Start seeds in fresh seed-starting mix

Garden soil and last year's potting mix can carry the fungi that cause damping-off, which topples seedlings overnight. Fresh seed-starting mix is fine, light, and clean.

When: Late winter

About damping-off →

Wash trays before you reuse them

Scrub off the old soil, soak trays and pots for 10 minutes in 1 part household bleach to 9 parts water, and rinse. It kills the fungi that cause damping-off.

When: Late winter

Don't start seeds too early

Tomatoes need about 6 to 8 weeks indoors, and peppers 8 to 10; squash and cucumbers only 3 to 4. Seedlings kept inside too long outgrow their pots and stall when you plant them out.

When: Winter, Late winter · For: Tomato, Cherry tomato, Pepper, Hot pepper, Eggplant, Zucchini / Summer squash, Cucumber

When to start each crop →

Test old seeds before you sow

Roll 10 seeds in a damp paper towel, put it in a plastic bag somewhere warm, and count the sprouts after a week. If 7 sprout, sow a little thicker. If only 2 do, buy new seeds.

When: Winter, Late winter

Sow two seeds per cell, then snip the weaker one

Not every seed sprouts, so sow two to a cell. If both come up, cut the weaker one at the soil line with scissors instead of pulling it, so the roots of the one you keep aren't disturbed.

When: Late winter

Water seedlings from below

Pour water into the tray under the cells and let the mix soak it up for 20 minutes, then tip out the rest. The top stays drier, which helps prevent damping-off.

When: Late winter

Stretching seedlings need more light

Tall, pale, floppy seedlings are reaching for light. Lower the lights to 2 to 4 inches above the leaves, and give them 14 to 16 hours a day.

When: Late winter

Build a light stand →

A breeze makes sturdy seedlings

Run a small fan on low near your seedlings for a few hours a day, or brush your hand over the tops. Stems grow thicker, and the moving air keeps mold off the mix.

When: Late winter

Feed seedlings once their true leaves open

Seed-starting mix has almost no food in it. Once the first true leaves appear, feed with a liquid fertilizer mixed at half strength every week or so.

When: Late winter

Move seedlings up to bigger pots

When roots fill the cell and start circling, move the seedling to a bigger pot. Tomatoes can go deeper than before, just like in the garden.

When: Late winter, Spring

Harden off seedlings for a week

Seedlings raised indoors burn in full sun and wilt in wind. Set them outside in shade for an hour the first day, then add more time and more sun each day for 7 to 10 days before planting.

When: Spring

Seed-starting plan →

Try winter sowing in milk jugs

Cut a milk jug almost in half, poke drainage holes in the bottom, and fill it with moist potting mix. Sow cold-hardy seeds like kale, onions, or native flowers, tape the jug shut with the cap off, and set it outside in late winter. The seeds sprout when the weather is right, already used to the cold.

When: Winter, Late winter · For: Kale, Onion (sets), Coneflower (echinacea), Black-eyed Susan, Milkweed