Should the grass seed be under barely under or on top of the top dressing? I have read conflicting advice on seed packing and internet sites.
Thank you for your inqury. Based on your question it is difficult to know if you are planning on a seeding and entire lawn from scratch or if you are planning on thickening an existing lawn. Regardless of your choice the best time to sow seed is early fall; mid-August to mid-September while the ground is still moist and warm, yet weed growth is slow and there is enough time for the grass plants to develop good roots before the weather turns very cold. Rake the surface thoroughly to prepare the seedbed and avoid any depressions that may hold surface water. Choose a mixture of at least two or three turfgrass varieties in accordance with your requirements. This will depend on the amount of sun and shade the area receives. Do not be tempted to oversow; if you do, the grass seed will not develop properly. Seed can be spread by hand or with a mechanical spreader. Whichever way the seed is spread, coverage will be more even if one applies half the seed moving in one direction across the area, and then the other half moving in the opposite direction. Grass seed doesn’t need to be covered, but it does need to make contact with the soil. This can be achieved by lightly going over the area with a fan rake or even with a light rolling. Make sure the seed isn’t buried more than 7mm deep. Give the newly seeded area a thorough initial soaking and then keep it well watered until the grass is established.
The following wesite provides detailed information on growing a lawn from seed: https://www.toronto.ca/compost/seeding.htm
Hope this helps!