Growing tomatoes from seed isn't as hard as you think. From sowing dates to tomato varieties, our step-by-step guide will help you grow thriving, healthy plants.
There’s nothing quite like a fresh tomato. Sweet, juicy, and delicious, homegrown tomatoes beat out their grocery store counterparts with a winning flavor that’s hard to match. That’s probably why tomatoes are one of the most popular plants to grow: they’re worth the space in any garden.
If you’ve ever wanted to jump on the tomato bandwagon, there’s no time like the present. And while most nurseries stock bestselling tomato seedlings, starting your own from seed gives you more control over the outcome.
Why grow from seed?
With over 10,000 tomato cultivars on the market, it’s easy to see why commercial greenhouse growers choose a select few. Popular varieties have many things going for them, but starting your tomatoes from seed means you’ll have access to a broader range of choices. That means finding a size, color, flavor, and maturation date tailored to you and your garden.
Where to start
If you’re used to buying transplants in the springtime, starting tomatoes from seed will require a few extra steps. You’ll need the following materials on hand to make your tomato-growing experience pleasant and seamless. Each item is discussed in more detail below.
What you’ll need
- Your favorite tomato seeds
- Sterile growing pots
- Sterile soil mix
- Organic fertilizer
- A sunny, warm location
Choosing what kind of tomatoes to grow
Tomato varieties can be grouped into a number of different categories. To find the best fit for your garden, consider how you’ll use your tomatoes, when you hope to harvest, and whether or not you want to save your own seed.
Tomato varieties by size and shape
Famous for their large size, beefsteak tomatoes reach diameters of up to 6 inches and can weigh as much as three pounds. They’re popular for sandwiches and generally need a longer growing season than smaller tomato varieties.
Tiny and sweet, cherry tomatoes pack incredible flavor into a fruit less than 1 inch in diameter. They produce an abundant crop and are perfect for container, balcony, and patio growing. Grow cherry tomatoes for a long season harvest that starts earlier than most other tomatoes, choosing from one of the many amazing flavors and colors.
Slightly drier than cherry varieties–but just as small–grape tomatoes are more oval in shape, with an elongated tip that can resemble an inverted teardrop. They grow more quickly than beefsteak varieties, hanging in dense clusters for easy picking.
If you’re looking to make sauces and pastes with your tomatoes, romas are ideal because they have few seeds, firm flesh, and a lower moisture content that’s quicker to evaporate while cooking. They’re also sweet, delicious, and easy to grow. Measuring about 2 to 5 inches, they come in a variety of sizes.
Salad tomatoes include a large number of varieties that fall between 2 and 4 inches. Their uniform shape makes them excellent for slicing into rounds or wedges. With a slightly higher acid content, they’re often a little tangier than cherry and beefsteak varieties.
Tomatoes by habit type
Most tomatoes varieties come in plants that form a bush and plants that form a vine. Choosing which one to grow will determine how big your plants will get, when they’ll set fruit, and how often you’ll need to prune them.
Bush-forming tomatoes (also known as determinate tomatoes) are the easiest tomatoes to grow in small spaces and containers. Their dense habit does well in tomato cages, which provide added support and keeps fruiting branches off the ground where pests may be waiting. With minimal pruning, bush tomatoes will form a concentrated harvest of large and abundant fruit.
Vining tomatoes (also called indeterminate tomatoes) require frequent pruning because they won’t stop making leaves and blossoms until cold temperatures arrive. For this reason, they need some form of trellis, since their rapid growth easily reaches 7 or 8 feet in a season. Vining tomato varieties will continue to set and ripen fruit throughout the summer, giving you a longer, but less concentrated, harvest.
Semi-determinate tomatoes are a mixture of the bush and vining types, meaning they will need some pruning, but won’t sprawl quite as far as classic vining tomatoes.
Tomato maturity dates
If you have ample space and would like to eat tomatoes all season long, consider choosing varieties that ripen at different times. In addition to growing tips, seed packets include information about days to maturity. Tomato varieties are generally grouped into early, mid, and late season varieties based on this information.
Hybrid, heirloom and open-pollinated varieties
The final thing to consider when choosing your tomato seeds is whether you’d like to grow heirloom (also known as heritage) or hybrid varieties.
Heirloom varieties grow from seeds that have been passed down for 50 to 100 years. They lack some of the characteristics that modern plant breeding has brought to today’s tomatoes–namely a longer shelf life and resistance to certain diseases–but they tend to be sweeter and more flavorful. Heirloom tomatoes are open-pollinated, meaning that wind, weather, and natural pollinators pollinate the plants. If you plan to save seeds at the end of the season for replanting next year, heirloom and open-pollinated seeds are your best choice.
Hybrids are plants produced by crossing the pollen of two different tomato varieties. While hybrids may sacrifice some taste in favor of uniform color, they do offer traits like early ripening and vigor. For seed-saving purposes, however, hybrids will not breed true.
The best soil recipe for tomato plants
When planting anything from seed, be sure to use sterile ingredients to prevent molds and fungi from growing on your soil. In fact, seedling mixes don’t need to contain any soil. We recommend the following mixture for seedlings and when potting up your transplants:
10 parts sterile potting starter mix
2 parts finished compost, screened through ¼” mesh
1 part glacial rock dust
Mix the ingredients together in a plastic bucket and leave the lid slightly ajar to allow some air movement. The glacial rock dust will add absorbency to the mix and prevent it from drying out too quickly. If you have the time, allow your mix to sit for 6 weeks before using.
Planting your tomato seeds
Once you’ve chosen your seeds and blended your potting mix, you’re ready to plant. To find your ideal sowing date, calculate back from the last frost date in your area 6 to 8 weeks. If you’re within that range, planting time has come.
Spread an even layer of potting mixture into your growing pots. The plants will outgrow these pots at least once before they end up in the garden, so be sure to have a variety of sizes on hand. A pot measuring 3 to 4 inches in diameter is a good starting place. Plant 2 to 3 seeds per pot, no more than ½ inch deep. Using a seedling heater beneath your plants will speed germination.
Keep soil evenly moist as your seedlings grow. Two weeks after planting, most of your seeds will have germinated. Tend them for another week before snipping off whichever plant appears the weakest, reducing your crop to one seedling per pot.
Now that your plants have emerged, they’ll need bright light to thrive. Growing tomato seedlings in a window will work, but it will usually produce leggy plants. But don’t worry: despite legginess, tomato plants will usually fill out as soon as they get outdoors. Just keep in mind that overhead grow lights will give your plants a better start if available.
Fertilizing and transplanting tomato seedlings
When the second set of true leaves appears, begin fertilizing once a week using a water-soluble organic fertilizer. Choose something with phosphorus, the middle number in the three-number fertilizer key, since this will help your plant develop strong roots.
When the seedling height is about three times the diameter of its pot, it’s time to transplant. At this point, one gallon pots offer enough space to take your plants into spring. Fill each pot with sterile mix, adding your seedlings one per pot. Tend them until outdoor nighttime temperatures reach 45 F (7 C) for early varieties and 50 F (10 C) for other varieties.
Hardening off your plants
When daytime temperatures have warmed, begin putting your tomato plants outside for a few hours each day. Exposure to outside air will help strengthen stems and get them ready for planting. Repeat this process for 7 to 10 days. When the nighttime temperature is above 50 F, leave outside them overnight. If they appear healthy and vital, they’re ready for transplanting.
Planting your tomatoes outside
This is the moment you’ve been waiting for: the time when your plants will need less help from you and will begin to take off in their growth. If you live in an area where late blight is common, plant your tomatoes in a greenhouse to prevent losing your crop later in the season. If you don’t have one, consider using polytunnels or raised bed covers to protect plants.
No matter where you plant them, tomatoes like lots of light and space. Space bush varieties 18 to 24 inches apart (up to 60 cm) and vining types 20 to 30” apart (up to 90 cm). Situate plants up against a south-facing building if you’re concerned about them getting enough heat.
To plant, dig a hole slightly deeper than your one gallon pots. Add 1 cup of complete organic fertilizer to each hole, along with finished compost or manure. Bury your plants up to their first set up true leaves, adding stakes or tomato cages at the time of planting.
Caring for your tomato plants
During the growing season, prune vining tomatoes every few days. Remove all suckers and trim back any branches that get out of hand. Some people prefer to leave 2 to 3 suckers on vining tomatoes: this will depend on which trellising system you choose and how often you like to prune. Bush varieties don’t need to be pruned, but many commercial growers remove suckers below the first flower cluster to keep leaves and branches off the ground.
Water your tomato plants evenly and regularly. One of the more common tomato diseases–blossom end rot–occurs when plants have uneven access to water. You can help prevent this by adding glacial rock dust or complete organic fertilizer to your planting hole and the surrounding soil–and by watering regularly.
When to harvest
Harvest fully ripe tomatoes when they are slightly soft and come away easily from the plant when tugged. You can also harvest your tomatoes before they fully ripen if you’re concerned about pests or want to speed up your remaining crop. Watch for the first blush of red on green tomatoes to indicate that they contain enough ethylene gas to finish ripening on the countertop.