When to Start Flower Seeds Indoors (Zone Map)

Knowing your frost dates is the key to perfect timing.

Count back from your last frost

Most flowers are started indoors 6–8 weeks before your area’s last spring frost. Look up your USDA hardiness zone, then find the average last frost date for your zip code.

A simple schedule

Sow indoors 8 weeks out (cold-weather plant) to 4 weeks out (fast growers like zinnias). Hardening off — putting seedlings outside for a few hours a day for a week — prevents shock before transplanting.

Indoors vs direct sow

Direct-sow warm, fast crops (sunflower, nasturtium, zinnia) after frost; start tender, slow flowers (petunias, snapdragons) indoors.