When starting seeds indoors for spring planting, timing is very important. The plants need to be large enough to move outdoors at the normal planting time, without being spindly and overgrown.
To figure out when to start your seeds, you need to know three things:
- Frost Date: Your average last spring frost date is the key to planting in your area.
- Growing Time: You need to know the average number of weeks between planting seeds and transplanting seedlings. The growing time varies depending on what you’re planting and should be on the seed packet label. The average growing time is usually between 4 and 12 weeks.
- Planting Time: Warm-season vegetables can’t go outside until after the last frost while cool-season veggies can go outside up a month before the last frost.
Once you’re armed with the correct information, it’s a matter of some simple math to figure out when to start your seeds. For example, tomato seeds require 6-8 weeks growing time until planting, and they can’t be transplanted until after the last spring frost.
Since the average last frost date is around April 8 in my area, I should start these seeds between February 11 and 25 to give them 6-8 weeks to grow for planting after April 8. To be safe, I err on the late side, to reduce the risk of a surprise late season frost or freeze.
Gardening Tip
For a longer harvest, schedule several plantings of seeds, each a week or two apart. Not only will staggered plantings extend your harvest season, but successive groups of seedlings act as insurance against a deadly surprise cold snap.
Working out your first seed schedule can be a little complicated, but with practice you’ll find that most vegetables and flowers fall into groups that can be planted together. Save yourself future work by transferring your schedule to a seed calendar that you can refer to year after year.
Spring Transplant Schedule for Popular Vegetables
Be sure to check the label of each seed packet, since different varieties of a particular vegetable may have different levels of cold tolerance. Here’s a general guide to help you plan your spring planting times:
| Vegetable | Indoor Growing Time | Outdoor Planting Time |
|---|---|---|
| Broccoli | 5-7 weeks | 4-6 weeks before last frost |
| Cabbage | 5-7 weeks | 4-6 weeks before last frost |
| Corn | 4-5 weeks | After last frost |
| Cucumber | 3-4 weeks | After last frost |
| Eggplant | 6-8 weeks | After last frost |
| Lettuce & Spinach | 4-6 weeks | 4 weeks before last frost |
| Okra | 6-8 weeks | After last frost |
| Pepper | 6-8 weeks | After last frost |
| Pumpkin | 3-4 weeks | After last frost |
| Summer Squash | 3-4 weeks | After last frost |
| Tomato | 6-8 weeks | After last frost |
| Watermelon | 3-4 weeks | After last frost |
Further Information
- How to Start Seeds for Your Garden Indoors (article)
- How to Determine Spring Planting Time for Your Garden (article)
- How to Get an Early Start on Your Spring Garden (article)
- Starting Seeds Indoors (Purdue University Extension)
- How to Divide and Propagate Shrubs (article)
- Vegetable Garden: Planning and Layout (article)
- Vegetable Garden: Growing Cool-Season Vegetables (article)
- Vegetable Garden: Growing Warm-Season Vegetables (article)
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