Dormant planting demonstrations

By Andrew Hollman

Although up to recently there was still snow on the ground, clear days with abundant sunshine bring hope of new growth on the vegetation in our landscapes and memories of warmer days.

The 2022 Minnesota State Fair brought many people to the turfgrass booth with questions about their lawns. With a second year of drought, many of the questions revolved around this issue. When I talked to people about the benefits of converting their existing turfgrass stand to newer cultivars or a different species that would fare better, many people were interested but were hesitant based on their perception of the effort, time and cost that it would require. For many people, I suggested that they could start transitioning their lawns to newer species or cultivars by dormant seeding in the fall.

Fall dormant seeding is done when soil temperature drops below 40F. At this temperature the seed is able to absorb water, but it does not germinate until conditions become favorable in spring. Typically this seeding could be done in the Twin Cities around the second week of November but this can vary. A danger of dormant seeding too early is that the seed will germinate and the seedlings will not survive winter. 

This past fall I decided to use a 9000 sq. ft. area we had kept fallow for a dormant seeding demonstration. The area wasn’t ideal for research plots because it is next to a gravel road and shaded during the morning from trees, but this variability made it more similar to a homeowner’s lawn. Since this area was also right next to the edge of a new perennial ryegrass trial, we killed off a strip of the perennial ryegrass so we could show the effectiveness of dormant seeding into existing killed vegetation. The size of this area also allowed for the creation of 15 different plots that are 9 ft wide and 65 ft long. Eleven of the plots were planted with a single turfgrass species, 3 were turfgrass mixtures and 1 was a bee lawn mixture (Table 1).  

The plots were seeded on November 8, 2022. Although soil temperatures were warmer than recommended for dormant seeding, the forecasted drop in temperature and snowfall dictated that we would miss our chance if we waited. Plots were strung out and the soil was loosened with a landscape rake prior to planting (Figure 1). Seed was applied using a drop spreader and then raked into the soil. Since this area was bare soil, we decided to use the remnants of erosion control blankets over most of the area. This would help to limit the potential of soil erosion if there was spring runoff from snowmelt and also hide the seed from birds if the winter lacked snow. One potential downside of the germination blanket is that its color, which is lighter than bare soil, might make the areas slower to warm up in spring. We left a strip of soil uncovered to see the differences that might occur between bare soil and covered soil (Figure 2). We also inserted temperature loggers around 2 inches deep into the bare soil, under the germination blanket and into the turfgrass to monitor if there were differences in soil warming (Figure 3). 

This demonstration will provide a useful visualization on how the different species respond to dormant seeding along with effectiveness on using germination blankets on bare soil or seeding into existing vegetation. As it matures it will be a good comparison of the different cool season lawn species and potentially a useful teaching tool. With the snow finally melted and these plots beginning to grow, we will prepare a future blog on how these plots are progressing and any interesting observations that we see.