When to Start Tomato Plants From Seed Indoors

Starting tomato seeds indoors is a great way to pass the time in late winter, but knowing when to start tomato plants from seed indoors is very important if you want to make sure you have healthy plants when it is time to transplant them into the garden.

Whether you are growing heirloom tomatoes from seed to get that special variety you can’t find in the local nursery or growing your favorite hybrids from seed to save some money, starting seeds indoors in later winter is fun and will save you money.

Determining Last Frost Date

Before you can determine when to start tomato seeds indoors you need to know your average last frost date for your hardiness zone. Check out the hardiness zone map from the USDA to get your specific date. Once you have this date you can determine the date you should plant your tomato seeds.

Time your seed sowing right so tomatoes will be just the right size for transplanting.

Time your seed sowing right so tomatoes will be just the right size for transplanting.

There are really two ways to determine your ideal date and which one you pick depends on how many times you want to transplant your plants indoors and how big you want them when you set them out in the garden. It is easier to avoid letting the plants get too big indoors because of the serious amount of soil and light they need to get that big, However, the choice is up to you.

How Soon to Sow Tomato Seeds Indoors

To get tomato plants that are about 6-8 inches high and big enough for the garden without the need to transplant them more than once, start your seeds around 8 weeks ahead of your last frost date. If you are willing to plant the up one more time and have access to some serious light, you can start plants 12 weeks ahead of time for bigger transplants.

Where to Find Tomato Seeds

Browse through a tomato seed catalog to find the seeds that are right for you. You will find a huge selection available to select from. There are also fantastic specialty websites that deal exclusively with tomatoes such as Tomato Fest where you just can’t go wrong.

Tips on Starting Tomatoes From Seed

Here are a few tips for getting your seeds started off right. Following these guidelines is the best advice you will get to end with healthy seedlings.

  • use a non-soil medium to grow tomatoes from seed – never real soil
  • plant 2-3 seeds in 2.25 inch pots to start with
  • as soon as they seeds germinate, never water from the top again
  • to water set individual cells into a bath of room temperature water and let them drink from the bottom
  • let them dry out between watering
  • once there are 1-2 sets of true leaves snip off (don’t pull) all but the best seedling with a scissors
  • now that there are true leaves you can apply liquid fertilizer to the next water bath and repeat every 2 weeks when watering
  • once the plants are as big or bigger than the pot (about 4 weeks in) transplant them into bigger pots
  • transplant them deep, like 3/4 of the plant below the soil for vigorous growth in the next 4 weeks
  • if you planted 12 weeks ahead expect another transplanting to be needed in the 8th week
  • a few days before your last frost date check the weather forecast to make sure the extended forecast looks good
  • harden the plants off for at least a few days before planting tomatoes in the garden
  • plant the seedlings deep in your garden soil with up to 3/4 of the plant underground
  • fertilize and water carefully for the first 2 weeks

Now that you know when to start tomato plants from seed indoors you can look forward to seedlings that are the perfect size to go out in the garden every time.

Photo credit: Ramsay2 via Flickr, CC BY-SA 2.0

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