Our allotment – although divided up into rudimentary veggie beds – has a rather shambling, rambling, unkempt feel to it. Pumpkins crawl over beetroot beds, berry bushes jostle for space with the cider apple trees, and our newly planted hops have gone feral and started strangling anything within frond-grasping distance. It’s a plant jamboree, and no mistake. Trying to keep on top of things can feel a touch overwhelming, so to bring a semblance of order to proceedings, we intend to build some raised beds.
Raised bed gardening is a great way to grow plants, especially vegetables. Your plants will be insulated from the chill of the ground – the soil inside the beds will retain its warmth for longer, thus creating favourable growing conditions – and, as plants are traditionally grown closer together in raised beds, they’ll create a tight leafy canopy which will help to ward off weeds. Another advantage is that soil conditions can be tailored to suit whatever you fancy growing. In theory you could build and fill a bed for plants that thrive in alkaline soil, and construct a separate bed for those that prefer to nestle down in soil more acidic.
You can purchase kit form, flat-packed raised beds that need minimum assembly skills to get them up and running, but for those who like a nice rewarding garden project to grapple with, building your own is the way forward. There are three main construction types to consider:
Wooden Raised Beds
Wooden raised beds are relatively easy to build. Grab a bag of nails, a hammer and some planks and away you go…
- Go for planks that have been pressure treated with Tanalith E, an organic based preservative which is safe to use around vegetables. Scaffolding boards are also a good shout – a polite word with your local scaffolder might help you bag a few old boards. Just saw off the metal ends and away you go. You could also try dismantling a wooden pallet – garden centres can be a good source for these.
- Mark out the size of raised bed required, then drive in square retaining stakes for each corner to a depth of 50 cm. For maximum stability, add additional square posts every metre or so.
- Remember to use galvanized fixtures for maximum corrosion protection when attaching the planks to the supporting stakes. Screws will last longer and make things easier if you want to deconstruct your work, but nails are the quickest, easiest option.
- Watch out for unwanted guests! Slugs and snails like to inhabit the damp recesses of wooden raised beds, so remember to check regularly and evict them when necessary.
Brick-Built Raised Beds
Brick built raised beds can be time consuming to make, but will last for years. Here’s a few tips on how to construct one…
- Mark out the designated area using stakes and string, and use a spirit level at every opportunity.
- For a strong and stable bed wall, tamp down a hardcore base of rubble, approx. 10 cm deep before laying your bricks.
- If you plan to construct your brick raised bed on concrete or an existing patio, leave a few gaps between brick joints to provide drainage, then cover the holes with mesh to stop them clogging with detritus.
Sleeper Raised Beds
A raised bed constructed from old railway sleepers look great and will give you years of planting pleasure. Here are a few points to consider…
- Old, recycled railway sleepers may look lovely and rustic, but will most likely have been treated with tar and creosote that will eventually seep into your soil. If you can afford the extra cost, it’s best to go for new, softwood sleepers that have been treated with eco-friendly preservatives. These types of sleeper are also a lot lighter to move around the garden. Hard on pockets, but better for backs!
- Ensure a nice, level surface to work on by tamping the ground around where you intend to build.
- Constructing a bed from sleepers is easy – simply overlap each sleeper as if you were laying bricks. As already mentioned, sleepers are heavy, so a strong, willing friend is very useful during this stage.
- To prevent your sleepers from moving around, hammer metal rods into the ground, either side of the sleeper walls.
Filling your raised bed
To aid drainage, first lay an 8 cm layer of gravel or stones, on top of which lay a weed inhibiting membrane. Fill your bed with topsoil. If you can, avoid filling with soil sourced from elsewhere in the garden to prevent any weed contamination spoiling your nice new bed. Remember to add a generous amount of well rotten manure, and dig over the area thoroughly before planting.
Next time: Keeping your allotment neat and tidy
The Two Thirsty Gardeners, Rich and Nick, are popular gardening bloggers who share their stories and experiences on growing fresh fruit and veg and their experiments turning this into alcohol!
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