There is something particularly satisfying about a raised bed.
Perhaps it’s the sense of order: a clearly defined patch of earth waiting to be planted. Or perhaps it’s simply that everything feels within reach – seedlings can be inspected, weeds spotted and vegetables harvested without having to venture quite so far down towards your toes.
Raised beds can be wonderfully useful, but they aren’t necessary in every garden.
Where the existing soil is good and drainage is reasonable, growing directly in the ground is often the simplest option. But where soil is heavy, shallow or difficult to cultivate, or where easier access is important, raising the growing area can transform what is possible.
They can become productive vegetable beds, herb gardens, strawberry patches or carefully planted displays of flowers and grasses.
And if you’re going to build one, it’s worth getting the foundations right.
Why grow in raised beds?
One of the greatest advantages of a raised bed is control.
Instead of having to work entirely with the soil you inherited with the garden, you can create growing conditions better suited to the plants you want to grow.
This can be particularly helpful on heavy clay, very shallow soil or ground that has been badly compacted.
Raised beds can also drain more freely than the surrounding ground, although this means they may dry out more quickly during summer.
They are especially useful in productive gardens because beds and paths create a clear structure. You can work from the sides without repeatedly walking over the growing soil and compacting it.
And, depending on their height, raised beds can make gardening considerably more comfortable.
Raised beds can make gardening more accessible
Not every raised bed needs to be particularly high.
A simple timber frame 15–30cm above the surrounding ground may be enough to define a vegetable plot and improve the growing conditions.
But taller beds can make an enormous difference for anyone who finds kneeling, bending or working at ground level difficult.
If accessibility is important, think about the whole area rather than simply the height of the bed.
Can you comfortably reach the centre? Is there room for a wheelchair or walking aid? Are the paths firm, level and wide enough to turn around?
A thoughtfully designed raised bed should make gardening easier, not introduce a new set of obstacles.
Choose the position carefully
Before buying timber or moving a single barrow of soil, spend some time looking at the proposed site.
For vegetables, herbs and most sun-loving flowers, choose somewhere receiving plenty of direct sunlight.
Don’t become too preoccupied with whether the bed runs precisely north to south. In a real garden, nearby buildings, hedges and trees often have far more influence over light than compass orientation alone.
Watch where shadows fall during the day.
Also consider practical things.
How far is the bed from the water supply? Can you get a wheelbarrow alongside it? Is it close enough to the house that you’ll actually wander out to pick herbs or salad leaves?
The most productive vegetable bed is often the one that’s easiest to visit.
How wide should a raised bed be?
The golden rule is simple:
You should be able to reach the middle without standing on the soil.
For a bed accessible from both sides, around 1.2m wide is usually comfortable for many gardeners.
If you can only approach from one side – perhaps because the bed sits against a wall or fence – make it considerably narrower.
Length is much more flexible and can be determined by the space available.
Think carefully about paths too. A narrow gap may seem perfectly adequate on paper but become frustrating when you’re carrying a watering can or manoeuvring a wheelbarrow.
If you’re designing for wheelchair access, allow generous space between beds and make sure the surface is firm and practical in wet weather.
How deep does a raised bed need to be?
That depends on why you’re raising it.
A shallow frame placed over healthy garden soil allows roots to continue growing into the ground beneath, so it doesn’t necessarily need to contain the entire root system.
A bed built over paving or another hard surface is different. Plants are completely dependent on the growing medium inside it, so greater depth becomes much more important.
Deep beds are also useful where accessibility is the main reason for raising the garden.
Remember that a large raised bed takes a surprising amount of material to fill. Work out the volume before construction rather than discovering halfway through that you need another several tonnes of soil.
Timber, brick or something else?
The material you choose affects both the appearance and lifespan of the bed.
Timber
Wood is one of the simplest materials to work with and suits both vegetable gardens and more informal spaces.
Untreated naturally durable timber can be a good choice, while treated timber intended for garden use generally lasts longer than ordinary softwood.
Whatever you choose, expect wood in permanent contact with damp soil eventually to deteriorate.
When buying new timber, look for responsibly sourced wood and build the bed so individual boards can be replaced when necessary.
Brick and stone
Brick and stone create much more permanent raised beds.
They work particularly well where the beds form an important part of the garden’s design, perhaps surrounding a terrace or defining a formal kitchen garden.
The top of a substantial wall can even provide somewhere to sit while gardening.
Construction requires more work and expense, however, and poorly built walls can move or fail under the pressure of wet soil.
Metal
Galvanised and other purpose-made metal beds have become increasingly common.
They’re quick to install, relatively slim and can work particularly well in contemporary gardens.
As with any material, choose something designed for outdoor growing and think about how its appearance will sit within the wider garden.
Should you line a raised bed?
Usually, an open-bottomed raised bed placed over soil doesn’t need a membrane covering its base.
In fact, keeping the bottom open allows plant roots, earthworms and other soil organisms to move between the raised bed and the ground beneath.
Begin by removing troublesome perennial weeds and loosening badly compacted soil where necessary.
If burrowing animals are a genuine problem, suitable wire mesh can sometimes be fitted across the base while still allowing drainage.
Timber sides can be lined where appropriate to reduce direct contact between damp soil and the wood, but avoid creating a watertight box.
Water must always have somewhere to go.
Don’t put gravel in the bottom for drainage
It’s tempting to fill the base with stones or gravel in the belief that this will improve drainage.
It generally isn’t necessary.
Good drainage comes from having an appropriate growing medium, an open route for excess water to escape and avoiding severe compaction.
If the underlying ground is persistently waterlogged, investigate the cause before building the bed.
Simply raising the soil above a serious drainage problem doesn’t necessarily solve what’s happening underneath.
What should you fill a raised bed with?
This is one of the most important decisions you’ll make.
A raised bed intended for long-term growing needs more than a great quantity of lightweight potting compost. You want a stable, fertile growing medium that will hold moisture while still allowing air and water to move through it.
For many vegetable beds, good-quality topsoil improved with well-rotted organic matter provides a useful foundation.
Exactly what you use should depend on the plants and the soil available rather than following a rigid recipe.
Be cautious about filling a deep bed entirely with fresh manure or very rich compost. More fertility isn’t always better, and some materials shrink dramatically as they decompose.
You may also come across beds filled with logs, branches and other woody material, sometimes described as hügelkultur. This is a particular growing method rather than an essential part of constructing a raised bed.
For a straightforward garden bed, there’s no need to create complicated layers.
Let the soil settle
Newly filled raised beds almost always settle.
After filling, water the bed and give the soil time to settle naturally. You can then top it up where necessary.
Avoid repeatedly trampling the soil down to make more fit inside. One of the advantages of a raised bed is creating an open soil structure that roots can explore easily.
Over subsequent years, the level will continue to fall gradually as organic matter decomposes.
That’s perfectly normal.
A layer of compost or other suitable organic matter added to the surface each year can help replenish it.
What can you grow in raised beds?
Almost anything – provided the bed suits the plant.
Vegetables are an obvious choice. Salads, beetroot, carrots, beans, peas, courgettes, onions and many other crops can thrive in raised beds.
Herbs are another excellent option, particularly if the bed is conveniently positioned near the kitchen.
Strawberries can be grown along an edge, where their fruit hangs temptingly within reach.
Raised beds can also be ornamental.
Free-draining beds can provide useful conditions for alpines and Mediterranean plants, while deeper beds can accommodate perennials and shrubs.
You can even use them to create deliberately different soil conditions, although it’s worth remembering that trying to maintain a radically different soil chemistry indefinitely can require ongoing management.
Raised beds still need watering
One disadvantage of raising the soil is that it can dry more quickly.
During warm, dry weather, raised beds may therefore need more attention than surrounding borders.
Water deeply when necessary rather than giving the surface a token sprinkle every day.
Mulching the surface with compost or another appropriate organic material can reduce evaporation, suppress annual weeds and gradually contribute organic matter to the soil.
And if you’re planning several vegetable beds, consider the water supply before building them.
A beautiful kitchen garden at the far end of a large plot becomes considerably less charming when you’re carrying your tenth watering can towards it.
Look after the soil, not just the plants
A raised bed is still soil, not simply a container for crops.
Try not to leave it bare unnecessarily.
Mulches, green manures and winter crops can all help protect the surface, while adding organic matter supports soil structure and the organisms living within it.
Avoid walking on the bed whenever possible.
One of the great advantages of a well-designed raised bed is that you can reach everything from the paths, leaving the soil relatively undisturbed.
Over time, that can create a wonderfully workable growing environment.
Think about crop rotation – but don’t become ruled by it
If you have several vegetable beds, rotating crops can be a useful way of organising what grows where from year to year.
It can help avoid repeatedly growing susceptible crops in exactly the same soil and makes it easier to plan feeding and soil preparation.
But in a small garden, perfect crop rotation isn’t always possible.
Good garden hygiene, healthy soil, sensible plant spacing and keeping an eye out for problems are just as important.
A gardening system should make life easier, not become another set of rules to worry about.
A garden within the garden
There’s something pleasing about the boundaries of a raised bed.
They encourage you to look closely.
A few lettuce seedlings become a crop to tend. A row of beans needs supports. Nasturtiums tumble over an edge while bees disappear into courgette flowers. Empty ground left after the first harvest suddenly presents an opportunity for something else.
Raised beds don’t magically produce better plants, and they aren’t the right answer for every garden.
What they can do is give you a defined piece of ground that is easy to reach, easy to improve and enjoyable to cultivate.
Build it carefully, fill it with good soil and look after that soil from one season to the next.
Before long, what began as four sides and a heap of earth becomes something much more interesting: a small garden in its own right.
Further Reading: My Garden Journal & Notes
