The Five Things Tomatoes Need Most
Tomatoes grow best when you give them full sun, consistent water, warm soil, support as they get tall, and nutrients in the right amounts. Most problems—slow growth, yellow leaves, fruit that won't ripen—come from missing one of these five things. The good news is that each one is something you can control, whether you're growing in a garden bed, a pot, or a raised box.
The order matters too. A tomato plant won't use fertilizer well if the soil is cold or the roots are drowning. It won't produce fruit if it's shaded half the day. Start with the foundation—sun and water—and add the rest from there.
Key Takeaways
- Tomatoes need at least six to eight hours of direct sun each day; less than that and they grow slowly and produce little fruit.
- Water deeply and less often rather than a little bit every day, so roots grow down into the soil instead of staying shallow.
- Soil temperature matters as much as air temperature; tomatoes barely grow when soil is below 60°F, and grow fastest between 70°F and 85°F.
- Stake or cage your tomato early, before it gets tall and heavy, so the plant doesn't break and fruit doesn't rot on the ground.
- Feed tomatoes with a balanced fertilizer when they start flowering, then switch to lower nitrogen once fruit sets, so energy goes to ripening instead of leaves.
Give Tomatoes Six to Eight Hours of Direct Sun
Tomatoes are sun plants. They need at least six hours of direct sunlight each day to grow at a normal pace, and eight to ten hours is better. If your tomato gets four hours or less, it will grow slowly, produce fewer flowers, and the fruit that does form will ripen late and taste less sweet.
Check your garden or patio in the morning and afternoon. If a tree, building, or fence casts a shadow over the spot for part of the day, move the pot or plant somewhere sunnier. If you're in a very hot climate (over 95°F regularly), afternoon shade can actually help prevent sunscald on the fruit, but morning sun is still essential.
Water Deeply and Let the Soil Dry Slightly Between Waterings
The most common mistake is watering a little bit every day. This keeps the top inch of soil wet but leaves the deeper roots dry, so the plant stays shallow-rooted and stressed. Instead, water deeply once or twice a week so water soaks down six to eight inches, then let the top inch of soil dry out before you water again.
How often you water depends on your climate, pot size, and soil type. In hot weather, a tomato in a five-gallon pot might need water every two to three days. In cool weather or in the ground, it might go five to seven days. The test is straightforward: stick your finger two inches into the soil. If it feels dry, water. If it feels damp, wait another day or two.
Inconsistent watering causes problems. If a plant gets dry, then floods, then dries again, the fruit cracks and the plant gets stressed. Aim for steady moisture, not wet-dry-wet-dry. Mulch around the base with two inches of wood chips or straw to keep soil temperature even and reduce how often you need to water.
Warm the Soil and Keep It Warm
Tomatoes are warm-season plants. They barely grow when soil temperature is below 60°F, and they grow fastest when soil is between 70°F and 85°F. If you plant too early in spring, the roots sit in cold soil and the plant just sits there, even if the air feels warm.
Wait until soil has warmed up before planting. In most places, this is two to three weeks after the last frost date. You can check soil temperature with a soil thermometer (they cost five to ten dollars at any garden center) or feel it yourself—if the soil feels cold to your bare hand, it's too cold for tomatoes.
If you're growing in pots, dark pots absorb more heat than light ones, so a black or dark brown pot will warm the soil faster than a white one. If you're in the ground, lay black plastic or landscape fabric over the bed a week or two before planting to trap heat. Remove it after planting so you can water, but the soil will stay warmer underneath.
Stake or Cage Tomatoes Early
Tomato plants get heavy. A full-grown plant with fruit can weigh twenty to thirty pounds, and the stems aren't strong enough to hold that weight without breaking. If the plant falls over, the fruit touches the ground and rots, and the stems snap.
Put a stake or cage in place when you plant or when the plant is still small—six to twelve inches tall. A stake should be at least five feet tall for most varieties (some grow taller). Drive it into the ground a few inches away from the stem so you don't damage roots. As the plant grows, tie the main stem loosely to the stake with soft string or cloth strips every eight to twelve inches, leaving a little slack so the stem can move in the wind.
A cage works the same way but is easier if you're growing several plants. Push the cage down over the plant when it's small so the stem grows up through the middle. Make sure the cage is sturdy—flimsy cages tip over when the plant gets heavy.
Feed Tomatoes at the Right Time with the Right Balance
Tomatoes don't need much fertilizer if your soil is decent to begin with. A handful of compost mixed into the planting hole is often enough. But once the plant starts flowering, it needs a boost to make fruit.
When you see the first flowers, start feeding with a balanced fertilizer—something labeled 10-10-10 or 5-5-5 works well. Follow the package directions for how much and how often (usually every two to three weeks). Once the first fruit starts to form, switch to a fertilizer lower in nitrogen, like 5-10-10 or 5-20-20. Nitrogen makes leaves grow; potassium and phosphorus make fruit. If you keep feeding high-nitrogen fertilizer, the plant will make lots of leaves but fewer tomatoes.
If leaves turn yellow, the plant might need nitrogen or it might be getting too much water. If the plant looks healthy but won't flower, it might be getting too much nitrogen (too many leaves, no flowers). Watch the plant and adjust based on what you see.
Prune Suckers on Indeterminate Varieties
Some tomato varieties grow as a single main stem (determinate), and some keep branching and growing all season (indeterminate). Indeterminate varieties—the ones that grow tall and produce fruit until frost—benefit from pruning.
Look for suckers, which are small shoots that grow in the angle between the main stem and a branch. These don't produce fruit; they just steal energy from the plant. Pinch them off with your fingers when they're small, or cut them with scissors. Leave the main stem and the main branches alone.
Don't over-prune. The leaves feed the fruit, so if you remove too many, the fruit won't ripen well. A light pruning—just removing the obvious suckers—is enough.
Frequently Asked Questions
Why are my tomato leaves turning yellow?
Yellow leaves usually mean either too much water (roots are drowning) or not enough nitrogen. Check the soil first—if it's soggy, let it dry out and water less often. If the soil is fine, feed with a balanced fertilizer. Lower leaves turning yellow as the plant gets older is normal and not a problem.
How do I know when to pick tomatoes?
Pick tomatoes when they're fully colored but still slightly soft to the touch. They'll ripen off the vine if you pick them at the "breaker stage"—when the first blush of color shows. If frost is coming and tomatoes are still green, pick them all and set them on a windowsill indoors; they'll ripen over a week or two.
Can I grow tomatoes in a pot?
Yes. Use a pot at least five gallons (a standard bucket size) and fill it with potting soil, not garden soil. Pots dry out faster than the ground, so you'll water more often. Everything else—sun, feeding, staking—is the same.
What's the difference between determinate and indeterminate tomatoes?
Determinate varieties grow to a set size, flower all at once, and produce most of their fruit in a short window. They're good for canning. Indeterminate varieties keep growing and producing fruit all season until frost. They need more staking and pruning but give you tomatoes from summer through fall.
Why do my tomatoes have hard spots or cracks?
Hard spots (blossom end rot) come from calcium deficiency, usually caused by inconsistent watering. Cracks come from the same thing—the fruit swells fast when you water after a dry spell and the skin splits. Water steadily and mulch to keep soil moisture even.