Planting Tomato Seeds - How To Start Tomato Plants From Seed

Tomato Seedlings
tomato seedling2
(Image credit: claudiawenk)

Growing tomatoes from seed can open a whole new world of specialty, heirloom, or unusual tomatoes. While your local nursery may only sell a dozen or two tomato varieties as plants, there are literally hundreds of tomato varieties available as seeds. Starting tomato plants from seeds is easy and requires only a little bit of planning. Let's take a look at how to start tomato plants from seed.

When to Start Tomato Seeds

The best time to start tomato plants from seeds is about six to eight weeks before you plan on planting them out into your garden. For areas that get frost, plan on planting out your tomato seedlings two to three weeks after your last frost, so you will start growing tomatoes from seed at four to six weeks before your last frost date.

How to Start Tomato Plants from Seed

Tomato seeds can be started in small pots of damp seed starting soil, damp potting soil, or in moistened peat pellets. In each container you will be planting two tomato seeds. This will help ensure that each container will have a tomato seedling, in case some of the tomato seeds do not germinate.

The tomato seeds should be planted about three times deeper than the size of the seed. This will be about 1/8 to 1/4 of an inch (3-6 mm.), depending on the tomato variety that you have chosen to grow.

After the tomato seeds have been planted, place the seedling containers in a warm place. For fastest germination, temperatures of 70 to 80 degrees F. (21-27 C.) are best. Bottom heat will also help. Many gardeners find that placing the planted tomato seed containers on top of the refrigerator or other appliance that generates heat from running works very well for germination. A heating pad on low covered with a towel will also work.

After planting the tomato seeds, it is just a matter of waiting for the seeds to germinate. The tomato seeds should germinate in one to two weeks. Cooler temperatures will result in a longer germination time and warmer temperatures will make the tomato seeds germinate faster.

How to Grow Tomatoes from Seed

Once the tomato seeds have germinated, you can take the tomato seedlings off the heat source, but they should still be kept somewhere warm. The tomato seedlings will need bright light and the soil should be kept moist. Watering from below is best, but if this is not possible, water the tomato seedlings so that water does not fall on the new sprouts. A bright south-facing window will work for light, or a fluorescent or grow bulb placed a few inches (8 cm.) above the tomato seedlings will work.

Once the tomato seedlings have a set of true leaves you can give them quarter strength water soluble fertilizer.

If your tomato seedlings get leggy, this means that they are not getting enough light. Either move your light source closer or increase the amount of light the tomato seedlings are getting. If your tomato seedlings turn purple, they need some fertilizer and you should apply the quarter strength fertilizer again. If your tomato seedlings suddenly fall over, they have damping off.

Growing tomatoes from seed is a fun way to add some unusual variety to your garden. Now that you know how to plant tomato seeds, a whole new world of tomatoes is open to you.

Heather Rhoades
Founder of Gardening Know How

Heather Rhoades founded Gardening Know How in 2007. She holds degrees from Cleveland State University and Northern Kentucky University. She is an avid gardener with a passion for community, and is a recipient of the Master Gardeners of Ohio Lifetime Achievement Award.