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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. 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 disease-causing 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 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 snugly 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 a healthy start.

Be sure to check the ingredients and avoid any products 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, such as the top of the refrigerator or radiator, you can take advantage of this heat to encourage seeds to sprout more quickly.

But if you really get hooked on flower growing, you’ll outgrow these spaces fast. For more consistent results, invest in a heat mat specially designed for seed starting.

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 by 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 such as 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 setup 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 I hope 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:

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

Lastly, if you find this information helpful, I would love it if you would share it with your friends.

 

52 Comments

  1. Shawna on

    I just bought a Earthway seeder. What seed plate works best for sweetpeas? What plat do you use for zinnia? Any recommendation will be greatly appreciated. Thank you

    Reply
  2. Heather on

    I’m not Floret but have grown seedlings for many years. Your seedlings need light – a sunny south window will never do the trick as plants get way too leggy (called etiliation). Grow lights are the only way to go. Regular fluorescent shop lights on chains, kept a few inches above seedlings are cheap and work well. (You have to keep moving the lights upwards, hence the chains.) I think the lighting is covered in this post. Give it another read.

    Reply
  3. Tori on

    I have another crisis. I started my snapdragons (I’m a newbie) and following the instructions on the seed starting posts, I put them on warmer mats. Nothing has happened. I then read on another website that snaps like it cold and they suggested NOT using heating mats. I’ve moved them off the mats but my question is are the seeds ruined or should I put them outside (night time temps in the 40s) and see what happens? Thanks much!!

    Reply
  4. Sandra blanks on

    I started my cosmos, poppies, sunflowers, foxglove seeds 10 days ago. They are coming up great, but they are extremely leggy. Should I pinch them back, or what can I do to encourage them to not be so leggy? Thank you

    Reply
  5. Paula on

    Suellen, temperature is really important and for our farm, I use germinating temperatures from 50-90+ depending on the seed variety. Fans and good air circulation is a big help. While good light is super important, direct sun can be just too hot in desert climates so creating filtered light or even some shade can help. Humidifying can also help if the air is super dry. In Montana, where we have a very simple system, but lots of growing houses, we open and close doors, raise the plastic on the sides of the greenhouses, use fans and shade to control temperature.

    Reply
  6. Clarice on

    What kind of lights do you use in the shop lights that you recommend?

    Reply
  7. Andy Smith (female) on

    I recently purchased your first book and also a pack of your zinia seeds. I live in Yuma, Arizona, zone 10. Vert hot summers. So, I looked in your book and on the package of the zinia seeds and I could not find the depth to sow the seeds. I have planted a large variety of seeds over the years, but haven’t kept track of depth of all varieties. I guess I could “google”, but was hoping to get an answer from the expert. Thanks in advance.
    Andy

    Reply
  8. Laura on

    I’m wondering, at what point in the seedlings early life do you begin feeding them?

    Reply
  9. Suellen Kolbo on

    I have a greenhouse and a seedling heating mat. My question: very early very warm spring = 107 degrees inside the greenhouse this morning. Obviously I’m not using the heat mat on the sweet peas. Any advice or experience (I know, Upper Washington is a *little* different climate from Far Northern California) but do you, Erin, or anybody else know how to start seeds when the goal is 90 degrees and the room temp reality is well over 100?

    Reply
  10. ELLIE KIRCHNER on

    Has anyone tried using the LED shop lights (Costco)? Wondering if plants like this light spectrum.

    Reply
  11. Tori Carver on

    I have read every article you have posted on seed starting and they are so helpful. I still have several questions though. With Sweet Peas do I still need a heating mat? It seems like everything I’ve read says they like it chilly. Secondly, lights before they sprout or only after? Third… I’m having major conflicting info on bulbs for shop lights. I think I’ve narrowed it down to T5 or T8 are better but I’m still confused on the warm vs. cool vs. daylight bulbs. I’ve invested a lot of money on seeds and getting things started indoors and I’m in full on panic mode. 😂

    Reply
  12. vivian gerard on

    i planted sweetpeas outdoors they came up and now gone i think it froze a couple times will they come back or do i need to replant thanks for all the imformation you give im in zone 7 abbotsford bc do i plant in house or outside

    Reply
  13. Katie R. on

    I was happy to see this email come out today as we sowed our first attempt at a cutting garden’s seeds last night! I said well if the Queen of flowers sent this out today, we’re on track! Only down side is I did seed zinnias and bells of Ireland! I may just buy some more seeds before the last frost for a safety net.

    Reply
  14. Emma on

    Hi there,
    This is great advice. Thankyou.
    Please could you tell me at what stage you remove the clear lid, and also, do you just leave one seedling per cell and pull out the others?
    Thankyou

    Reply
  15. Elma Riedstra on

    I am so excited to start seeds which I purchased from you!! I will start in the house and hopefully we find a small green house this year. I am soooo ready for spring!!

    Reply
  16. B.Scafone on

    I grow seedlings inside so top watering can be too messy. I bottom water everything. To make this easier, leave a cell or two empty in the tray and water directly into it. Then I tip the tray to make sure the water is distributed evenly. If things get dry on top, I spray them with a spray bottle.
    This year I am also going to color code the fronts of the seed packets for seed treatments (i.e. a red dot means it needs light to germinate, a blue dot means it needs an individual pot, etc.). This way I’m not reading and rereading the tiny print on the packets.

    Reply
  17. JOANNE Le Dressay on

    Good morning Erin, my tip for everyone is to fill your Bottom tray ahead with water. I prefill ahead time ensure my trays do not vs leak. I had the misfortune loosing plants for several years as in my green house I would have a tray leak onto a tray below. After a while I noticed I had a dried out tray and ariettes tray below of seedlings. Finally as I started checking I had an identical small hole dripping water in every tray. As well after a few years of use some trays would have sneaky drips. As well I toss the discarded trays in a pile and then to recycle. That way I don’t recheck a damaged tray and loose the minute it takes to fill and discard. Although I have bought my trays from a professional growing store I find it worth it to order them from Johnnys as I have mini flower farms in both Washington state and in Vancouver Canada.

    Reply
  18. Pam on

    Hello ! Appreciating all of the helpful articles !
    This is my first year and I thought it would be super helpful to add the succession recommendations to the shop pages?
    This morning I also thought it would be super neat if you had a forum for growers to share experience
    Thank you for being such a powerful pioneer

    Reply
  19. Marta Matson on

    You can sprout your sweet pea seeds in Tupperware boxes – a layer of damp paper towels at the bottom of the container, lay the seeds on that, and cover with another layer of paper towel. Use a sprayer to dampen top layer, seal the box, and leave somewhere warm. It only takes a few days to sprout, and then I can plant them in root trainers, knowing that every cell has a growing plant in it. Also deters the mice in the greenhouse who seem to lose interest in digging up the seeds once they have sprouted. I found this advice on Instagram a few years ago (can’t remember who, sorry!) and have done it ever since.

    Reply
  20. Ingrid Ann Perry on

    I am so pleased you are directing our fellow flower growers to Johnny’s Selected Seeds here in Maine. I have bought their seeds since they first began. Thank you for your generosity is sharing your beautiful flowers and growing advice. Happy growing from Rockport, Maine!

    Reply
  21. Milana on

    Hi, do you have tutorial on how to grow edible flowers from seeds ?
    Thank you

    Reply
  22. Christopher on

    Hi there! So happy to begin my flower seeding adventure with my Floret seeds. Question: how many seeds per little pot do I drop into the soil?

    Reply
  23. 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
  24. 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
  25. 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
  26. 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
  27. 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
  28. Mary on

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

    Reply
  29. 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
  30. mimi strouse on

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

    Reply
  31. 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
  32. 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
  33. 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
  34. 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
  35. 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.

  36. 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
  37. Megan on

    Thanks again your posts have been super helpful!

    Reply
  38. Debbie on

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

    Reply
  39. 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
  40. sophie on

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

    Reply
  41. 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.

  42. Gioconda Padovan on

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

    Reply
  43. 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
  44. 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
  45. 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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