Sandy soil is the great frustration and the quiet advantage of gardening by the sea. It drains in minutes, warms early in spring, and is a joy to dig — but it holds almost no nutrients or moisture, and the salt-laden wind strips away anything you leave exposed. The good news is that sandy soil responds faster to improvement than heavy clay ever does. Feed it little and often, keep it covered, and within two or three seasons you will have a genuinely productive plot.

Understand what you are working with

Coastal sand is mostly large mineral particles with big gaps between them. Water and dissolved nutrients simply run through. There is very little humus to hold things together, so structure collapses and the surface dries and blows. Salt spray adds another stress: it scorches foliage and can push up the salinity of the top few centimetres, especially on exposed sites.

Before you buy anything, do two quick checks. First, dig a spade-deep hole and squeeze a handful of moist soil — if it falls apart instantly and feels gritty, you have classic sand. Second, look at how far the water table sits in winter; many seaside plots have gravel or shingle just below the surface, which limits what you can grow without raised beds. Both facts will shape how much organic matter you need and how often you must apply it.

Add organic matter in bulk and often

This is the single most important job, and it is never a one-off. Aim to work in or lay on 5–8cm of well-rotted organic matter at least once a year, ideally twice — in autumn and again in early spring.

• Garden compost is the backbone. Build a bin or two; even a small coastal plot can produce enough for a decent mulch each year.
• Well-rotted horse or cattle manure adds bulk, nutrients and water-holding capacity. Make sure it is at least a year old and not smelling of ammonia.
• Leafmould is superb for sandy soil — light, spongy and free if you bag leaves in autumn and forget them for a year.
• Coir and composted bark are useful bought-in options when you cannot make enough of your own.
• Seaweed is a traditional seaside resource. Take only loose, washed-up material from the strandline, never living plants, and check with the local council or landowner first. Rinse it if you are worried about salt, then add it to the compost heap or use it as a mulch.

Do not dig organic matter deep into sand and expect it to stay. In sandy soil, humus oxidises quickly. It is far better to practice no-dig: lay material on the surface and let worms and roots pull it down. You will build a darker, richer top layer year on year.

Hold on to moisture

Watering sandy soil is a Sisyphean task unless you improve its structure first. Once you have a decent layer of humus, these habits make a real difference:

• Mulch every bed with 5cm of compost, leafmould or composted bark. A thin gravel mulch over the top also reduces evaporation and stops the wind lifting dry soil.
• Water deeply and less often rather than little and often. A slow soak encourages roots downwards into cooler, damper layers.
• Use a soaker hose or drip line on a timer for thirsty crops such as courgettes, beans and tomatoes. Overhead watering in a sea breeze wastes most of the water.
• Plant in slight dips, or create shallow basins around individual plants so water soaks in rather than running off.
• Group plants by their water needs, and keep the thirstiest ones closest to the tap or water butt.

Build fertility without it washing away

Nutrients leach out of sand with every heavy rain, so the aim is to feed steadily rather than in one big dose. Mix a slow-release organic fertiliser into the top layer at planting: seaweed meal, blood, fish and bone, or a homemade blend with rock dust for trace elements. Top up with a liquid feed — comfrey or nettle steeped in a bucket, diluted to the colour of weak tea — every fortnight through the growing season. A mulch of compost each spring will supply most of what established shrubs and perennials need on its own.

Green manures are the secret weapon on light coastal soil. Sow field beans or grazing rye over winter to catch nutrients before rain washes them away, then cut and leave the tops as a surface mulch in spring. Phacelia and crimson clover work well in summer gaps, and their roots help bind the sand.

Shelter the soil from wind and salt

Wind dries soil and carries it away. A permeable hedge is the best long-term answer — sea buckthorn, escallonia, griselinia, tamarisk and hardy roses all cope with coastal conditions — and it will slow the wind without creating damaging turbulence. While it establishes, use woven windbreak netting or hurdles at about 50 per cent density, positioned so that it filters rather than blocks the airflow. After a heavy salt-laden gale, rinse the foliage of tender plants with a watering can, and give beds a light mulch to dilute surface salinity.

Raised beds are worth considering where shingle or gravel lies close to the surface. Filled with a mix of topsoil, compost and a little loam or clay to improve water retention, they give you 30cm of genuinely good growing space — plenty for salads, herbs, beans and soft fruit.

A simple year-round routine

• Autumn: spread 5cm of compost or manure over empty beds, sow a green manure, and collect leaves for leafmould.
• Winter: protect bare soil from wind and rain with mulch or netting; plan crop rotations.
• Spring: cut and incorporate green manures, top up mulch, plant with a slow-release organic fertiliser.
• Summer: water deeply, liquid feed fortnightly, and keep mulching any bare patches as crops are cleared.

None of this is complicated, and the rewards are quick. Sandy coastal soil will never behave like a rich loam, but with steady additions of organic matter, a protective mulch and a windbreak or two, it becomes warm, workable and remarkably generous.