How To Build Raised Beds
This article deals with how to build raised garden beds, what is the best size to make them and what is the best material to use. We will also look at preparing the soil, what to grow in raised beds and where to place them in the garden once you have them.
What Is The Best Size For Raised Beds?
Raised beds are all about easy gardening so choose a width that allows easy access to the middle of the garden bed from either of the sides. Around 3 or 4 feet is the optimal width for most gardeners. Try gardening from a fixed position and find your furthest comfortable reach across the bed, double this to get the idea width for you.
If possible try to avoid overly long beds so people don't get tempted to step across them to reach the opposite side, 6ft - 8ft long is perfect. Leave adequate pathways between beds, you should be able to move easily between them so leave approximately 30 cm for foot traffic or 45cm for wheelbarrows, allow extra for wheelchair users if needed.
Next think about height, 7 inch high raised beds are ideal to start off with and are perfectly suited to growing shallow root crops. Before deciding on a height ask yourself 'How much bending down do I want to do/can I do?'. Taller raised beds will make gardening much easier for those with mobility issues or experiencing back strain.
We stock raised beds in a range of different sizes and heights to suit as many gardeners as possible. Easy Access or accessible raised vegetable beds are also available which are constructed at waist height to both eliminate bending down and to accommodate wheelchair users.
Having settled on a size, the raised bed must be capable of containing the weight of the soil when wet. Taller raised beds may need to be reinforced to prevent bowing, this can be done using timber cross supports across the width of the bed or by driving steel reinforcing bars (rebar) into the ground at the outside of the bed mid-length. If in any doubt just give us a call, we are always delighted to help.
What Material To Use
Raised Beds can be constructed from all different kinds of materials, the most common ones are made from timber. The first question you should ask yourself is 'does it fit in with existing garden design?', nobody wants their vegetable garden to look out of place. Timber is the most popular material used because it has a natural look and fits in to most garden designs. The wood can be painted or stained to match existing garden furniture or fencing, but just make sure to use a water based paint or stain that is safe to use with food crops.
Timber raised beds all have a approximate lifespan, our timber planters are pressure treated and will last approx 10 years but can last longer depending on local weather conditions. Blocks, bricks, and concrete can be used to make a more permanent raised bed but timber boards are cheap, easy to construct and move and don't require foundations. Moulded plastic can also be used and is now available with a wood finish effect to mimic the standard timber version.
Preparing The Ground For Raised Beds
Break the soil surface on the ground where the bed is to be placed down to a depth of approx 30cm and remove rocks and debris that might obstruct healthy root growth. This won't be an issue with shallow root crops but for deeper root crops like carrots, parsnips and potatoes good soil preparation will make all the difference. For beds of 14 inches high or more you need only strip the grass sod off the surface and invert before filling the bed with soil.
Look out for any roots from nearby trees, as a tree grows it sends it's roots out laterally as well as down in search of nutrients in the soil. Tree roots spread over a surprisingly large distance and can sneak in and steal the nutrients from the soil in your raised bed!
Check the ph levels with a simple soil test kit and adjust as required. Most soils unless very acid or alkaline may only need minor adjustments if any. As a rule of thumb most vegetables will be happiest at a slightly acid PH of 6.5 with some exceptions like blueberry plants which like a very acid (or ericaceous) soil of about 4.5.
Acid soil can be balanced using ground limestone to which adds calcium whereas an alkaline soil (more unusual) can be rectified over time with the application of compost. Of course the beauty of using raised beds is you can add or 'build' the soil you need for your intended crops if the soil on your site is unsuitable.
In general the darker the soil the better as dark soil contains more organic material than light. Organic material is what feeds the biology in the soil (good bacteria, earthworms etc...) and convert it into food for your plants, it is the good stuff.
We can't stress enough the importance of soil in the vegetable garden, it is the secret to 'green fingers' as a well fed soil grows healthy resilient plants while plants on poor soil will struggle and are more prone to pests and diseases.
With vegetable plants, most of their roots are in the top 6 inches of soil which will be within the raised beds. Remember to keep this soil nice and light and well aerated so the roots can access nutrients easily. If you need to improve your soil use bulky organic matter like well rotted manure, garden compost or soil improvers like our 'Envirogrind' fish/compost mix.
What Can I Grow In Raised Beds?
Almost anything can be grown in raised vegetable beds, they are perfect for an organic kitchen garden but can also be used to create a fantastic tiered ornamental shrub and flower garden.
Most vegetables, fruit, all herbs, and salads can be grown with greater ease and success than planted straight in the ground due to the greater soil depth. Raised beds are also particularly useful in areas with high rainfall as they provide extra drainage meaning you can successfully overwinter crops like onions, garlic, parsnips and carrots.
You can vary the height of your garden beds to suit the crops you wish to plant with lower beds (7 inches high) for shallow root crops like salad and spring onions up to deeper beds for carrots, parsnips and other root crops.
Planting By Height
Arrange crops at planting time to ensure smaller plants aren't having the sun blocked by taller plants. If you plant a range of vegetables, for instance, in a raised garden, the plants will reach maturity at about the same time.
Taller vegetables like peas, beans, peppers, and brussels sprouts will begin to overshadow shorter crops like lettuce and radishes etc depriving them of the sun. The best position for your raised beds is facing south with the tallest crops placed at the northerly end of the bed.
Portable Raised Planters / Containers
If your garden isn't large enough to grow in raised beds you can still grow a surprising amount of fruit and vegetables using smaller containers. We also supply mobile raised beds which can be moved around a small garden to achieve maximum exposure to sunlight or to move to one side when entertaining.
Soil or compost choices in container gardening is a little different than growing in larger planters as you will need to use a more compost based soil; this is because smaller volumes of soil are unable to hold enough moisture for healthy plants. For smaller containers use compost only while large pots (too big to move when full) can be filled with a 20% soil and 80% compost mix. Remember due to the smaller growing space and limited nutrient availability you will need to add extra feed to your plants; we recommend a natural feed like our 'Seafeed' seaweed and manure pellets.
Watering is always an issue in urban gardening so before filling it, ensure your planter has adequate drainage and is strong enough to contain it's fill of soil when wet. It is also much handier to arrange your pots to your liking before adding compost and panting up, they will be a lot more difficult to move when they're full!
Help and advice Please feel free to contact us if you need any help and advice with your growing, we are happy to help anyone interested in growing whether our customers or not!
Click here to visit our raised garden bed Dept.