Starting transplants from seeds indoors can be very enjoyable for a gardener, especially after a long winter. I love watching life emerge from the tiny seeds and flourish into healthy seedlings. Starting transplants from seed is also less expensive per plant and offers a greater variety than buying nursery plants.
Now the challenge is to figure out when you should sow the seeds.
Start some seeds too soon and you will end up with lanky plants under the lights. Too late and the plants will be too weak when transplanted to the garden or may not mature in time to produce before your frost.
To help keep you organized, it is a good idea to develop a seed starting schedule. A seed-starting schedule provides a guideline of when to sow seeds and when to transplant seedlings to your vegetable garden.
Planning a seed starting schedule for the first time can be a bit daunting. It becomes easier the following year because you can use the same schedule and adjust according to your notes and observations.
How to Develop a Seed Starting Schedule:
1. Find Your Last Expected Frost Date. The key information to establishing the seed-starting schedule is the last expected frost date for your area. This date will be used as a starting point for your schedule.
There are various sources of finding the date such as asking your neighbors, your local nursery, extension office, or enter your zip code here at PlantMaps.com. Don’t become too concerned if you find that different sources provide you with slightly different last expected frost dates. It is only an estimate and may vary from various sources, year-to-year, or even from one side of town to another. Select the average date among the sources as your starting point.
2. Set Up a Chart. I use a spreadsheet with the following headers: Description, # of plants, Seed Starting Date, Actual Seed Starting Date, Germination Date, Transplant Date, and Actual Transplant Date. For simplicity, I round my dates to the nearest Sunday date.
3. Figure Out the Sow and Transplant Dates of Each Seed. Most often, the back of the seed package provides instructions on when to sow your seeds indoors and when to transplant the seedlings into the vegetable garden.
For example, the pepper seed package above says to “start seeds indoors 7-8 weeks before the last spring frost.” If my last frost date is May 20th, counting 7-weeks backwards on a calendar lands me on April 1st. The seed package also tells us when to transplant the seedlings, “…in the late spring after the soil has warmed.” This means that peppers should be sown around April 1st and transplanted to the garden after May 20th, my last frost date. Since peppers love the heat, I usually add a week to be on the safe side and schedule peppers to be transplanted on May 27th.
Below is a general guideline on when to start you seeds based on your estimated last frost date:
- 10 weeks: Celery, Leeks, Onions, Parsley, Shallots, and some Herbs.
- 8 weeks: Asparagus, Eggplant, Leeks, Onions, Peppers, Shallots, and some Herbs.
- 6 weeks: Broccoli, Brussels Sprouts, Cabbage, Cauliflower, and Tomatoes.
- 4 weeks: Cucumbers, Lettuce, Melons, and Squash.
4. Record the Dates in Your Chart. In my spreadsheet, I fill in the name of the seed in the description column, the number of seedlings I will need based on my vegetable garden layout, the date to sow the seeds, and the date to transplant the seedlings into the garden. I continue this for each seed I plan on growing.
5. Keep Notes for Next Year. You will notice that I have a column in my spreadsheet where I can record when the seed germinated and the real dates of when the seed was sown and transplanted into the garden. That way I can see whether I need to make changes next year. One adjustment I made the second year was the seed starting date for peppers. My seed starting area is in an unheated basement so peppers tend to grow more slowly in cooler temperatures. I added on a couple weeks of growing time under the lights.
Direct seeded crops: Some crops should not be started indoors because either they won’t transplant well or won’t benefit from an early start. Sow the following directly into the vegetable garden according to the instructions on the seed package: Beans, Beets, Carrots, Corn, Radish, Turnip, Parsnip, and Peas. See my post on Homemade Seed Mats for sowing small seeds such as carrots. Also see 13 Easy Vegetables to Direct Sow.
I have also found that Spinach, Cilantro, and Pak Choi are sensitive to having their roots disturbed and it may cause the plants to bolt or go to seed prematurely. Using Soil Blocks for Growing Seedlings reduces transplant shock. Or you can direct seed in the garden in early spring as soon as the soil can be worked.
Hardening off: Start hardening off your seedlings about 2-weeks before their transplant date. Hardening off is the process of adapting plants to the outside so they can adjust to sunlight, cool nights, and less frequent watering. Watch your weather for freezing temperatures. If the days are warm enough, begin hardening off your seedlings in a sheltered location for a few hours on the first day, increase a little each day, until the seedlings are outside overnight. Also see How to Harden Off Seedlings for more info.
Developing a seed starting schedule is the last step in my yearly vegetable garden planning. Soon it will be time to sow some seeds and tend to the young seedlings under the lights. I find making up a schedule ahead of time makes it easy to know what seeds should be started each week. Also, the schedule provides a record of when each seed was started and makes it easy to adjust from year to year.