How to Choose a Trellis for Clematis and Climbing Flowers

Start With How the Plant Climbs

Choose a trellis by the way the plant holds on. Clematis climbs by twisting its leaf stalks around a support, so it needs thin wire, mesh or light lattice. Climbing roses do not grip at all and need a sturdy frame they can be tied to. Then size the structure for the mature vine: most large-flowered clematis reach 8 to 12 feet, so a trellis sized to the plant in its nursery pot will be too short.

University of Maryland Extension sorts vines into four groups. Grabbing vines use tendrils or leaf-like appendages. Twining vines wrap their whole stems around the support. Sprawling vines, such as roses, lie on their supports and may hook on with thorns. Clinging vines stick directly to a surface with small root-like holdfasts.

Clematis belongs to the grabbing group, with a limitation. The leaf stalk, or petiole, is short, so the support has to be fairly slender for the stalk to wrap all the way around. Clemson’s clematis fact sheet is blunt about it: the vines cannot grasp thick branches or heavy trellising. A handsome panel of wide wooden slats gives a clematis nothing to hold.

Match the Support to the Plant

The table pairs common flowering climbers with how they climb, how tall they get, and the support that suits them. Heights come from Iowa State University Extension, Clemson and NC State Extension.

Plant	How it climbs	Mature height	Suitable support
Large-flowered clematis	Leaf stalks wrap	8 to 12 feet	Thin wire, mesh, light lattice
Anemone clematis	Leaf stalks wrap	20 to 30 feet	Wires or mesh on a wall, fence or arbor
Sweet pea	Tendrils	6 to 8 feet	Lightweight trellis or fence
Morning glory	Twining stems	10 feet	Trellis or post
Black-eyed Susan vine	Twining stems	3 to 6 feet	Small trellis or obelisk
Scarlet runner bean	Twining stems	10 to 20 feet	Tall trellis or arbor
Climbing rose	Sprawls, must be tied	Varies by variety	Sturdy trellis or horizontal wires

Twining vines are the least fussy. Clemson notes that their stems twine around any available support and that they grow best on wires, trellises or arbors. Sweet pea tendrils cling easily to a lightweight trellis or fence. If you are choosing between annual and perennial climbers in the first place, our guide to annuals versus perennials sets out the trade-offs.

Clinging vines such as trumpet creeper and climbing hydrangea need no trellis, since their adventitious roots act like suction cups on a wall. Clemson warns that those roots work their way into cracks and crevices and can pull stucco off a wall, and it suggests building a trellis a few feet away from the structure to carry the vine instead.

Size the Trellis to the Mature Vine

Height varies more than most gardeners expect, even within clematis. Iowa State University Extension notes that some clematis grow 8 to 12 feet in a single season while others reach only 2 to 4 feet. Clemson gives 8 to 12 feet for most large-flowered hybrids and 20 to 30 feet for anemone clematis, which is a plant for a long fence or a pergola and far too big for a garden obelisk.

Annual vines are quick as well as tall. Iowa State reports that morning glories reach 10 feet just two months after planting. Sweet peas grow up to 6 feet tall by Iowa State’s figure and up to 8 feet when allowed to climb, according to NC State. Black-eyed Susan vine stays at 3 to 6 feet, short enough for a small container trellis. Scarlet runner bean climbs 10 to 20 feet.

Read the plant tag for the mature height of your variety and buy a support at least that tall. The compact clematis are the ones to choose for pots. The Royal Horticultural Society describes smaller-growing clematis as attractive container plants when trained up an obelisk or small trellis.

Strength and Materials

Weight is the second sizing question. University of Maryland Extension warns that large-maturing vines put a lot of weight onto a support structure, which needs to be very sturdy and rot-resistant. Clemson makes the same point from the other side: many vines are vigorous, and their weight may collapse a weak structure.

In practice that divides supports into two classes. An annual that grows 6 to 10 feet and dies with the frost, such as a sweet pea or morning glory, can go on a light frame that only has to last one summer. A woody perennial that will stay in place for years, such as a climbing rose or a 20-foot clematis, needs posts and fixings that will not rot or bend under it. For those plants, look at how the trellis is joined and anchored before you look at its style.

Whatever the frame is made of, the parts a clematis touches must stay thin. A strong timber or metal frame with wire or mesh stretched across it meets both needs. The frame carries the load, and the wire gives the leaf stalks something they can wrap. Low-care planting partners for the base of a permanent trellis are listed in our guide to low-maintenance perennials.

Mounting a Trellis on a Wall or Fence

A trellis fixed flat against a wall leaves no room for stems to pass behind it. For clematis, the Royal Horticultural Society advises that mesh or trellis protrude from the wall or fence by at least 1 inch, and the simple way to do that is to attach it to 1-inch-deep battens at either end.

Set the plant itself out from the wall. The same guide puts the rootball around 12 to 18 inches from the base of the wall, with the stems led back to the support.

Climbing roses are usually trained on wires. They are not self-clinging and need a trellis or horizontal wires to which the shoots can be tied. The Royal Horticultural Society sets the lowest wire 18 inches off the ground and spaces the following wires 1 foot apart. Training the main shoots as close to horizontal as possible encourages flowering shoots to form low down, so a wide support suits a rose better than a tall narrow one.

Where to Put a Clematis Trellis

The trellis decides where the plant will live for years, so place it for the plant. Clematis needs at least 6 hours of sun a day to flower well, and Clemson adds that in South Carolina it benefits from some shade in the hot afternoon. The roots like the opposite conditions. Iowa State recommends keeping them cool by mulching the soil at the base of the vine or by planting other perennials to shade the root zone, and Clemson specifies a 2-inch layer of mulch.

That combination points to a spot where the top of the trellis stands in sun and the base is shaded by low plants. Put the trellis up before or at planting, since working around an established vine risks snapping it.

Tying In and Yearly Care

New clematis shoots often need help reaching the support. The Royal Horticultural Society notes that the stems are fragile and may need tying in place until they have secured themselves, using loose figure-of-eight knots with the twine crossing between the stem and the support. Start early, before the shoots tangle with each other.

Roses need tying for their whole lives, so check the ties each year and loosen any that have become tight as the canes thicken. The end of the season is also the time to cut out dead growth and look over the fixings on a wall-mounted trellis. A clean pair of bypass pruners handles most of that work, and our guide to choosing pruning shears covers what to look for.