Growing your own in a raised bed

Do you need a raised bed at all?

Not necessarily. The RHS says vegetables grow just as well in the ground. A raised bed earns its place when your soil is poor, heavy or wet, when you want to grow on a hard surface, or when bending and kneeling are hard. The soil in a raised bed also warms up sooner in spring, and it keeps plants closer to hand.

If you have a sunny patio and a few large pots, you can grow potatoes, dwarf beans, salads and herbs in those first, and see how you get on.

Easy crops to start with

The RHS's advice for beginners is to grow only what you really like. These are forgiving and quick:

• Radishes: ready in about four to six weeks. Sow a short row every couple of weeks rather than a lot at once.
• Salad leaves and loose-leaf lettuce: pick leaves from about four to six weeks after sowing, and they keep coming for weeks.
• Herbs: handy in a corner of the bed or in pots by the door.
• Beetroot: sow from spring to July and pull when the roots are 4-7 cm across.
• Dwarf French beans: no supports needed, and they crop for weeks if you keep picking.
• Early potatoes: plant in spring and dig in early summer. They grow well in a deep bed or a 30 cm bag.

Where to put it

From the RHS guide to making a raised bed:

• Sun. Most vegetables need a sunny spot. The RHS suggests a south- or west-facing part of the garden, away from overhanging trees.
• Water. Beds and pots need regular watering through the season, so a tap or water butt nearby helps.
• Drainage. Put it on free-draining ground if you can. On a hard surface, the bed needs plenty of drainage holes.

Size: what you can reach

From the RHS's guide to making a raised bed:

• Width: under 1.5 m, so you can reach the middle without standing on the soil. If you can only reach from one side, make it narrower.
• Depth: about 30 cm is enough for salad leaves and strawberries. Bigger plants such as fruit bushes need 45 cm or more.
• Paths: at least 45 cm for a wheelbarrow, and at least 1 m if someone uses a wheelchair.
• Height: a tall bed, or a planter on legs, saves bending. Check you can reach it comfortably, and that there's room for your knees if you garden from a chair.

Timber, metal or something else?

Pressure-treated timber is the usual choice: it's easy to work with and lasts for years. Coated steel kits are slim, tidy and don't rot. Bricks, stone, scaffold boards and recycled plastic all work too. Whatever the frame, the soil matters more.

Filling it, and what it costs

The filling often costs more than people expect, because a bed holds a lot. The RHS suggests a mix of about seven parts topsoil, three parts organic matter (such as compost) and two parts sharp sand.

• The steel bed below needs 743 litres in its standard layout.
• The planter on legs below needs 420 litres.
• The 90 cm square frame below is measured over its 40 mm timber sides, so inside it's about 82 cm square. At 14 cm deep that holds about 94 litres (our calculation), plus the dug soil beneath it. For any kit, work it out from the inside measurements and the soil depth.

Price the topsoil and compost, and the delivery, before you choose a kit. Then add seeds, plant food and water through the season.

Will it save money?

Honestly, we don't know for your garden, and we haven't found a reliable UK figure. It depends on what you grow, how well it does, and what you'd otherwise buy. The best way to find out is to keep a simple notebook: write down what you pick and what it would have cost in the shop, and take away what you spent on the bed, the filling, seeds, plant food and water.

When to sow: a simple table

These are the RHS's general timings. In colder parts of the UK, start later; in milder areas, a little earlier. Always check the seed packet.

Build the bed in winter, so it's ready for spring. On heavy clay, the RHS suggests late summer instead, when the ground is drier. Want to start earlier and grow tomatoes too? See polytunnel or greenhouse.