How Long Does It Take for Tomato Seeds to Germinate?

It’s important to understand germination when you’re starting tomato plants from seed. Know what to expect and how to troubleshoot if things don’t go quite as planned.

Tomato Seedlings In Deep Pots

Tomato Seedlings In Deep Pots

Choose deep pots for growing tomatoes from seed. Peat pots minimize transplant shock because you plant both the seedling and pot.

Photo by: Gardener’s Supply Co. at Gardeners.com

Gardener’s Supply Co. at Gardeners.com

Germination is the first step toward making a plant, when a seed breaks open to form a root, then a stem, then leaves, at which point it can be called a seedling. Tomato seeds typically germinate in 5 to 10 days if given optimal conditions. You’ll know seeds have germinated as soon as you see green plant emerging from the growing medium. That’s a time to celebrate.

The rate of germination for a particular packet of tomato seeds depends on the source and age of the seed. This can be called the viability of the seed. Typically, the older the seed, the lower the germination rate and less viability. Increase your chances of getting the number of plants you desire by planting 25% or more seeds than you actually think you’ll need. Some may not germinate, but you’ll still have what you need.

If you have issues with germinating your tomato seed, temperature may be the problem. Ideal temperatures for germination are 70-80 degrees Fahrenheit. Temperatures much lower than 70 degrees will cause slower germination, and if temperatures dip far below, germination may not occur at all. Likewise, hot temperatures well above 80 can also cause germination to fail. If you need to increase temperature, a plant heating mat is a good helper.

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How to Start Tomato Seeds Indoors

Tomato seeds can be sown directly outdoors but may not have enough time to grow to full size and produce, depending on your climate. Tomato transplants are available for purchase at your local garden centers, but you can also start your own tomato plants indoors using seeds and seed-starting techniques and tools. Tomato seeds should be started indoors 6-8 weeks before your last frost date in spring, which is the average date of last frosts in your area. This allows them time to grow into a healthy transplant before being moved outdoors.

Tomato seeds should be started indoors in soilless seed-starting mix, which is usually a mix of peat and perlite; don’t start seeds indoors in regular garden soil, which will hold water and could also contain organisms harmful to baby plants. Start seeds in plastic planting trays or plantable peat pots, or reuse yogurt cups or other household items — just be sure to clean the pots well before planting.

When starting seeds, the temperature indoors should be 70-80 degrees. The growing mix should be moist, but not wet, to aid germination. Seeds don’t need light to germinate, although after germination, you should ideally give the seedlings 14 or more hours of light a day. If you’re growing indoors on a windowsill, be sure to place pots in a warm, sunny spot that gets a good amount of natural light. Otherwise, you can supplement with a fluorescent grow light to increase hours of light.

When seedlings have been growing indoors for several weeks and look strong and healthy, it’s time to start thinking about moving them outside. It’s best to set tomato transplants out in your garden after your last frost date. This gives you and your tomatoes a leg up on the season. We recommend waiting a couple weeks after the last frost date to move your tomato transplants outdoors, just to be safe.

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