We prefer to do the seeding in the fall. There is a few reasons for this: If we were to do seeding in the spring you would not be able to receive crabgrass control as this does not know the difference between a grass seed or a weed/crabgrass seed. If you have any crabgrass or weeds in the lawn they would overpower the newly planted grass seed and choke it out The fall provides optimum soil and air temperatures for grass seed germination As we treat for weeds and crabgrass in your lawn throughout the season this will leave thinner areas so that when we seed in the fall it will help fill those areas in.