July is make-or-break for tomatoes. The heat is on, the plants are loaded with fruit, and what you do right now determines whether you're harvesting through September — or watching your plants fizzle out before August. The good news? A little attention this month goes a long way. Here are seven things to do for your heirloom tomatoes in July to keep them producing all summer long.
1. Prune Suckers and Lower Leaves
Suckers — those shoots that sprout in the crotch between the stem and a branch — compete with your fruit for energy. Pinch them off while they're small, especially on indeterminate (vining) varieties. At the same time, remove any yellowing or diseased lower leaves to improve airflow and reduce the risk of soil-borne disease splashing up onto the plant.
2. Deep Water, Less Often
Frequent shallow watering encourages shallow roots. In July, switch to deep, infrequent watering — aim for 1–2 inches per week, delivered slowly so it soaks in rather than runs off. Water at the base of the plant, not overhead, to keep foliage dry and reduce disease pressure. Consistent moisture also helps prevent blossom end rot and cracking.
3. Side-Dress with the Right Fertilizer
By mid-summer, your tomatoes have shifted from building leaves to setting fruit. That means they need less nitrogen (which drives leafy growth) and more phosphorus and potassium (which support flowering and fruiting). Side-dress with a balanced compost or a low-nitrogen tomato fertilizer to give them what they need without pushing excessive foliage at the expense of fruit.
4. Mulch Heavily
If you haven't mulched yet, do it now. A 3–4 inch layer of straw, wood chips, or shredded leaves around the base of your plants does several things at once: it regulates soil temperature, retains moisture between waterings, suppresses weeds, and reduces the splash of soil-borne pathogens onto lower leaves. In the July heat, mulch can be the difference between a stressed plant and a thriving one.
5. Scout for Pests and Disease — Early
July heat brings out tomato hornworms, aphids, and the early stages of fungal diseases like early blight and septoria leaf spot. Check the undersides of leaves regularly. Hornworms are easiest to spot by their frass (dark droppings) on leaves below them. Catch problems early and you can manage them without losing the plant. Once disease spreads or a hornworm population explodes, it's much harder to recover.
6. Stake, Cage, or Tie Up Sprawling Growth
Heavy fruit loads and summer storms are a bad combination for unsupported plants. Walk your rows and tie up any branches that are drooping or at risk of snapping. Use soft ties or strips of fabric — nothing that will cut into the stem. Keeping plants upright also improves airflow and makes it easier to spot pests and ripe fruit.
7. Harvest Promptly and Often
This one surprises a lot of gardeners: leaving ripe tomatoes on the vine too long actually signals the plant to slow down production. Harvest as soon as fruit is ripe — or even a day or two early if you're worried about cracking or pests. The more you pick, the more the plant puts energy into setting new fruit. Check your plants every day or two in peak season.
Keep Growing All Summer
Heirloom tomatoes are some of the most rewarding plants in the garden — but they reward attention. A little pruning, consistent watering, and timely harvesting in July can extend your season by weeks and dramatically increase your total yield.
Looking for new varieties to try next season? Browse our full Heirloom Tomato Collection — from classic slicers to snacking cherries to rare bi-colors. And if you're thinking ahead, stay tuned for our upcoming guide on saving seeds from your summer garden.