June 27, 2025, 1:35 am | Read time: 3 minutes
Tomatoes are among the most popular vegetables to grow at home—and for good reason. Compared to store-bought tomatoes, homegrown ones can offer superior taste and value despite the extra effort involved. myHOMEBOOK gardening expert Franka Kruse-Gering explains why it’s crucial to water tomato plants correctly.
Many gardening enthusiasts make a crucial mistake when watering tomatoes: they pour water over the entire plant–including the leaves. This can promote diseases and, in the long run, jeopardize the harvest. Tomatoes should always be watered from below.
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1. Wet Tomato Leaves Promote Fungal Diseases
Tomatoes are prone to fungal diseases such as powdery mildew. Constantly wet leaves create a humid microclimate around the tomatoes. Wet leaves play a central role in this–they provide the ideal breeding ground for spores that are spread by wind, rain, or contact. While avoiding wet leaves doesn’t guarantee that tomatoes will remain disease-free, it does minimize the risk.
2. Plants Get Sunburned
Not only fungal diseases but also sunburn can become a problem if the leaves of the tomato get wet during watering. If water droplets remain on the leaves after watering and then strong midday sun hits them, the droplets act like small magnifying glasses. The concentrated sun rays can literally “burn” the plant tissue.
The result is light, dry spots on the leaves, sometimes even on the fruits. These are irreparable damages. Young plants or freshly pruned shoots are particularly at risk because their tissue is still sensitive. Therefore, it’s best to water tomatoes early in the morning, directly at the root–so any moisture on the leaves can evaporate before the hot part of the day.
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3. Disrupted Air Circulation
Moist leaves increase the humidity around the plant. Combined with dense planting or stagnant air, the risk of heat buildup and mold increases.
Tomato plants need fresh air–not only to grow healthily but especially to allow moisture to dry quickly. If the air around the plant doesn’t circulate well, water remains on the leaves longer after watering or a rain shower. This creates a humid-warm microclimate, ideal for the development of fungal diseases–especially late blight and brown rot, which can destroy entire plants within a few days.
Therefore, it’s important to plant tomatoes with sufficient spacing and to ensure that the leaves don’t get wet when watering.