Starting Vegetable Seeds Indoors - Get a Jump on the Growing Season

Starting Vegetable Seeds Indoors: How to Get a Jump on the Planting Season

Starting vegetables from seeds is one of the best ways to grow your own food at home. Many of us that enjoy growing our own vegetables like to get a jump on the season by starting our vegetable seeds indoors. This has quite a few benefits that include:

  • Earlier harvest & sometimes you will even get 2 harvests
  • Increased variety by selecting your own seeds
  • It’s fun! Sometimes you just can’t wait to start growing!

You can always buy a few veggie starts from a garden center, but why not choose a few awesome new tomato or pepper varieties they don’t carry in the stores?

How to start your vegetable seeds indoors - Kick off the growing season by starting your seeds inside

When Should I Start My Vegetable Seeds Indoors?

This is always the first question I get asked & in many cases, the answer might be right on the seed packet. Take a look at this packet of Burpee Organic Tomatoes.

As a general rule, the best time to start your vegetable seeds indoors is 6-8 weeks before the average frost date. This gives your vegetable seedlings enough time to emerge and grow to a size safe enough to transplant outside by the time the first frost has passed.

  1. Get the average date of the last frost from the Farmer’s Almanac.
  2. Take a look on your seed packet to get the planting date to see if you need to make any adjustments.
  3. Count backward from the last frost date.

Here Is What Will You Need To Get Started

Once you know the correct time to plant, it’s time to gather your supplies. Here are the 5 things you will need before you start.

  1. Light
  2. Heat
  3. Potting Mix
  4. Small Containers
  5. Seeds

Light – Use A Supplemental Light Source

Your growing seedlings will need several hours of strong light each day. Fluorescent lights or grow lights are a perfect light source for growing plants indoors since they produce a high lumen output without giving off too much heat that could burn your seedlings.

young seedlings reaching for the light

When starting seeds indoors, the natural light from a window is almost always not enough light to grow young plants. They will stretch themselves silly trying to get closer to the sun. This creates an unhealthy start for your veggies and they may become too tall and simply fall over once they start to bush out.

Heat/Temperature – Seeds Need Warmth to Germinate

In order to germinate, your seeds will need to be kept warm. This is the same signal that they receive from Mother Earth when the ground heats up & it is safe to start growing. An average temperature to start seeds is about 75-80 degrees Fahrenheit.

Some varieties like it cooler or hotter to germinate. For example, Spinach does best at 70 degrees while cucumbers like it hotter at around 90 degrees F. Check your seed packet to be sure.

seeds just starting to germinate

If you don’t have a warm enough room in your house, here are a few other options you can set the trays near a window sill where the sun will warm them up. The top of a radiator can also work well.

Water – Seedlings Drink From Their Roots (not their heads!)

Another factor in getting your seeds to germinate is water. The potting medium must be both damp and warm for a seed to sprout. Once your seeds have sprouted you want to keep it moist. Best practice is to set a tray underneath the seedling tray so they absorb the water from the ground up. This feeds your seedling from the roots without displacing their growing stems.

Planting Medium

Seed starting soil is sold in most garden outlets. The soil should be light and sterile to prevent the dreaded “damping off disease” that causes our young seedlings to perish too early. Try to always purchase fresh soil each year to give yourself the best chance.

Seed Starting Containers

You can use a variety of containers to start seeds indoors. Either purchase seed starting pots at a garden center or make your own from household items.

Seedlings can be planted in a variety of containers including any small plastic cups or containers you have in the house.

Pretty much any container that is at least a few inches deep and is water-proof will do.

A few great DIY seed starting containers include Dixie cups, Red Solo cups, small trays with lids (like the kind you gift cookies in), Chicken roaster containers, tin-cans and more. It’s even better if they come with a clear plastic lid. Punch drainage holes in the bottom of your homemade pot before planting and find a tray to set underneath so you can water from the bottom.

Small seeds can be grown in larger trays, then you will transplant then once they are older. Larger seeds like tomatoes or peppers prefer their own pots so the roots don’t get disturbed. If grown together, give them enough room between plants so it is easier to divide them.

My favorite containers for starting indoor seeds are the small plastic pots or trays. These make it easy to remove for repotting or transplanting once your seedlings begin to grow.

Can I use peat pots for seed starting?

Some folks like to use the peat pots that you can plant right in the ground, but personally, I find this to be troublesome. The roots don’t always break free from the pot & it can stunt your plants’ growth. I stick with the re-usable plastic pots.

What Are the Best Vegetables to Start Indoors?

Here is our list of vegetables that are easy to begin inside. You may also want to choose one or two vegetable varieties that grow well in pots all year long.

  • Broccoli
  • Brussel Sprouts
  • Cabbage
  • Cauliflower
  • Celery
  • Chard
  • Cucumber
  • Eggplant
  • Lettuce
  • Onion
  • Pepper
  • Squash
  • Tomato
  • Watermelon

How To Start Vegetable Seeds Indoors

OK – Now that you have everything you need, it’s time to prepare.

Prepare Your Containers

First, prepare your containers by washing & drying them thoroughly. We want to plant the seeds in the cleanest environment possible. If you are using recycled containers, wash them in soapy water with a tiny drop of bleach to make sure there is no food residue and rinse them well.

Next, make sure your containers have drainage holes in the bottom. A small cup needs about 3 holes. Larger trays should have one every inch or two depending on the size. The holes should be big enough so the soil can absorb water through them & can drain off in case of overwatering from the top.

Mix Your Soil

Mix the potting medium with so it is just damp. To test the soil, grab a handful and squeeze it into a clump with your hand. The soil should just hold together but not be dripping wet. Fill your containers to about an inch below the top.

handful of potting soil with small pots in the background
Test your potting mix to make sure it is just damp enough to hold together.

Sowing the Seeds

Then, we have two options for planting seeds depending on the type of container chosen.

Starting Seeds in a Flat

Create several rows in the soil as deep as mentioned on the seed packet – typically about 1/4 inch deep. If there is no information given, plant seeds 2-3 times deeper than their size. Sprinkle the seeds lightly in each row. Cover the seeds with potting mix and press down gently to ensure good seed to soil contact.

Starting Seeds in Individual Containers

Push the individual seed about 1/4 inch (check the seed packets) and cover them with soil. Plant 3 seeds per pot. We need to plant more seeds than we need in case a few don’t germinate and we may lose a few along the way.

watering seeds after sowing in plastic pots
You can mist the seeds after planting to ensure they get enough water.

Add a little water after planting to ensure good seed/soil contact. You can use a light sprayer or even your kitchen sink. Just don’t overwater them at this stage, we want the soil damp, not wet.

Cover the seeds with Plastic & Keep Them Warm

Place a clear cover over the planted seeds to ensure the soil stays moist until they germinate. This way you won’t have to water them again until they sprout. Covering the seeds will also keep them warm to help wake them up and let them know it’s time to grow!

As soon as one seed breaks through the ground, remove the cover so it gets enough oxygen. Don’t wait until they all spring up since this will smother the early birds. Don’t worry the other ones are probably close behind.

Transplanting to Individual Containers

Before planting your seedlings outside we need to transplant them into individual containers. This ensures they have enough room to grow strong & develop good root systems. You’ll know it’s time to transplant once your seedlings have a few true leaves.

comparison seed leaves and true leaves
It’s time to transplant when a few sets of true leaves have formed.

The first set of leaves are the seed leaves, they will be round in size & many different plants’ seeds leaves will all look the same. The second set of leaves is what we call the true leaves & will have the same shape size and texture as the leaves of a mature vegetable plant.

Determine which seedlings you will keep – selecting only the strongest looking ones. Cut the remaining plants off at the base of the soil to give the chosen ones their best chance at growing to full potential. Don’t worry about the old roots, they will decompose in the soil providing additional nutrients.

Prepare a new pot for each seedling that needs to be transplanted by filling it with potting soil and making a hole big enough to fit the seedling’s roots and soil. Use a knife or toothpick to gently lift the seedling out of its old container by the roots. Try not to touch the stem or put it up by the leaves or you could kill the young plant.

Gently place the seeding in the new pot add more damp soil around it so the soil is level. Try to keep the seedlings at the same depth they were growing in their previous container.

Caring For Your Seedlings

pepper plants growing in plastic seed starting containers

Continue to let your seedlings grow until it is time to plant them outside. Your young seedlings need plenty of light. Keep the light source just a few inches above the tops of the plant, moving it up as they grow. If the light is too far away they will grow too tall too fast trying to get enough light. We often call this leggy seedling so because they look like they are all legs!

Continue to water your young seedlings as they grow. Watering from the bottom is always best when possible. Once your seedlings are established & have several sets of true leaves you can even let them dry out a little in between watering so their roots grow longer reaching for the bottom of the container. This creates a nice healthy root system perfect for making the transition from your house to the vegetable garden.

Moving Transplants into the Garden

Once the weather has warmed up, it’s time to plant them in the garden. First, you will need to harden them off.

Hardening Off

Seedlings that have been started indoors need time to get used to the outdoor elements – stronger sun, breezes, and fluctuating temperatures. This is what is known as hardening off. Up until now, the seedlings environment was very stable, but it’s about to become very different!

We do this by taking them outdoors for a few hours a day in a shady location such as a covered porch or up against the house when they will get just a little filtered sun. Start with just a few hours, gradually increasing this to a full day, then a full night.

This process may take 1-3 weeks, depending on your environment. Don’t forget to keep watering during this transition period since the weather can dry out the soil fast.

If your seedlings are still doing well and growing strong Once your seedlings have had at least a week or two getting used to the elements, they can be moved to the garden.

transplanting tomatoes to the garden

Planting Outdoors

Similar to how we dit it when transplanting to individual pots, we’ll dig new holes in the garden. Wait for a cloudy mild day before transplanting.

  1. Dig a hole a little larger than the root system and loosen the soil.
  2. Gently lift the seedling out of its container, holding it under the roots or the leaves. Never hold a young seedling by the stem or you could kill it.
  3. If the roots are all tangled up or have grown into the shape of the pot, gently tease them apart or pinch off the bottom to encourage new growth.
  4. Place the plant in the soil and gently tap it around the base of the plant so it is snug in its new home.
  5. Water the ground around the plant so the dirt fills in any air pockets created.
  6. Watch your young seedling carefully in the next few days to make sure it is doing well. If you are going to get any type of bad weather you may need to give your new plants a little extra protection.

Starting Seeds Indoors: Frequently Asked Questions

When should I start my vegetable seeds indoors?

6-8 weeks before the last frost date in your area.

What seeds should I start indoors?

Almost all seeds can be started indoors, but some favorites include tomatoes, peppers, cucumbers, and squash. See our full list above.

How deep should I plant my seeds?

Check the seed packet for the correct depth. If this information is not listed the general rule of thumb is to plant seeds 2-3 times deeper than their size. Tiny seeds can be placed on the surface and gently covered with a potting mix.

Do you need a grow light to start seeds indoors?

Yes, when planting vegetable seeds indoors you will need an additional light source. Fluorescent or grow lights are the most popular for seed starting.

How many seeds do I need to start indoors?

Plant at least 3 times the amount of seeds as you want full-grown plants. Not all your plants will make it through the seedling or hardening off stage, so it’s good to have extras. Plus if you grow extra plants you can give them away as gifts or trade them for other varieties with your gardening buddies.

young peas grown from seed

Summary: Starting Vegetable Seeds Indoors

Starting seeds indoors is one of the best ways to get a jump on the planting season. Not only is watching your seedlings grow very rewarding, but you will also be able to grow a wider variety of vegetables than being limited to the same boring types available in the stores.

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