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Seed Starting Date Planner

Determine when to start seeds indoors and transplant outdoors based on your last frost date and plant type.

Last Frost Date

Enter the average last frost date for your area.
Used to check if the growing season is long enough.

Select Plants

No plants selected yet. Add plants above to calculate dates.

Custom Plant (optional)

How It Works

This planner calculates planting dates by counting backwards and forwards from your average last spring frost date. Each plant has specific timing requirements based on its growth characteristics.

Indoor Seed Starting

Many plants benefit from being started indoors before the last frost to give them a head start on the growing season. The indoor start date is calculated by subtracting the recommended number of weeks from your last frost date.

Indoor Start Date = Last Frost Date − (Weeks Before Frost × 7 days)

Transplanting Outdoors

After the last frost date, seedlings can be transplanted outdoors once conditions are warm enough. Hardy plants can go out earlier, while tender plants like tomatoes and peppers need warmer soil.

Transplant Date = Last Frost Date + (Weeks After Frost × 7 days)

Estimated Harvest

The estimated harvest date is based on the "days to maturity" for each plant, counted from the transplant date (for transplanted crops) or from the direct sow date.

Growing Season Check

If you provide the first fall frost date, the planner checks whether each plant has enough growing days to reach maturity before the season ends.

Seed Starting Reference Guide

Plant Start Indoors (weeks before frost) Transplant (weeks after frost) Days to Harvest Notes
Tomato6–81–260–85Needs warm soil above 60°F
Pepper8–102–360–90Slow to germinate, start early
Broccoli6–82–350–70Cool-season crop, tolerates light frost
Lettuce4–60–130–60Can also direct sow early
Cucumber3–4250–70Don't start too early, dislikes transplanting
Squash / Zucchini3–4245–65Direct sowing is often preferred
Basil6–8250–75Very frost-sensitive
Eggplant8–102–365–80Needs warmth, similar to peppers
Kale4–60–150–65Very cold-hardy, flavor improves with frost
Watermelon3–42–370–90Needs long warm season

Tips for Success

Starting Seeds Indoors

  • Use sterile seed-starting mix, not garden soil
  • Provide consistent warmth (65–75°F) for germination
  • Ensure 12–16 hours of light daily
  • Keep soil moist but not waterlogged
  • Label everything with plant name and date

Transplanting Outdoors

  • Harden off seedlings for 7–10 days before transplanting
  • Transplant on a cloudy day or in the evening
  • Water deeply after transplanting
  • Watch weather forecasts for late frosts
  • Use row covers for extra frost protection

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