Starting Seeds Indoors: How and When to Start Seeds

Learn All About Starting Vegetable Seeds Indoors This Winter

February 14, 2020
Cabbage Seedlings

Starting seeds properly can make or break your entire growing season! Here are some tips that include when to start seeds, which seeds to start indoors, and how to do it correctly.

Why Start Seeds Indoors?

  • Mainly, people start seeds indoors 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 baby 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.) 

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.

Tomato seedlings

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. 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.

Things to Keep in Mind:

  • You may have to soak, scratch, or chill seeds before planting, as directed on packet.
  • Seeds sprout best at temperatures of 65 to 75°F (18 to 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. 

    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

    You could transplant the

    You could transplant the seedlings into bigger containers that can be put outdoors during warmer days and moved back indoors at night. The only problem may be space (the runner beans grow really tall and need a trellis).

    Thank you for your response.

    Thank you for your response. I have already moved them into bigger pots and have staked them with bamboo, I guess I just have to hope that they survive until I can plant them.

    I started some tomato plants

    I started some tomato plants indoors and have some seedlings. Unfortunately they are yellow. What did I do wrong? Is there anything I can do to save them or the pots that haven't germinated yet? Any help would be appreciated.

    It could be related to

    It could be related to over-watering, but it could also be a disease called Fusarium Wilt which affects seedlings; the symptoms are yellowing and wilting lower leaves.  Take a sample to your local garden nursery or cooperative extension as it is hard to diagnose online.
    The most practical way to control Fusarium Wilt is to plant disease-resistant tomato varieties. Ask you local nursery.
    Spraying with a copper-based fungicide such as Kocide or Fungus Fighter may help in some cases but usually the plant will need to be pulled. You really want to avoid replanting tomatoes in that diseased soil for at least two years, some say four years. Crop rotation is always essential.

    Thank you for the advice. I

    Thank you for the advice. I stopped watering and they're looking ok, but now I'm dealing with moldy peat pots. I'm learning as I go!

    I live in WNC and would like

    I live in WNC and would like to start my tomato plants today, in peat pots. I have many different kinds of heirloom tomato seed. The signs are in the reigns today but the full moon is waning. What to do? My mom always planted by the signs.

    We recommend to plant and

    The Editors's picture

    We recommend to plant and transplant when the Moon is in a fruitful sign (Cancer, Scorpio or Pisces). It is also suggested that you plant veggies that bear above ground crops in the light of the Moon (from the day the Moon is new to the day it is full). Feb. 20-21 are Scorpio if you want to follow the signs. If you want to wait for a waxing Moon it will be new on March 1.

    Thank you for your response!

    Thank you for your response! I had already planted 7 peat pots with tomato seeds. I will definitely follow your advice and come next light moon, I will plant more. Thank you again.

    Hello! I am a new gardener.

    Hello! I am a new gardener. I've been composting for about 18 months now and I've been doing a lot of research at my local library. Needless to say, I was so excited to actually begin planting my asparagus seeds indoors last week. I know asparagus takes at least one season to be harvestable, but it's been a week and I haven't had any germination. I used a 60/40 Miracle Gro potting mix (I'll use seedling mix next year)/compost mixture. I put a "hot house"--a shallow under-the-bed storage unit--over my seedlings only to grow mold! I sprinkled some cinnamon on my seedlings and replaced the "hot house" today. So, all in all, I haven't had any germination. The plants are being grown in my basement. I don't the exact temperature of my basement, but I'm assuming it's about 65 degrees. Should I just be more patient? Does asparagus take a long time to germinate? Sorry this post is long. I just want to start growing food for my new family! Thanks!

    Asparagus is slow to get

    The Editors's picture

    Asparagus is slow to get going from seed. It can take three weeks before the seeds germinate. The seeds should be planted about 1/4-inch deep using a sterile seeding mix for best results.

    How do you get rid of

    How do you get rid of earwigs? Over the past 2 years I tried to grow lettuce but at harvest they were full of drawings.

    You can trap earwigs in

    The Editors's picture

    You can trap earwigs in rolled up newspapers or in old tuna fish cans baited with fish oil or vegetable oil. Place traps near the problem areas and check them each morning. Shake live insects into a pail of soapy water to kill them.
    Converting the backyard to a dry, sunny environment with few hiding places will also help control earwigs. Remove any shelter sites, prune low-growing bushes, avoid growing the earwigs' favored food plants, and destroy moss and algae. Avoid overwatering and don't use thick organic mulches.
    A variety of insecticides available labeled for earwig control. Talk to your garden center. Read the label to determine the proper sites and vegetable restrictions.
    We appreciate your interest in The Old Farmer's Almanac and our web site.

    Last year...WOW...sluGs...! I

    Last year...WOW...sluGs...!
    I live in north western Washington state...what in the world to do about slugs ...I've tried beer in a bowl...salt at every strategic makes a huge problem for gardening...but keeping them off of my sliding glass door and windows would be nice...they even slip in under the threshold from time to time?
    Please advise...
    Thx, Serena

    For slugs use a small, fairly

    The Editors's picture

    For slugs use a small, fairly shallow dish. Put oil (canola, corn, vegetable) in the dish, about 1/2 cup or so. Then pour some soy sauce in the dish. The slugs are attracted to the soy sauce and once they get in the dish they can't get out because of the oil. Here are a couple of more tips. Spread wood ashes, crushed eggshells, or copper sheeting around the area where you see the slugs. You can also try this spray: Stir together 1 quart of water, 1 tsp of liquid dish soap and a pinch of cayenne pepper. Do not dilute before spraying.
    Also, you might enjoy our video, "The Slug Board Game" (humor required) here:

    This will be my first year

    This will be my first year attempting to grow herbs indoors in a small apartment in Newark, NJ. I have the perfect spot picked out for my 'babies' but I was wondering if I needed to invest in a heating mat, as I'd like to start germinating in mid-February.

    A heating mat isn't

    The Editors's picture

    A heating mat isn't necessary, but it does help to encourage germination, so seeds sprout faster, which is especially helpful for those plants that have a long germination period. Some herbs may prefer different soil temperatures than others; check the seed packet or catalog description. There are also home-made versions that provide bottom heat as well; some people set their containers on top of the refrigerator, which provides a little warmth. A heating mat specifically made for seed starting provides more control over the soil temperature.

    How do you get rid of the

    How do you get rid of the mold/mildew on the plants?? I just noticed my flats are covered in it! We are going to be moving them outdoors soon. Should they even be moved or will it infect everything else?

    You should physically scrape

    You should physically scrape off the mold/mildew and then try sprinkling your flats with ground cinnamon.

    Why do you recommend not

    Why do you recommend not using potting soil? I live in the Midwest and have used potting soil for the past couple of years and didn't seem to have a problem using it. Why would using soilless peat moss, mixed with equal parts vermiculite and perlite be better, besides allowing oxygen to flow?Thanks!

    Potting soil is often heavy

    Potting soil is often heavy and doesn't drain well. Delicate new roots of young seedlings have a harder time developing in potting soil. Soilless medium is much lighter and easier to handle when you move pots around. Potting soil that hasn't been sterilized may also spread diseases.

    I've found that for most

    I've found that for most small ant and bug problems, Bergamot essential oil works really well. If you burn three drops in a tea light per large area, or put a couple drops along the window sills or door entryways (every few months), they hate that stuff. Not sure if it helps in the actual seedlings, but if someone can answer that it'd help me too. Thanks!

    What make your plants so

    What make your plants so leggy when planted indoors from seeds

    Hi Shirlley, The most likely

    Hi Shirlley, The most likely cause is not enough sunlight. The seedlings stretch for the sunlight. To solve this problem, repotting the seedlings in bigger pots and maybe adding a grow light will help. Some seeds are better planted directly in the garden when the soil has warmed up.

    Good basic article on

    Good basic article on starting seeds indoors. Just one VERY IMPORTANT tip is missing. Even when using clean pot, etc., Damp-off is often a problem. (mold/mildew that kills young seedlings) The solution? Cinnamon! I have a jar of Cinnamon. I replaced the sprinkle top with a piece of nylon stretched tight... like the foot of pantyhose, knee-hi, etc., and hold on with an elastic.
    When I'm through planting a seed flat, pots, six-packs, I lightly dust each one with the cinnamon. Organic, natural, proven to work every time! Will no slow, prevent, harm newly sprouted seeds of any kind!

    You could always move north,

    You could always move north, we don't have fireants here in BC. Just sugar ants and borax mixed with icing sugar is a good bet. our bigest problem here is the deer

    Where can you find info on

    Where can you find info on when to dig to plant post?

    i was told by an old farmer

    i was told by an old farmer that the dark side of the moon will keep posts in. The light side will pull them out. Has always worked for me.

    Fire ants are the bane of a

    Fire ants are the bane of a Texan gardener! I am going to try dehydrated molasses...anyone else done that?

    The most effective solution

    The most effective solution is fire ant baits with Spinosad. Don't wait. Sprinkle it around each mound in the later afternoon or when fire ants are foraging. See this page for brand names: