March and April are prime months to start your tomato seeds indoors. Just remember that you need to understand the process in order for it to be successful. Sometimes people assume they’re experts because they have done it before, but let me tell you that’s not always the case. I have started many, many tomato plants and have done something wrong every time. The one time I didn’t do something wrong was because I asked a lot of questions. But still main question is when to start tomato seeds indoors?

Tomatoes are easy to grow from seed and can be grown indoors or outside in your garden. Some are improved varieties some are heirloom varieties (my favorite), but they all produce delicious tomatoes!

What People Think?

Some people say that if you start tomato plants indoors, they will produce a bigger plant and therefore a larger fruit set. This has not been my experience. In fact, I don’t think my plants have been any larger than their outdoor counterparts. My tomatoes are obviously smaller than those of the ones I grow outside, but the quality of my tomatoes is still the same. I’ve never had this happen with drip irrigation plants in the ground but there are certainly some that do!

In order to germinate your tomato seeds successfully, you need to make sure you understand how it works; otherwise you’re just guessing or hoping and that’s not enough. I have a lot of seeds starting indoors each year and I’ll share the best way to germinate them this week. Often time’s people don’t start them the right way and they never get a plant in the ground.

Your best source of information is another gardener! If you go to a local gardener, they’ll probably be happy to tell you what they do and how long it takes. As I mentioned, this isn’t always guaranteed, so hopefully this will help you.

How Much Temperature is required for Seeding Tomato?

If you want to know when to start tomato seeds indoors, you need to know that temperature is the most important factor. It’s also the main reason seeds fail.

March and April are prime months for starting tomato seeds because the temperature is somewhere between 60 – 75 degrees which is ideal for germination. If your home is warm enough, the seeds will germinate. Even if you hit the temperature right on the nose, you can still fail if you give them too much water, not enough light and then don’t move them to an indoor grow light soon enough. There’s also a chemical that makes seeds germinate faster. It’s called gibberellic acid, the same chemical that causes kittens to be born healthy and strong. Gibberellic acid feeds on light and will start life right along with the tomato seeds. The amount of gibberellic acid in the soil determines when they will germinate. If you buy seeds from a reputable company, they will provide you with soil with the appropriate amount of GA3.

Frequently Asked Questions

What month do you start tomato seeds?

I recommend starting tomato seeds indoors sometime between March and April. You’ll want to look at the charts on the back of the seed package and find the appropriate month, so you can start seeds as close to that date as possible.

How do I know when to put tomatoes in a light?

Put them under a plant light bulb (fluorescent fixture) when they have two true leaves. If you wait too long, you’ll stunt the plant and it will just sit there. If they don’t get enough light, they’ll start getting leggy. Now some people will say that if they’re not growing in sunlight, they won’t need any light at all. That’s simply not true. Fluorescent bulbs are cheap and easy to install and you have a lot more control over the growing conditions.

What happens when I put them under the light?

You’ll see rapid growth. The plant will grow from seed to leaf in 2 – 3 weeks. Once the first true leaves appear, you’ll start to see green and the branches will begin to grow. Once the branches have developed, you’ll want to start them under a full spectrum fluorescent bulb (600 – 900 watts). If they’re getting more than that amount of light, they’ll begin growing too fast and will be tall by early summer.

Can I start my tomato seeds in May?

Yes, but you’ll have to wait a few days or so before putting them under the light. The seeds must go through a period called “germination shock”. Think of it as giving them a cold shower or getting them ready for bed. Just give the seeds time to recover and then put them under the lamp. Once they have the light, the rest will take care of itself.

What type of light should I use?

There are several types of lights that you can use. The most popular lights are fluorescent tubes and high pressure sodium (HPS) lights. Fluorescent lights work well because they provide a full spectrum of light (white to red). HPS bulbs provide some extra heat and are great for late summer tomatoes.  Don’t forget to shield your plants with aluminum foil or paper so they don’t burn.

If you live in an area where you can’t use lights, Mother Nature can provide enough light if you start your tomato seeds indoors and then move them outside following the first true leaves.

If you’re going to use fluorescent lights, make sure that the bulb is rated for plants. The best type of fluorescent light for growing tomatoes is a compact flourescent bulb (27 – 40 watt). Fluorescent lights are not as bright as HPS bulbs, but are more than enough for seedlings.

What about cloche?

Cloche can be helpful for plants that are sensitive to lack of light, but to be honest, tomatoes don’t need a cloche. They will grow just fine with a simple fluorescent fixture. Although I have heard some people say that tomatoes need a cloche because they’re weaklings and need all the help they can get, I have never grown tomatoes in a cloche. I just put my seedlings in an environment that is conducive to growth and then move them under the light when they are ready.


Some people are successful from day one and others have problems. It’s not always easy to tell when they’re ready and you have to have the patience of a saint. Tomato seeds can be very frustrating sometimes, but I haven’t had problems starting them indoors this year. I’ve got a nice crop coming up in the garden this year!


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