Plants are the world’s great opportunists. If they spot a niche, they’ll occupy it. If they spot any little chink of light, they’ll grow towards it. Patches of bare soil are colonized within days, and a drop or two of moisture brings a sudden flush of new growth.
Climbing plants, though, are among the most innovative entrepreneurs of all. Why waste energy on producing woody lignin for self-supporting trunks, plus the deep roots to support it all, when you can just borrow your neighbor’s instead?
Climbers evolved on the ground, where little light reaches. If they were to flower and fruit, they had to find a way to get up to that light. Their evolutionary breakthrough was to co-opt the larger, stronger trees they grew alongside instead of trying to compete with them.
Climbing plants start by creeping about until they find something they can borrow for support. There’s evidence when they’re in this scrambling, horizontal stage, they grow away from the light, as they’re more likely to come across a tree trunk if they grow into the center of the forest than out of it.
Once climbing plants hit something, this physical contact triggers chemical changes which completely alter the way the plants grow. Instead of growing sideways, they now start reaching up, against the direction of gravity. The stems may start twisting round or leaves may modify into tendrils that search out further supports to hitch it upwards. Once they scramble up and over neighboring plants for long enough and high enough, they eventually reach sunlight and can flower and fruit.
It’s a form of parasitism and an incredibly efficient way of saving energy for the important stuff (the flowers and fruit they need to procreate). Luckily for us, those fruits are also some of the most delicious and nutritious you can grow.
A good third of the crops we grow have evolved into climbing plants. They include peas, climbing beans, cucumbers, melons, mashua, grapes, kiwi fruit, and blackberries. You can exploit their natural inclination to tuck themselves in just about anywhere and find a way to the light, meaning you can squeeze a climber into any garden or growing system. They’re the ultimate survivors.
Types of Climbing Plants
Not all climbing crops grow the same way and understanding the different habits they’ve evolved tells you a lot about the conditions they need to thrive.
Examples: Peas, cucumbers, melons
Support with: Wide-gauge netting, pea sticks
Some climbing plants send out delicate, tendril-like feelers to find potential supports. As soon as a cucumber or pea tendril touches something, it hooks on and winds itself in like a corkscrew, pulling the plant closer to the support and creating a spring that can bounce in windy conditions like a car’s suspension system.
Pea tendrils are modified leaves. Other tendril climbers like grapes and passion fruits use shoots produced separately from their stems. Either way, tendrils are too delicate to grip a sturdy pole. They’re better trained onto slender structures like twiggy pea sticks or string mesh netting, though make sure the mesh is about five inches square or those waving tendrils won’t sense the gap.
Larger tendril climbers like melons and cucumbers can be very vigorous, so a little editing helps them concentrate on quality as well as quantity of fruit. Pinch out the growing tips of melons when plants have four strong side shoots. Then, once four good fruits have formed on each stem, pinch out the ends. Pinch out cucumber side shoots two leaves beyond a female flower to encourage more side shoots and more fruits to form.
Twining Climbing Plants
Examples: Pole beans, mashua, kiwi fruit
Support with: Beanpoles and canes in wigwams or A-frames
Other climbers are twiners, winding leaves or stems around their supports as they grow. These are the plants that grow straight up a tree in the wild. Some, like the strangler fig, throttle the host plant to death, leaving the climber free-standing like a hollow pole.
Luckily, twining vegetables aren’t anywhere near as aggressive, though they do tend to be among the most vigorous plants. Pole beans wind round supports with hawser-like strength. Some plants, like mashua use their powerful petioles (leaf stems) to hold on as the plant climbs.
Stem twiners like thicker supports up to three inches in diameter, so build them a sturdy wigwam or A-frame of hazel poles. Leaf twiners need something finer to wrap around, so give mashua slimmer poles, such as bamboo canes, or a post-and-wire framework to grow up.
Scrambling Climbing Plants
Examples: Tomatoes, sweet potatoes, squash, blackberries and other cane fruit
Support with: Trellis, post-and-wire systems, beanpoles, or canes
This group includes all sorts of plants that aren’t, strictly speaking, climbers. Plants that evolved to scramble don’t change chemically when they hit a vertical object like true climbers do, so they don’t hold onto things by themselves. They don’t bother to grow a strong, self-supporting stem either, preferring instead to ramble about on the ground until they find a nice sunny spot where they can fruit. Some have developed adaptations to help them along, like the thorns on blackberries, which hook themselves onto any structure they come across to help the stems leapfrog across vast distances. Squash have tendrils and though they can use them to climb over other plants, they drape over the top rather than holding on tight.
In the garden, scramblers are easily persuaded upwards onto trellis, wigwams, or arches, though you’ll need to tie them in regularly as they won’t hold on by themselves. Train indeterminate tomatoes as cordons (see below).
Training Reluctant Climbing Plants
Plants enjoy many benefits when they climb. They’re able to grow quickly since they don’t have to generate woody stems, meaning they can afford to flower and fruit prolifically too. They don’t need large expanses of bare earth, just a foothold alongside something to clamber up. They’re also adaptable and flexible, making the most of sunshine to ripen their fruit. All these are also good reasons to persuade plants to grow like climbers when they wouldn’t normally do so.
Training can sometimes seem technical, but it all uses the same basic principle: you develop a stem framework, then shorten any side shoots to persuade them to bear fruit instead of developing into extra branches. There are three main formulas, each used for different types of crop:
Used for: Tomatoes, apples, gooseberries, redcurrants
A single stem with side shoots trimmed back so the plant concentrates on fruiting rather than producing any extra vegetative growth. Tomato cordons are trained vertically onto a cane, and the side shoots are snapped out completely at the junction between leaf and main stem. Fruit cordons, on the other hand, are usually grown at 45 degrees from vertical, as this prompts the plant to produce more fruiting spurs, and the side shoots pruned back rather than removed completely.
When to prune: In winter while establishing and in summer for shaping and maintenance. Tomatoes are pruned continuously throughout the growing season.
Getting started: Plant trees at a 45-degree angle and add a cane for support and to keep the stem straight, tied in to the support wires. Leave the leader and any short side shoots unpruned to begin with, but trim back any side shoots longer than four inches to three buds.
As it grows: Each year, trim back new growth on the main shoot by a third, cutting just above a bud to encourage it to form new strong leader growth. Once it reaches the extent of the cordon, just snip it back to bounds each year. Each summer, cut back all the side shoots to six or seven leaves. If there are any sub-shoots growing from these spurs, prune these harder to four or five leaves.
Used for: Apples, pears
A ladder-like formation trained flat against a wall or fence with pairs of branches emerging horizontally from the stem on each side at about one-foot intervals. You’ll need a 12-15-foot expanse of six-foot high fence per plant.
When to prune: In winter while establishing and in summer for shaping and maintenance.
Getting started: Tie the stem to a vertical cane and cut it back to just above the first wire, leaving at least three buds on the main stem. Two of these will grow on to make your first tier of side shoots and the topmost will make a new leader (main shoot). Remove any other unwanted side shoots as they emerge from the main stem. Tie the new leader into the cane and in the following years, repeat this process for the tiers above.
As it grows: Once all your tiers are established, cut back the leader to just above the topmost wire. Each summer, prune side shoots back to six or seven leaves (these will be your fruiting spurs) and shorten them by a third. Once they reach the limits of the available space, just prune them back into bounds. Entirely remove any unwanted shoots growing from the main trunk or into the wall.
Used for: Stone fruit like cherries, plums, apricots, peaches
A formation created by shortening the trunk, then selecting strategic branches to fan out evenly across the space. A basic framework of canes tied to horizontal wires helps guide the shape. Takes up a similar amount of space to espaliers.
When to prune: Summer only.
Getting started: Cut back the leading shoot to about 18 inches, just above two well-chosen side shoots, one on each side. Then, tie two canes onto your support wires at 45-degree angles and train these two laterals on to them as they grow.
As it grows: Choose two well-spaced shoots from the top of each branch and one from the bottom and train them along more canes attached to the support wires. Completely remove any shoots growing in the wrong direction. Pinch out all side shoots at three or four leaves, then after harvest, prune them right back to the basal cluster of leaves; these will form your fruiting spurs.