Growing Up on an Exposed Scottish Plot: What Pays Off

A vegetable bed only has so much ground, but it has no ceiling. Every runner bean, pea and cucumber trained upward frees the soil beneath it for something else, and the crop grows away from the soil, so the harvest is cleaner and there's less bending. Going up turns a two-dimensional plot into a three-dimensional one.

But height cuts both ways. A row of French beans on canes barely notices a stiff breeze, because netting and foliage let most of the wind through. A 2m obelisk wrapped in sweet peas, or a solid trellis panel standing alone in open ground, behaves more like a sail: the taller and more solid a structure, the more wind force it has to resist. Scottish allotment and garden sites can sit open to hillside, coastal or farmland exposure (see the guide to allotment layout and orientation), and there wind resistance decides whether a structure survives its first real gale rather than just its first summer.

Which crops benefit from going vertical

Not every crop that can climb should be made to. Height is worth building for when it solves a real problem: not enough ground space, fruit that needs to hang clean, or a plant that can't stand on its own.

Runner beans and climbing French beans are the clearest case: they climb by nature and need tall supports in place before sowing or planting. Dwarf French beans need no support at all, and are particularly suitable for containers and exposed sites.

Peas split the same way. Tall varieties can reach 1.8m and become top heavy, so they need supports that are suitably tall and sturdy, especially in windy locations, such as netting or chicken wire attached to posts or bamboo canes. Dwarf varieties get by with pea sticks (twiggy prunings) pushed in between the plants.

Cucumbers reward training with cleaner fruit and a smaller footprint, which matters in a compact garden or a greenhouse. Cordon (single-stemmed) tomatoes get very tall, don't cling on their own and need tying in to a tall, sturdy cane or string. A single stake of about 1.8m is the usual figure for tomatoes and for standard courgettes trained upward. Bush tomatoes need none of this.

Squash and pumpkins are the crop where "vertical" is a choice rather than a given. Trailing squashes can be trained up a structure that is large and sturdy enough for the plant and its crop, with heavy individual fruits supported in netting or hessian hammocks. Where there's ground to spare, most fare best sprawling on the soil, and the largest, heaviest-fruited varieties are the ones where that's the more practical option, since a support carrying that weight is a bigger build than a wigwam or A-frame.

Trained fruit forms belong here too. A cordon is a single stem, grown at an angle of about 40-45° with short fruiting side-shoots, and can be planted as little as 60cm apart. An espalier trains branches out flat in horizontal tiers, and a stepover is a horizontal cordon kept to knee height. Cordons need permanent support, traditionally three horizontal wires 60cm apart on sturdy 1.8m posts or fixed to a wall or fence, and summer pruning each year to keep them compact and fruiting. Full detail is in the apple growing guide and the guide to fan-training fruit trees.

Cane spacing, tying and timing for each vegetable are in that crop's growing guide: runner beans, French beans, peas, cucumbers, tomatoes and squash.

Choosing a structure: cost, durability and wind stability

The right structure depends on what's being grown, how exposed the site is and how long it needs to last.

The traditional runner bean support is a double row of bamboo canes or hazel poles about 2.5m tall, sloped inwards and tied at the top to form a sturdy A-frame. Space the canes 15-30cm apart in the row and 45-60cm between the two rows, with at least 1.5m between double rows. An X-frame, with the canes sloped more sharply so they cross in the middle, makes picking easier but can be less stable. A wigwam uses five or more canes tied together at the top and spaced at the base. Put supports in before sowing or planting.

Three material points are worth weighing. Bamboo canes and jute netting are the cheapest options and the most weather-dependent: left out over a wet Scottish winter they're likely to rot and split faster than if stored dry. On a coastal plot, a plain steel obelisk or wire support is worth a spring check for rust, since salt air tends to corrode bare metal faster than inland air, and galvanised or powder-coated metalwork needs less upkeep. And an untreated timber post set directly in wet, heavy soil rots at the waterline years before a pressure-treated one, which is worth the extra cost on anything meant to stay up for more than a season or two.

Anchoring tall freestanding structures against wind

Anchoring is a different question from siting a windbreak. Windbreaks filter wind across the whole plot, whereas this is about a single obelisk, arch, wigwam or trellis panel staying upright and square under the load the wind puts directly on it.

Freestanding trellis and wire screens carry a real wind risk and suit sheltered sites only. Small obelisks can be pushed into the soil, but larger structures may need anchorage into concrete footings. There's no fixed height at which a structure crosses from one to the other, so on an exposed plot build to the sturdier end of the options. Mutually braced structures (a wigwam or A-frame, where several canes tie together and hold each other up) cope with wind better than a single post or unbraced panel of the same height.

Wind isn't the only load. Netting can hold a surprising weight of wet snow across a hard winter, and the sagging puts a different strain on posts and ties than a summer gale. Take netting down once the season is over rather than leaving it up empty over winter.

Where a concrete footing is right, a tall post resisting sideways force is normally buried to roughly a third of its above-ground height, with extra depth on an exposed site. Concrete is a standard postmix bag mixed and poured around the base and left to cure before the post takes any load. Treat that as a starting point rather than an exact figure.

On an open allotment, then: push canes about 30cm into the ground (tall climbers on 2.5m canes; check each crop's guide for exact depth), tie multiple canes together near the top so they brace each other, and set any single-post or solid panel structure in a concrete footing rather than relying on soil alone. Get supports up and firm at planting time, since firming a loose one later with a plant already climbing it is far harder. The bigger risk usually comes after the season: autumn and winter gales topple wigwams and obelisks that coped all summer, so check anchoring going into autumn. A wigwam or obelisk that's done its job can be dismantled and the canes stored dry, which sidesteps the worst of the winter gales. A permanent pergola or wall-fixed trellis can't, and that's where solid anchoring matters most.

If you fix trellis to a wall or fence instead, screw it to timber battens so it stands off the surface, which lets air circulate and leaves room to tie plants in, and keep its bottom edge about 30cm above the soil to prevent rotting.

Where vertical growing falls short

Vertical growing isn't a universal upgrade. In an RHS trial, pots fixed high on a wall dried out faster in drying winds, and runner beans grown there gave a "small, rather tough" crop, with climbing French beans and nasturtiums also among the disappointing performers (a hot summer made container growing harder). Height that clears ground space can work against a crop if it also means more wind exposure or a drier root run. On an exposed plot, choose the sturdier, lower-profile structures (wigwams, A-frames, netting on posts) over tall wall-mounted or freestanding options, unless the site is sheltered.

Common questions

Sources