Many plants require support in order to grow healthy. In the case of vegetables, supports also make harvest easier, as the fruit is more visible and easier to access. Supports consist of cages, stakes and trellises. Ideally, the supports are installed at the time of planting and are tall enough or long enough for the plants' maximum height.
Sometimes, especially in the case of indeterminate varieties of tomatoes, the supports may be too short and this isn't realized until halfway through the season. Extending supports without damaging plants depends on the type of support used.
Determine how much bigger the support needs to be. Often an additional 1 or 2 feet is sufficient.
Lengthen a stake with a second stake that is the needed height plus 1 foot. Overlap the second stake 1 foot over the end of the first. Secure to the first with plastic zip-ties or wire.
Extend cages with concrete reinforcement wire. Make a loop of wire the slightly wider than the existing cage. Slide it over the cage until they overlap 1 foot, then attach them together using plastic zip-ties or wire.
Extend the length of trellises using the same supplies used to make the original. Drive a second post into the ground 3 to 4 feet from the end post of the old trellis. Attach the wires or lattice board, depending on what was originally used, between the new post and the last old post.
Extend the height of trellis systems with stakes. Place a 4-foot stake overlapping the top 1 foot of each support post. Attach the stake to the posts with zip-ties, wire or nail in place. Zig-zag twine between two stakes to provide the structure for the plants to climb.