Why Raised Beds Need a Spring MOT

By the time February rolls around, most of us are itching to get a fork in the ground. But raised beds that have spent the winter being battered by rain and wind rarely look their best. Compost settles, soil sinks, weeds sneak in at the edges and drainage can quietly go to pot. Spend a weekend giving your beds a proper once-over now and you will be sowing into a far kinder seedbed come March.

The good news is that raised beds are forgiving. Because you are working with a contained volume of soil, you can fix problems quickly, often in an afternoon, and the results show almost immediately in how well your seedlings establish. Here is how I tackle mine.

Start by Clearing and Inspecting

Begin with a fork and a bucket. Work along each bed removing anything that should not be there: overwintered brassica stumps, bolted leeks, dead herb stems and any weeds that have clung on. Chickweed and bittercress seem to survive anything, so pull them before they set seed. If you find perennial favourites such as couch grass or bindweed roots, dig them out completely rather than chopping them up, or you will simply propagate them through the bed.

As you clear, look at the structure of the soil. Fork it over gently to about a spade's depth, but do not turn it upside down the way you might on a field scale. Raised beds thrive on a living soil, and inverting it buries the aerobic life that does your fertility work. Just loosen, lift and crumble the top few inches.

• Check the timber or board edges for rot and replace any panels that are bowing.
• Pull out any weeds growing tight against the sides, where they hide.
• Remove slug eggs and leatherjackets as you go, and let the birds have them.
• Note where the bed has sunk furthest, as that is where you will add most compost.

Top Up with Well-Rotted Compost

This is the single most valuable job of the spring. A raised bed loses volume every year as organic matter breaks down, so plan on adding a good two to three inches of well-rotted compost across the surface. For a standard bed of about 1.2m by 2.4m, that means roughly four to six barrowloads.

Only use compost that is genuinely finished. If it still smells sour, or you can recognise what went into it, it is not ready. Fresh manure and half-rotted material will burn young roots and harbour pests. Spread it over the surface and let the worms do the incorporation, or tickle it into the top inch with a hand fork. Do not dig it deep, as the nutrients you want for early salads sit near the surface.

If your soil is naturally heavy clay, a little horticultural grit or sharp sand raked in will improve texture. If it is very light and sandy, the compost is doing the water-holding work for you, so be generous. A handful of blood, fish and bone per square metre is a sensible bonus for hungry crops, but it is no substitute for the compost itself.

Sort Out Drainage Before You Sow

Waterlogged beds are the ruin of early sowings. Carrots will rot, salads sulk and hardy herbs turn yellow. Before planting anything, check that water is not sitting in the base of the bed.

On most plots the culprit is a compacted layer just below the raised bed, or a path that sheds water straight into it. Fork over the ground around the outside of the bed to open it up, and make sure any drainage channels or gravel margins are clear of leaf litter. Inside the bed, a gentle ridge along the centre, or slightly raised rows, will keep seeds out of standing water.

• If the bed holds water badly, add grit and extra organic matter, then reassess next year.
• Never walk on the beds. Compaction is the enemy of drainage.
• Consider a cloche or fleece tunnel to shed rain and warm the soil before sowing.
• Check that any raised bed on a hard surface has drainage holes in the base.

Warm the Soil and Time Your Sowing

Soil temperature matters far more than the calendar. Early salads, carrots and hardy herbs such as parsley, thyme and coriander will germinate well once the soil holds around 7C at seed depth. A cheap soil thermometer is worth every penny, and it will stop you sowing into cold, claggy ground that simply rots the seed.

Cover beds with fleece, a cloche or even a sheet of black polythene for a fortnight before sowing. This warms the top few inches and dries the surface, giving you a head start of two or three weeks over open ground. On my own plot, the difference between a covered and an uncovered bed in early March is startling.

When you do sow, work in small successional batches. A short row of cut-and-come-again salad, a pinch of carrot seed in a fine tilth, and a few herb seeds in modules for transplanting later. That way, if a cold snap catches you out, you have not lost the whole bed.

A Few Final Checks

Before you walk away, firm the surface gently with the back of a rake, water lightly if the compost is dry, and label everything. Then stand back and look at the whole bed. Are the edges level? Is there a low corner where water will pool? Is the compost sitting at least an inch below the rim, so mulch and watering do not spill over?

Raised beds reward this sort of quiet attention. Half a day's work now — clearing, topping up, checking drainage and warming the soil — sets you up for a productive season with far fewer disappointments. Once the first bright row of radishes and rocket appears, you will be very glad you did it.