Cover & Nurse Crops

Native seedlings are slow to cover the ground. A nurse crop, a fast and short-lived grass sown along with the native mix, holds the soil, competes with some of the weeds and shows where seed has gone down, then fades away as the natives take over.

When to use one

A nurse crop earns its place on slopes, swales and other erosion-prone ground, on dormant seedings where bare soil would otherwise sit exposed all winter, and on sites where a soil erosion and sediment control plan sets stabilization requirements. On flat, weed-free ground with a fall seeding and straw mulch, it often isn’t necessary.

Choosing the species

Oats are the usual first choice. They establish quickly, and in our region a fall sowing generally winter-kills, leaving a mulch of dead stems rather than competing with the natives in spring. Oats work well for spring seedings too. Winter wheat is the other common option. Because it survives the winter, it keeps the ground covered through winter and early spring on fall seedings, though it needs to be mowed before it sets seed.

A few species are best avoided. Cereal (winter) rye is very competitive and suppresses germination of the seed around it, and annual ryegrass is aggressive and can reseed itself. Perennial cool-season grasses such as tall fescue, perennial ryegrass and Kentucky bluegrass should never be used as a nurse crop, because they persist and compete with the natives for years.

Keep the rate low

Sow a nurse crop at only a fraction of its standalone rate. For oats, that’s often around 15–30 pounds per acre, compared with the 60 pounds or more a cover-crop planting would use. Too much nurse crop shades out the very seedlings it’s meant to protect. Where a specification or erosion plan sets a rate, follow it.

Managing it

Treat the nurse crop like any other first-year growth: mow it whenever it reaches 12–18 inches, never cut it lower than 6–8 inches, and don’t let winter wheat go to seed. Establishment & Management covers first-year mowing in more detail.