When to Start Your Seeds – Learn how to create a seedstarting schedule

Tomato seedlings in a seed-starting tray

Tomato seedlings in a seed-starting tray

YEARS ago, I was diligent about keeping a gardening journal. I didn’t make daily entries like Thomas Jefferson and other famous journal keepers, but on a weekly basis I would record the major tasks I’d accomplished, a general weather summary (hot, dry, wet, cold), what plants were in bloom, and what crops were coming in. As my life became more and more crowded, those entries trailed off. It’s a shame, because I really miss being able to peruse journal entries from years past. I would like to be able to remember when I picked my first tomato, or whether the lilacs bloomed early or late. But all those rich and wonderful details of prior gardening seasons are now lost.

One piece of record-keeping that I have managed to maintain are my annual seed starting calendars. I do know which week I planted my pepper seeds last winter, and the date I sowed the alyssum. And I know whether I started my onion seeds earlier or later than the year before. Because I start over 40 types of plants from seed (and about 70 different varieties), my seedstarting schedule is essential.

Week 11
(Feb 20-26)
heliotrope, candytuft, primula, leek, early greens (to be planted out in the cold frame or greenhouse beds), viola, snapdragon
Week 10
(Feb 27-Mar 4)
delphinium, matricaria, onion, parsley, Greek oregano, impatiens, rudbeckia, early broccoli
Week 9
(Mar 5-11)
pepper, coleus, shallot, eggplant, cherry tomato
Week 8
(Mar 12-18)
tomato, alyssum, cleome, salvia horminum
Week 7
(Mar 19-25)
ageratum, zinnia, more lettuce, radicchio
Week 6
(Mar 26-Apr 1)
bachelor’s buttons, agastache, aster, basil, marigold, sweet pea, calendula
Week 5
(Apr 2-8)
sanvitalia, cabbage, convolvulus, nicotiana, lavatera, nigella, phlox, phacelia
Week 4
(Apr 9-15)
morning glory, nasturtium, melon, cucumber, squash

You’ll find my own schedule on this page, for reference, sorted by “start” week. But this is not the schedule I’d recommend for you. I garden at the cold edge of zone 4. My grow lights are in a cool upstairs bedroom where seedlings grow quite slowly. But once it’s April, all the seedlings go out into my warm and sunny greenhouse where they grow very rapidly. Each year, I consult my records and make a few adjustments to  my schedule. My goal is to produce seedlings that are mature—but not overgrown—when it’s time to go into the garden.

Your own seedstarting conditions are probably quite different from mine, and your planting schedule should be adjusted accordingly. Asking a garden-savvy neighbor when they sow their seeds is one easy way to get started. But if you want to figure out your own planting schedule from scratch, here’s how to do it:

Sort your Seed Packets

Seed packets sorted by planting date

Seed packets, sorted by planting date.

Start by separating all your packets of seed into two piles: those that will be “direct-sown” (planted right in the garden) and those that will be started indoors. The outdoors pile will include most vegetables, such as peas, beans, corn, radishes, carrots, beets, lettuce, spinach, melons, cucumbers, and squash. Put a rubber band around whatever seeds you’ll be planting outdoors and set them aside.

Most annual flowers will also go into the direct-sow pile: zinnias, asters, lavatera, nasturtiums, sunflowers, bachelor’s buttons, nigella and calendula. If your growing season is very short or your garden conditions are especially difficult, you may decide to put some of these annual flowers into your “sow indoors” pile. Most perennial flowers will need to be started indoors.

Now spread out your “sow indoors” pile and start reading the back of the seed packets. Unfortunately, you’ll probably find that planting instructions are pretty vague. Home gardeners would have a much easier time if seed companies would provide us with the information we need. At the very least, you should find something like, “For earliest bloom or fruit production, start 6 to 8 weeks before last frost date.”

Sort your packets into piles according to these recommendations, making separate piles for 5, 7, 9 weeks, and so on. Some packets, especially those for perennials, may only tell you how long it takes the seeds to germinate. If that’s all you have to go on, take that figure (which is usually a range) and add 6 weeks. Then put the packet into the appropriate pile.

If there’s no information on the seed packet, you can pretty safely just start all your seeds about 6 weeks before you’ll plant them outdoors. Make note of which plants are too big or too small at planting time, and then you can make adjustments next year based on your notes. For detailed instructions on starting 500 varieties of annual and perennial flowers, I highly recommend Eileen Powell’s book, From Seed to Bloom (Storey 1995).

Creating the Calendar

Start by finding the average last frost date in your area. You can get frost dates online by entering your zip code. To calculate your planting dates, you need to count back from last frost date in one-week increments. (I base my calendar on Saturdays, because that’s the day that I usually have available for seedstarting). In my area, the last frost date is May 15. For me, when I count back from May 15, Week 4 is April 15, Week 11 is the week of February 26, etc. Simply write the week number (8,4, 6 or whatever) on each seed packet and use a rubber band to keep each pile together. When the planting week arrives, you just grab the right packet and start planting.

Making Adjustments

Now that you have a great schedule, here are a couple reasons you may want to make some adjustments:

Pop-up cover protects tomato plant from spring chill

A pop-up-style cover protects transplants from spring chills.

Start earlier: Seeds take longer to germinate and plants grow more slowly when air and soil temperatures are cool (below 70 degrees F). If you plan to start your seeds in a cool basement or cool bedroom, you may want to shift your whole schedule a week or two earlier.

You can see on my schedule that I start some greens and broccoli at the end of February. That’s because these seedlings get planted outside about a month before the last frost date. If you have a
cold frame or
greenhouse, — or if you use other season-extending techniques, such as row covers or pop-up covers — you can plant tender seedlings several weeks before the last frost date. Just count back from that expected planting date to get the right date to sow your seeds.

Start later: If you grow your seedlings in a greenhouse or an especially warm room (more than 70 degrees F.), you should cut a week or more out of your schedule. Heat promotes rapid growth, and you could find yourself with giant plants that are ready for the garden before warm weather arrives.

I hope you find this information helpful rather than intimidating. I find making up a schedule ahead of time makes it easy to figure out what I should be planting each week. When you start transplanting into the garden, write a few notes on your schedule so you can make adjustments next season. Remember that every year will be a little different and you’ll never get it exactly right. But for me, that unpredictability is part of what makes gardening fun.