Dormant seeding tall fescue as a strategy to improve crabgrass infested lawns

Sun, 10/13/2024 - 22:47

By Andrew Hollman

With most of Minnesota experiencing drought again after a wet spring and summer, questions about conversion to species that are drought tolerant or avoidant come from both homeowners and professional turf managers. Dormant seeding is a method to plant turfgrass that occurs in the fall when soil temperatures are below 40F. The seed then germinates in spring when the temperatures warm up and moisture is usually more prevalent. We have conducted several different dormant seeding trials/demonstrations and tall fescue appears to work well with this method. Tall fescue is a species with a deeper root system than other commonly used cool season turfgrasses, which allows it to access water deeper in the soil and stay green longer during a drought.

turfgrass research plots with dead brown weeds — Figure 1. Dead crabgrass plot where different turfgrasses were dormant seeded on 11.20.23.

small turfgrass seedlings under a germination mat with sunglasses off to the side — Figure 2. Germination of turfgrass seedlings dormant seeded in the fall of 2023. Picture was taken on 3.14.24.

In a trial area that was established in 2023, different species (tall fescue, Kentucky bluegrass, fine fescues) were dormant seeded into an area that was all crabgrass (Figure 1). The seed was applied with a drop spreader calibrated to the recommended rate for each species. No plot preparation was done before or after seeding so that we could test the effectiveness of just placing seed down. In March of 2024 germination was observed (Figure 2) and rainfall was the sole method of irrigation for the plots. Since these were newly seeded plots, an application of starter fertilizer was applied at the end of April. By May of 2024 we were starting to see broadleaf weed pressure and crabgrass had germinated (Figure 3). By mid May the tall fescue plots were starting to easily be distinguished from the other species (Figure 4) and just a couple weeks later plots and crabgrass increased cover over the trial area (Figure 5).

soil with crabgrass seedlings germinating in spring — Figure 3. Germination of crabgrass seedlings among dormant-seeded tall fescue on 5.7.24.

research plots with germinating turfgrasses and some weeds — Figure 4. Dormant-seeded trial with plots of tall fescue starting to become more visible. Picture was taken 5.14.24.

turfgrass research plots with different shades of green vegetation — Figure 5. Dark green tall fescue plots standing out among other species and crabgrass in a dormant-seeded trial on 5.29.24.

As the summer progressed crabgrass continued to germinate and fill in most of the plots obscuring the turfgrasses; however, the plots dormant seeded with tall fescue were easy to spot (Figure 6); the quicker growth rate of tall fescue likely allowed it to fill in and limit the space for crabgrass to grow. By the beginning of October, the decline of the crabgrass clearly showed how successful the tall fescue dormant seeding was with minimal inputs (Figure 7).

turfgrass research plots with different shades of green vegetation in summer — Figure 6. Dormant-seeded species trial where dark green tall fescue stands out among the thick stand of crabgrass on 8.27.24.

turfgrass research plots, some with green vegetation and some with brown — Figure 7. Dormant-seeded tall fescue plots stand out among dying crabgrass and other turfgrass species on 10.3.24.