Whats the best way to sow grass seed on a lawn that already has grass?
With new grass seed the tops grow many times faster than the roots and they can be easily dislodged as a result. Cylinder mowers tend to pull them out, but a rotary mower will be OK if not set too low and keeping the old grass short will help the new growth. The disadvantage is that a rotary mower used in very dry conditions will blow the seed about a bit. My seed merchant advises that the seed will germinate in about three weeks and can be mown in three months (new lawns). I don`t think that particularly applies to filling patches. The best time to do it (UK) is September when it is warm and damp and the old grass is not growing so fast. Its got all winter to get some roots down then. Best of luck with it.
