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Home Blog Seed Starting Basics
February 20th 2019

Seed Starting Basics

Written by
Floret

flower seedlings pushing through soilStarting 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 it 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 (such as cosmos, sunflowers, and zinnias) 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 by the time you can plant them out into the garden.

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 soon you can start them indoors.

Flower seedlings in greenhouseWhile you can start seeds in just about anything that holds soil and drains water (think egg cartons, Dixie cups, etc) I recommend getting yourself set up right. 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.

If you’re reusing old pots or trays, be sure to wash them thoroughly with a 10-percent bleach-water solution to kill any lingering diseases or pathogens.

Floret Seed Starting Trays-1Cell trays 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).

bottom watering seed traysIn addition to cell trays and pots, you also need flat 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 cell tray, a flat drainage tray, and plastic dome lid.

acrylic dome lids for seed starting traysI highly recommend getting a few clear acrylic lids that will fit snuggly over your seed trays and flats of pots. These maintain the humidity that will speed up germination and growth significantly.

filling seed trays with potting mixIt’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.

flower cuttings on heat mats with domesFor 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.

flowers growing under lightsOf 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. 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.

flower seedlings growing in greenhouseI 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 setting out established plants that have a better chance of contending with the weeds crowding or shading them out.

direct seeding with earthway seederBut 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.

flower seedlings growing in seed traysWith the right set up and a few essential supplies, your garden possibilities are limitless.

Once you get hooked on seed starting, you’ll be a convert for life!

One of my goals here on the site is to provide you with the best information, to help you grow great flowers and hopefully dispel the notion that success is only possible for professionals. You can do it!

In addition to the tips included in this post, I want to make sure you know about the following resources:

– My recent book, Floret Farm’s Cut Flower Garden: Grow, Harvest & Arrange Stunning Seasonal Blooms has detailed seed starting tips and tricks.

-In the Floret Resources section, I have created a little Starting Seeds 101 tutorial and photo essay (be sure to click the arrows to advance the images) with some of the basics.

-Here on the blog, you’ll find a post that shares more tips plus detailed do’s and don’ts of seed starting.

-In the Floret Shop, I’ve included sowing and growing instructions for dozens of my favorite flowers.

Please share any tips or tricks that you use when it comes to seed starting in the comments below. Note: If your comment doesn’t show up right away, sit tight, we have a spam filter that requires we approve comments before they are published.

30 Comments

  1. Michelle on

    I have sweet peas that are about 10 inches tall! Do i need to do anything with them, other than wait to plant outdoors?

    Reply
  2. Danielle on

    Hey there! Question on my Sweet Pea seeds. I planted a small tray 2 weeks ago. They have been under a plastic dome on a heat mat. No movement yet. Each cell has 2 seeds. Should I wait longer, start over, do something different?

    Reply
  3. Jana on

    Thank you Floret: I’ve added seed trays and heat pads this year! I’ve been selling flowers at our local Farmers Market for two summers and am adding lots of new seeds this year so it’s exciting.

    Reply
  4. Olivia on

    Thanks for the tips! I’m not quite at the seed tray stage yet, so my sweet peas are happily growing in empty yoghurt pots for now as I’m on a budget! They’ve started shooting and it’s so exciting to see them grow a little bit more everyday :-) I’m hoping they’ll be ready for a wedding in June.

    Olivia

    Reply
  5. Jenny Kosinski on

    Hi Floret & Team!
    Thank you for sharing! You are a wonderful resource. What are your thoughts on Pre-soaking seeds prior to sowing? Can you provide any guidance on that?

    Reply
  6. Mary on

    Do you ever use the Earthway seeder to direct seed sunflowers? If so, what seed plate do you use? Thanks!

    Reply
  7. Sarah Bailey on

    I have read differing advice regarding what sort of bulb to use in the shop lights. One reliable source said to buy a warm and a cool for full sunlight spectrum – I have not found this. I did find what is called “agro light bulbs” from a lighting co online. Would this work? Any tips or sources would be greatly appreciated! Thank you!

    Reply
  8. mimi strouse on

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

    Reply
  9. 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!
    Carolyn

    Reply
  10. 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 :)

    Reply
  11. 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?

    Reply
  12. 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.

    Reply
  13. 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!

    Reply
    • 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.

  14. 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!

    Reply
  15. Megan on

    Thanks again your posts have been super helpful!

    Reply
  16. Debbie on

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

    Reply
  17. 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!:)

    Reply
  18. sophie on

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

    Reply
  19. 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!

    Reply
    • 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.

  20. Gioconda Padovan on

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

    Reply
  21. 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!

    Reply
  22. 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.

    Reply
  23. Alexandra Ward on

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

    Reply

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