Question: I started a new lawn last fall, and I am very happy with the results. I want to reseed the areas that came up a bit thin. When and how should I do that so I don’t damage the rest of it? I was also considering aeration of my new lawn soon. I always did every winter at my previous home with great results. Should I aerate this younger lawn?
I understand your concern about the lawn being too thin, but this can often be the case in a new lawn, particularly with cool season grasses such as fescues. Fescues fill in voids between seedlings primarily by “tillering.”
They do not have the capacity to fill voids with strong rhizomes (underground stems) and stolons (above ground stems that lay on the soil surface). Frequently, this type of growth is associated more with warm season grasses such as Bermuda grass.
Tillering is the “sprouting” of side shoots from the base of the plant. As a grass plant emerges from the seed, it shoots up one stem with an associated leaf. This stem and leaf will grow very tall before it sends up tillers unless the tip is cut off. The tip is cut off by mowing (prior to lawn mowers it was done by grazing animals).
Once the grass has been cut, the plant kicks into a survival mode and sends up side shoots (tillers) from the base. The tillers begin to fill in voids between individual plants and the lawn “thickens.” So mowing a lawn when it is young is a good thing.
However, if you feel the distance is still too far apart between these plants, I would use the same seed, apply it to these areas and lightly cover the seeds with topdressing. Now is a good time to do that.
Aerating, or punching holes in the surface of the soil with a machine called an “aerator,” is best done after the soil has been established for one year.
Bob Morris is a professor emeritus in horticulture with the University of Nevada and can be reached at firstname.lastname@example.org. Visit his blog at xtremehorticulture.blogspot.com.