Once again, we delve into that land of garden mysteries, Ask the Snarky Farmer!
Mary of Sacramento wants to know:
Hey! Mr. Garden Master: I need a low maintenance ground cover for 500 sq. ft. under two large oak trees. Must be hardy, drought resistant, no (or little) mowing. I'm thinking maybe some type of Bermuda grass. I know it can be invasive, but will it thrive if not watered? Does Round-up work on Bermuda grass? Would like to find it in sod form, and one that stays green most of the year. Hope to hear from you soon. Grandkids are coming this summer and there is nothing there now but DIRT. Love your radio show! Don't always get to hear it for various reasons.
OK, I'm better now (thank you, Bowmore!). Bermuda grass needs to be mowed regularly, needs regular water in the spring and summer to stay green, yet it will turn brown in the fall and winter here in the Central Valley of California.
I think the best "groundcover" for beneath that oak tree might be a few inches of an organic mulch, such as ground or shredded bark, which is now available in several different colors!
Here is some more info from my website about planting under oaks:
Oak trees that thrive here in the Valley, especially the native blue oak, coast live oak, interior live oak and the ubiquitous valley oak, are a definite plus in anyone's home landscape. Their statuesque beauty is complemented by the variety of tasks they perform, including providing screening, shade, protection from wind and serving as a wildlife habitat.
Because native oaks have adapted to our environment (especially in our hot, rain-free summers), oak trees have root systems than not only can go deep to find water, but also extend out beyond the canopy of the tree just below the soil surface. This sensitive root system is vulnerable to overwatering and physical injuries such as tilling beneath the tree. At most risk: those old oak trees that predate the surrounding homes. Old stands of oaks that are now part of housing developments may be threatened because of extensive plantings of thirsty shrubs, perennials, annuals and lawns -especially lawns - beneath them. Frequent waterings encourage root rot and root fungus in oaks, causing death by disease or by toppling in a heavy storm.
To maintain healthy oak trees, keep them out of the range of lawn sprinklers and lawns, don't use plants beneath oaks that require a lot of water, don't pave the area beneath the tree and don't compact the soil under their canopy by using tillers, shovels or trenchers.
There are, though, several plants that can be utilized in an oak tree-dominated landscape. Plant these (by hand) at least ten feet away from the trunk; plant them sparingly, as accent plants. Among the non-thirsty specimens that need watering once a month or less (when established) in the summer: manzanita, ceanothus, toyon, California buckeye, dwarf coyote bush, California buckwheat, creeping thyme (below, left), yarrow, California poppy (below, right) and lupine.