A trellis only works if it is built for the way the plant climbs. Climbing beans wind the whole stem around the support, sweet peas and cucumbers grip with thin tendrils, clematis curls its leaf stalks around anything narrow, and ivy fastens straight onto the wall. The measurements that decide the outcome are the thickness of the battens, the spacing between them, the height, and how far out from the wall the trellis sits.
Four ways plants climb and what each one needs
The most common reason a climber refuses to climb is that the support is the wrong shape, not that the plant is weak. A bean that meets a 9 x 9 cm square post never gets a full turn around it and slides back down. A pea tendril cannot close around that same post.
| Way of climbing | How the plant attaches | Examples | The right support |
|---|---|---|---|
| Twining climbers | The whole stem spirals around the support | Climbing beans, runner bean, hops, wisteria | A vertical cane or pole, 1 to 3 cm across. Any thicker and the stem never completes a turn |
| Tendril climbers | Thread-thin tendrils grip whatever they touch | Sweet pea, pea, cucumber, cup and saucer vine, passionflower | Netting, strings or thin battens. A tendril grips something a few millimetres thick, not a 25 mm batten |
| Leaf-stalk climbers | The leaf stalk wraps around the support like a hand | Clematis | Netting or a trellis with thin parts, standing clear of the wall so the leaf stalk can reach around |
| Self-clinging | Aerial roots or adhesive pads fasten straight onto the surface | Ivy, Boston ivy | No support at all, but they hold so hard that the wall is left marked when the plant is taken off |
Twining climbers always turn the same way and the direction is fixed by the species, so winding a shoot back the other way does not work. The cup and saucer vine is often counted among the twiners, but it climbs with tendrils that sit at the end of the leaf and carry small hooks at the tip. It wants netting or strings. At Florea we run three or four vertical strings against the wall when cup and saucer vine Violet Blue is going up a house wall.
How far out from the wall the trellis should sit
A trellis must not be screwed flat against the wall. The smallest air gap is about 2.5 cm, and 5 to 10 cm is better. Two things depend on that gap. Twining climbers have to be able to take the stem the whole way around the batten, which is impossible when the back of the batten rests on the render. The air between the foliage and the wall also lets the leaves dry faster, which keeps powdery mildew down on cucumbers and sweet peas and lets the render dry out.
Solve it with spacer blocks behind every fixing point, set vertically so that water runs down behind the trellis instead of collecting on top. Set the plant itself 30 to 45 cm out from the base of the wall, not tight against it. The ground closest to a house wall lies in a rain shadow and is the driest spot in the garden.
Material, batten thickness and batten spacing
Untreated timber: Larch and oak have high natural durability and need no surface treatment. Spruce and pine rot quickly in contact with soil and only work on a wall.
Pressure-treated timber: Use it for posts that stand buried in soil. At Florea we choose untreated larch closest to the vegetables.
Bamboo canes: 180 to 240 cm long and 10 to 20 mm thick. The cheapest option, and the thickness sits in the middle of what twining climbers grip best.
Steel reinforcing mesh: Squares of 15 x 15 cm and wire of 5 to 6 mm, sturdy enough for cucumbers in full crop. The wire is at the upper limit for tendrils, so help the first shoots into place with string.
Battens: 15 to 25 mm thick in a frame of 45 x 45 mm timber, with openings of 10 to 20 cm. Once the battens go thicker than 25 mm the tendrils get no grip and you tie the plant up by hand all summer.
Height by plant
Build for the final height of the plant, not for how it looks in June. A support that runs out halfway gives a tangled clump at the top.
Sweet pea: 1 to 2 m. A support of 1.8 m is enough for most of the varieties among our sweet pea seeds. Sowing, pinching out and cutting are covered in the article on how to grow sweet pea.
Peas and sugar snap peas: Low varieties manage with twiggy branches pushed in between the plants, while tall varieties reach up to 1.8 m and need netting stretched on posts.
Climbing beans: 2 to 3 m. Canes of 2.5 m are the standard length, for example for pole bean Neckarkönigin. Sowing and care are covered in the article on how to grow beans.
Cucumber: 1.5 to 2 m outdoors, with 30 cm between the plants. Pinch out the main shoot once it reaches the top, so the strength goes into the side shoots where the fruit sits.
Fixing to a wall and into the ground
A support that feels solid in May can fold in August. By then a full grown plant is sitting on it, the foliage is heavy with rain and the wind takes hold of the whole surface as it would a sail. Size it for that moment.
On a wall you screw into studs or masonry, never into the render alone, with a fixing at least every 60 cm up the height and stainless or hot dip galvanised screws. Freestanding, dig the posts at least 50 cm into the ground, or use drive-in post anchors so that the timber never stands in wet soil. A trellis that stands completely clear needs bracing both ways.
Wigwams and A-frames in a raised bed
Canes are the simplest climbing support and take a quarter of an hour to put up.
Wigwam: Five to eight canes in a ring with 15 to 30 cm between the canes at the base, tied together at the top and pushed 20 to 30 cm into the soil. Sow two seeds at each cane and thin to the stronger plant.
A-frame: Two rows of canes with 45 to 60 cm between the rows and 15 to 30 cm between the canes in each row. Lean them against each other and tie each pair to a horizontal cane at the top. An A-frame stands more steadily in wind than a wigwam.
In a raised bed: A pallet collar bed of 80 x 120 cm takes an A-frame along one long side or a wigwam of six canes at one end. Fix the canes to the sides of the bed with cable ties so the structure cannot lift. See also the guide on how to grow in a pallet bed.
What you gain by growing upwards
A plant standing upright gets air around all of it. The leaves dry faster after rain, which cuts powdery mildew and downy mildew. The fruit hangs free instead of lying on the soil, so the cucumbers stay clean and out of reach of the slugs. You can see where they are and pick standing up instead of on your knees.
Space is the second gain. A cucumber plant lying down spreads across the ground, while the same plant on a vertical net takes 30 cm in width. On a balcony that is the difference between growing cucumbers and leaving them out.
Common mistakes
The support goes up too late: The canes should stand in place when you sow or plant. Push them in during July and they go straight through the root system of the plant they are meant to carry.
Battens too thick: A trellis of 45 mm battens looks solid but gives neither tendrils nor twining shoots anything to hold on to.
The trellis screwed flat to the wall: Without an air gap the plant cannot get around the batten and the wall behind never has time to dry.
The support built for the June plant: Weight and wind load multiply several times over between then and harvest. Make the posts thicker and deeper than it feels necessary in May.
Self-clinging plants on a rendered wall: Ivy and Boston ivy need no support, but they leave marks in the surface when they are taken off. If you want them on the house, put them on a trellis that can be unhooked.
Author: Emma Vogiatzi
Fact-checked by Erik Hoekstra
Last updated 2026-09-01