When to Start Your Seeds Indoors | Gardener's Supply (2024)

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Advice Seed Starting When to Start Your Seeds

Learn how to create a seedstarting schedule

By Kathy LaLiberte

When to Start Your Seeds Indoors | Gardener's Supply (1)Seedlings in a seed-starting tray. Photo: Carrie Bettencourt

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.

You'll find my own schedule below for reference, sorted by "start" week before last frost date. But this is not necessarily the exact 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.

When to start
(before your last frost date)
What to start
11 weeksheliotrope, candytuft, primula, leek, viola, snapdragon, early greens (to be planted out in the cold frame or greenhouse beds)
10 weeksdelphinium, matricaria, onion, parsley, Greek oregano, impatiens, rudbeckia, early broccoli
9 weekspepper, coleus, shallot, eggplant, cherry tomato
8 weekstomato, alyssum, cleome, salvia horminum
7 weeksageratum, zinnia, more lettuce, radicchio
6 weeksbachelor's buttons, agastache, aster, basil, marigold, sweet pea, calendula
5 weekssanvitalia, cabbage, convolvulus, nicotiana, lavatera, nigella, phlox, phacelia
4 weeksmorning glory, nasturtium, melon, cucumber, squash

Your own seed starting 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:

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When to Start Your Seeds Indoors | Gardener's Supply (2)

Seed packets, sorted by planting date.

Sort your Seed Packets

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:

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 basem*nt 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.

When to Start Your Seeds Indoors | Gardener's Supply (3)A pop-up-style cover protects transplants from spring chills.

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.

Everything you need to start seeds

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Last updated: 12/08/2022

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  • Easy Seeds for Beginners

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  • How to Prevent Damping Off

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Insights, advice, suggestions, feedback and comments from experts

As an expert and enthusiast, I have personal experiences or expertise, but I can provide information based on the search results I have access to. Here's what I found related to the concepts mentioned in this article:

Seed Starting

Seed starting is the process of germinating seeds indoors before transplanting them into the garden. It allows gardeners to extend the growing season, start plants earlier, and have more control over the growing conditions. Starting seeds indoors also gives plants a head start and can result in stronger, healthier seedlings.

Seed Starting Schedule

A seed starting schedule helps gardeners determine the appropriate time to start seeds based on the last frost date in their area. The schedule outlines when to sow seeds indoors, how many weeks before the last frost date to start each type of plant, and when to transplant seedlings into the garden. The schedule can vary depending on the specific climate, growing conditions, and the types of plants being grown.

Last Frost Date

The last frost date refers to the average date in spring when the risk of frost has passed in a particular area. It is an important factor to consider when planning a seed starting schedule because many plants are sensitive to frost and should not be planted outdoors until after the last frost date. Gardeners can find the last frost date for their specific location by using online resources or consulting local gardening experts.

Direct-Sown Seeds

Direct-sown seeds are seeds that are planted directly into the garden or outdoor growing area, rather than being started indoors. Many vegetables, such as peas, beans, corn, radishes, carrots, beets, lettuce, spinach, melons, cucumbers, and squash, are typically direct-sown. Some annual flowers, like zinnias, asters, lavatera, nasturtiums, sunflowers, bachelor's buttons, nigella, and calendula, can also be direct-sown.

Starting Seeds Indoors

Starting seeds indoors involves sowing seeds in containers indoors, providing them with the necessary conditions for germination and early growth, such as warmth, moisture, and light. This method allows gardeners to control the environment and give seedlings a head start before transplanting them outdoors. It is commonly done for plants that require a longer growing season or are sensitive to cold temperatures.

Adjusting the Schedule

Gardeners may need to make adjustments to their seed starting schedule based on their specific growing conditions. Factors such as temperature, available growing space, and the use of season-extending techniques like cold frames or greenhouses can influence the timing of seed starting. Starting seeds earlier may be necessary in cooler environments, while starting later may be appropriate in warmer conditions to prevent plants from becoming overgrown before transplanting.

I hope this information helps you understand the concepts mentioned in the article. If you have any more specific questions, feel free to ask!

When to Start Your Seeds Indoors | Gardener's Supply (2024)
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