Watermelon plants are vigorous vining crops that traditionally sprawl across the ground, consuming a large amount of garden space. While they do not strictly require a trellis, they benefit significantly from vertical cultivation. The decision to use a trellis depends primarily on the available space and the specific variety of watermelon being grown. For gardeners with limited space or those aiming to improve plant health, trellising is an effective cultivation strategy.
Deciding Whether to Grow Vertically
The most compelling reason for growing watermelons vertically is the efficient use of limited gardening space. A single watermelon vine can easily spread out to cover a 15-foot diameter circle on the ground, making ground cultivation impractical in small yards or container gardens. Utilizing a trellis allows the plant to grow upward, maximizing yield within a minimal footprint.
Selecting the right variety influences the decision to trellis, as smaller melons are more manageable. Varieties classified as “icebox” or “midget” types, such as ‘Sugar Baby’ or ‘Golden Midget,’ typically produce fruit weighing under 10 pounds, which is ideal for vertical support. Standard ‘picnic’ watermelons, which can weigh 20 to 30 pounds, require an exceptionally strong structure and are generally too challenging for the average home gardener to trellis effectively.
Lifting the foliage off the soil provides health benefits by improving air circulation around the vines. Enhanced airflow allows the leaves to dry more quickly after rain or watering, deterring common fungal diseases like powdery mildew and anthracnose. Vertical growing is also advantageous when the native ground soil quality is poor or has drainage issues that could lead to root problems.
The trellis structure must be built with significant sturdiness to support the combined weight of the vines, leaves, and developing fruits. Common designs like A-frames or cattle panel trellises are popular because they are inherently strong and provide ample surface area. Watermelon tendrils are not strong enough to grip the support structure on their own. Therefore, the vines must be manually tied to the trellis using soft materials as they grow.
Supporting the Developing Fruit
Once the vines are trained to climb, the unique challenge of vertical cultivation is providing mechanical support for the heavy fruit. Unlike lighter vining vegetables, watermelons must be physically cradled to prevent the vine from snapping under the weight. The weight of a developing fruit exerts tension where the stem attaches to the vine, which can cause the fruit to prematurely drop or damage the main vine.
Support must be implemented relatively early in the fruit’s development, ideally as soon as the melon reaches the approximate size of a tennis ball or softball. Waiting until the fruit is much larger increases the risk of damaging the vine while attaching the sling. The most effective method is to create a sling or hammock for each developing fruit.
Slings can be fashioned from various flexible and durable materials, such as old nylon stockings, strips of soft t-shirt fabric, or mesh produce bags. The material should be breathable and stretchy enough to accommodate the melon’s rapid growth without constricting it. When securing the sling, it is crucial to tie the material directly to the main trellis structure, not to the fruit stem itself.
This technique ensures that the weight of the growing fruit is transferred directly to the rigid trellis frame, relieving strain from the tender vine. As the melon continues to expand, the gardener must monitor and adjust the sling to guarantee the fruit is resting fully within the cradle. This support system allows the plant to focus its energy on ripening the fruit rather than struggling to hold it aloft.
Managing Ground-Grown Watermelons
For gardeners with ample space, the traditional method of allowing watermelon vines to sprawl across the ground remains a viable option. This approach requires providing sufficient area, as the sprawling vines need a large, unobstructed radius to grow effectively. Proper spacing of at least 6 to 8 feet per plant is necessary to allow the foliage to spread and maximize sun exposure.
Cultivating watermelons on the ground requires specific mitigation strategies for pests and disease. Placing a thick layer of straw, plastic mulch, or cardboard beneath the developing fruit and vines serves as a protective barrier against soil-borne pathogens and pests. This barrier keeps the underside of the fruit clean and dry, significantly reducing the chance of rot or insect damage.
A common practice in ground cultivation is the gentle “turning” of the fruit every few days once it starts to swell. This rotation helps ensure that the entire surface of the melon receives even sun exposure for uniform ripening and color development. Turning also prevents the bottom side of the fruit from developing a flat spot or becoming overly wet, which can lead to rot.
Ground-grown melons signal their readiness for harvest through a specific change in the tendril closest to the fruit stem. When this tendril withers and dries out completely, it is a reliable indicator that the melon is likely ripe. Additionally, the pale spot on the underside of the melon, where it rests on the ground, should change from a pale white or light green color to a creamy yellow hue.