The Type Of Grass That Won't Thrive If You Have An Oak Tree In Your Yard

While big, leafy oak trees can provide a welcome shade canopy for your yard, the same shade might be overwhelming to some plants you want to grow — especially your grass. This is why, in nature, it's unusual to find trees and turf grasses growing together. Instead, native grasses tend to form fields — or grasslands — and the space below trees in forests is more likely to be carpeted with shade-tolerant plants like ferns or moss. When planning your lawn, you'll want to consider what trees are present and come up with a plan. Perennial ryegrass (Lolium perenne), in particular, is a popular cool-season turf grass that's also used for overseeding Bermudagrass during the winter. Unfortunately, this species does not do well in the dense shade that is found under oaks.

What's more, attempting to grow perennial ryegrass and oak trees together risks harming both plants. While you may think that oak trees have deep roots, that's not entirely true. They have "feeder roots," which grow close to the surface. The roots are located this close to the surface for several reasons, including access to warmth, water, and nutrients. While the mighty shade tree may appear to have the upper hand in the fight for resources due to its size, that's not always the case. Oak trees definitely have an advantage when it comes to absorbing sunlight, but grasses can steal necessary moisture from them, causing harm. To make sure both the trees and the turf continue to receive their life essentials, avoid growing your oaks in close proximity to perennial ryegrass. 

In addition to siphoning off each others' life essentials, both oak trees and perennial ryegrass release chemicals that make it harder for the other plant grow in a process called allelopathy. In fact, trees surrounded by grass have been found to grow slower than those that aren't. Ultimately, the close competition for nutrients, water, and sunlight, along with the release of allelopathic chemicals, makes pairing perennial ryegrass with oak trees a recipe for stress and poor growth for both plants.

Now that you know why planting perennial ryegrass under your oak tree is a bad idea, you may be wondering what to plant beneath them instead. You could consider shade-loving succulents, which are excellent companion plants for oaks. In addition, the Christmas fern (Polystichum acrostichoides) and wood fern (Dryopteris marginalis) can be great options, as they don't require much sunlight or moisture, reducing the competition for resources.