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potting seeds indoor

Some vegetables, like Tomatoes, Eggplants, and Peppers require a long growing season. To ensure healthy growth, most gardeners start seeds for these vegetables indoors in Spring. Starting your own seeds is not only less expensive than purchasing transplants, it also generally results in a more productive harvest season. Plus, it’s a fun, rewarding way to kick off on the gardening season!

How to Start Vegetable Seeds Indoors

Some vegetables, like Tomatoes, Eggplants, and Peppers require a long growing season. To ensure healthy growth, most gardeners start seeds for these vegetables indoors in Spring. Starting your own seeds is not only less expensive than purchasing transplants, it also generally results in a more productive harvest season. Plus, it’s a fun, rewarding way to kick off on the gardening season!

How do you start vegetable seeds indoors? Here are 10 tips for successfully starting seeds:

Purchase your seeds from a trusted source. Fresher, higher quality seeds will have a higher germination rate (meaning more will sprout), and will give you a head-start in growing delicious, nutritious vegetables. (Check out Landreth Seed, our line of heritage and heirloom vegetable seeds!)

Pot with seed-starting mix. These mixes don’t contain any actual soil, but they provide ideal conditions for sprouting seeds. Most importantly, they provide a good balance of drainage and water-holding capacity, and they minimize problems with disease on vulnerable seedlings. If possible, don’t use garden soil to start seeds indoors; it generally doesn’t drain well and may contain plant disease spores.

Make sure your containers have drainage holes. You can use recycled pots — for example, empty yogurt containers — but be sure to poke holes in the bottom for draining, so that your seeds are not over-watered. Plastic six-packs and flats are good choices and can be reused year after year. Biodegradable pots are fine, too.

Plant seeds at the proper depth. Check the seed packet for planting depth. You don’t need to measure precisely, but be careful not to plant any deeper than the directions suggest. The rule of thumb is to plant the seed two-to-three times as deep as the seed is wide. For example, tiny seeds should be barely covered by soil mix, while large seeds like beans should be sown about an inch deep. If you sow seeds too deeply, they won’t have enough stored energy to make it to the surface. Plant extra seeds, because it’s likely not all of them will germinate; you’ll thin out the extra ones later.

After sowing, set the containers in a warm location. On top of the refrigerator or near a radiator are usually good spots. Check your pots every day for signs of growth!

Keep seed-starting mix moist. Seedling roots need both air and water. Strive to keep the mix moist but not saturated with water — think of it as a damp sponge that contains both water and air.

As soon as seedlings emerge, place pots in a bright location. A sunny window will do, but adding consistent light from supplemental fluorescent lights will give you the best results. Suspend the lights just an inch or two over the tops of the plants.

Cool room temperature is best for seedlings. You’ll get sturdier, stockier seedlings if you grow them at temperatures in the high 60s. Finding a cooler room in your house or garage, while still maintaining a good light sorce, will help them thrive. At higher temperatures, seedlings may get leggy.

Begin fertilizing weekly. Use a half-strength fertilizer once your seedlings have one or two sets of leaves. Organic fertilizers are a good choice, since they provide a range of nutrients, including micronutrients.

Once seedlings have two sets of leaves, it’s time to thin. You want one seedling per pot, so choose the healthiest, strongest-looking seedling to keep. Snip the other seedlings off at the soil line and discard them.

Potting seeds indoor
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!

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Starting Seeds Indoors

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

Why Start Seeds Indoors?

  • Mainly, people start seeds indoors in order to get a jump on the gardening season. Doing so allows you to gain a few weeks of growing time, which can really matter in regions with short growing seasons.
  • If you want to grow a lot of plants, buying packs of seeds is usually cheaper than buying young 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 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 6 to 8 hours of direct sun, 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 carton compartments make good containers, 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.
  • Label your containers now! There’s nothing more frustrating than forgetting what you planted.

When to Start Seeds

  • We’ll get right to the answer: Just check our Planting Calendar, which lists when to start your vegetables and herbs indoors. We’ve created a customized tool, based on your zip code!
  • As a general rule, most annual vegetables should be sown indoors about 6 weeks before the last frost in your area.
  • 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. Use soilless peat moss and mix in equal parts vermiculite and perlite to hold enough water and allow oxygen to flow. 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 according to 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 planting seeds, plant the largest seeds in the packet to get the best germination rate.
  3. Cover containers with plastic to keep them from drying out too quickly. Poke a few holes in the plastic with a toothpick for ventilation.
  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. Try using a meat-basting syringe (turkey baster), which will dispense the water effectively without causing too much soil disruption.
  5. When seedlings start to appear, remove the plastic and move containers into bright light.
  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.

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.


Photo by Sergii Kononenko/Shutterstock

Moving Seedlings Outside

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 add water 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:

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 will capture and retain moisture, drain well, and allow easy penetration by seedling roots.
  • Soak the soil around new seedlings immediately after transplanting.
  • Spread 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

Also, consult the Almanac Plant Growing Guides which provides planting, care, and harvesting information for all your common vegetables, fruit, and herbs.