My Topsy Turvy Tomato Planter Has Black Leaves

Watering

• Water on the leaves can cause fungal diseases that look like black spotting. Anytime it rains a lot or you wet the plant while irrigating, the wet spots can attract fungal diseases. If your upside-down tomato is inside or on a closed patio, the breezes or sun may not dry out the plant sufficiently. If the drainage at the bottom of the container is insufficient, water can pool inside and heat up when sun warms the container, creating an ideal environment for various types of root rot, bacterial and fungal diseases. To prevent these problems, make sure the container drains well. Water at least every other day and avoid spraying water on the leaves.

Fertilizer

• Potted tomatoes are easily over-fertilized. Fertilizer salts can accumulate in the pot over time, especially if you fertilize frequently with liquid tomato fertilizers. Excessive fertilizer in the container soil can burn the leaves of the tomato plant, especially if the leaves are wetter than the soil, as in damp, rainy or foggy weather.

Spacing

• Tomato plants need room to grow, even the upside-down ones. Containers should be hung 2 to 3 feet apart or more to allow plenty of room for sunlight to reach the leaves and for breezes to pass between the plants. This helps keep the foliage dry and improves pollination. If plants are too close together or touch each other, it can encourage the establishment of diseases among your plants, including the types that blacken leaves.

Early Blight

• Alternaria leaf spot causes brown to black target-shaped spots on the older leaves of tomato plants. Alternaria, also called early blight, eventually turns leaves yellow with large black spots. The leaves drop off and expose the fruit to sunscald. The best way to control for blight is to remove any diseased plant material on the plant or nearby. Increase spacing between the plants to improve air circulation and dust with sulfur dust if the leaves were heavily infested to prevent reinfestation.

Wilt and Crown Rot

• Fusarium wilt and Fusarium crown rot begin as yellowing on older leaves. In crown rot, leaves turn brown, black and then wilt and fall off. In wilt, the leaves yellow first, droop, blacken and fall off. Fusarium oxysporum, a common tomato fungus, causes both condition. It lives in the plant's vascular system and grows where the soil is warm and moist. The effects of both over and under-watering can look like fusarium, but check for discolored roots. Discolored roots indicate root rot. You may also find a canker at the base of the stem. You may need to partially shade your plant as the pots are probably getting too hot and creating an ideal environment for fusarium.

Choosing Varieties

• Nurseries label tomato seeds and transplants with a code like "VFN," "VFNA," or "VFNT". The codes indicate what the tomato hybrids are resistant to. V stands for verticillium wilt, F for fusarium wilt, N for southern root-knot nematode, A for early blight and T for tobacco/tomato mosaic virus. If you have problems with blackened leaves, pick a variety that includes “F” in the code as fusarium is resistant to fungicides.