conditions, but if the soil is consistently wet, or the ground underneath the plants stays wet/soggy, the plants just cannot take it. Clay soils in particular can be very problematic for lavenders. Another possibility could be that the plants have grown up too close together and the moisture is staying within the plant branches rather than being dried with good airflow. Finally, remember that lavenders love the sun; they require 7-8 hours of sun per day.
So a couple of things to check: first, ensure that the plants have adequate airflow between them. Prune them back by a few inches if they do not. Second, check the amount of sun where the plants are located and ensure it’s enough. If not, move them to a sunnier location in the garden. And finally check the soil underneath the plants – if it’s consistently moist, amend it with lots of sand or small gravel to create drier conditions at the base of the plant.