Growing Tomatoes from Seed: A Step-by-Step Guide

Starting tomatoes from seed is deeply rewarding—especially for heirloom or San Marzano plum varieties prized for sauce. Here's how to succeed.

Seed & Timing

• Source fresh, trusted seeds. San Marzano excels for Italian gravy but adapts to local conditions.
• Start 6–8 weeks before last frost. Transplant outdoors 1–2 weeks after last frost.

Seed Starting Mix

Use commercial seed-starting mix (won't compact). Moisten with warm water, let sit overnight—damp like a wrung sponge.

Containers & Sowing

• Any small container with drainage. Germination flats with domes work well.
• Sow ⅛–¼" deep. Lightly firm mix around seeds.
• Cover with dome or vented plastic. Warm spot (70–80°F), out of direct sun. Germination: 5–10 days.

Light & Water

• Once sprouted, need intense light: fluorescent 2–3" above, 12–18 hrs/day, or south window.
• Water by soaking, then let nearly dry. Avoid constant wetness.

Transplanting Up

• First leaves (cotyledons) are embryonic. True leaves signal time to pot up.
• Don't let roots bind—move to larger containers as needed.

Hardening Off

Before permanent outdoor placement: gradually expose to outdoors (hours at a time), shield from wind/full sun initially. Once adapted, plant out.

Patience and attention yield vigorous, productive plants.