We really discourage seeding lawns in the spring.
Spring seeding: bad. Spring seeding typically results in very poor germination of the desired grasses, yet leads to excellent germination of crabgrass and other weeds. That’s because spring rains keep the soils cool (especially this year with the heavy spring rainfall across many of our customer areas) — below the 65 degrees grass seed needs to germinate, but right around the 55 degrees that encourage crabgrass and other weeds to sprout. What’s more, you cannot discourage the weeds with pre-emergent herbicides because those materials would kill off the grass seedling as well. Doh!
The photo below, taken earlier this week, is a good illustration of the downfalls of spring seeding. When we’d arrived at the property last spring, we learned that the section of lawn on the left side of the photo had been newly-seeded by a landscaper. As a result, we could not apply any pre-emergent herbicides to that section because it would have prevented the new grass seed from germinating. On the section of lawn on the right side of the photo, we had mature turf – no new grass seed – that we were able to treat effectively in April and mid-May with integrated applications of herbicide and fertilizer. I think you can see how much healthier the lawn on the right is.
Fall seeding: good. Early fall provides ideal conditions for seeding new grass. The ground is still warm enough to aid germination, we still get some rainy days to supply needed moisture, and the cooler temps give young plants stress-free growing conditions. By the following spring, the new turf is adequately established, so we can safely fertilize the grass and suppress the weeds. Mission accomplished.