LAST SPRING FROST (e.g. 05/10/2015)
Use the average date of the last spring frost in your garden over the past 5 years or so. If you don't know this date, use the date from Burpee or NOAA. For year, enter the current year.

11 weeks before last frost:
Sow onion, celery and celeriac seeds indoors.

9 weeks before last frost:
Sow leeks, broccoli, cabbage, collards, kale, cool weather lettuce, escarole, eggplant, parsley and thyme seeds indoors.

8 weeks before last frost:
Sow pepper seeds indoors (keep temp above 78*F for germination).
Also sow indoors marigold, basil and beet seeds.

Up to 6 or 7 weeks before last frost:
Start watching the soil for the first direct planting! As soon as the soil can be worked its time to sow peas, fava beans, arugula, spinach and radish directly in the garden. (Note: In warmer climates, where the soil doesn't freeze, this tool may not give an appropriate pea planting date. Check with local gardeners for best date.)

6 weeks before last frost:
Sow tomato, caulifower and Swiss chard seeds indoors.

4 weeks before last frost:
Transplant onions, cabbage, collards, escarole, lettuce and kale seedlings to garden (use row cover if necessary).
Succession sow 2nd crop cool-weather lettuce seed indoors or in garden.

3 weeks before last frost:
Sow pumpkin, cucumber and zinnia seeds indoors.

2 weeks before last frost:
Sow summer squash, watermelon and melon seeds indoors.
Transplant leeks, beets, cauliflower, Swiss chard, parsley and broccoli to garden.
Succession sow 2nd crop of peas seeds in garden.

1 week before last frost:
Sow 2nd crops of cool-weather lettuce, beets and spinach either indoors or in garden.

Week of last frost:
Sow directly in garden seeds for sunflowers, nasturtiums, carrots and parsnips.
Plant potatoes and onions sets in garden.

1 week after last frost:
Transplant tomatoes, thyme, celeriac and celery to garden.
Plant corn, marigolds, beans and soy beans seeds directly in garden.

2 weeks after last frost:
Sow 3rd cool-weather lettuce crop indoors or in garden.
Transplant peppers, basil, eggplant, pumpkins, squash, cucumbers and melons to garden if soil is well warmed.

5 weeks after last frost:
Succession sow beet and warm-weather lettuce seeds indoors or directly in garden.
Succession sow bean and cilantro seeds in garden.

8 weeks after last frost:
Succession sow summer squash, cucumbers, warm-weather lettuce, beets, beans and cilantro.

11 weeks after last frost:
Succession sow warm-weather lettuce, beets, beans and cilantro.

Thanks to BYTES for help with this code!