Raised Beds: the pros, cons and how to make them
Being based in St Albans, we are surrounded by thick clay soil which is notoriously bad at draining and becomes very boggy very quickly. Raised beds are a great way to grow plants and vegetables in better quality soil, with more effective drainage. They are also nice features to have in the garden and are easily customisable to suit your needs and tastes.
They are traditionally made from wood (2” x 6” planks are perfect), and that’s our preference too as they have a more natural look to them. Plastic, brick and concrete raised beds are also available.
The Pros of raised beds
They are great if your garden has a heavy clay soil as they drain well and enable you to plant a wider variety of plants as you can set the soil conditions to match the type of vegetation you want to plant
They are easier to maintain as you don't have to bend over or crawl around on all fours to tend your plants
They warm up faster in Spring meaning you can plant earlier in the season and therefore have earlier crops
They are visually appealing as you can make them in any shape and paint them any colour!
The soil does not get too compacted as there is no need to walk on them, preventing damage to saplings
They are easier to protect your plants from pests using netting or fleeces, or clear plastics to create a greenhouse environment for early saplings
The cons of raised beds
They require an initial outlay of money to purchase the wooden borders and screws etc, as well as the initial bags of soil and compost.
Given they are more susceptible to temperature, they heat up quickly and may require more frequent watering
Whilst they last for several years, the borders will need to be replaced at some point as they age and become more susceptible to rot. Be careful if you are looking to treat the wood with a preservative, as some are dangerous if growing edible plants near them.
How to construct the beds
Our favourite method is quick and easy and provides a nice-looking raised bed. If you are more skilled at woodwork, you may want to look at securing the corners where the planks join with dovetail joints.
The first step is to measure out the area that the raise bed is going to sit on. Drive a square stake in to the soil at each corner (2” x “2 is easy to work with). Assuming the ground level is relatively flat, try to leave the same height sticking out of the ground at each corner, about the same height as your boards standing on edge. Clear the area that the raised bed will sit on of vegetation and till it over to about a depth of 6 inches. Then simply screw the boards you are using as your border to each corner post (screw through the board first and then in to the post) so that the posts are inside the raised bed area. Start with a base plank resting on the ground and work your way up to the required height by placing additional boards on top. Galvanised decking screws are great as they don’t easily rust and remain secure and we recommend drilling a small pilot hole in to each piece of wood first to prevent splitting.
For larger beds or where you need to join additional lengths of board, it may be necessary to include more support posts at intervals along the borders to prevent the wood bowing under the weight of the soil and compost when full. To do this, simply drive additional stakes in to the ground at the required intervals (we recommend every 2 metres or wherever there is a join with a new board) and screw the board to the supporting post. Remember that ideally you want to be able to reach all areas of your raised bed whilst standing outside of it, so don't make them too large!
For smaller beds, you can use corner brackets to join short pieces of wood together at right-angles instead of the wooden posts (see image at the top of this blog post as an example). These are available from most hardware shops. These are slightly less robust and therefore good for small beds but not suitable for larger raised beds.
Once the border is complete, fill with a mix of good quality topsoil, sand or fine gravel and compost or other organic matter and turn it over well. We usually find a mix of 1 part organic matter, 1 part sand and 2 parts soil works well. The sand/gravel is important to improve the drainage of excess water and prevent the soil becoming too compacted over time. The organic matter helps to evenly distribute and retain some moisture in the soil - remember that raised beds are more susceptible to heat and therefore drying out. It’s easy to underestimate the amount of soil required, so if in doubt order slightly more than you think you’ll need!
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