What You Need to Start Tomato Seeds
Starting tomato seeds doesn’t require fancy equipment or expensive tools. Keep it simple.
Tomato Seeds
Growing tomatoes from seed allows you to experiment with heirloom tomato seeds, rare tomato varieties, and types you’ll never find as store-bought plants.
Best Soil for Starting Tomato Seeds
Use a seed-starting mix. While regular garden soil might seem convenient, it’s too heavy for young tomato seedlings and often causes poor drainage and weak growth. A light seed-starting mix helps roots develop quickly and evenly, saving you many problems later.
Containers for Starting Tomato Seeds
Almost any small container will work: plastic cups, yogurt containers, or sour cream tubs are all great options. Just make sure each container has drainage holes in the bottom so excess water can escape. Place containers on a tray or lid to catch runoff.
Avoid paper pots and egg cartons. Paper breaks down quickly, gets moldy, and egg cartons are far too small for tomato seedlings.
When to Start Tomato Seeds Indoors
Timing is critical when growing tomatoes from seed, and starting too early is one of the most common mistakes.
How to Calculate the Right Time to Start Tomato Seeds
Start tomato seeds 6 weeks before your last frost date.
What Is the Last Frost Date?
The last frost date is the point in spring after which freezing temperatures are unlikely in your area. Tomato plants are sensitive to frost, so this date determines when seedlings can safely go outside.
To find your last frost date:
- Search online for “last frost date” plus your town or nearest city.
- If a range is given, always choose the latest date.
- Count back six weeks from that date.
Example:
You live in Barrie, Ontario.
Google gives you a range: May 11–20
➡️ Your last frost date is May 20
Now count 6 weeks back from May 20. That brings you to April 8.
Start your tomato seeds around April 8.
Why Starting Tomato Seeds Too Early Causes Problems
It’s tempting to start early—especially when it’s sunny outside or social media is full of seedlings. Resist the urge!
Unless you have a greenhouse, strong grow lights, and lots of space, starting tomato seeds too early usually results in tall, leggy seedlings. These plants are weak, fragile, and slow to recover once planted outdoors.
Smaller, sturdy tomato seedlings are far healthier. Once planted outside, they quickly catch up and grow into strong, productive tomato plants.
How to Start Tomato Seeds: Two Easy Methods
There are two ways to start tomato seeds. Both work equally well, so choose the method you prefer.
Method 1 – Planting Dry Tomato Seeds Directly in Soil
- Open your seed-starting mix and check moisture—it’s often very dry.
- Pre-moisten the soil by mixing it with water in a larger container until evenly damp. The soil should feel moist but not drip water when squeezed.
- Fill your containers with soil and lightly press to remove large air pockets.
- Water the soil before planting seeds. Watering afterward can pull seeds too deep.
- Make holes about ¼ inch deep using a toothpick or similar tool.
- Place one seed per hole and gently cover with soil. Do not press down.
- You can plant several seeds per pot and transplant them later. If you grow only a couple of plants you can plant 2-3 seeds per pot and just remove weaker seedling later, leaving the only strongest one.
- Loosely cover containers with a plastic dome or bag and place them in a warm spot.
Method 2 – Germinating Tomato Seeds Before Planting
This method takes a little more attention but lets you see which seeds sprout first.
- Lightly moisten a paper towel so it’s damp, but not soaked.
- Place seeds inside and put the towel into a shallow container or ziplock bag.
- If germinating multiple varieties, use separate towels and label them directly with a pen.
- Keep the container in a warm location.
- Check every day to ensure the towel stays moist.
Once seeds sprout, carefully plant them into soil just like dry seeds.
⚠️ Be extremely gentle—if the tiny root breaks, the seedling will not recover.
After Planting: What Happens Next?
Do not water after planting seeds. Keep containers covered to prevent drying out.
As germination time approaches, check pots every 5-6 hours. The moment you see a seedling:
- Remove the cover
- Move containers away from heat
- Place seedlings under bright light
Tomato seedlings need bright light as soon as they emerge. Grow lights work best, but a sunny windowsill can also work. If seedlings stay warm, dark, or covered after they emerge they will become leggy very quickly.
Your Tomato Seed-Starting Journey Begins Here
That’s it—you’ve officially started growing tomatoes from seed. With the right timing, good soil, and proper light, your seedlings will grow into strong, healthy tomato plants ready for the garden. 🌱
In the next steps, you’ll learn how to pot up tomato seedlings, harden them off, and plant them outdoors for a successful harvest.