Answer: Tomatoes crack in the summer heat when the water supplied to the plant has been irregular. When tomatoes are almost ripe, the skin stops growing but the tissues inside swell when they get a big drink of water. The resulting pressure causes the skin to crack, and cracking can lead to bacterial soft-rot (black holes). Try giving your plants only one-inch of water per week, making it a thorough soaking of the root mass. Then allow the soil to dry before watering again.
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