Some crops need a longer season than your climate offers. Starting seeds indoors buys tomatoes and peppers 6–8 weeks of growth before the garden is warm enough for them — and one packet of seeds costs less than a single nursery transplant.
Count back from your last frost: Everything anchors to your average last frost date. Peppers: start 8 weeks before it. Tomatoes and eggplant: 6 weeks. Brassicas: 5 weeks. Cucumbers and squash: only 3 weeks (they grow fast and sulk when root-bound). Sage's task list nudges you when each window opens.
What you actually need: Light — a sunny window is rarely enough; seedlings stretch and flop reaching for it. A basic LED shop light 2–3 inches above the seedlings, on 14–16 hours a day, changes everything. Total cost: about $25.
Containers — cell trays, yogurt cups with drainage holes, egg cartons. Anything 2–3 inches deep with drainage.
Seed-starting mix — lighter and finer than potting soil, and sterile (garden soil indoors invites damping-off fungus, the #1 seedling killer).
Warmth for germination — most seeds sprout fastest at 70–80°F. The top of a refrigerator works; a $20 heat mat is more reliable for peppers, which are famously slow.
The two failure points: Damping-off — seedlings collapse at the soil line overnight. Prevent it with sterile mix, a small fan for air movement, and watering from below.
Leggy seedlings — pale, stretched stems from too little light. Get the light closer (2–3 inches) and longer (14+ hours).
Hardening off — do not skip this: Indoor seedlings have never met wind or direct sun. A week before transplanting, set them outside in shade for 2 hours, then add an hour of morning sun each day. Skip this step and transplant shock can erase your entire head start in one sunny afternoon.
Quick wins: Start with tomatoes, peppers, and basil — the payoff-per-effort champions. Direct-sow everything else (beans, squash, radishes, carrots actively RESENT transplanting).