Why Are My Baby Watermelons Starting to Shrivel, Get Squishy & Then Rot on the Vine?

Blossom End Rot

• Blossom end rot can occur even when there is enough calcium in the soil. Acidic soils do not allow baby watermelons to absorb the available calcium. When your soil pH is below 6.3, baby watermelons are unable to absorb the nutrients, including calcium, in the ground. Other factors like inconsistent watering or excessive use of nitrogen fertilizers contribute to the plant's inability to absorb calcium. It is important for gardeners to test their soil's pH to find out if they need to make the soil more alkaline.

Symptoms

• Monitor your developing baby watermelons during the growing season for signs of blossom end rot. Symptoms include dark lesions on the blossom end of your baby watermelon, watermelons taking on a leathery texture and watermelons shriveling and rotting. Fruit exhibiting signs of blossom end rot must be removed from your garden. Plants may be treated with a spray to stop future fruit from developing blossom end rot.

Treatment

• Spray your affected plants with a calcium chloride solution, as suggested by the University of Minnesota. Mix up 2 tbsp. of calcium chloride solution with 1 gallon of water, according to gardening writer Walter Reeves. Apply the mixture to your baby watermelon plant in the morning. Late afternoon applications run the risk of evaporating during the hot temperatures of the afternoon. Apply a layer of mulch around your watermelon plants to help conserve moisture.

Prevention

• Test your soil to ensure that there is enough calcium for plant growth. You can send 1 cup of soil to your local cooperative extension to obtain a soil analysis. Furthermore, avoid applying a fertilizer that contains ammonium nitrate. When fertilizing your watermelon planting area, make sure that you water deeply to allow the nutrients to absorb into the soil for root uptake. Using a soaker hose helps a provide slow, steady watering.