Free tool

Seed-starting calendar.

Enter your average last spring frost. See when to start common container crops indoors, and when they can go outside.

Seed starting dates for the chosen frost date
Crop	Start indoors	Outside	Note
Broccoli	Feb 18 – Mar 4	Mar 18 – Apr 1	One plant per deep pot. A cool-season crop.
Kale	Mar 4 – Mar 18	Mar 18 – Apr 1	Set out before the last frost. Heat makes it bitter.
Leaf lettuce	Mar 11 – Mar 25	Mar 18 – Apr 1	Or direct-sow. Repeat every two weeks.
Radish	Direct sow	Mar 18 – Apr 1	Sow in place. Many are ready in about a month.
Carrot	Direct sow	Mar 25 – Apr 8	Sow in a deep pot. Don’t transplant.
Parsley	Feb 4 – Feb 18	Apr 1 – Apr 15	Slow to germinate. Cool weather suits it.
Cilantro	Mar 18 – Mar 25	Apr 1 – Apr 15	Bolts in heat. Sow small batches.
Marigold	Feb 18 – Mar 4	Apr 15 – Apr 22	A cheerful filler while you learn container rhythm.
Tomato	Feb 18 – Mar 4	Apr 22 – Apr 29	Patio types in 5 gallons. Indeterminate vines want 10 or more.
Basil	Mar 4 – Mar 18	Apr 22 – Apr 29	Wait for warm nights. Cold soil stalls it.
Cucumber	Mar 18 – Mar 25	Apr 22 – Apr 29	Direct-sowing works too. Give them a trellis.
Zucchini	Mar 18 – Mar 25	Apr 22 – Apr 29	One plant in a large pot, 15 gallons or more.
Bush beans	Direct sow	Apr 22 – Apr 29	Sow after frost. Beans dislike transplanting.
Pepper	Feb 4 – Feb 18	Apr 29 – May 6	Warm soil matters. Don’t rush them outside.
Eggplant	Feb 4 – Feb 18	Apr 29 – May 6	Same window as peppers. One plant in a 5-gallon pot.

A window, not a deadline

These ranges are the usual lead times printed for home gardeners in the US: weeks before last frost for indoor sowing, and a transplant or direct-sow window around that date. Balconies run warmer than open ground. If your nights stay mild, you can lean toward the early side for greens and the careful side for basil, peppers, and tomatoes.

Harden seedlings off for several days before they live outside full time. This is a planning aid. Your seed packet still wins if it disagrees.