Garden Q&A: Beware ivy-like wavyleaf basketgrass and why oak trees are in decline
By Ellen Nibali
Sep 19, 2019 | 7:00 AM
A wavy “ivy” is growing on the ground in my woods. It’s a small flat patch with kind of cute leaves. Is it native or invasive? Kill it or keep it? It has seeds now, and I’ve noticed they stick to my skin, so I need to decide fast. Potential new groundcover?
Nooooo! Wavyleaf basketgrass covers ground all right — it smothers everything. It’s worse than stiltgrass, if that’s even possible. The barbed seeds appear in late August-early fall. They stick to clothes, animal fur, even rubber boots.
Pull and bag immediately. It is extremely aggressive, spreading fast. It is destructive to parks and natural areas, but also will invade throughout shady home landscapes. Though perennial, wavyleaf basketgrass is easy to pull and that is the best option. Large areas can be sprayed with a glyphosate herbicide, but because this is a total vegetation killer, all desired plants must be shielded.
The oak in our yard leafed out late, then the leaves all turned brown fast in June and July, starting at the top. They are still hanging on. Some of the bark looks loose. Trees around the perimeter of our yard look okay. What can we do to help it?
Oak trees are in decline all over our region, unfortunately — both red and white oaks. There is no single cause. To occur over many oak species and a wide area points to environmental and/cultural causes. Higher summer temperatures are a factor.
White oaks, like yours, are intolerant of saturated soil, so last year’s excessive rain is undoubtedly causing damage. Red oaks are especially affected by years of drought. Drowning and drought both kill roots, and the first symptom is dieback at the extremities (top). Then trees stressed by unfavorable environmental conditions become more susceptible to secondary pest and disease issues. Bacterial leaf scorch is active, more commonly in red oaks. (Oak wilt, however, is not active in Maryland generally.)
Most declining oaks are 50-70 years old. Bigger trees need more resources than smaller trees and are less resilient. Many trees are surrounded by turf that intercepts rain and nutrients. Whereas a forest tree’s fallen leaves are entirely recycled into nutrients to feed the tree, homeowners rarely leave those leaves on the ground for the tree. Lawn mowing itself can compact soil, so rain and oxygen can’t penetrate.
There isn’t really much you can do to reverse decline in mature oak trees. A certified arborist can evaluate the tree for pests and diseases and structural integrity. Find one near you at the International Society of Arboriculture website: treesaregood.org. Since oaks are premier trees, it’s good to replant oaks. Be sure to protect saplings from deer.
University of Maryland Extension’s Home and Garden Information Center offers free gardening and pest information at extension.umd.edu/hgic. Click “Ask Maryland’s Gardening Experts” to send questions and photos.