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February 22nd 2017

Seed Starting Basics

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Floret_Seed Starting 101-5Starting your own seeds is a great way to get a jump on the season. It also gives you access to hundreds of specialty varieties that you won’t find at your local nursery and is the most affordable way to fill a cutting garden fast. You just need to keep a few key things in mind before you start. Throughout this post I will provide links to the necessary supplies, so if you can’t find them locally you can order them online from the fine folks at Johnny’s Selected Seeds.

Before you go crazy sowing seeds in late winter and early spring, it’s important to know just how early you can start—if in doubt, ask your local Master Gardener group or staff at a trusted nursery for the expected last frost date. Fast-growing annuals that bloom in summer (those that take less than 90 days to harvest, such as cosmos, sunflowers, and zinnias—the number of days to harvest is indicated on seed packets) shouldn’t be started more than 4 to 6 weeks before the last spring frost, otherwise they’ll get too big for their growing container and have soft, weak foliage and overgrown roots.

On the other hand, slow-growing plants like perennials can take a couple of weeks to germinate, so sow them indoors 10 to 12 weeks before the last spring frost date. Once you know your last frost date, check the back of each seed packet, or catalog description for days-to-harvest to figure out how many weeks early you can get them started indoors.

Floret_Seed Starting 101-3You can start seeds in just about anything that holds soil and drains water, including egg cartons, old pots, and plastic cups with holes poked in the bottom. If you’re reusing old pots, be sure to wash them thoroughly with a 10-percent bleach-water solution to kill any lingering diseases or pathogens. But for the best results, I highly recommend picking up some seed starting cell trays, and bottom flats since they produce the most uniform results. They can be found at most garden centers this time of year, or online from Johnny’s Selected Seeds.

Floret Seed Starting Trays-1Flats come in numerous sizes, so choosing can be a little overwhelming. I’ve tested them all, and my two favorites for both annual and perennial seeds are the 72-cell and 50-cell flats. Both produce large, bulky plants that won’t require repotting before it’s time to transplant them into the garden. For vines, pumpkins, and sweet peas, I use 4-inch (10-cm) pots; for sweet peas, I also love root trainers (long, skinny growing containers that give vigorous roots room to develop).

Floret_Seed Starting 101-13In addition to seed flats and pots, you also need drainage trays to set the containers on, as well as some type of plastic covering to keep up the humidity seeds need to germinate properly. You can often find kits that include all three components: a seed flat, drainage tray, and plastic dome. If you’re in a bind, plastic wrap is an option, but you’ll need to monitor your trays closely for signs of germination and remove it immediately once they break through the soil surface. I strongly recommend getting a few clear acrylic lids that will fit snuggly over your seed trays and flats of pots. These maintain the humidity and high heat that will speed up germination and growth significantly.

Floret_Seed Starting 101-5It’s important to start plants off right with the highest-quality seed starting mix. You get what you pay for, so don’t go for the cheapest option. These special blends contain the right mix of ingredients to ensure that your little seedlings get off to a good start. Be sure to check the ingredients and avoid any that contain synthetic fertilizers or bark, since young plants can be burned or stunted by either. Seed starting mix is fine and suited to tiny seeds. For varieties that have larger seeds and will be started in bigger pots, like vines and squash, use a high-quality potting soil.

For seeds to germinate rapidly, they need to be kept warm and moist. If you have a cozy spot where you can tuck a few trays, like on top of the refrigerator or radiator, this heat will encourage seeds to sprout more quickly. But if you really get hooked on flower growing, you’ll outgrow these spaces fast. Invest in a heat mat specially designed for seed starting, for more consistent results.

Floret Seed Starting Lights-3Of course there’s nothing better than having your very own greenhouse or sunroom to propagate plants in, but if you don’t have this kind of space, don’t worry. You can still get great results with a homemade seedling chamber, which can be as simple as a warm indoor spot with shop lights. The first few years I grew flowers, I started all of my seeds in the basement, on shelves, under lights. For very little money, you can pick up a few shop lights that are available at just about any hardware store. Hang them from some inexpensive chains, and you’re in business. To give plants the full spectrum of light needed to thrive, be sure to get one cool and one warm bulb (they’ll be labeled as such) for each fluorescent light ballast. Suspend the lights a few inches above your seedlings and put them on a timer, making sure to give plants about 14 to 16 hours of light a day. As the plants get taller, be sure to keep raising the lights so they are 2 to 3 inches (5 to 7 cm) above the tallest plant.

Floret_Seed Starting 101-9I start roughly 90 percent of my seeds inside the greenhouse, or under lights. This gives me a jump on the season, since I can set out larger plants once the weather has warmed. It also helps cut down on weeds, since I’m planting established plants that have a better chance of contending with the weeds and crowding or shading them out.

Also, I’ve put together a detailed step-by-step guide called Seed Starting 101 in the resources section of our site. Be sure to click the arrows at the edge of the photos to see the next image and step.

6744744479_a94c4cf256_bBut not all plants need this special treatment. Many gardeners direct seed—that is, they sow seeds directly in the ground outside. This approach can be used for certain varieties including fast-growing summer annuals like grains, grasses, sunflowers, and zinnias, which all sprout within a few days of seeding. Just be sure to wait to sow them until all danger of frost has passed. Also, many hardy annuals, like bells of Ireland, larkspur, and love-in-a-mist resent transplanting and actually do best when sown directly into the soil.

Direct seeding can be done by hand, but if you have more than a few tiny rows to do, use a walk-behind seeder, like the Earthway, to make this chore a snap. This handy tool digs a furrow, drops the seeds into it, and covers them all with soil while you walk at a normal pace. With it, you can direct seed a 25-foot (7.6 m) row in less than 30 seconds.


  1. mimi strouse on

    How do you know which seed wheel to use with the earthwat? Jonny seem to have only vegetable wheels

  2. Carolyn Yeager on

    Hello Floret!
    When you use the Earthway seeder and rows are fairly close together, how do you control weeds there. We were going to plant in plastic but I would like to be able to use the seeder! Thanks!

  3. beth on

    Hello Floret! I’m trying my hand at seed starting this year… I have all my trays under fluorescent lights in the basement and they are doing beautifully, except for my honeywort seedlings. They’re growing nicely but have developed yellow spots on the leaves. Any idea why? Suggestions on what I should be doing differently for them? Thank you! LOVE your site, blog, book… all of it :)

  4. Eleanor on

    Thank you Floret! A great blog post as always- simple/concise/generous with links and tricks of the trade. I loved your blog post about being generous with what you have learned. I agree! My friend and I are starting a small CSA this year and our local veteran farmers have been so supportive and generous so far with offering hard earned stories and tricks of the trade. Curious if you or anyone reading here has much experience using the soil blockers for flower seeds? Eliot Coleman swears by them for vegetables, but I am pretty new to them. I know you say you love the 50 and 72 cells, and the soil blocker definitely takes a little more time, but I’d love to hear others thoughts on it?

  5. Jennifer on

    Thank you for this info! Do you have lights on the seed trays before they sprout? I’ve read some seeds need the extra light to germinate and others do not. So I’m not sure. Also I’ve read that a fan blowing over the starts helps them develope. Any experience with this? Thanks again.

  6. Kathy Horn on

    When filling the cell trays with moistened soil, I use a hand scoop to pile it on and my hand to spread and level it into the cells.
    Then take a couple of EMPTY but NESTED (same size) cell trays to tamp all the cells at once. Add additional soil to fill the cells and repeat the tamping. VOILA! Ready to plant!

    • sue on

      Pro tip! You’re actually using the empty trays pressed down from above like the time-tested “Dibbler” used by volume seed starters for centuries. They were boards with small short pegs on the underside, used to sow evenly-spaced seedlings in open flats before cell-packs were invented. This method is still valuable for strong rooted seedlings–no cell trays necessary. Cut the flat like a tray of brownies and lever seedlings out with a dinner fork. Most useful when transplanting seedlings to larger growing-on containers rather than planting in the field, as Floret uses them.

  7. Lori B on

    Great post, thank you! I’m just getting started this year, so have a “beginner” question. Can you share a picture of the pots and root trainers you prefer for the Sweet Peas? They look different than the flats, correct? Your information is invaluable, we are so excited to get started this year!

  8. Megan on

    Thanks again your posts have been super helpful!

  9. Debbie on

    Thanks for the great info Team. You are building my confidence with each posting!

  10. Christie on

    Hi- I’m wondering what your thoughts are on double seeding cells? Is this something that should be avoided or will this work to get more seeds started in a smaller space?
    I love Sunset Magazine for directing me to you and your website. I have found so much useful information and I LOVE! all of the beautiful photos!:)

  11. sophie on

    Thanks for sharing your experience, this post is very helpful for ” seeds lovers ” like me.

  12. Susan on

    Hoping you can clear something up for me. On your Bells Of Ireland sowing instructions it says to sow indoors 8-10 weeks before last frost and to put the seeds in the freezer or let them sit outside potted up for a couple of weeks before putting in a warm environment for growing. In this seed starting series you recommend direct sowing Bells Of Ireland as they resent transplanting. Which is th better way to go? Thanks!

    • sue on

      You’ll have much better germination if the seeds are exposed to freezing temps before germination. Use the freezer tip but make sure they don’t pick up moisture in the freezer. Then direct seed into the ground. Once established, the B of I will self sow around your garden.

  13. Gioconda Padovan on

    Thank you so much for sharing this knowledge. You are the best!!!

  14. Linsey on

    Thank you for the tips Floret! Lately, I have been in the process of researching basic indoor seed starting and found this information extremely helpful. It’s hard finding reliable and easy to follow information on this topic. Thank you!

  15. Justine on

    This is, without doubt, the most incredible sharing of knowledge and lessons learnt. I am in the very early stages of my own tiny flower farm and your blog has not only inspired me to keep at it even when things are hard, wet and lonely but you have shared your expertise and skills in such a way that I feel I have an old friend and mentor cheering me on and showing me how. Thank you.

  16. Alexandra Ward on

    So enjoying your Blog series Floret! It is such a relief to have simple, clear instructions to follow. Many thanks


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