Where can I get good button mushroom spawn and how do I check quality?

Always buy spawn from a reliable, licensed source rather than an unknown seller, because bad spawn is the most common reason a beginner crop fails. Good options include the ICAR Directorate of Mushroom Research (DMR) at Solan, State Agricultural Universities, KVKs, and well established private spawn labs that many growers in your area already trust. Good spawn looks pure white, has an even cottony growth through the grain, smells fresh and mushroomy, and shows no green, black, yellow or orange patches and no sour smell. Use it fresh, as spawn weakens with age and poor storage. Ask the supplier for the spawn date and the strain, and start with a small order to test germination before you commit to a large quantity. Confirm the current approved spawn suppliers for your state with your local KVK or DMR Solan.