By Scott Aker
Special to The Washington Post
Thursday, July 16, 2009
Q Can you recommend any shrubs that would thrive in a boggy area with dense shade?
A Virginia sweetspire or summersweet are two shrubs that can take some shade and wet conditions. Flowering and fall color are greatly reduced by shade, though, so they should have sun for at least a portion of the day to reach their full potential. If you want a larger shrub, you might want to try buttonbush, Cephalanthus occidentalis, or spicebush, Lindera benzoin.
Some smaller shrubs function a bit like ground cover. Yellowroot, Xanthorrhiza simplicissima, is one such plant that is a lovely but seldom-used plant for moist shade. It grows no more than two feet tall and has good fall color.
I have a colony of ants living in a sunny perennial bed, the nest now covering about five by three feet. The plants there have suffered drought more severely (many have died) than in other parts of the garden. The ants churn up the soil to such a degree that it holds very little moisture. I cultivated the soil regularly to try to discourage the ants, but to no avail.
This garden is a real pollinator hot spot, and I hate to use anything that will harm the bees and butterflies, not to mention the occasional amphibian that wanders through. What can I do?
You may need to dig deeper to find out what the soil is like. Ants like rocky soil, so you may have to remove stones and debris that are buried. You may have to dig as deep as two feet.
Eliminate food sources for the ants; this includes the honeydew excreted by aphids that are feeding on your plants. Limit aphids by cutting back on fertilizer and water. Food waste in nearby trash cans or compost bins might be serving as a food source. If you have an adjacent patio that is used for eating or consuming sugary drinks, spills and crumbs may provide meals for the ant colony.
You mention that plants have been killed. Allegheny mound ants inject plants near the colony with formic acid, killing them. This species constructs very large mounds. It can be controlled with insecticides. It is best to scrape the top off the mound to reveal the large tunnels before drenching it with the pesticide.
The ants will attack anything that threatens their home in this way, so tuck your pants into your socks and have a brush ready to sweep them off. You can treat the mound remnants with a residual insecticide. There are several labeled for ants, and you can apply it by mixing the material in a bucket and pouring it on the mound. This will have little or no impact on the pollinators in your garden because you are treating the ground and not spraying plants.
Scott Aker is a horticulturist at the U.S. National Arboretum.