Seed Starting Calendar Calculator
Enter your last spring frost date to see when to start seeds indoors, harden off, transplant and harvest 24 crops, or one of your own from a seed packet. How it works
Use the Seed Starting Calendar Calculator
About the Seed Starting Calendar Calculator
With an average last frost of April 15, start peppers indoors on February 4 and tomatoes on February 18, harden both off for the week before April 15 and plant them out on that date. The seed starting calendar counts every date from your last spring frost: weeks before it to start seeds indoors, then weeks before or after it to transplant or sow outdoors, for 24 vegetables, herbs and flowers, plus one crop of your own from a seed packet.
Dates for a last frost of April 15
| Crop | Start indoors | Transplant or sow outdoors | Harvest |
|---|---|---|---|
| Onions (seed) | Dec 31 | Mar 11 | Jun 19 to Jul 9 |
| Parsley | Jan 14 | Mar 25 | Jun 8 to Jun 23 |
| Peppers | Feb 4 | Apr 15 | Jun 14 to Jul 14 |
| Celery | Feb 4 | Apr 15 | Jul 24 to Aug 13 |
| Cabbage | Feb 4 | Mar 25 | Jun 3 to Jul 3 |
| Lettuce | Feb 11 | Mar 25 | May 9 to May 24 |
| Spinach | Feb 11 | Mar 25 | May 4 to May 14 |
| Kale | Feb 11 | Mar 25 | May 19 to Jun 8 |
| Broccoli | Feb 11 | Apr 1 | May 31 to Jun 30 |
| Tomatoes | Feb 18 | Apr 15 | Jun 14 to Jul 9 |
| Cauliflower | Feb 18 | Apr 8 | Jun 7 to Jul 17 |
| Marigolds | Feb 18 | Apr 15 | Jun 4 to Jun 14 |
| Basil | Feb 25 | Apr 22 | Jun 21 to Jul 21 |
| Sunflowers | Mar 25 | Apr 22 | Jul 1 to Jul 31 |
| Cucumbers | Apr 1 | Apr 29 | Jun 18 to Jul 8 |
| Squash (Summer) | Apr 1 | Apr 29 | Jun 13 to Jul 3 |
| Squash (Winter) | Apr 1 | Apr 29 | Jul 28 to Aug 17 |
| Zucchini | Apr 1 | Apr 29 | Jun 13 to Jul 3 |
| Corn | Apr 1 | Apr 22 | Jun 21 to Jul 21 |
| Peas | Direct sow | Mar 25 | May 24 to Jun 3 |
| Carrots | Direct sow | Mar 25 | Jun 3 to Jun 13 |
| Beets | Direct sow | Mar 25 | May 19 to Jun 3 |
| Beans (Bush) | Direct sow | Apr 15 | Jun 4 to Jun 14 |
| Beans (Pole) | Direct sow | Apr 15 | Jun 14 to Jul 14 |
The calendar’s own figures for 2026. Harden off in the 7 days before the transplant date. Harvest counts the days to maturity from the transplant or sowing date. For another frost date, every date moves by the same number of days.
How to use this tool
- Find your average last spring frost date (your county extension office or a frost-date table for the nearest weather station has it) and enter it, or tap one of the four presets.
- Tick the crops you grow, or press Select All. For a crop that is not listed, tick Add my own crop and type the seed packet's weeks indoors, weeks before or after the frost to plant out, and days to harvest.
- Read each card: start indoors, the hardening-off week, the transplant or outdoor sowing date and the harvest window. Cards are in order of indoor start date, with direct-sown crops last.
Frequently asked questions
- How do I find my last frost date?
- Ask your county extension office or look up the frost-date table for the weather station nearest you, which gives the date with a 10%, 50% and 90% chance of a later frost. The average (50%) date is the usual one to enter here. The 10% date, which some guides call the 90% date because the last frost falls before it in 9 years of 10, is the cautious choice for tender plants: in NC State Extension's Raleigh example the 36 °F frost dates are April 12 at 50% and April 26 at 10%.
- When should I start tomato seeds indoors?
- 8 weeks before your last frost date, which is the date this calendar transplants them. With a last frost of May 1, that is March 6, with hardening off from April 24 to 30.
- Can I plant tomatoes out on the last frost date?
- The calendar does, but the average last frost date still carries about a 50% chance of a later frost, and tomatoes, peppers, celery and marigolds all go out on that very day. Entering the 10% date from your frost table lowers that risk and shifts every other date with it: with April 26 instead of April 12, tomatoes start indoors on March 1 instead of February 15 and go out on April 26. Or keep a frost cover ready.
- What does hardening off mean?
- Getting seedlings used to sun, wind and cooler nights before they go in the ground, by setting them outside for longer each day. The calendar gives it as the 7 days before each transplant date.
- Which crops are sown straight into the ground?
- Peas, carrots and beets 3 weeks before the last frost, and bush and pole beans on the frost date. They get no indoor start date, and their harvest is counted from the sowing date.
- Can I add a crop that is not on the list?
- Yes, one at a time: tick Add my own crop and copy the seed packet's numbers. Leave weeks indoors empty for a crop sown outdoors. Eggplant started 8 weeks indoors, planted out 2 weeks after an April 15 frost and ready 70 to 85 days later starts on March 4, hardens off from April 22, goes out on April 29 and is ready July 8 to July 23. Weeks indoors go up to 20, weeks to plant out up to 12 and days to harvest up to 365. Share link carries the crop.
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