A GUIDE TO DIFFERENT TYPES OF RAISED GARDEN BEDS
Article by David Marks.
If you have decided to buy your raised garden beds rather than making your own, then the choice of suppliers is bewildering as are the different types available and the huge difference in prices. This easy to use guide to raised beds will help you select the correct one at the best price. If you want to go straight to our raised bed features and price comparison then click here now.
Before selecting a raised bed for your
yourself a few questions. What material is best for your
gardening needs, will you want to expand the raised bed at a
later date, what price do you want to pay, what size is
required and what company is it best to buy from.
Answer those questions with our help below and you will end up with the correct raised bed.
PRICES OF RAISED BEDS
Comparison of prices between the different raised beds available is meaningless without considering other factors such as delivery costs, materials used, guarantees and similar factors. To help you compare prices we have compiled a list of online retailers and the various raised beds they sell.
The list is based on a raised bed which is approximately 1.8m by 1.8m and 30cm high. It includes all the relevant factors we thing are important for raised beds - name of the retailer, their website address, material used, thickness of timber, guarantee, expandable etc.
To confuse matters as far as price is concerned, different retailers offer their beds in a variety of different sizes avoiding easy price comparison. This is the reason that we quote an approximate raised bed area of 3.15 sq m above to get round this problem.
Beware of cheap headline prices because they inevitably refer to raised garden beds which are tiny and are not high enough to grow anything other than dwarf plants and vegetables. A minimum height for growing many vegetables is 30cm, if you restrict yourself to a 15cm high raised bed then you will be limiting the range of vegetables which will grow well.
Click here to see our one page feature and price comparison table and then come back here for more information about raised beds.
MATERIALS AVAILABLE FOR RAISED BEDS
Price, durability, ease of construction and good looks are the key decision making factors when selecting the material for a raised bed. Wood, plastic and galvanised metal are the available materials to the amateur gardener and each has it own pros and cons.
Wood is the best looking without a doubt, there are some beautiful examples for sale if you look for them. If the wood has been sourced from a sustainable source it is also the most environmentally friendly. As far as durability is concerned, you get what you pay for with wood. The more expensive wooden raised beds will last for decades, especially if treated every couple of years. The cheaper ones will not stand the test of time so well.
Look for timber which is 3cm+ thick, pressure treated and guaranteed for a few years. If you treat this type of product every two or three years it may well outlive you!
One wood option which stands out on its own is to use railway sleeper kits to construct your raised bed. We have included one company that supplies kits of this type in our comparison page. For obvious reasons this is a more expensive option but there may well be an option that is correct for you.
Plastic raised beds are likely to last in excess of 20 years and require no maintenance. Clearly they don't look as good as wood versions but some look better than others.
Double skinned plastic raised beds are the standard to look for, the trapped air rapidly heats up and this transfers to the soil enabling earlier crops in the spring and later crops in the autumn.
We only found one example of a metal raised bed, sold by Everedge. To be truthful, we no experience of metal raised beds so cannot comment on their advantages or disadvantages. If you have any knowledge of metal raised beds then we encourage you to leave a comment in the comments box at the bottom of this page.
DURABILITY OF RAISED GARDEN BEDS
The durability is first dependant on the material the raised bed is constructed from.
Fist you need to make sure that the wood has been pressure treated with a preservative (sometimes called tanalised) which won't damage your plants. Most retailers do this nowadays but just check their product description.
Next is the thickness if the wood. In general, a thickness of 3cm or more will ensure that your raised garden bed lasts for a decade or more. There shouldn't be a need to maintain them but if you do they are likely have a longer life. A thickness of 2.5cm or less is likely to reduce the durability of the raised bed.
it is very difficult to judge how long a plastic raised garden bed will last just by looking at it. The only problem you are likely to encounter is that some plastic reacts to being outside and eventually becomes brittle and cracks. Price is the main criteria here but is not 100% reliable. The more you pay for the same sized raised bed, the longer it is likely to last.
Galvanised metal should last a decade or more although we have no specific experience of metal raised garden beds.
If you haven't already seen it, click here for our one page comparison table for raised garden beds. It compares a range of products for prices, size and many other features. It includes a link to each of the major online raised bed retailers.
LINING THE BASE OF RAISED BEDS
You need to consider also if the base of your raised bed needs a lining, this is often suggested as necessary by raised bed retailers and offered as an accessory.
If your raised bed is placed a solid surface you may want to place a membrane at the base of the raised bed to protect solid surface from marking. However we have no experience of this but we do doubt that a permeable (one which allows water to pass through) membrane would offer much protection.
If you are placing your raised bed on grass or open soil we suggest that a membrane is not necessary unless the raised bed is very shallow or there are some extremely lively weeds in the soil. Even then, a lining of newspaper, five sheets deep, would do the same job at no cost. All our raised beds are lined in this way and to date we have never had any weeds grow through the newspaper and then through 30cm of compost.
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READER COMMENTS AND QUESTIONS ABOUT THIS PAGE
ANSWER: Definitely don't use creosote, it's poisonous to many plants and toxic as well. As far as paint goes look carefully at the label to ensure it is safe for using near edible plants.
ANSWER: Beetroot, radish and lettuce should cause no problems in the same raised bed for three or four years. The real problem crops are tomatoes, potatoes and the brassicas (cabbage, cauliflower etc). French beans also cause little problems. But what I do, just to be ultra-safe, is to take a picture of the raised bed(s) each year with the crops in them. Then the next year I change the position of the crops just to ensure the soil has a little variety. Beyond a change of position each year I have no rotation plan for beetroot, lettuce, radish and French beans and have suffered no problems.
ANSWER: Plastic will do fine as a liner (black bags laid over the area to be lined are a cheap method) just make sure it has lots of holes in it to allow drainage, especially at the bottom. I would line the side as well, if only to prevent wet compost rotting any wooden sides. If the sides are plastic then no liner is required around the sides. Good luck.
ANSWER: Good drainage is the first point to consider, the second is preserving the veg table. I would suggest lining the table with plastic (bin bags are a cheap idea) and piercing lots of holes in the plastic liner to allow water to drain away freely. That will allow drainage and also protect your veg table to a large degree.