Gardening is an activity that is enjoyed by millions worldwide and while it is very relaxing, it is safe to say that it can be hard work. Bending over, reaching across vegetable patches, kneeling down, standing up again - a long gardening session can really take its toll. Raised beds are brilliant for taking away some of the strain and pain of this otherwise serene hobby. By lifting up your plants, you bring them to a more accessible level. This means that you will no longer have to bend down so far (or at all depending on the type of bed), making them a great choice for any gardener, but particularly older or disabled gardeners where their mobility may limit them.
Having said that, garden beds have more benefits than just making it easier to interact with your plants. Here are a few more important positives:
-
Raised beds hold more soil than pots. This means that they dry out slower and therefore need to be watered less
-
It is easier to control soil composition than it is when growing in the ground. This is particularly beneficial if your native soil is thick clay, or very loose and sandy. It also allows you to introduce a new soil type to your garden, for example if your native soil is alkaline, you could fill a raised bed with acidic soil to grow ericaceous plants
-
As the soil is raised above ground level, drainage is better. This is ideal for areas where the soil is very heavy
-
Many raised beds are tall, which can help keep out some pests and may even prevent low flying insects such as the carrot root fly, which tend not to fly higher than 50cm in the air
How do you fill a raised garden bed?
Before filling up your bed, it is really important to ensure that the bed is level. This can be quite strenuous depending on how flat your garden is, but shouldn't take too long. It is definitely worth doing because your bed can’t be easily moved once filled, and because a flat bed is easier to work with than one on a slope. Similarly, if your bed is not flat, water, nutrients and soil will all flow to the lowest point, causing them to distribute unevenly, and can also cause soil erosion. Bear in mind, again, that once a bed is built, it is not easy to move, so make sure that it is in a good place where it can stay forever.
Once your bed is level, it is time to fill it. The best way to fill depends on the type of raised bed. Shallow beds (around 25-45cm/10"-18") can be simply filled with garden soil. Depending on the material of the frame, you may wish to line the inside of the bed with porous landscape fabric (we'll get onto that later).
For taller beds, I like to use the hugelkultur method. Hugelkultur (literally meaning mound bed/culture) is a horticultural technique where decaying wood and other compostable plant debris is used as the base of a raised bed. It is a cheap and effective way of filling a raised bed, all while using up your garden waste, helping maintain soil temperature and improving the water retention and fertility of your soil.
The bed can be filled as follows:
1. Logs:
Fill the bottom with big logs. These will take up a lot of the space at the low, unused parts of the bed, helping to fill it quickly and cheaply. There is no point wasting your fertile, high quality soil at the bottom, where it won’t be used. Logs will provide a lot of organic matter that will slowly break down over time, allowing it to hold water that can be released when necessary, all while providing a home for beneficial insects and microbes within the bed. These logs can also help to prevent digging pests such as moles, voles and gophers. In areas that have a lot of this sort of pest, some gardeners also choose to also put some wire mesh at the very bottom of their bed, beneath the logs.
Some gardeners like to put gravel, sand or crushed granite at the bottom of their garden bed to help with drainage but we have found that with the hugelkultur technique, drainage has never been an issue.
2. Filler material:
Bulky logs leave gaps, so the next step is to fill the gaps with smaller bits of organic matter, but still not your fertile growing medium. Wood chips, weeds, branches, lawn clippings, dead plants & leaves, excess waste soil & mulch, any garden waste can go in at this point. Ideally, this would all be aged rather than fresh to prevent sinkage, and to stop the bed from heating up too much as the material breaks down as this can burn roots and kill your plants.
At this stage, it is a good idea to squash everything down and compact it as much as possible. As your fill decomposes more, the soil on top will sink down, but by doing this it minimises the amount of sinkage you will get and you won't need to keep topping the beds up as frequently in the first few years.
3. Soil:
Finally, the top 30-45cm (15"-18") or so should be filled with your growing soil. This should be good quality, nutrient rich soil. It shouldn't be too thick and heavy, or too loose or sandy. It should hold together well when squeezed, but then be able to easily crumble out when you push it apart. This is best achieved by mixing in organic matter such as compost or manure with soil. For even better soil health, make sure that your soil is 'alive' with plenty of worms and insects.
We like to overfill our beds by a few inches to allow for some sinkage. Although we compacted our lower levels earlier, there will always be sinkage in any bed, pot or planter - even if you filled the whole thing with soil. After you've added your growing medium, it’s time for mulch.
Ah, mulch! *chef’s kiss*
Be sure to add a layer mulch to prevent soil erosion and to help hold moisture. This can be straw, leaf mould, grass clippings, sugarcane, wood chips, compost, the list goes on. The layer should be a couple of inches thick. The mulch will help the soil to retain moisture better, suppress weeds, protect your plants' roots from very hot or very cold weather, deter some pests and provide a barrier between the plants and the soil (which is particularly useful for plants like tomatoes that can easily pick up diseases from the soil). As if those aren't enough, as the mulch breaks down it will release nutrients back into the soil and boost your plants - I just love mulch so much!
What materials are best for raised beds?
Garden beds are available in all sorts of materials which vary in cost, lifespan and appearance. Here are some of the most popular:
Wood:
I really like the look of wooden planters, and it is a natural material. Wooden beds tend to be cheaper than some other materials too. However, it can be quite heavy and untreated wood will decompose over time. This may be fine for dry regions where this breakdown takes longer, but the wood will need to be replaced regularly if you live in a wetter area. Certain types of untreated hardwoods such as oak and western red cedar should take longer to break down, but tend to be expensive. Treated wood also takes longer to decompose, but may contain harmful chemicals and heavy metals that can leach out into the soil as the wood degrades. While most modern wood treatments don't tend to contain these, so are safe to use, if you are unsure, you can line the inside of the bed with a porous plastic liner so that your plants are not affected.
Galvanised steel:
These are a great choice as they are relatively easy to construct and should last for many years. Since they are rot and rust resistant they are great for wet and humid environments. They come in many different colours, heights and shapes so are suitable for almost any garden. Metal beds do, however, tend to be expensive.
Plastic:
This is another versatile option for your garden. Plastic raised garden beds are available in a wide range of colours. They are easy to put together and take apart, can last for up to 50 years, and many can then be recycled afterwards. These also tend to be relatively cheap and weather resistant. Some types, however, can be prone to breaking or bending if they are not properly supported.
Stone:
A strong, durable, long lasting option for your garden. Raised beds made from stone are aesthetically pleasing but are generally very expensive. They also require a lot of skill and time to build, and are very difficult to move.
How big should a raised bed be?
Raised beds shouldn't be more than about 1m (39") wide (although they can be as long as you would like). If a bed is wider than 1m (39"), it can be very difficult to reach plants in the centre without standing or leaning on the soil, which compacts it - and compacted soil is not good for growing plants. Bear in mind that if your bed is longer than about 1.5m (59"), you should add extra support at the weakest point. This will help prevent it from bowing out or collapsing due to the pressure of the soil pushing against the sides.
A garden bed should be at least 25cm (10") deep to allow for proper root development. Most plants need about this much depth to grow, although many benefit from having more room to extend down. We like to give around 45cm (18") of growing space to ensure that our plants have plenty of room, and to give enough space to till the soil if necessary.
The bottom line
For many gardeners, raised garden beds have been a game changer. The benefits that come with them give your garden a level of versatility that simply can't be matched by pots or native ground. Whether you are young or old, mobile or not, there is a raised bed for you. I personally love taller, hip-height beds because, although they are harder and more expensive to initially fill than shallower ones, they allow me to garden while standing up. This has helped remove a lot of the effort required, and has made gardening a lot more enjoyable. If your space and budget permits, I would certainly recommend trying raised bed gardening. It is taking the world by storm and it is clear to see why!
