Garden
Building a raised bed that lasts ten summers
A raised bed is the quickest way to grow on poor soil. Done well, the frame outlives the plants by years. Done badly, it bows within a season and rots at the corners.
Start with the wood. Untreated larch or Douglas fir holds up for a decade without chemicals. Pine is cheaper but needs a liner on the inside faces.
Size it to your reach
Keep the bed no wider than 120 cm, so you can reach the middle from either side without stepping on the soil. Length matters less; two metres is easy to fill.
Height depends on what you grow. Thirty centimetres suits salads and herbs. Root vegetables want forty or more.
Lay the frame on level ground and check the diagonals. If they match, the corners are square.
Fill it in layers
Coarse prunings go at the bottom, then turf turned upside down, then compost mixed with topsoil. The lower layers rot down over the first year, so top up each spring.
Water deeply and less often. Shallow daily watering keeps roots near the surface, where they dry out first in a heatwave.
By the second summer the soil has settled, the worms have moved in and the bed mostly looks after itself.