How Deep to Plant Tomato Seeds (+ Spacing Guide)
I've started thousands of tomato seeds over the years, and the single most common reason people get poor germination? Planting too deep. It seems like such a simple thing, but getting the depth right makes a huge difference between a tray full of healthy seedlings and a tray full of nothing.
The short answer: plant tomato seeds 1/4 inch deep. That's it. About 6 millimeters. Roughly the thickness of two stacked quarters. Whether you're starting them in cell trays on your kitchen counter or direct sowing into garden soil (which I don't recommend, but we'll get to that), the depth stays the same.
Planting depth by tomato type
Here's what surprises some people — the depth doesn't really change based on the tomato variety. A tiny cherry tomato seed and a beefsteak seed both go 1/4 inch down. But spacing and other factors do vary:
| Tomato Type | Seed Depth | Cell/Pot Spacing | Garden Spacing | Days to Germination |
|---|---|---|---|---|
| Cherry (e.g., Sun Gold, Sweet 100) | 1/4 inch | 1 seed per cell | 24-30 inches | 5-8 days |
| Grape (e.g., Juliet, Red Grape) | 1/4 inch | 1 seed per cell | 24-30 inches | 5-8 days |
| Roma/Paste (e.g., San Marzano) | 1/4 inch | 1 seed per cell | 30-36 inches | 6-10 days |
| Slicing (e.g., Better Boy, Celebrity) | 1/4 inch | 1 seed per cell | 30-36 inches | 6-10 days |
| Beefsteak (e.g., Brandywine, Big Beef) | 1/4 inch | 1 seed per cell | 36-48 inches | 7-10 days |
| Heirloom (varies) | 1/4 inch | 1 seed per cell | 30-48 inches | 7-14 days |
Heirloom seeds tend to be a bit more finicky about germination. Older varieties and seeds saved from previous seasons sometimes have lower germination rates, so I'll plant 2 seeds per cell with heirlooms and thin to the strongest one.
Why 1/4 inch specifically?
Tomato seeds are small — roughly 3mm long and fairly flat. They contain just enough stored energy (in the endosperm and cotyledons) to push a sprout about half an inch through soil before they need to reach light and start photosynthesizing.
Plant them at 1/4 inch and they've got plenty of margin. Plant them at 1/2 inch and you're pushing it. Go deeper than that and many seeds simply won't make it to the surface. The ones that do will be leggy and weak because they burned through their energy reserves just getting above ground.
On the flip side, seeds that sit right on the soil surface dry out fast. The top layer of soil or seed mix loses moisture quickly, and a tomato seed that dries out mid-germination is done for. That 1/4 inch of cover keeps them consistently moist without burying them too deep.
Step-by-step: starting tomato seeds indoors
- Fill cells or pots with moistened seed-starting mix. Not garden soil — it's too heavy and can carry diseases. Press it down gently so it's firm but not packed.
- Make a shallow depression about 1/4 inch deep. I use the eraser end of a pencil. Works perfectly every time.
- Drop one seed in each hole (two for heirlooms or older seed). Don't handle them more than necessary.
- Cover with fine mix or vermiculite. Vermiculite is great because it holds moisture and lets light through a little, which doesn't matter for tomatoes but does make it easy to see when seedlings emerge.
- Mist the surface. Don't water from above with a heavy stream — you'll displace seeds. A spray bottle or bottom-watering works best.
- Cover with a humidity dome or plastic wrap and place somewhere warm (70-80°F). A heat mat is ideal.
- Remove the cover as soon as you see the first sprouts poking through.
For the best timing on when to start your seeds based on your specific location, check our planting calendar tool. It calculates dates based on your zip code and frost dates.
What about direct sowing tomatoes?
Honestly? Don't. In almost every climate, you're better off starting tomatoes indoors 6-8 weeks before your last frost date and transplanting them out. Tomatoes need a long, warm growing season, and direct sowing means you lose those crucial early weeks.
The exception is if you live in USDA zones 9-11 where the growing season is incredibly long. Even then, transplants give you a head start. If you do direct sow, the depth stays at 1/4 inch but you'll want to thin seedlings to proper spacing once they're established.
We've got a detailed guide on when to start seeds indoors if you want the full timeline breakdown.
Transplanting depth is different (and important)
Here's where tomatoes are special: when you transplant seedlings into the garden, you can bury them much deeper than you planted the seed. Tomatoes grow adventitious roots from any buried stem tissue. I bury my transplants up to their first set of true leaves — sometimes deeper.
This gives them a massive root system and a sturdier base. It's one of the best things you can do for tomato plants and it's unique among common garden vegetables. Don't try this with peppers or other crops.
Common mistakes that kill germination
- Planting too deep — The #1 issue. If you're not seeing sprouts after 14 days in warm conditions, depth is the likely culprit.
- Cold soil — Tomato seeds need 65-85°F soil temperature. Below 60°F, germination drops dramatically. Use a heat mat.
- Letting seeds dry out — Even a few hours of drying during germination can kill the emerging root. Keep things consistently moist (not waterlogged).
- Old seed — Tomato seeds stay viable for 4-5 years if stored cool and dry. After that, germination rates decline. If you're using old seed, plant extras.
- Wrong soil mix — Heavy garden soil compacts in containers, making it hard for seedlings to push through. Use a light, sterile seed-starting mix.
Soil temperature and germination rates
| Soil Temperature | Germination Rate | Days to Germination |
|---|---|---|
| 50°F (10°C) | Very low (under 30%) | 20+ days |
| 60°F (15°C) | ~60% | 12-14 days |
| 70°F (21°C) | ~85% | 7-10 days |
| 75°F (24°C) | ~95% (optimal) | 5-7 days |
| 80°F (27°C) | ~90% | 5-6 days |
| 90°F (32°C) | ~70% | 6-8 days |
| 95°F+ (35°C+) | Very low | Often fails |
That 70-80°F sweet spot is why heat mats are so popular with serious gardeners. Room temperature (around 68°F) works fine too — germination just takes a couple extra days.
Seed depth for container vs. raised bed vs. ground
The depth stays the same regardless of where you're planting: 1/4 inch. But the growing medium matters. Raised beds with fluffy amended soil make it easier for sprouts to push through compared to heavy clay ground soil. If you've got heavy soil and you're direct sowing (which again, I wouldn't recommend for tomatoes), you might go slightly shallower — 1/8 to 1/4 inch — to compensate.
For a broader look at timing your whole garden, not just tomatoes, take a look at our spring vegetable garden planting schedule.
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Frequently asked questions
How deep should I plant tomato seeds?
Plant tomato seeds 1/4 inch (6mm) deep. This applies to nearly all tomato varieties whether starting indoors or direct sowing.
Can you plant tomato seeds too deep?
Yes. Seeds planted deeper than 1/2 inch often fail to germinate because the seedling can't push through the soil before running out of stored energy.
Should I cover tomato seeds with soil or leave them exposed?
Lightly cover them with 1/4 inch of fine seed-starting mix or vermiculite. Tomato seeds need darkness to germinate, unlike some other seeds.
How long do tomato seeds take to germinate?
Typically 5-10 days at 70-80°F (21-27°C). Cooler temperatures slow germination significantly — below 60°F it can take 2-3 weeks or fail entirely.