Germinating tomato seeds fast isn’t rocket science.
And that’s a good thing.
Because I’m no rocket scientist.
And I bet you’re not one either.
So what’s the simple secret to getting your lazy little seeds to wake up?
If you want faster tomato seed germination you need to do 3 things.
- Use fresh seed
- Give your seeds enough heat
- Keep your seeds moist.
Don’t bother trying to germinate tomato seeds outdoors. You need to get them going in a controlled environment early in the season.
That means germinating your tomato seeds indoors and using a couple of tricks to help them get going.
In this Grow Guide, I’ll go over my easy method for sprouting tomato seeds in just a few days, and then you’ll know how to germinate tomato seeds faster.
Let’s dive in!
How To Germinate Tomato Seeds faster? Use The Optimum Temperature
Tomatoes are a warm season crop and they need lots of heat to germinate.
If the temperature isn’t warm enough for your tomato seeds to germinate they’ll take forever to emerge, and in the worst case, they’ll just sit in the soil and rot.
Let’s go to the experts at the University of California Cooperative Extension to get the range of germination temperatures for tomato seeds.
They state the ideal range for the fastest tomato seed germination is 77ºF to 86ºF with a minimum viable germination temperature of 50ºF and an upper limit of 95ºF.
For gardeners working in Celsius that’s an optimal range of 25°C to 30°C, with a minimum of 10°C and a maximum of 35°C.
That’s quite a spread isn’t it?
And while tomatoes can germinate at the minimum temperature of 50ºF (10°C) those seeds will take 42 days to germinate, and the rate of germination (how many actually germinate) will be poor.
At the upper limit of 95ºF (30°C) tomato seeds take 9 days to germinate, and over that temperature they don’t germinate at all.
But in the optimal range of 77ºF (25°C) to 86ºF (30°C) tomato seeds take just 6 days to sprout according to the university extension figures.
The best way to achieve those temperatures and speed up tomato seed germination is to place your tomato seeds on a heat mat. With a heat mat seeds get constant gentle heat right where they need it 24 hours a day.
The heat mat I use keeps soil temperature at a nice 77ish degrees and my tomato seeds germinate fast. In fact this year, they began to emerge in 3 days!
If you don’t have a heat mat, think about getting one. You’ll be thrilled with the results you get when seeds have a heat boost to get them going. Heat mats don’t cost much and they’re cheap to run, consuming around 1/2 kWh per day, which costs pennies.
The alternative to a heat mat is to find a spot in your home that is consistently warm, or use the hot water bottle trick.
The results you get with a hot water bottle won’t be as fast as with a heat mat because the water in your hot water bottle will continually cool down, but you’ll still get faster results. Just remember to keep reheating the water.
Be careful that you don’t use water that’s too hot, and remember that upper temperature limit.
And it’s a good idea to place a folded towel or piece of thick cardboard on top of the hot water bottle to act as a buffer so your seeds don’t overheat.
Okay, now we know what temperature we need, let’s move on to sowing the seed.
How To Sow Tomato Seed For Faster Germination
For the fastest germination you have to place your tomato seeds in a warm place but you’ve only got a limited amount of space on a heat mat. So the best way to sow your seeds is in a seed tray, rather than in pots, because a seed tray takes up less space on a heat mat.
If you’ve only got a few seeds to germinate, you’ll have enough room on your heat mat or hot water bottle to sow in pots. But if you’re planning to grow lots of tomato plants, then you’ll quickly run out of room on your heat mat.
The downside to using seed trays is needing to prick out the seedlings and transplant them one by one into pots once they’ve grown an inch or so tall. It’s a bit of a time consuming job and you need to do it before the seedlings grow too big. If you wait too long their roots will grow together and it will be difficult to transplant them without damaging the roots.
I don’t use purpose-made seed trays, we’re frugal around here 🙂 Instead I re-purpose plastic meat and produce trays. Once they’ve been washed in hot soapy water, they’re good to go.
In this photo, I’ve sown roughly 60 tomato seeds in a tray measuring 10” x 7” (25cm x 17cm). I sowed these seeds on April 16th 2022. The varieties are Tiny Tim, San Marzano, Roma, and Marmande. The extra row at the end is lettuce seed.
If you want to make your own seed trays, poke some drainage holes in the bottom of a tray, then place it inside another tray to catch any excess water.
The compost I use isn’t any special mix. Tomato seeds are small, but they’re not tiny, so they do fine in a fairly coarse compost. But if you want to buy or make a seed starting mix, you can do that.
Once your seed tray is filled with a couple of inches of moist compost, take a pencil and use it to make shallow furrows 1” to 2” apart. Then drop your seed along the furrow.
Make sure you label the rows if you’re sowing more than one variety of tomato seed.
Use your finger to carefully push the sides of the furrow closed again to cover the seeds.
This next step is very important. To get fast tomato seed germination, you need to cover the seed tray so that the compost doesn’t dry out.
You can do this in 2 ways.
The first way is to cover your seed tray with another plastic tray like this. Those other seedlings are peppers by the way.
Or you can slide the seed tray inside a plastic bag and tuck the ends underneath the seed tray to keep the bag closed.
Then place the seed tray on the heat mat and wait.
Here are the seedlings 3 days later on April 19th. They’re just coming through.
How To Care For Your Tomato Seedlings
Once the tomato seeds have germinated, the seedlings will be fine at a lower temperature, they don’t need to stay on the heat mat as long as they’re in a room that’s at least 50ºF (10º) though warmer is better.
But they will need a lot of light and some light watering.
The best way to give seedlings enough light is with a grow light. If you only have a few seedlings, they might get enough light on a south facing windowsill. But if you’re starting seeds early in the spring and you get lots of cloudy days, your light levels will be too low for good growth.
I use a grow light that clips onto the edge of a table. It’s got 4 flexible arms so it’s easy to get the light where it needs to be.
With this grow light I can raise and lower the lights as needed, set the intensity and tone of the lights, and set them to turn on and off automatically each day.
It’s important to keep the lights as close to the seedlings as possible or they will “reach” for the light and grow leggy. Don’t worry too much if this happens because when you pot tomato seedling up, you can bury them deeply and they’ll be fine.
To water tomato seedlings, use a misting bottle to gently spray the seedlings, or water them at soil level with a small amount of water from an egg cup or some other small container. I use a squeeze bottle to direct water where I want it to go.
Once the seedlings are big enough to handle, you can transplant them into pots.
These are the seedlings 2 days later on April 21st. It’s been 5 days since they were sown, and they need transplanting.
Transplanting Tomato Seedlings From Seed Trays To Pots
For seedling pots, I use yogurt pots with holes poked in the bottom.
Whatever pots you use, you just need to add moist compost or potting soil, then use your finger or a pencil to make a hole in the compost. The hole needs to be deep enough for the seedling to go all the way in so that the stem is buried, leaving just a little of the stem above the soil.
By burying the stem deeply, you’ll encourage roots to grow along the length of the stem. The more root zone you have on your tomato plants the stronger they will be because more roots can mine more nutrients from the soil.
If you look closely at a tomato plant you’ll see fine hairs all over the stem. When those hairs meet soil, they become roots.
To remove your seedlings from the seed tray, take a pencil and carefully work it underneath a seedling. Lever the seedling up, and work it free. Then gently pick it up by its leaves and place it into its pot. Push the soil around the stem and give it a small amount of water to help it settle in.
Keep the seedlings under the grow light, and water occasionally until it’s time to pot them on again, and move them outdoors when the temperatures are warm enough.
And that’s all there is to it. Now you know how to germinate tomato seeds faster!
Before I close this post, I’ll show you how important light is to young plants.
Because I’m growing a whole bunch of tomatoes there isn’t room for them all under the grow lights. I really need to buy another set.
Here are some tomato plants with very different levels of growth. Remember all of these were sown at exactly the same time. The seedlings on the left were just outside the full light zone. I struggled for space trying to keep the tomato and pepper plants under the lights.
And these were even further outside the well lit zone. They had enough light to prevent leggy growth but not enough to grow well.
The above photos were taken on May 10th. Ordinarily I would have moved all of these plants out to my polytunnel at the beginning of May where they would get a lot more light, but the weather has been too cold at night for tomatoes so they’re still inside the house making do with the grow lights.
The temperature is warm enough now though, so I’ll pot them on and move them out in the next day or two.
The smaller plants will soon catch up once they get more light.
For the first few days in my polytunnel, I’ll give them a little shade to help them transition, then they can have full sun and the extra warmth of the polytunnel until it’s time to plant them outdoors.
Getting tomato seeds to germinate quickly isn’t rocket science. You just need to give the seeds what they want, and that’s heat and moisture. Then, once they’ve sprouted, set the seedlings up under a grow light until it’s time to move them out to their growing position.
Update – Here’s How Those Tiny Seedlings Grew
Ready For Moving Into Bigger Pots
Homemade Deep Pot Made From A Plastic Bottle
June 16th Ready For Planting (later than usual because of cool nights)
Digging A Deep Hole
Easing The Tomato Plant Out Of The Deep Pot
Tomato Plant Goes Into The Hole With Plenty Of Compost
Firming The Plant In
Giving The Plant A Big Drink Of Water To Help It Settle In
July 15th Mini Tomato Forest
September 13th – Lots Of Green San Marzano Tomatoes…
…And Plenty Of Juicy Ripe Ones
Still Enjoying The Crop In October
We’ve had a great crop from these tomatoes, even though the cold weather held us back earlier in the year. Lots of tomatoes to cook with, to eat with salad and sandwiches, and to share with the goats and chickens.
Thank you for reading How To Germinate Tomato Seeds Faster. I hope you found this post useful. Good luck with your seeds 🙂