Why Raised Beds Earn Their Keep

A raised bed gives you better drainage, warmer soil in spring and far more control over what your vegetables are growing in. You also stop walking on the soil, so it stays loose and roots can push down without a fight. For anyone with heavy clay, poor chalk or a garden that floods, a raised bed is less a luxury and more a practical fix. The frame holds a defined mix of topsoil and well rotted compost, which means you are not battling the existing ground every season.

They are also kinder on the back. Raising the growing surface by 25–30cm makes sowing, weeding and harvesting far more comfortable. If you build two or three beds with paths between them, you can rotate crops properly and keep everything tidy without a grand redesign.

Pick a Spot with Plenty of Light

Most vegetables want sun, and lots of it. Aim for a spot that receives at least six to eight hours of direct light between March and September. South-facing is ideal, but east or west will do for leafy crops and roots. North-facing beds will struggle, especially for tomatoes, courgettes and beans.

Watch out for the shade cast by fences, hedges and buildings. A bed that looks bright in February may sit in deep shade by June when the sun is higher. Also think about access. Leave a path at least 60cm wide so you can kneel, wheel a barrow and reach the middle of the bed without stepping on the soil. A water butt nearby saves endless trips with a watering can.

Size, Depth and Materials for the Frame

A comfortable width is 1.2 metres. That lets you reach the centre from either side without treading on the bed. Length is up to you, but 2.4 metres is a manageable size for a family plot. Depth matters more than you might think. For salads, herbs, onions and most brassicas, 25cm of soil is enough. For carrots, parsnips, maincrop potatoes and long beetroot, go for 40–45cm.

• Timber: untreated oak, larch or sweet chestnut will last many years. Tanalised timber is also fine for vegetables and widely available.
• Avoid: old railway sleepers treated with creosote, and any reclaimed wood of unknown origin.
• Alternatives: brick, stone, or interlocking concrete blocks. These last longer but cost more and hold less warmth.
• Fixings: use galvanised screws or nails. Reinforce corners with internal corner blocks to stop the frame bowing under the weight of wet soil.

Prepare the Ground and Line the Base

Before you fill anything, clear the site of perennial weeds such as docks, bindweed and couch grass. Cut them back, fork over the ground and firm it lightly. If you are building on grass, cut it very short and leave the clippings to break down.

Now line the base. This is a step many people skip, and they regret it. A layer of plain cardboard, overlapped generously, suppresses weeds and slowly rots into the soil. Damp it thoroughly before adding soil. If you are placing the bed on concrete or paving, use a permeable weed membrane instead, and add a 5cm layer of gravel or broken crocks for drainage. Never use solid plastic sheeting — it traps water and turns the bed into a bog.

If the bed sits on soil, you do not need a solid bottom. The cardboard will do the job. Roots will eventually find their way down, and worms will move up into your new mix.

Mix and Fill the Bed

The filling is where raised beds succeed or fail. The summary is simple: use a mix of topsoil and well rotted compost. Aim for roughly 60% topsoil to 40% compost by volume. A 50/50 mix also works well, but pure compost shrinks dramatically and can dry out in summer. Pure topsoil, on the other hand, lacks the richness and water-holding capacity that hungry vegetables need.

If your topsoil is heavy clay, add a few handfuls of horticultural grit or sharp sand to improve drainage. If it is very sandy, extra compost will help it hold moisture. Fill the bed in layers, firming gently with your hands or the back of a rake as you go. Do not stamp on it — you want a loose, open structure. Leave the surface about 5cm below the top of the frame so you can mulch without soil spilling over.

Water the bed thoroughly after filling and let it settle for a week before planting. Top it up if it sinks. A well-filled bed will settle by 5–10% in the first season.

Planting, Feeding and Keeping It Cropping

Raised beds dry out faster than open ground, so water regularly, especially while seedlings are establishing. A mulch of well rotted compost or straw will lock in moisture and suppress weeds. Feed leafy crops with a nitrogen-rich liquid feed every fortnight, and switch to a potassium-rich feed for tomatoes, peppers and beans once flowers appear.

• Rotate: move crops between beds each year to avoid soil-borne pests and diseases.
• Top up: add a 5cm layer of well rotted compost every autumn or spring.
• Do not walk on the bed: use planks or kneelers if you must reach across.
• Sow little and often: small successional sowings of salad, radish and spinach keep the bed productive without gluts.

With good light, a lined base and the right soil mix, a raised bed will reward you for years. Start with one, learn how it behaves in your garden, then add another when you are ready.