I am on a well and have a fairly large yard that I would like to overseed now (early April). What happens to the grass seed if it is not watered? Does it die or just longer to germinate? I see seeding along road construction sites that receive no water and still grow.
Seed will sit there until it gets thoroughly soaked and absorbs water. Then it will germinate (sprout). If it absorbs the water but dries out before it can germinate, the seed will die.
The bottom line is that you don't have much control over how it does, since you can't water it. We'd suggest that you spread a light layer of straw over it after you seed to help retain moisture so the seed does not dry out. The straw not only shades the soil, but it cuts down on drying wind.
The best time to seed is going into a wet season, so early fall is best. Spring invariably leads to a dry summer in Maryland and many new spring lawns dry up and die because the grass has not had enough time to establish a good root system yet. Early spring is the 2nd best time. Hope for regular rains. And bear in mind that you may have to overseed in fall.
Here is an excellent pub from our website about seeding: http://extension.umd.edu/sites/default/files/_images/programs/hgic/Publications/HG102%20Lawn%20Estab...