Starting Seeds Indoors: How and When to Start Seeds

Learn All About Starting Vegetable Seeds Indoors

March 19, 2020
Cabbage Seedlings

Starting seeds properly can make or break your entire growing season! Here’s what you should know about starting seeds, including when to do it, which seeds to start indoors (or outdoors), and how to do it correctly.

Why Start from Seeds?

Rather than start vegetables from seed, many folks opt to just buy young plants from commercial sources. While there’s certainly nothing wrong with that practice (in fact, it can save you from a few headaches later on), there are good reasons to start your own plants, too!

  • Mainly, people start seeds in order to get a jump on the gardening season.
    • In regions with short growing seasons, starting seeds indoors allows you to gain a few precious weeks of growing time, which can really make a difference when frost looms in the fall. 
    • In warmer regions, starting seeds indoors can allow you to get in an extra round of crops (especially cool-weather crops) before the heat of summer stifles growth. 
  • If you want to grow a lot of plants, buying packs of seeds is usually cheaper than buying individual seedlings from the nursery.
  • While some nursery plants are grown really nicely, others are poor quality. When you plant your own seeds, you have control over the way the young plant is raised. This may be especially important if you are an organic gardener.
  • Finally, there isn’t always a great selection of plants at local nurseries. When you plant from seed, you have a much wider choice of varieties, tastes, and textures—and you can experiment with new ones, too!

Which Seeds Should You Start Indoors?

Consult the table below to see which crops are typically started indoors, which are typically started outdoors, and which can be variable. (Note that gardeners in warmer climates will be able to start more crops outdoors than gardeners in colder climates.) 

Keep in mind that there isn’t a hard-and-fast rule about what you can start indoors and outdoors; it varies by your experience, your location, and the plant itself.

It is important to consider how each type of vegetable grows. For example, root vegetables like carrots and beets don’t like having their roots disturbed, so it’s usually safer to just start them outdoors in the ground rather than transplant them later on. Meanwhile, veggies like tomatoes and peppers are very susceptible to the cold temperatures of spring, so it’s best to start them indoors and keep them safe from unpredictable weather. Finally, plants like peas are so fast growing and cold tolerant that it just makes sense to get them right in the ground! 

For seed-starting information customized to your location, check out our free online Planting Calendar.

Start Indoors Start Outdoors Variable
Broccoli Beets Beans
Brussels Sprouts Carrots Celery
Cabbage Corn Kale
Cauliflower Garlic Spinach
Eggplant Okra  
Lettuce Onions  
Peppers Peas  
Pumpkins Parsnips  
Swiss Chard Potatoes  
Tomatoes Radishes  
Watermelons Squash/Zucchini  
  Sweet Potatoes  

Before You Start Seeds

  • Be seed-savvy. Obtain seed catalogs from several companies and compare their offering and prices. Some of the regional companies may carry varieties better suited to your area.
  • Make a list of what you’d like to grow. A good rule-of-thumb is to imagine your garden one-quarter the size that it really is. This allows for good spacing practices! See Vegetable Gardening for Beginners for popular beginner vegetables.
  • Prepare for some losses. Though it’s good not to plant too much for your garden space, it’s also good to assume that some of your seeds won’t germinate, or that they will inexplicably die off later. Plant a few extra, just in case.
  • Consider a grow light if you start in late winter. Most veggies need between 6 to 8 hours of direct sun (minimum), so it’s important to have a grow light if you are sowing your vegetable seeds indoors in late winter. A grow light will also keep your seedlings from getting too leggy. Learn more about using grow lights.
  • Team up with a neighbor and share seeds if you have leftovers!
  • Use clean containers. Most seed catalogs offer seedling flats, peat pots, and other growing containers, but egg cartons make good containers for the earliest stages of seed starting, too. Be sure to poke holes in the sides near the bottom of the containers you use in order to allow excess water to drain. Keep in mind that you might need to transplant your seedlings into larger containers at some point before moving them into the garden.
  • Label your containers now! There’s nothing more frustrating than forgetting what you planted, especially when you are testing out different varieties of the same plant.

Seedlings. Photo by Sergii Kononenko/Shutterstock
Photo by Sergii Kononenko/Shutterstock

When to Start Seeds Indoors

  • We’ll get right to the answer: Just check our Planting Calendar, which lists the ideal dates to start your vegetables indoors. We’ve created a customized tool that’s based on your zip code and local frost dates!
  • As a general rule, most annual vegetables should be sown indoors about six weeks before the last frost in your area. See local frost dates.
  • Don’t start your seeds too early, especially tomatoes. Wait until six weeks before your last frost date to start tomato seeds.

How to Start Seeds

  1. Fill clean containers with a moistened potting mix made for seedlings. If you don’t use a pre-made seed-starting mix, you can make your own by combining peat and equal parts vermiculite and perlite (see the video on creating your own seed-starting mix further down on this page). This combination holds enough water, but allows oxygen to flow and the delicate roots to easily penetrate the soil. Don’t use regular potting soil, as it may not be fine enough for seeds to root through properly. Pre-formed seed starters (such as Jiffy pellets) work well, too.
  2. Plant your seeds at the depth listed on the seed packet. Most seeds can simply be gently pressed into the mixture; you can use the eraser end of a pencil to do so. When choosing which seeds to plant, choose the largest seeds in the packet for the best chance at germination.
  3. Cover containers loosely with plastic or an otherwise clear, waterproof covering to keep them from drying out too quickly. Poke a few holes in the plastic with a toothpick for ventilation; mold growth can occur if containers are not allowed to “breath.”
  4. Water newly started seeds carefully. A pitcher may let the water out too forcefully, dislodging the seeds or young seedlings’ fragile roots. A mist sprayer is gentle but can take a long time. We recommend using a meat-basting syringe (aka “turkey baster”), which will dispense the water effectively without causing too much soil disruption.
  5. When seedlings start to appear, remove the plastic covering and move containers to a bright window or under grow lights. 
  6. When the seedlings get their second pair of leaves, prepare individual pots filled with a potting mix with plenty of compost. Move the seedlings carefully to the new pots and water well. Keep seedlings out of direct sun for a few days, until they’ve had a chance to establish themselves in their new pots.
  7. As seedlings continue to grow, be sure to water them as needed; while young, they are very susceptible to drying out.

Tips for Success:

  • You may have to soak, scratch, or chill seeds before planting, as directed on packet.
  • Seeds sprout best at temperatures of 65-75°F (18-24°C).
  • Find a place in the kitchen where there is natural bottom heat—on top of the refrigerator or near the oven are good spots. (Move the tray if the oven is on, as it may become too hot!)
  • If you keep your seedlings next to a window, remember to rotate the containers every so often to keep the seedlings growing evenly. If you’re using a grow light, remember to raise it a few inches above the tallest seedling every couple of days.

Make Your Own Seed-Starting Mix

Seeds should be planted in a potting mix that caters specifically to their delicate roots and sensitivity to moisture. It’s easy enough to buy a pre-made seed-starting mix—or, create your own:

    Moving Seedlings Outside (aka “Hardening Off”)

    Before transplanting seedlings to your garden, you’ll first need to do something called “hardening off.” This will prepare the seedlings for the harsh realities (i.e., climate) of the outside world! 

    1. During their last week indoors, withhold fertilizer and water them less often.
    2. Seven to ten days before transplanting, set the seedlings outdoors in dappled shade that is protected from winds for a few hours each day, gradually increasing their exposure to full sun and windy conditions. This is the hardening-off period.
    3. Keep the soil moist at all times during this period. Dry air and spring breezes can result in rapid transpiration. If possible, transplant on overcast days or in the early morning, when the sun won’t be too harsh.

    Watch our video on hardening off for more info:

    How to Transplant Seedlings

    After the hardening-off period, your seedlings are ready for transplanting. Here are a few tips:

    • Set transplants into loose, well-aerated soil. Such soil should capture and retain moisture, drain well, and allow easy penetration by the seedlings’ roots.
    • Soak the soil around new seedlings immediately after transplanting.
    • Spread a light layer of mulch to reduce soil moisture loss and to control weeds.
    • To ensure the availability of phosphorus in the root zone of new transplants (phosphorus promotes strong root development), mix 2 tablespoons of a 15-30-15 starter fertilizer into a gallon of water (1 tablespoon for vining crops such as melons and cucumbers), and give each seedling a cup of the solution after transplanting. 

    Read more about transplanting seedlings.

    Tomato seedlings

    Learn More About Gardening

    Here’s another “quick and easy” method to plant seeds. Also check out our video on the top tips for starting seeds.

    Also, consult our library of Growing Guides, which provide planting, care, and harvesting information for all the common vegetables, fruit, and herbs.

    Reader Comments

    Leave a Comment

    Seed starts in Western Ontario

    Hello! When should I start my veggie seeds here in this part of Ontario, Canada? If I started now, I'd expect it to be about 7-8 weeks before the last frost.

    Most vegetable and annual

    Most vegetable and annual flower seeds can be started indoors about 6 weeks before the last frost. Check our Planting Dates for Seeds chart. Link is at the top of this page.



    What do I do if my seedlings are flowering but they cannot be moved outdoors for 3-4 weeks.

    Starting cucumber seeds

    At what point can I start germanating my cucumber seeds for my first garden. I live in south east Texas so I have no idea about last frost, so I want to be ahead of game but don't want to start to soon thanks

    cucumber seed starting

    The Editors's picture

    You might be interested in our cucumbers page here:

    On it, it says:

    • Cucumbers are seeded or transplanted outside in the ground no earlier than 2 weeks after last frost date. Cucumbers are extremely susceptible to frost damage; the soil must be at least 65ºF for germination. Do not plant outside too soon!
    • For an early crop, start cucumber seeds indoors about 3 weeks before you transplant them in the ground. They like bottom heat of about 70ºF (21ºC). If you don’t have a heat mat, put the seeds flat on top of the refrigerator or perch a few on top of the water heater.

    To find out your frost date, go to this page and type in your zip code:

    Then, count back 3 weeks from the last expected spring frost date to find the date to sow the seeds indoors. Good luck!


    Perennial Seed starting

    Do you have an Indoor seed starting chart for annual/perennial flowers ?

    School Garden - starting some plants indoors -

    Hello! I am a teacher-librarian in a K-8 school in Bowmanville, Ontario. Our school is starting a habitat area on the school yard with some native plants (eg woodland sunflower, and hopefully a raised bed for veggies. I want to transform part of my large library space into an indoor growing space so we can start seedlings in the spring. What will I need in the space to start seeds indoors. It is in a corner with about 10 feet of two storey windows that face west and one window about 3 feet wide that faces north. Do I need special lighting?
    Also, is it possible for me to grow anything indoors through the winter? Herbs, maybe?
    I don't have a lot of background in gardening but lots of enthusiasm and a school full of students who want to learn to be responsible, sustainable citizens in suburbia.
    Thanks for your help. I have appreciated reading the comments you left for other folks.

    How early is too early


    I am in Ottawa, Ont. Canada.. Zone 5a.

    I am curious of early is too early to start plants indoors. I started some pepper plants and tomato plants beginning of Dec with hopes to grow mature plants and transfer them outdoors in april/may.

    I would still keep them in pots while hardening them off for 2 weeks before transplant.

    I will also start new seedlings in Feb to be safe but wanted to know if my December plants would help me get a bigger headstart or bigger headache than worth.

    and yes.. i have bigger pots and room in the house.

    starting seeds early

    The Editors's picture

    If you start seeds too early, it can make it difficult for the plant to survive transplant shock when transferred outdoors, even after they were hardened off. Also, keep track of the days to maturity. For example, if you have a determinate tomato plant that matures in 80 days, and it was growing indoors since mid-December, then it might produce fruit (if pollinated) before it gets transplanted out in April/May. It would probably be too hard on the plant once it is in fruit, but you can certainly try it: at that point, it might be best to just keep growing it indoors (especially if you have a greenhouse). Indeterminate tomato varieties might be better than determinate, as they might continue to flower and set fruit after recovering from transplant shock.

    Tomato seeds from last summer

    Tomato seeds from last summer reseeded in my vegetable garden and 4-5 of them look very healthy. Do you think they'll produce fruit, or since they were in the ground with very cold temps (in MD) over winter, should I throw them out?
    Thanks for your feedback.

    Hi Dana, Don't throw them

    Hi Dana,
    Don't throw them out. If you have room in your garden let them grow and hopefully you'll have a nice harvest later this summer. If these plants are from heirloom varieties you should get some tasty tomatoes.

    I started some flower and

    I started some flower and vegetable starts indoors and one morning woke to them all eaten. What could have done this? I have looked for worms, but none around. No bugs of any kind to be seen.

    Hi, Bradford, our condolenses

    Hi, Bradford, our condolenses for your seeds. It sounds like dampening off. Even in the best soil, this rot can happen: the seedsling just disappear. Some sources recommend having a blower on them (a fan is just too powerful). Heat lights might help, as they promote drying. At this point, consider it a valiant attempt and put it behind you—and go out and get some seedlings and get growing! You can still have a fabulous harvest.

    hello This year if my first

    hello This year if my first year gardening and me and my father decided to grow multiple types of flowers from seeds and use paper pots and potting soil, we lightly water them every day and we make sure not to over water them, we occasionally taken them outside on nice days to get some sunlight and oxygen, we use stardarnd light bulbs and keep them next to a window when they are inside. The flowers have sprouted into stems and they looked great for a while until the steams either started to die, slouch, or just not bloom into flowers? my dad told me he heard that this could be "stemming" where they grow a little and die?
    is there anything I can do so save these flowers? please help
    thank you!!

    One of my indoor seeds

    One of my indoor seeds recently sprouted but 95% of the others have not Yet. It has only been about 3 days since planting. Should I remove the plastic cover and move them into the sun or wait until more have sprouted?

    Do no remove the covers until

    Do no remove the covers until the seeds have sprouted. There is more advice above.

    I.started my seed indoors

    I.started my seed indoors yesterday march 24 was that too late to start the seeds?

    Hi Stacey, It depends on

    Hi Stacey, It depends on which vegetable and where you live. Here is a personalized planting calendar that will give you dates for starting seeds indoors and outdoors for your location, based on your frost dates:
    Hope this helps!

    Hi, Stacey, It's not possible

    Hi, Stacey,
    It's not possible to know the answer to that question without knowing, for starters, where you are. In starting seeds, your goal is to have them ready to plant safely after the last frost in your area. Anyone can only estimate this event, based on historical weather patterns. To find the average date of your last frost, see here:
    For the frost date in your area, put in your zip code, and when that date approaches, be aware of local current and expected weather conditions. (The dates are averages, not absolutes.)
    For more advice on how to make sure your seedlings succeed, see the advice above.
    Best wishes for a bountiful harvest—

    Help! I started my seedlings

    I started my seedlings indoors about 4 weeks ago. There was not enough light and now they are about 3 inches tall and leggy. Should I start over or if I correct the lighting will the seedlings fill out?

    Hi Cindy, Some seedlings

    Hi Cindy,
    Some seedlings start out by growing tall before getting more leaves. Move the seedlings to a spot with more light. You can also start some new seedlings as a backup. Good luck!

    I have covered my ground with

    I have covered my ground with plastic do you keep plastic down for the cucumber area

    You can keep the the plastic

    The Editors's picture

    You can keep the the plastic on the ground and cut holes to plant the cucumbers.

    I need help.. First time

    I need help.. First time growing anything ever.. I started tomatoes indoors under t5 high output lights.. They were doing great.. Now all a sudden the leaves r turning black on the edges and in the middle.. Starts out looking like someone put clear coat on parts of the leaves then it turns gold color then turns black brown and gets crispy.. Anyone have any ideas for me I'd be very grateful

    It sounds as if you may have

    It sounds as if you may have a tomato disease called early blight which is caused by a fungus. To avoid this, avoid overhead watering and only water at the base. Make sure plants are spaced farther apart to improve air circulation. If the infestation is heavy, sulfur dust may help protect new leaves from infection. Ask your garden center.

    I started seeds indoors and

    I started seeds indoors and they were doing good. I took them outside and I forgot to bring them in one night and it poured the rain and they got over watered and died. I want to start the seeds over by planting new ones. I was wondering if I could just let the soil dry out and take the plants that died out or if I would have to start over with new soil? I read about plants damping off and it has me worried that that happened because they turned yellow and died. But can I reuse my soil or not?

    Most plants won't die because

    Most plants won't die because of one night of rain.  If the soil is stays wet, however, they could certainly yellow and die. We're not clear that they have a disease.
    If you can get the soil to dry out, you need to bulk it up by mixing in plenty of organic matter; the rain washes away nutrients so you need to add those nutrients back to the ground.
    If poor drainage and waterlogging are a consistent problem, you may need to rethink your planting site, the type of plants that you grow, how to add drainage, and/or a raised bed option.

    I have 2 questions...I want

    I have 2 questions...I want to plant all of my vegetables, flowers and herbs by the moon phase and sign. #1 When starting seeds indoors, would go by the phase/sign favorable for that particular plant or is that only for sowing directly into the ground? #2 When transplanting my seedlings into the ground (I know favorable signs are Cancer, Scorpio and Pisces), do I follow the moon phase favorable for that plant as well or is that only for seeds? Thank you!

    Hi Crystal, It's great to

    Hi Crystal, It's great to hear from you!  Gardening by the Moon applies to both seeds and transplants.
    The dates are related to whether the plant bears its crops below or above the soil.
    We just added our Gardening by the Moon calendar to make planting dates easier! See below page--and then click on your region:
    All the best! The OFA staff.