How to Start Tomato Seeds
for Strong, Healthy Plants
Starting tomatoes from seed is one of the most satisfying steps in the growing process. With a little planning and the right conditions, you can raise robust, vibrant plants that thrive in your garden or containers. Here's how to do it right from the start.
1. Know Your Timing
Tomatoes are typically started indoors 6–8 weeks before your last expected frost. In USDA Zone 7a (like mine), that means sowing seeds indoors in early to mid-February. Check your local frost dates to get it right.
Last year, I started mine in early February and had seedlings ready to pot up just as the weather began to settle. If you’ve never timed your seed-starting before, jot down this year’s start date in a notebook or garden journal — it’ll come in handy next season.
2. Choose the Right Setup
I’ve used about every kind of setup. The main thing is working with the space you have available and making sure you can maintain stable moisture, airflow, heat, and light. Whether it’s a greenhouse, a shelf rack lined with plastic sheeting or a vapor barrier, or even a converted baker’s proofing chamber — what matters most is creating the right environment for germination and healthy seedling growth.
Containers: Use seed trays, soil blocks, or recycled containers with good drainage.
Seed starting mix: Use a sterile, lightweight mix — not garden soil.
Humidity dome or cover: Helps maintain moisture during germination.
Heat source: A heat mat set to 75–85°F improves germination rates.
Light: After sprouting, seedlings need 12–16 hours of bright light daily (use grow lights if needed).
If you’re using a windowsill, rotate trays daily to keep the plants from leaning toward the light.
3. Sowing the Seeds
Moisten the mix before sowing. The rule of thumb is simple: stick your finger, stick, or any proportional wooden tool into the soil. If it comes out clean, the soil is too dry. If it has some soil bits clinging to it, it's just right — moist and ready. If it comes out clumpy or muddy, it's too wet and needs time to dry a bit.
Plant seeds about ⅛" deep. A good rule of thumb is to plant seeds at a depth roughly two to three times their diameter — smaller seeds need less coverage, while larger seeds go a bit deeper.
Keep the soil evenly moist but not soggy.
Most tomato seeds germinate within 5–10 days.
I usually see the first sprout in about 7 days — always a little thrill.
4. After Germination
Remove the humidity dome.
Move seedlings under lights or into a bright window.
Begin brushing or lightly fanning seedlings daily to simulate wind and strengthen stems.
Water from the bottom when possible to avoid damping-off disease.
Use a fan on low nearby or run your hand gently across the tops of the seedlings each day. It may sound silly, but it makes a difference.
5. Potting Up
Once seedlings have two sets of true leaves:
Transplant into larger pots to encourage root growth.
Bury stems deeply to the first set of leaves — tomatoes grow roots along buried stems.
Optional: begin diluted FPJ or LAB applications for early resilience.
I’ve found that starting light FPJ once a week during this phase helps prepare them for the stress of transplanting later on.
6. Hardening Off
Before planting outdoors:
I keep a shelf on wheels to make this step easier. It lets me move plants in and out of the greenhouse or position them in shade as the day warms up, helping take the stress off the plants during the adjustment phase.
Gradually expose seedlings to outdoor conditions over 7–10 days.
Start with a shaded spot for a few hours, increasing exposure daily.
Don’t skip this step — seedlings that go straight from indoors to the garden often suffer from sunburn or wind shock.
7. Pro Tips
Label everything — it’s easy to mix up varieties.
Keep a grow log or notebook.
Don’t rush transplanting — wait for warm soil and settled weather.
And don’t be discouraged if a few starts don’t make it — it happens to all of us. Starting from seed is part science, part faith, and a whole lot of observation.
In Part 3, we’ll talk about transplanting tomatoes into the garden and how to set them up for a productive season!
