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Gardening Guides » Vegetable Seeds » How to Start Vegetable Seeds Indoors

How to Start Vegetable Seeds Indoors

Starting vegetable seeds indoors is a great way to increase yields and get a jump-start on the gardening season. It also satisfies an itch to garden during late winter. This easy, rewarding activity doesn't require lots of equipment—and it's such a joy to tend to emerging seedlings while the weather outside isn't warm enough for gardening. Some of the most common vegetable seeds to start indoors are tomatoes, peppers, eggplant, cabbage and broccoli. Many annual flowers are also started indoors.

Why Start Vegetable Seeds Indoors

While many vegetables will grow just fine and produce bountiful harvests from seeds planted directly in the ground, some need a head start, especially in areas with short growing seasons.

Warm-season crops, like tomatoes, peppers and eggplants, require warm soil for germination. If direct sowing into the ground, many gardeners would have to wait until May to sow seeds—and the plants wouldn't reach maturity before the first fall frost hits. If started indoors, some cool-season crops, like broccoli and cabbage, can reach maturity before the heat of summer sets in.

Starting seeds indoors has other benefits too. It gives you more variety. You'll find more varieties of seeds than you do of vegetable plants. Seed-starting is economical, too. Growing vegetables from seed costs less than buying transplants. Many gardeners also like to grow a few extras and share them with their gardening friends.

When to Start Vegetable Seeds Indoors

When starting seeds indoors, timing is key. You want your young transplants to be big enough to plant in the garden when the time is right, but not so big that they're outgrowing their pots and becoming root bound. As a general rule of thumb, start vegetable seeds indoors about six weeks before the last frost date for your area. Your seed packet will give a more specific time frame.

Starting Vegetable Seeds Indoors in 8 Steps

Starting vegetable seeds indoors can be done in 8 easy steps. Below are the general steps to follow to successfully start sowing your seeds indoors.

  1. Read the information on the seed packet. It will tell you when to start your seeds and what they need in the way of soil and air temperature, humidity, and light, as well as any special pre-planting treatment.
  2. Start vegetable seeds in a flat or a seed starting tray with holes in the bottom for drainage, such as Gurney's Seed Starting Tray.
  3. Fill the tray to about 1 1/4 inches from the top with a sterile growing medium made especially for starting seeds, such as Garden Solutions® First Start Seed Starter. Put the filled tray in a larger pan and add water to about halfway up the sides of the flat. Let the flat stand overnight to moisten the soil.
  4. Press the seeds into the planting mix to the depth recommended on the seed packet. Water with a misting spray bottle or with a fine overhead spray from a watering can. Keep the growing medium evenly moist, but never waterlogged.
  5. Ensure sufficient humidity by placing a thin pane of glass on top of the flat, and keep it in a spot where you can provide the soil and air temperatures and the amount of light recommended on your seed packet.
  6. Make up for any deficiency of sunlight by placing fluorescent light above the flat. Keep the lights on around the clock until the seeds germinate.
  7. Watch for signs of germination: The first thing you'll see will be a set of what appear to be small leaves. These are actually food storage cells called cotyledons. (Germination times vary greatly; again, your seed packet will tell you when to expect the first signs of life.) Continue to water so that the soil stays evenly moist. When the next set of true leaves appear, thin the seedlings to the spacing recommended on the seed packet.
  8. Choose the smallest and weakest-looking seedlings, pull them out gently so you don't disturb the remaining plants, and add them to the compost pile. Begin to feed the plants once a week with a good fertilizer, such as Garden Solutions® Vegetable Food.

Seed Starting Supplies

Before sowing seeds, gather your seed-starting supplies. Essential supplies for seed-starting are seeds, growing medium, containers and a light source. Other supplies make the job easier.

  • Seeds: We recommend ordering your seeds in the winter months. This gives you time to read the packet labels and determine the date for starting seeds.

  • Growing Medium: Avoid using garden soil, as this can spread disease. Instead, use a quality seed-starting mix, preferably one designed specifically for seed starting.

  • Containers: If starting a few seeds, some gardeners use yogurt or other food containers. Just make sure you put drainage holes in them. If growing a lot of seedlings, seedling trays are a good option. Peat pots make ideal homes for transplanted seedlings, because at planting time you set the pot itself into the soil, thus avoiding damage to delicate roots. Grow Tub transplant pots are easy to use and reusable for several years.

  • All-in-one kits: Seed-starting kits are great options because they often provide everything you need to get started.

  • Heat source: Heat mats can warm up the soil 10-20 degrees above room temperature and speed up germination.

  • Artificial light: When starting seeds indoors, seedlings need between 12 and 16 hours of sunlight per day to grow. That means some added artificial light is needed. Place containers on windowsills or below windows. Place your artificial light about 1-3 inches above seedlings for the first few weeks, then raise to 4-6 inches until transplant time.

How to Transplant Seedlings

Transplant the seedlings to individual pots filled with potting soil when you see two or three sets of leaves. Just before transplanting, water the seedlings, then gently lift them out with a spoon or a miniature trowel.

Set each seedling into its pot, carefully firming the soil around the roots. Water gently but well, and continue feeding until it's time to harden off the plants and move them to the garden.

About 7-10 days before you plan to transplant your seedlings to the garden, start hardening them off, or gradually introducing them to the outdoor elements, including sunlight and wind. Set the seedlings in dappled sunlight outdoors for about an hour. Over the next week, increase the amount of time outdoors by about an hour a day.

When hardening off seedlings, make sure to keep the soil moist.

If possible, transplant the seedlings into the garden on a cloudy or overcast day.

More Tips and Tricks

  • Read your seed packets carefully. Some seeds need a period of chilling before you plant them; others need to be soaked in water overnight or scarified (nicked with a file or knife) to speed germination. Some seeds need light to germinate; others require total darkness.
  • Rotate your seedling trays under a light source so that the seedlings do not get spindly.
  • Mirrors or aluminum foil can be used to reflect sunlight or artificial light to give the seedlings the fullest benefit.
  • Avoid overwatering. While moisture is needed for germination and growth, too much moisture can cause the seedlings to die off or rot.
  • Pay attention to spacing! Overcrowding plants in the garden reduces air circulation among the plants and can make them more susceptible to disease. When planning your garden, note how much spacing the plants need.
  • Use row covers. The weather can be unpredictable, and row covers can protect your plants from a light frost.
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