Best Seed Starter Mulch: Compost vs. Hay & Straw

Neither straw nor hay is recommended for spreading over fresh grass seed. Both contain weed seeds that can germinate and compete with the new grass seedlings for water and nutrients. Additionally, straw and hay can mat down and prevent the grass seeds from getting the sunlight they need to germinate and grow. A thin layer of compost or peat moss is a better option for covering grass seed.