Trellising provides structural support for tomato plants, maximizing health and harvest. Allowing vines to sprawl across the ground exposes the fruit to soil-borne pathogens and pests. By lifting the foliage, trellising improves air circulation, reducing the risk of fungal diseases like blight. This vertical orientation also ensures that developing fruit receives optimal sunlight exposure, leading to better ripening and higher-quality tomatoes.
Understanding Determinate and Indeterminate Growth
The required trellis height is determined by the plant’s genetic growth pattern, which falls into two main categories. Determinate tomato plants, sometimes called “bush” varieties, grow to a compact, predetermined size before setting fruit. Once the terminal bud produces flowers, the plant stops growing taller, focusing energy on ripening the fruit it has already set. This growth habit means determinate plants produce the majority of their harvest within a short, concentrated period.
Indeterminate tomatoes, in contrast, are vining plants that continue to grow, flower, and set fruit continuously until frost. These plants do not have a predetermined maximum height, behaving more like perennial vines. The main stem keeps lengthening throughout the entire growing season, resulting in a steady, season-long supply of tomatoes. Because of this indefinite growth, indeterminate varieties require a substantially taller and more robust support system.
Recommended Trellis Heights
The specific height of the trellis must correspond to the expected mature size of the tomato variety. For determinate varieties, which generally reach 3 to 5 feet, a shorter support system is sufficient. Standard tomato cages or stakes between 4 and 5 feet tall are adequate to keep the plants upright and the fruit off the ground. The goal is to support the heavy, concentrated fruit load rather than accommodate continuous vertical growth.
Indeterminate tomatoes require significantly taller trellises to manage their vining habit, often needing support between 6 and 8 feet high. In regions with long growing seasons, these vines can easily exceed 8 feet, sometimes reaching 10 feet or more, necessitating even taller supports. Systems like the “string trellis” or vertical wire mesh structures are commonly used to maximize this vertical space. While a 6-foot structure might suffice, a height of 7 to 8 feet is advisable to fully support the plant through a long season.
Ensuring Stability for Tall Structures
A tall trellis system, particularly for indeterminate varieties, must be structurally sound to handle the combined weight of the vine, developing fruit, and environmental forces like wind. A mature tomato plant can become heavy, especially when laden with large tomatoes. Therefore, stability is just as important as the height itself.
Anchoring the vertical posts deeply into the ground provides the necessary foundation against high winds and top-heaviness. Sturdy posts, such as metal T-posts or thick rebar, should be driven at least 1 to 2 feet into the soil to ensure they do not shift or lean under load. For structures exceeding 6 feet, using thicker materials is recommended, as thinner bamboo or light-gauge wire will quickly buckle.
Using cross-bracing or a sturdy overhead support wire can significantly increase the overall rigidity of the structure. In systems like the Florida Weave or overhead string trellising, a horizontal wire beam is often run along the top of the posts, connecting the entire row into one strong unit. This method distributes the plant’s weight across multiple anchor points, preventing individual stakes from being pulled out by the heavy canopy.