Watermelon Seedlings Views

General Goods

The fungal diseases gummy stem blight, Alternaria leaf blight, and anthracnose can be introduced into the greenhouse on watermelon seed or through inoculum from a previous crop. To minimize the occurrence of these diseases, the greenhouse should be disinfected before planting (benches, walls, walkways, etc.). The seed source should have tested negative for the pathogen with a minimum assay number of 1,000 seeds. Use clean transplant trays (disinfect trays if they will be reused) and new soil. Destroy any volunteer seedlings and keep the area in and around the greenhouse weed free. Avoid overhead watering if at all possible, or water in the middle of the day so that the plants dry thoroughly before evening. Keep relative humidity as low as possible through proper watering and good air circulation in the greenhouse.

Bacterial fruit blotch (BFB) of watermelon is caused by a bacterium that also is seedborne. Initial symptoms of BFB are water-soaked areas on the lower surface of the cotyledons. BFB lesions will become necrotic often with yellow halos. Lesions are frequently delimited by veins. Infected seedlings collapse and die. Angular leaf spot, which also is a bacterial disease, occurred in Delmarvas’s greenhouses several years ago. Symptoms are small, dark brown, irregular lesions on cotyledons or leaves. ALB is favored by cool wet weather. Usually conditions after transplanting to the field do not favor ALB disease development.

Watermelon vines require considerable space. Plant seed one inch deep in hills spaced 6 feet apart. Allow 7 to 10 feet between rows. After the seedlings are established, thin to the best three plants per hill. Plant single transplants 2 to 3 feet apart or double transplants 4 to 5 feet apart in the rows.

Start the seeds inside 3 weeks before they are to be set out in the garden. Plant 2 or 3 seeds in peat pellets, peat pots or cell packs and thin to the best one or two plants. For expensive seedless types, plant one seed to a pot or cell and discard those that do not germinate. Do not start too early - large watermelon seedlings transplant poorly. Growing transplants inside requires a warm temperature, ideally between 80 and 85°F. Place black plastic film over the row before planting. Use a starter fertilizer when transplanting. If you grow seedless melons, you must plant a standard seeded variety alongside. The seedless melon varieties do not have the fertile pollen necessary to pollinate and set the fruit.