No one knows when man first started manipulating agricultural crops through trellising, but nature had already discovered the value of upward mobility long before that fateful day dawned.
Many vining plants are natural climbers; they seek higher ground, as elevation provides less competition for sunlight. In the garden, agriculture, and the growroom, the benefits of trellising are obvious. It saves space, making it possible to grow plants closer together and still achieve impressive results.
Garden maintenance doesn’t require as much bending and stooping, either. Trellised plants may be in a better position to thrive than their ground dwelling brothers, too. Trellising often enhances air flow to plants, reducing problems with powdery mildew, other fungi, and diseases that thrive in moist, still conditions.
It also provides some degree of protection from pests that either can’t, or are reluctant to, climb to make a meal of tender vegetation aloft. Depending on the crop, these advantages can reduce losses. Getting fruiting plants up off the ground may also produce more attractive and uniform results, such as eliminating white spots on cucumbers and squash.
Even though some crops produce smaller or lower weight specimens when trellised, overall yields can be higher to make up for the shortfall. Even better, it’s not hard to implement a trellis system.
Although a trellis is traditionally considered either a horizontal or vertical latticed structure, trellising a plant can be as simple as constructing a bamboo tripod or growing beans up a corn stalk (similar to the classic three sisters approach).
A trellis doesn’t just keep plants from falling over, though. It’s a support structure that allows plants to develop vertically, or even laterally, in a way their stems would not otherwise support. A white picket fence groaning under a luxuriant growth of bougainvillea vine is assuming the duties of a trellis.
Ivy clinging to an oak tree is using the tree’s branches as a trellis, too. The type of vertical trellis many gardeners envision for their vegetables and other plants can accommodate multiple specimens. It is usually constructed inside a sturdy frame or attached to vertical supports pounded two to four feet into the soil.
Plants grow along a wire grid, fabric net, or series of suspended cables or lines secured to the structure. A variety of materials can be used in the construction of the frame and posts, like wood, steel, aluminum, or bamboo.
Depending on design, grid materials can include cotton clothesline, nylon, or other plastic mesh (trellis netting), polyester twine, hemp or flexible wire secured with knots, U-shaped fencing nails, and sod staples.
Prefabricated materials designed for gardening or other applications are sometimes employed, too. Some favorites are PVC tubing, metal fencing like hog panels or cattle panels, and, of course, complete trellis kits.
A trellis can be almost any height or length, though anything over six feet high and longer than six feet wide may cause maintenance headaches (you’ll have to reach up or walk around the structure for maintenance).
Trellises can also be angled to help maximize the sunlight hitting plant leaves, or they can be designed as decorative yet functional elements in the landscape. Arbors are examples of trellising at its most beguiling, and we’d be remiss if we didn’t mention the remarkable French art of espalier (stylized fruit tree trellising), which requires dedication and expert pruning.
Not all trellis materials are compatible with all plants or all growing strategies, though. For instance, climbing plants that have leafless stem tendril structures typically require narrow gauge horizontal and vertical gridded support to achieve firm, stable attachments, while many plants without tendrils work well with trellises that employ clips or those that can be secured easily with string or zip ties.
Here is another example: Rotating your crops annually is a common recommendation when growing tomatoes. If your goal is to trellis tomatoes, a portable trellis (or one that can be disassembled easily or re-purposed) would be preferred to a fixed, durable structure. Adding a large mesh or grid network to that trellis would also make it easier to harvest the tomatoes once they ripen.
The types of plants you grow will inform your decisions about materials and the overall style of the trellis you choose. Still, even with this wealth of diversity in trellis design and function, successful plant trellises do have characteristics in common.
First, they must be established on a site compatible with the plants you plan to grow, and you must prepare the soil as you would normally.
For the best utilization of sunlight, choose a north/south row orientation. Next, leave 12-14 inches of open space along the bottom of the trellis frame to help increase air flow and make it easier to monitor the bed and keep it free of debris.
If you plan to install multiple trellises, place them far enough apart that they won’t cast unwanted shade on one another. You can guestimate the distance by determining the likely width of the plant canopy for each mature trellis.
Also, if using twigs to build a rustic trellis like the classic British “pea stick,” position the finished structure 10 feet or more from the nearest building to avoid making your home attractive to wood-eating pests.
Finally, be sure to erect all your trellises before adding the plants. One of the biggest complaints about trellises is that they can topple under the weight of a maturing crop if not built and secured properly. Plants may look delicate, but they get heavy, especially after a rain or when laden with fruits or vegetables.
A mature cucumber is about 96 per cent water, and a mature tomato is 94 per cent water; at more than eight pounds per gallon, water weight adds up. Add an inch of fresh rain and you have a potential recipe for disaster.
In a trellis, the load is supported by vertical posts or poles. If anything, design and build a sturdier structure than you think you’ll need, especially when it comes to choosing materials and pounding posts or digging post holes.
Posts inadequate to the job will pull right out of the ground and undersized PVC pipe will bow from the weight of heavy plants, destroying a season’s worth of effort. Your plants will only be as secure as the structure you built for them.
Although vining plants are a natural choice for a trellis, they aren’t the only options. Some popular non-vining plants can be “trained” to climb. One of the most popular examples is the tomato.
Although most tomatoes aren’t vines, tomatoes can be manipulated into growing along a single or double stem by pruning away suckers, the growth between the Y of the main stem and branch. Tomatoes trellised this way won’t produce anchors like tendrils, but judicious manual anchoring will direct the plant’s energies into aerial growth and its resulting benefits.
Even vining plants can develop side shoots and create problems on a trellis if they aren’t carefully pruned. Cucumbers are a good example. Carefully removing suckers to maintain a single main stem can keep cucumbers and other vines on the straight and narrow, just like it can tame a sprawling tomato plant.
When pruning some fruiting vines to achieve a single stem habit, use caution. All that side greenery isn’t necessarily extraneous. On the same Y juncture where you may find a sucker, which is characterized by its leaf development, you might also encounter essential growth like a tendril, flower, or small fruit.
Familiarize yourself with the appearance of all the plant’s growth stages before you grab your shears or prepare to pinch. If you do want side shoots to develop, control their numbers to help maintain good air flow and curtail excess growth below waist level, where competition for light is fierce.
Pay attention to the anchoring structure of the vines you’re installing, too. Instead of the tendrils we discussed above, some vines attach by hugging surfaces with elongated leaf stems, in which case they may prefer wider or narrower supports. Others use adhesive disks (yes, like glue) to attach themselves.
These anchors are effective, but to make good contact, they need a textured surface rather than a smooth material like PVC or vinyl. Vines with aerial roots also require textured surfaces. Yes, a plant, even a vine, can be manually secured using clips or twine, but taking advantage of its natural inclinations makes the job of maintaining a successful trellis easier.
The plants will secure themselves, even though their choices may occasionally need some adjustment. When you do manually secure growing vines or other plants, select materials that won’t cut delicate stems, and tie or loop them loosely enough to allow for stem expansion as the plant matures.
There are proponents of most of the popular securing material options on the market. Detractors warn that thin poly twine can cut plants, while natural fibers can only be used for a single season and may break under heavy weight.
Plant clips, sometimes called vegetable clips, are common. They’re typically more expensive than twine, but can be used season after season and are available in a number of sizes. Clips open to reveal a groove, and once the plant is closed inside the groove, the clip, usually a ring in shape, will lock in place.
Simple zip ties are becoming popular securing choices, too. They’re inexpensive, reusable, and can be utilized with many different trellis grid materials.
Additional Tips for Trellising Your Plants
Choose young specimens that will grow into the trellis structure. Plant these seedlings a few inches in front of the trellis, but not so far that the stems have to bend or lean to make contact as they grow. To help train them in place, tie the seedlings with loose twine.
Also, fertilize on a regular schedule. Although you can typically place trellised plants closer together than you would if they were growing along the ground, they will still be competing for nutrients in the soil.
When the time comes, prune your plants in accordance with the instructions for each variety you’re cultivating. Removing less foliage more frequently is usually better for a plant than marathon pruning. With the exception of winter prep, avoid taking more than a third of a plant in a single pruning session.
Also, if pest or disease problems aren’t an issue, waiting until spring to clear away stiff, dead stems and leaves can make the work easier. Finally, some crops may need additional support as they ripen.
For example, large melons and squashes may require slings or hammocks for individual fruits. (See: Delectable Delights: Growing Hydroponic Melons and Eggplants)
Adding a trellis to your landscape will offer plants enhanced access to sunlight and better air flow. This can increase vegetable crop yields and keep trellised plants healthier.
A trellis can also create a focal point in your garden and free up some space for other things. If you’re a plant lover, that means more seedlings to enjoy. That’s a lot of traction for a project you can complete in a weekend.