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how to start seeds: 18 confidence-building tips

how to start seed indoorsWONDER HOW TO start seed indoors, or which seed to sow directly in the garden, and how? Becoming a confident seed starter unlocks a garden of possibilities; you can try your hand at anything offered in any catalog, no longer limited by the local garden center’s palette. As daunting as it may seem, remember this: In nature, seeds sow themselves successfully–usually emerging when the soil’s moist and starting to warm up, then enjoying fresh air and plenty of sunshine, with hopefully just enough rain.

Following the links in my 18 simple seed-starting tips for more detail, and examples of the gear I use. I also have an FAQ page of seed-related questions and answers, if something’s not covered here, plus how-to links for some popular vegetables at the bottom of this page.

Details of spacing and depth are not included, since they vary by crop. Your seed packet (or better yet, the company’s website it came from) will offer specifics. My basic guidance: Except with large seeds like peas and beans and squash, which I direct sow outdoors and deeper, I make a shallow depression or furrow, press the seed gently in, and lightly cover it with more medium.

Cheat sheet: If you’re only going to do one thing on the list to improve your seed-starting results, focus on the light.

Too little light is the most common reason for seed-sowing failure by home gardeners, making tips Number 11 and 12 probably the key advice of all.

18 tips for starting seeds indoors and out

1. Don’t be in a rush. Get your timing right for each crop (this free, printable Seed Starting Calculator is one way to pinpoint dates).

2. Don’t be cheap; buy fresh seed if there’s any doubt. Check on average viability (in years) of a given type of leftover seed, but also ask yourself how well you really cared for it. Seed is alive (but not if you left it in the hot, humid garage all summer).

3. Don’t use just any old potting soil; some brands may be too coarse, especially for smaller seeds. A fresh bag of sterile medium labeled “germination mix” or “seed-starting mix” is a safer bet.

4. Cleanliness counts. When re-using flats, trays, cells, and pots, wash with a dilute bleach solution (1:10 bleach:water) or at least hot, soapy water, if you wish to skip the bleach.

5. Do pre-moisten the mix before putting in flats or cells, so it’s barely moist and no longer powdery dust. As I said: barely moist, just to take the edge off; not sodden! Trick: If working indoors, I just run water from the kitchen-sink sprayer into the plastic soil bag ahead of time; massage and turn the bag to distribute; then repeat a few times.

6. Do use bottom heat, from a germinating mat, and a dome lid or plastic wrap to create a “germination chamber” of around 70F…

7. …but don’t leave the mat plugged in, or the lid on, once the plants have emerged. Seedlings generally don’t like it as warm, or moist, as seeds trying to sprout do.

8. Don’t let seeds dry out before they germinate (a recipe for death!)…

9. …but don’t overwater once they do. Water requirements drop dramatically as soon as they’re up and growing, when letting the soil go slightly dry between waterings is generally the best practice.

10. Do invest in a watering device that’s gentle enough for seeds and seedlings. (The mister I use cost a whopping $20; I also use a turkey baster and cream pitcher, among other improvised tools. If watering with a garden hose, a breaker nozzle like the Dramm Lemonhead is recommended.)

11. Don’t skimp on light once seedlings have emerged, or anytime thereafter. (Don’t be surprised if they get spindly if you do.) To be perfectly clear: No windowsill growing!

12. Do take advantage of fair days outside to make up for the limitations of artificial light; I carry my seedlings outside by day. Even closely spaced, super-efficient T5 high output bulbs might put out just one-fourth to one-fifth the light of a clear day in May outdoors, where the occasional breeze also helps toughen plants up. Between indoor and outdoor light sources, I like my plants to have 12 hours or even 14 daily. (The T5 lights I use. Newer LEDs to retrofit into my T5 hoods are coming down in price and up in efficiency; I’m keeping an eye out.)

13. Do direct-sow crops suited to it…but not unless you are committed to keeping the seedbed free from weeds that can outcompete tiny emerging seedlings. (One expert kale grower explains why she transplants, despite how easy kale is to sow directly outside.)

14. Don’t rush to transplant, especially with warm-season crops like tomatoes, peppers, eggplants. Nothing is gained by making them shiver before the weather really settles, and much can be lost in the wildest spring weather.

15. Don’t transplant seedlings into the open garden that haven’t been hardened off gradually, with a few hours a day outdoors over a week or so before to allow for acclimation.

16. Do sow extra, and do “cull the herd” by discarding any weak or “off-type” seedlings at any stage of the process. More is not better if they are runts. One expert seed-farmer friend even starts her careful selection process even before sowing, discarding the smallest seeds from each packet. Give yourself the best chance for success with a bit of ruthlessness.

17. Do plan for succession sowings of many crops, sowing only a short row every couple of weeks and avoiding 40 servings of lettuce or 10 pounds of green beans in a single day’s harvest. Take advantage of both cool ends of the season to repeat sowing certain crops, such as peas. And in the hottest months, it may be easier to start more seedlings in cellpacks or flats in a protected spot near the house to transplant into garden spaces that become empty, than to get direct-sown seed to germinate in baking soil.

18. Don’t blame yourself for every failure. Old seed or poorly stored seed or just crappy seed can outsmart your best efforts. Sometimes seed was viable (had the ability to germinate) but lacked sufficient vigor (the ability to thrive). Learn the difference. And then you have the weather to invoke as the guilty party. This is gardening, remember? We can always blame the weather, and then try again.

growing specific vegetables from seed

my favorite seed-starting gear

HYDROFARM T5 HOODS: Hoods with T5 high-output tubes range from 2 to 4 feet and with 2 to 8 bulbs. Must be fitted with hardware to raise and lower from a stand or shelf you provide.
GROWEASE SELF-WATERING SEED STARTER: A felt-like capillary mat between cells and lower water reservoir wicks moisture up to seedlings. (Sizes up to 24 cells/flat.)
SOLO 2-LITER ONE-HAND PRESSURE SPRAYER: I mostly bottom-water seedlings, but during germination and when seedlings are tiny I mist them with this handy sprayer.
10-GALLON TRUG FOR SOIL MIXING: A 10-gallon trug or larger plastic bin is a great vessel for slightly moistening germinating mix before filling flats.
SURGE PROTECTOR TIMER: No more one timer per growlight! With 8 outlets, program multiple lights to turn on and off for the required hours per day.
HYDROFARM JUMP START T5 SYSTEM: One 4-foot T5 high output bulb on an adjustable super-lightweight frame= can accommodate two flats. (2-foot size also.)
JOHNNY'S 512 MIX: I've ordered this for germinating purposes for years. Has organic nutrients (fishmeal, not chemicals) added. Works for soil-blocking, too.
SEEDLING GERMINATING MAT: I use single tray-sized mats (approx. 8.5x18.5"), but mats also come in double-wide or double-long (for 2 trays), and up to 5-foot-long pro versions.
LADBROOKE SOIL BLOCKERS: Many experts swear by soil blocking (as opposed to sowing in cells or open flats without blocks). The tools for making blocks, in various sizes. Note: The mix you use must be rated for blocking.
NITRILE-COATED GARDEN GLOVES: I like mine black, and by Atlas or Bellingham. I eventually poke through the right hand middle finger from digging with my hands...but other than that they'd last a long time.
PULLEY HARDWARE FOR GROWLIGHT: To hang and adjust your hood, you'll need to rig S-hooks and chain, or even easier pulley with store-bought hardware. (Shown: Vivosun brand.)

(Disclosure: Products purchased from Amazon affiliate links yield a small commission.)

    1. margaret says:

      Welcome, Sherry, and always glad to coax anyone into seed-starting. :) (I find it so exciting, every seed that sprouts, even after more than 25 years of doing it.)

  1. ljfq says:

    May I offer additional tips that may be useful? Try to water from underneath, and try to water in the morning, not in the evening. Damping off fungus is often what discourages new seed-starters. The seeds germinate, the plants look great, then they begin to get pinched stems at soil level and keel over. The most useful tip I ever learned was from Jim Crockett, the original Victory Garden guy. He suggests sprinkling a little bit of milled sphagnum moss on the soil surface after you sow your seeds. It somehow inhibits the fungus from advancing across the surface of the soil. I put some plain sphagnum in my blender to make a bit, and it lasts for years.

  2. Carolyn says:

    Margaret,
    You use to suggest using self watering systems for seed starting. Do you not use them anymore ? If not , why?

    1. margaret says:

      I do use them for some seeds, yes, with the provided felt capillary mats beneath, like the APS system, for instance. For the purpose of this basic post, I figured most people probably had generic flats or cellpacks or small pots, so I didn’t digress and just mentioned watering from above. But it’s a good point — making the investment into the other systems can mean less work/worry with watering.

  3. Marta says:

    On an internship at Chelsea Physic Garden in 2005, I worked under Helen, the seed propagator, and washed *a lot* of pots. They had eliminated bleach in the interest of the environment, but used an antibacterial dish soap. Now with all of the issues emerging on Triclosan etc., I just add a little vinegar to any plant-based, biodegradable dish soap.

    1. margaret says:

      Good suggestion, Marta. Thanks you–and lucky you to have interned there. I have visited several times and always enjoyed it so.

  4. Julie says:

    Thanks for all the great tips and the seed calculator. I feel silly that I left the lid on my starter trays last year way to long – I thought it was to keep them warm. I couldn’t figure out why everything was going so terribly wrong. And of course it created all this extra moisture….etc…Cheers to 2015! I am going to get it right this year.

  5. Beverly, zone 6, eastern PA says:

    Regarding #8…
    If a gardener is making a seed tape using flour/water glue and moistens the seed to stick it to the long piece of toilet paper “tape”, then it dries out…. does this render the seed useless ?

    Is there a special trick to adhering seeds to a seed tape that avoids this?

    I just made a carrot seed tape and your tips got me wondering.

  6. Matt says:

    Great tips and thanks for the link to seed calculator. Wanted to ask, when you mentioned you use the self watering system with the mats beneath on some of your seeds. Why only some? Do you find it works better or only with certain seeds, if so which ones?

  7. Lynn says:

    After my seedlings have grown their second set of leaves and are growing well, do I transplant them from their single cell seedling pot to a larger pot until they can be planted into the garden?

  8. Katherine says:

    Hi Margaret!

    I love your website and so does my mom! I’m new at gardening and I have a question. I am growing seeds indoors and a few have sprouted but the majority have still not come through yet. Should I take the plastic cover off so the few seedlings that have sprouted can thrive? If I do so, then the other seedlings won’t germinate? I’m a little confused!

    1. margaret says:

      That’s always tricky, Katherine, and frankly I wait till a good solid percentage, at least, are up. But not like 2 extra weeks, or a month. :) It’s natural for some in a sowing to come up a little later — so don’t worry about leaving them in the chamber awhile longer.

  9. rebecca a garland says:

    My poppies have failed to show their lovely heads this year..I live in East TX..have had numerous freezes..let some of seed pods drop on their own n harvested some also..then put some around in other parts of my flower beds ..only place I see them are in cracks on patio..the harvested seeds were kept in freezer

    1. margaret says:

      Hi, Rebecca. We have had a very unusual winter here in the opposite direction (generally warmer) and I wonder what it will do to the bloom cycle of familiar things. I know what you mean about the patio cracks — seems like everything wants to germinate there!

    2. David Marshall says:

      Hi Margaret,
      I grow a lot of seedlings, and have designed my own grow light systems at a fraction of the price of commercial units They use 13 or 23 watt 65K daylight compact fluorescent bulbs (CFLs), which cost $3 each at our local dollar store (Dollarama here in Toronto). I screw four plastic ceiling lampholders to a 12 by 24 inch piece of plywood and set it on top of a 24 inch three sided box 14 inches high, to hold two flats. Cost about $60
      A second system accommodates six flats in a three level 24 inch wide resin shelving unit. (30 from Home Depot)using the same light setup Cost about $110

      1. margaret says:

        Great idea! I have a homemade rig, too, but have recently upgraded the light source to T-5s because of the significantly higher light output…but still prefer to carry all my babies outside on fair days for some sunshine.

  10. Good advice here. Wish I’d known to turn off the heating mat as soon as the plant sprouts before I tried this in the classroom. We did unplug and save the plants, but it was touch-and-go for a while. We did find one additional trick. We got a sprouting try with a water tray underneath and a wicking mat. That way the plants only need their water tray filled once a week.

  11. Chris says:

    Hi Margaret! Thanks for these great tips! I have been using soap and bleach to wash my pots and gardening equipment and I like the suggestion from Marta to use vinegar instead of bleach. I will definitely try that next time!

  12. Carolyn Sheaffer says:

    Help! My yard is overrun with chipmunks. They have a sophisticated colony under my yard. Last year they popped up in my raised bed garden, gobbling up my pea and squash and fava seeds to mention a few. I plan to start these types of seeds indoors this year but prefer to direct sew my peas and beans. Any soon how to humanely deal (if possible) with these industrious thieves? I have 2 dogs that play in my yard, also lots of favorable wildlife and I am allergic to cats. Thanks

  13. Thanks for the detailed advice! I’ve been wanting to grow my vegetables from seeds for a long time, but it hasn’t been working out so well, and now I think I probably haven’t been providing them with enough heat. I will definitely try some of your tips, I’m already looking for a good heat mat. Thanks again!

  14. Kathy F. in Westminster says:

    Hello Margaret. It seems I may be a year late with my question. I too, love paste tomatoes and I was wondering which ones are your favorites. I love the San Marzano but it requires quite a bit of pruning. Are you good at keeping up with your tomato pruning? Do you have favorite paste tomato varieties? I only have space for three tomato plants so I’m researching what to plant. Early Girl is not a paste tomato but she is easy to grow. Although I’m in Colorado I’m in zone 5. I’m glad you’re home and safe. Stay well.

    1. margaret says:

      San Marzano is a lovely fruit, yes. I am partial to smaller but very prolific “paste” tomatoes like ‘Juliet,’ which was sold by Johnny’s (not sure who sells it now). There is a newer version (‘Verona’ I think) that Johnny’s does sell, but this year seed is hard to get from them because of coronavirus demand. It’s different but wonderful. Here is the article about it.

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