String trellising is a vertical support method widely used for growing vining tomato plants. This technique involves suspending a strong string from an overhead support down to the base of each plant, allowing the main stem to be trained upward along the line. It is a highly efficient, space-saving practice favored by commercial growers for managing vigorous growth.
Why Choose String Trellising
The string trellising system is uniquely suited for indeterminate tomato varieties, which continue to grow, flower, and fruit throughout the entire season. These vining plants can easily reach heights of ten feet or more, and traditional cages or short stakes often fail to provide adequate support for their continuous growth and heavy fruit load. This method manages the plant’s height while promoting a single, vertical stem structure.
Maximizing vertical space allows gardeners to plant tomatoes closer together, increasing the total yield in a small area. Keeping the foliage off the soil surface improves air circulation, which reduces humidity within the canopy. This enhanced airflow minimizes the risk of common soil-borne fungal diseases that thrive in moist conditions. The single-stem column also makes it easier to inspect the plant, prune effectively, and access the fruit for harvest.
Preparing the Supports and Materials
Setting up the infrastructure requires sturdy materials that can withstand the significant weight of mature, fruit-laden tomato plants. Indeterminate tomato plants can exert a downward pull of ten to twelve pounds each, so the overhead support must be robust. This support system typically consists of a high horizontal line, such as a strong wire, pipe, or wooden beam, suspended at least six to eight feet above the ground.
If a greenhouse or permanent structure is not available, vertical supports like T-posts, thick wooden posts, or rebar must be driven deep into the ground to hold the horizontal support. The string used for the trellising should be heavy-duty, such as thick polypropylene or baling twine, which is strong, weather-resistant, and gentle on the stems. Synthetic materials like polypropylene are often preferred for their durability throughout the long growing season.
Step-by-Step Guide to Tying Tomato Plants
The process begins with securing the string at the base of the tomato plant, ideally when the plant is young, around one foot tall, and before it produces its first fruit cluster. The string must be anchored securely near the main stem without risking girdling or cutting into the stem as it thickens. One common technique is to tie the string to a landscape staple or metal pin driven into the soil next to the plant.
Alternatively, the string can be tied in a loose loop around the main stem just beneath a strong, low leaf branch, using a slipknot to allow for stem expansion. The string is then run straight up and tied tautly to the overhead wire or support beam. This tension is essential for the system’s stability and provides the necessary vertical resistance for the plant to climb.
As the plant grows, the main stem is gently trained to wrap around the string in a consistent direction, typically clockwise, to keep the plant close to the support. This winding action is done by carefully twisting the top few inches of the plant around the string. Handle the stem gently to avoid snapping the tender growing tip, which would terminate the upward growth. This training must be performed weekly to keep pace with the plant’s rapid vertical growth and maintain the single-stem structure.
Maintenance and Ongoing Care
The success of string trellising is closely linked to consistent pruning, which focuses the plant’s energy into the single main stem and fruit production. The primary maintenance task is the removal of suckers, which are the small side shoots that emerge in the axil between the main stem and a leaf branch. Removing these suckers directs energy toward the main stem and fruit, rather than diverting it into unnecessary foliage.
Suckers should be pinched off when they are small, ideally less than four inches long, to create a smaller wound that heals quickly. In addition to suckering, the lowest leaves, especially those touching the soil, should be removed to prevent soil-borne pathogens from splashing onto the foliage. Regular weekly checks are necessary to continue winding the plant around the string and to remove any new suckers.
If the plant grows taller than the support, a commercial technique known as “lowering and leaning” can be used. This involves gradually lowering the string and leaning the plant’s base to the side to keep the fruiting zone within reach. At the end of the season, the plant and the string can be cut at the base and removed for easy cleanup.