Starting Seeds Indoors

Count back from your last frost date

Most crops need 6–10 weeks of indoor growing before transplanting. Tomatoes and peppers want 8–10 weeks; brassicas 4–6 weeks; cucumbers and squash just 2–3 weeks (they hate root disturbance). Sow too early and you'll have overgrown, stressed seedlings.

Use a proper seed-starting mix

Regular potting soil is too dense for seeds — it compacts and restricts tender roots. Seed-starting mix is fine-textured and sterile. Don't reuse last year's mix; it may harbor damping-off fungi that kill seedlings.

Light is the most limiting factor

A sunny south window is rarely enough. Seedlings need 14–16 hours of bright light per day. Without it, they become tall, spindly, and weak (etiolated). A basic shop light with full-spectrum or "cool white" bulbs held 2–4 inches above seedlings works extremely well and costs very little.

Sow two seeds per cell, thin to one

Germination rates aren't 100%. Sow two seeds per cell and clip out the weaker seedling with scissors once both have sprouted. Don't pull — you'll disturb the survivor's roots.

Bottom heat dramatically improves germination

Most vegetable seeds germinate best at 70–80°F soil temperature. A seedling heat mat placed under trays speeds germination by 3–7 days and improves germination rates. Once seedlings are up, they no longer need bottom heat.

Keep soil consistently moist, never soggy

Water seed trays from the bottom by placing them in a shallow tray of water and letting the mix absorb it for 30 minutes, then drain. This prevents disturbing seeds and reduces damping-off risk from surface moisture.

Fertilize lightly once true leaves appear

Seedlings get their initial energy from the seed itself. Once the first true leaves appear (after the seed leaves, or cotyledons), begin feeding with a dilute liquid fertilizer at half strength every 1–2 weeks.

Hardening off is non-negotiable

Plants grown indoors have never experienced direct sun, wind, or temperature swings. Put them directly in the garden and they'll sunburn, wilt, or die. Spend 7–10 days transitioning them: start with 1–2 hours of dappled shade, gradually increasing sun and duration each day.

Protect from wind as much as from sun

Wind is as stressful as sun for indoor-grown plants. Stems thicken in response to movement, so gentle airflow (like a small fan indoors) during the last week before transplanting helps prepare them.