Why bother with garden edging? Why not just let plants grow up to the edges of lawn (if you have it) or of paths? Unfortunately, soil and mulch migrate from garden beds because of rain or birds which love to scratch in it. And some plants send their roots further than the bed and, conversely, some lawn grasses will enter your garden beds. Some sort of edging is necessary if you want raised beds.
There are many forms of edging commercially available, but they differ significantly in their sustainability. However, natural or recycled materials make excellent edging and can add uniqueness to your garden as well as minimising manufacturing impacts and waste going to landfill.
Let’s look first at new materials.
Commercially available edging
Most commercial ready-made edging comes with a considerable environmental impacts. For low beds, roll-out plastic has the embedded energy of manufacture as do wire, brushed alloy aluminium and flexible or corrugated steel. The latter metal options also have had land and water impacts of mining the metals. However, sometimes you may have no easy alternative available – especially if you want raised garden beds with sides 50 – 60 cm high. At least in these cases you have edging which is strong and durable.
Many attractive garden designs utilize wooden sleepers for raised beds as well as for other purposes such as retaining walls, path borders or steps. Unfortunately, because timber is so popular there is the tendency to cut down native Redgum trees to make new sleepers. Plantation timber sleepers such as Hoop Pine or Blue Gum (which are native timbers and the best choice, if you can source them) are a good alternative to new Redgum and will last a comparable number of years.
Treated pine has long been regarded by sustainable gardeners as an inappropriate product for raised bed edges because it is CCA (chromated copper arsenate) treated to preserve it against insect and fungal attack. This means that arsenic leaches into the soil. However, now there are alternatives, although they differ in their safety. ACQ treatment is similar to CCA but the problematic arsenic is replaced with copper and ammonium compounds. The safest is MICROPRO pressure treated pine which uses micronized copper as preservative. It is certified under the Scientific Certification Systems Environmentally Preferable Product (EPP) program and is considered safe for children’s playgrounds. Nevertheless, chemicals are used in treatment and the Micropro developers indicate that small amounts will leach into soil over time, and, if that is a concern, a thin plastic line for the sides of vegetable beds should be used.
Volcanic rock and granite are collected from private land. This has a relatively low impact on the environment, although bush rocks do provide places for lizards to sunbake! You might be lucky, though, and find rocks discarded by other gardeners. An alternative may be to use artificial rocks made from materials such as fibre glass, although the production process for these products is not without significant environmental costs.
Fallen/pruned branches or trees
These can be used flat on the ground or, if you have enough, they can be cut into 20 – 30 cm lengths and placed vertically.
Woven thin branches
This method of edging has been used traditionally by taking flexible canes from prunings and weaving them around vertical supports.
Anything recycled is going to have less environmental impact – reduce resource use, travel miles, energy in production, avoid pollution that often results from manufacture. We have included two options which readers submitted as part of a photo competition in 2014.
If Redgum sleepers are a must, then ex-railway sleepers may be a recycled alternative. But beware they have usually been impregnated with creosote which you wouldn’t want for your veggie garden.
Other options might be old fence palings (care would be needed to avoid chemicals leaching into the soil.
This material is very durable and some of the products have the advantage of being flexible to form curved beds. However, it is not cheap and energy is involved in its formation.
You may be able to find various metal products e.g. old roof decking or Colorbond fencing which can make durable raised beds. The image at the top of this post is a good example.
These are generally readily available – either around your own house of from brick recyclers. Although new bricks have high embedded energy, used ones do not, and because they are very durable can be used over and over again. If they are the sort that have holes, they create some mini-pots.
Other items from around the house
With some imagination, other items can make interesting edging – hub caps, glass bottles, tin can lids or whole cans, roof tiles, floor tiles, old plates or saucers.
Avoid the need for an edge
Polystyrene fruit/broccoli boxes can be used as small beds and they have their own edges. If they have no holes in the base, you can either drill some or create a wicking bed. These have the advantage of being portable – useful if your garden tends to be shady since you can move the box to chase the sun.
Combination of new and recycled
An innovative edge can be made by nailing fine wire to short pieces of recycled timber sunk in the ground. The bed is then lined with straw which will stop soil from “leaking” out. In this instance an attractive ground cover turned out to be a useful natural invader.