Choosing Cedar for Durable Garden Furniture Projects

Why Cedar Earns Its Place in the Garden

Cedar has a reputation that has been earned over centuries, and once you have worked with it, the appeal is obvious. The timber contains natural oils — thujaplicins, among others — that make it unpalatable to insects and hostile to the fungi that cause rot. In practice this means a cedar bench left out through a wet Cumbrian winter will still be sound years later, while an untreated softwood one will be showing soft corners and blackened joints by the second spring.

Under the European durability classification, cedar heartwood generally sits in durability class 2, with some stock rated class 1 — broadly comparable to oak for outdoor use, but at a fraction of the weight. It is also dimensionally stable, which matters more than most gardeners realise. A timber that swells and shrinks dramatically will open up joints, crack around fixings, and let water into places you cannot reach with a brush. Cedar moves, but modestly, so your joints stay tight.

For anyone running an orchard or a productive garden, that stability is a quiet advantage. Trellis posts, espalier frames, and tree guards made from cedar do not need replacing every few seasons, and they will not shed preservative chemicals into the soil around your fruit trees.

Know What You Are Buying

The cedar most commonly sold in the UK is Western red cedar, botanically Thuja plicata — technically a cypress rather than a true cedar, though the trade name has stuck. It is the pale, straight-grained, slightly aromatic timber you will see in good garden joinery. True cedars — Atlas cedar and cedar of Lebanon — are also grown here and produce a harder, more resinous timber, but they are rarely available in useful garden dimensions.

When you are at the timber yard, look for:

• Heartwood, not sapwood. The pale, creamy sapwood band carries almost none of the natural oils. Ask for all-heart or premium grade, and check the end grain — the heartwood is a richer, darker tone.
• Straight grain and tight knots. Knotty grades are perfectly serviceable and cheaper, but large loose knots are weak points that will shrink and fall out.
• Moisture content. Kiln-dried stock around 12–15 per cent will machine cleanly and take a finish. Wet timber will shrink after assembly and open your joints.
• Consistent thickness. For structural garden work, 38mm or 45mm stock is a sensible minimum for legs, frames, and rails.

Sourcing It Responsibly

Cedar is slow-grown and, in the main, imported. That is not a reason to avoid it, but it is a reason to ask questions. Look for timber carrying a credible certification scheme, and ask the merchant whether the certificate covers the actual consignment rather than the company's general policy. Reclaimed cedar is also worth hunting for — old greenhouses, conservatory frames, and church pews turn up in salvage yards and often yield beautifully seasoned boards.

If you would rather build with homegrown material, Leyland cypress and other fast-grown conifers from British woodlands can be used for the same jobs, though they are less durable and will need a protective finish and a design that keeps the timber dry. Use them for the parts that never touch soil, and save the cedar for the parts that do.

Benches, Planters, and Trellises

Each project puts different demands on the timber, and cedar rewards a bit of thought at the design stage.

• Benches. Use 38mm slats with a 10mm gap between them so rainwater drains and air circulates. Seat slats should be fixed from underneath with stainless steel screws, and any leg that meets paving should sit on a plastic or rubber pad rather than directly on stone, so the end grain is not sitting in standing water.
• Planters. Line the inside with a permeable membrane to slow moisture transfer into the boards, and leave a 20mm gap between the internal soil level and the rim. Bore drainage holes in the base, and raise the whole planter on battens or feet. Cedar is safe for growing food, but do not use old railway sleepers or treated offcuts as fill.
• Trellises and orchard supports. Slimmer sections work here — 32mm square is ample for a fan-trained plum or a climbing bean frame. Space horizontal rails roughly 300mm apart for fruit training, and set posts at least 600mm into the ground, or better, into a concrete shoe so the timber never touches soil.

Use stainless steel or hot-dip galvanised fixings throughout. Cedar is mildly acidic and will corrode plain steel screws, leaving black stains and, eventually, loose joints.

Finishing and Looking After It

Left bare, cedar will weather gracefully to a soft silver-grey within a couple of seasons. It is a lovely look, and it does the timber no harm at all. If you prefer to keep the warm honey tone, apply a UV-filtering garden oil every year — a thin coat in late spring, worked in with a brush and wiped back, is plenty. Avoid varnish and other film-forming finishes; they crack, trap moisture beneath, and are miserable to remove.

An occasional check with a screwdriver is worth more than any product. Probe the feet, the joints, and anywhere two boards meet. Cedar is forgiving, but it is not indestructible, and a bench that is allowed to sit in a puddle will eventually disappoint you despite everything the oils can do.

Build it well, keep it out of standing water, and a cedar piece will outlast most of the plants around it — which, for an orchard gardener, is exactly the sort of quiet, long-term investment worth making.