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They're also invaluable if you have poor soil, or have soil that doesn't suit the plants you want to grow. Mediterranean plants, for example, are hard to grow in heavy, clay soils, but a raised bed filled with gritty compost solves the problem. Similarly, if you're gardening on chalky, alkaline soil, you won't be able to grow acid-loving plants such as blueberries and rhododendrons. But in a raised bed you can add ericaceous compost and grow a range of acid-loving plants.
Raised beds also warm up quickly in spring, making them ideal for sowing and growing veg.
Raised beds can be made from a number of materials, including scaffolding boards and breeze blocks, and can be as big, small, high or low as you need them. Get advice on how to build different types of raised beds.
To get the best from them, there are a number of important things to consider. Here are our tips for gardening in raised beds.
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Location
The location of your raised bed will affect what you can grow in it. Think about how much sun the bed will receive and plant accordingly. Lots of plants can be grown in sun and shade, though areas of deep shade will limit you more. Raised beds next to fences and walls may be in a rain shadow, and so require more watering.
Materials
You can construct your raised beds from a variety of materials. Scaffold boards are one of the easiest and cheapest options, but they won't last as long as, say, wooden sleepers. Find out more about the different woods to use for raised beds. Other materials to use for raised beds include breeze blocks, sheet metal and gabions.
Size and shape
Avoid stepping on the soil in your raised beds when weeding or harvesting - a maximum width of 1.5m metres is about right. The depth of a scaffold board is fine for growing veg, but more depth is needed for shrubs, perennials and bulbs. Beds don't have to be square or rectangular - they can be L-shaped or curved, too.
Seating
If you want to sit on the edge of your raised bed, it should be around 40-50cm high. A wall 10cm wide will make a good perch, but go for 20cm wide or more for comfort.
Plants
This particularly applies to plants that have more specific growing requirements, such as plants that like acid or alkaline soil. Acid lovers will need to be grown in ericaceous compost, whereas alkaline lovers will benefit from the addition of some mushroom compost. Discover plants for acid soil and alkaline soil.
Drainage
If your raised bed is on top of an existing border or lawn, you don't need to worry about drainage as any excess water will seep away. If your bed is on top of concrete or paving, you should add drainage in the form of rubble, stones or crocks at the base.
Compost
For most plants, fill your raised bed with a well-mixed combination of organic matter (i.e. well-rotted manure), sharp sand and topsoil, at a ratio of 3:2:7. Specialist beds, for example those for growing bulbs or alpines, will need grittier mixes for extra drainage.
Watering
Raised beds can dry out more quickly than topsoil in the garden, so be sure to keep on top of watering. Alternatively, you could install a drip irrigation system as a low-maintenance alternative.
Feeding
Consider long-term feeding with a slow-release fertiliser at the outset, then top up with a liquid feed through the season if needed. Soil-based mixes are more efficient at holding onto nutrients than lighter planting mediums.
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Topping up
Fill the beds right to the top, then leave for two weeks to settle before planting. Over time, the compost in your raised beds will compact, leading to a tall brim around the edge that can shade the plants within. Top it back up where possible.
Avoid treated railway sleepers
Avoid using treated railway sleepers. They can work well, but those treated with tar can leach toxins into the soil, plus they can damage your clothes when you kneel on them.
Frequently asked questions
Help! I've got ants in my raised bed
Ants are are attracted to warm, dry places, so if you cover your raised bed with membrane to suppress weeds you could well end up with ants living in it. The easiest way to encourage ants to move on is to water the bed, as they need conditions to be dry. Give them plenty of space and time to move their eggs to an alternative location, before planting.
Should I use a waterproof liner in my raised bed?
If you use wood to make raised beds it should be treated to make it last longer than untreated wood, but to further extend its life, it's a good idea to line the sides and any buttresses with plastic. This could be a bespoke damp proof membrane or old compost bags, cut to size. Add drainage holes if they are covering the base (or use a geotextile membrane layer for the base, which allows water to pass through). Make sure you fit the membrane securely to the sides, using staples, so there's no exposed wood, and fill compost in the bed only up to the top of the liner.
What's the best material to use to make a raised bed?
Lots of materials can be used to make a red bed, including bricks, concrete blocks, plastic, metal and wood. Wood is by far the most popular material, with treated wood lasting for several years.
Should I put rubble at the base of my raised bed?
For raised beds deeper than 50cm, a layer of rubble or stones at the base can help to improve drainage. However, with shallower beds, it's best to not add rubble so the plants have a good root run to grow properly.
