Tomatoes are among the most rewarding plants a home gardener can grow, and indeterminate tomatoes are especially popular for their large harvests and extended growing season. If you’re dreaming of a summer filled with juicy tomatoes fresh off the vine, learning how to properly grow and care for indeterminate varieties is key. Here’s everything you need to know to get started — from planting to harvesting.
What Are Indeterminate Tomatoes?
Before diving into care tips, it’s important to understand what “indeterminate” means. Unlike determinate (or “bush”) tomatoes, which grow to a set size and produce all their fruit at once, indeterminate tomatoes keep growing, flowering, and producing fruit until frost kills them. These varieties can reach 6 to 10 feet tall — sometimes even taller — and require regular support and pruning to stay healthy and manageable.
Popular indeterminate varieties include ‘Brandywine’, ‘Cherokee Purple’, ‘Sungold’, and ‘Beefsteak’.
Starting Seeds Indoors
If you’re growing from seed, you’ll want to start indoors about 6-8 weeks before your area’s last frost date. Use seed trays or small pots filled with a quality seed-starting mix. Sow the seeds about ¼ inch deep, keep the soil moist, and place the trays somewhere warm (around 70–75°F/21–24°C).
Once the seedlings emerge, move them to a bright, sunny window or place them under grow lights. When they develop their first set of true leaves, you can transplant them into slightly larger containers to keep them growing strong until outdoor planting time.
Hardening Off
Before moving your indeterminate tomato plants outside, it’s crucial to harden them off. This means gradually introducing them to outdoor conditions over 7–10 days. Start by setting them outside in a sheltered spot for a couple of hours a day, slowly increasing the time and exposure to sunlight and wind. Hardening off helps prevent transplant shock and sets the stage for a healthy growing season.
Planting in the Garden
Once the danger of frost has passed and nighttime temperatures consistently stay above 50°F (10°C), your indeterminate tomatoes are ready to be planted outside. Choose a sunny location — tomatoes need at least 6–8 hours of direct sunlight daily.
Prepare the soil by working in plenty of compost or well-rotted manure. Tomatoes prefer slightly acidic soil with a pH of 6.0 to 6.8. When planting, bury the seedling deeper than it was in the pot — up to the first set of true leaves. Tomatoes can develop roots along their buried stems, which results in stronger, more resilient plants.
Space your plants about 24–36 inches apart to allow for good air circulation, which helps prevent disease.
Supporting Your Tomatoes
Indeterminate tomatoes grow tall and heavy, so they need support from the beginning. There are several methods you can use:
- Tomato Cages: Easy to use but may not be sturdy enough for very large plants.
- Stakes: Drive a strong wooden or metal stake into the ground near each plant and tie the plant to the stake as it grows.
- Trellising: A strong trellis or string line can help train tomatoes vertically, saving space and improving air circulation.
Start supporting your plants when they are young to avoid damaging roots later on.
Watering and Mulching
Tomatoes need consistent moisture, especially once they start setting fruit. Aim for about 1–2 inches of water per week, either through rainfall or supplemental watering. Water deeply and at the base of the plant to encourage deep root growth and to keep the foliage dry, which helps prevent fungal diseases.
Adding a thick layer of mulch (such as straw, shredded leaves, or grass clippings) around your plants has several benefits:
- Retains soil moisture
- Reduces weeds
- Keeps soil temperatures stable
- Prevents soil from splashing onto leaves (reducing disease risk)
Feeding
Indeterminate tomatoes are heavy feeders. Start with rich soil, but once the plants begin setting fruit, feed them every 2–4 weeks with a balanced fertilizer or one slightly higher in phosphorus (the middle number in fertilizer ratios). Organic options like compost tea, fish emulsion, or bone meal can also provide steady nutrition.
Be cautious not to overdo it with nitrogen-rich fertilizers, as they encourage leafy growth at the expense of fruit production.
Pruning
Pruning is one of the most important aspects of caring for indeterminate tomatoes. These plants naturally grow lots of side shoots, called suckers, which appear in the joint between the main stem and a branch. Left unchecked, suckers can make the plant bushy, crowded, and more prone to disease.
To prune:
- Pinch off suckers when they are small (2–4 inches long).
- Focus on creating one or two main stems for the plant.
- Remove lower leaves that touch the ground as the plant grows taller.
Pruning improves airflow, reduces disease risk, and encourages the plant to focus energy on producing fruit instead of excess foliage.
Managing Pests and Diseases
Indeterminate tomatoes are susceptible to common garden pests like aphids, hornworms, and whiteflies, as well as diseases like blight, fusarium wilt, and powdery mildew.
Good practices to manage these problems include:
- Inspecting plants regularly for pests and hand-picking them off
- Using insecticidal soap for minor infestations
- Rotating crops each year to avoid soil-borne diseases
- Watering at the base to prevent fungal infections
- Keeping foliage dry and removing any diseased leaves immediately
If blight or another disease takes hold, remove and destroy infected plants to prevent spread.
Harvesting
One of the joys of growing indeterminate tomatoes is their long harvest season. Tomatoes are ready when they are fully colored and slightly soft to the touch. Pick fruit regularly to encourage more production.
If frost threatens in the fall and you still have green tomatoes on the vine, you can pick them and ripen them indoors by placing them in a warm, dry place out of direct sunlight.
Final Thoughts
Growing indeterminate tomatoes requires a bit more attention and effort compared to determinate varieties, but the rewards are well worth it. With the right care — from good soil preparation to consistent watering, support, and pruning — you can enjoy fresh, flavorful tomatoes from early summer all the way to the first frost. Whether you’re slicing them into salads, making sauces, or simply enjoying them right off the vine, few gardening experiences are as satisfying as harvesting your own homegrown tomatoes.