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How to Germinate Seeds: All the Basics of Seed Starting Indoors

By
Mary Marlowe Leverette
Mary Marlowe Leverette 2018
Mary Marlowe Leverette

Mary Marlowe Leverette is one of the industry's most highly-regarded housekeeping and fabric care experts, sharing her knowledge on efficient housekeeping, laundry, and textile conservation. She is also a Master Gardener with over 40+ years of experience and 20+ years of writing experience. Mary is also a member of The Spruce Gardening and Plant Care Review Board.

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Published on 03/05/24
Sprouting vegetable seeds on a paper towel

ThamKC / iStock / Getty Images Plus

You can give your flower and vegetable garden a head start and save money by knowing how to germinate seeds. With the right amount of heat and moisture, starting seeds indoors is simple.

When the seedlings emerge, be sure that they have a good light source and a warm spot to continue growing. Soon, you'll have plants ready to transfer to the garden or a container.

Learn all the basics of germination and seed starting indoors below.

What Is Germination?

Germination of seed begins when moisture uptake activates the metabolic pathways stored in the seed to produce a plant. Dormant seeds need water, oxygen, and proper temperatures to germinate and allow the seed coat to break open and the root to emerge. 

Once the root is established, a shoot that contains the stem and leaves will appear and require sunlight to thrive.

How to Get Seeds to Germinate the Quickest Way

checking for seed germination

The Spruce / Michelle Becker

If you are in a hurry to see if the seeds you saved from last year will germinate or if you want to teach others about germination, all you need is a paper towel, water, a sealable plastic bag or container, water, a permanent marker, and seeds.

Here's how:

  1. Make sure the paper towel is damp. Wet the paper towel, wringing out excessive water, and lay it flat.
  2. Lay the seeds on the towel. Place several seeds in neat rows on half of the paper towel and fold the other half over the seeds.
  3. Place the paper towel in the plastic bag. Seal it to prevent the towel from drying out.
  4. Label the bag. Write down the plant name and the date.
  5. Keep the bag warm. Be sure to place the bag in a warm area with a steady temperature of around 70 degrees.
  6. Check in on the seeds periodically. After three or four days, check the seeds to see if they need more moisture. Most vegetable and flower seeds germinate in seven to 10 days. If you have purchased seeds, the packet often lists how many days it takes for seeds to germinate.

Additional Method for Germinating Seeds

While using the paper towel method to germinate seeds is interesting and easy to do, it is usually not the best method for producing strong seedlings. If the seeds are left too long in the paper towel, the tiny, hair-like roots grow into the paper towel fibers and are damaged during transplanting slowing or preventing a seed from maturing into a strong seedling.

The quickest way to germinate seeds in soil is to be sure they have good contact with the seed-starting mixture, sufficient humidity, and lots of warmth. Heat mats placed under the seed starting tray are an excellent way to give the seeds a quick start.

  1. Prepare the seed starting medium and container. Choose a commercial seed-starting mix and moisten it well. Fill the container to within 3/4-inch from the top. The mixture should be level and firm without air pockets.
  2. Sow the seeds. If you are using a seed-starting tray with individual cells or small individual containers, place two or three seeds in each cell or pot. If the container is a large flat, sow the seeds uniformly in rows about two inches apart.
  3. Label the seeds. This is especially important if you are sowing different types of seeds in the flat or seed-starting tray.
  4. Lightly cover the seeds. Cover the seeds with enough dry vermiculite or seed-starting mix to equal two times the diameter of the seed. Very tiny, fine seeds can be left uncovered. Lightly pat down the soil.
  5. Moisten the surface. Use a mister or spray bottle to lightly moisten the surface of the seed tray or containers with water.
  6. Capture the moisture. Place the lid on the seed starter tray or cover the container with plastic wrap or a plastic bag to create a mini-greenhouse. Capturing the moisture means that no additional watering should be needed until after the germination of the seeds.
  7. Keep the seeds warm. Place the covered container in a warm place (65–75° F.) or a heated seed-starting mat.
  8. Watch for seedlings to emerge. At the first sign of green shoots, remove the lid or plastic covering and place the container in a bright south-facing window. The seedlings need lots of light to flourish. You can also use a grow light.
  9. Maintain moisture levels. Allow the seed-starting mixture to dry out slightly between waterings but do not allow the seedlings to wilt. Do not overwater and allow water to stand in the containers or the seedlings can dampen off (rot).
  10. Thin the seedlings. If every seed germinated and the seedlings are crowded, use garden snips to remove the excess at the soil line. Most seedlings should be transplanted to individual/larger containers when there are three sets of leaves on the stem.

What Seeds Can You Start Indoors?

Vegetables and Herbs

Flowers

What Seeds Should Not Be Started Indoors?

Vegetables

Some plants mature quickly enough that starting seeds indoors is not necessary. Beans, corn, peas, spinach, leaf lettuce, kale, pumpkins, melons, and squash can be direct-seeded in the garden or outdoor container.

Root crops do not transplant well from seed-starting trays. Direct sow carrot, radish, kohlrabi, beet, and turnip seeds. Seed potatoes (potato eyes) should be planted directly into the garden or a container.

Flowers

Nasturtium (Tropaeolum majus) and Sunflower (Helianthus annuus) do not transplant well from a seed-starting tray. If germinating the seeds indoors, they should be started in biodegradable pots that can be directly planted into garden soil.

Additional Tips for Successful Seed Germination

  • If reusing containers to germinate seeds, be sure they are cleaned and sterilized before using them. Wash the containers in warm, soapy water and then dip them in a solution of one part chlorine bleach and 10 parts water. Allow them to air dry completely before adding the seed-starting mix.
  • Do not use garden soil for seed germination. It is too heavy and the seeds will have a difficult time sending down roots and sending up green shoots.
Do Seeds Always Need Light to Germinate?
The Spruce uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

  1. Germinating Seeds. West Virginia Extension.