I am often asked, ‘How often do you water tomato plants?’ Overwatering roots can break or split ripening fruits. Lack of water can diminish production or induce blossom end rot.
Watering tomato plants: how often? has no simple fix. The tomato plant's growth stage (transplants need less water than fully established plants), soil type (gardens and containers), pot material, and weather (hot, dry weather need more watering).
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It's easy to determine when to water indeterminate, determinate, hybrid, or heirloom tomato plants. Gardeners recommend watering tomato plants an inch or two per week. Daily, I check if my tomato plants need water.
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My tomato plants need watering twice a week early in the season. After they mature and start flowering and fruiting, I irrigate my container-grown tomatoes almost daily and deep water my garden tomatoes once a week. I also discovered some basic watering reduction measures, which are below.
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Understand that irregular tomato watering is as terrible as too little. Bloom end rot can occur in tomato plants, especially potted ones, that dry out. Jessica's great essay explains blossom end rot, calcium deficit, and prevention.
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Plum, cherry, and sandwich tomato plants in the garden need less watering than those in containers, especially if mulched. Weather, soil type, and whether you cultivate in raised beds or in-ground gardens affect watering frequency. In-ground garden beds dry slower than raised beds.
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My raised bed tomato plants are watered weekly in summer unless it's gloomy and damp. Three inches of straw mulch around my tomato vines retains moisture and reduces watering.
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Growth stage is another consideration. After my tomato plants start fruiting in mid to late summer and I start getting red fruits, especially large-fruited heirloom tomatoes like Brandywine, I cut back on watering to concentrate flavors and reduce splitting and cracking.
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Tomatoes in pots, planters, window boxes, cloth bags, and other containers need more water than those in garden beds. Since they're grown above ground, the container's top and sides get full sun.
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Potted tomato roots have less soil than garden bed roots. There are advantages to growing tomatoes in containers. Fusarium and verticillium wilt reduction is the main benefit.
The size of the tomato plant, the container, the growing medium, and the weather determine how often it needs watering. In late spring, my transplanted tomato seedlings need less watering than my late July plants.
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I reduce watering my garden beds' large-fruited tomato plants in mid to late summer when their clusters of fruits ripen. This concentrates fruit tastes and minimizes water-induced cracking and breaking.
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