Filling Your Garden Bed
When it comes to gardening, almost nothing is more important than soil. No amount of care or maintenance will make up for having poor soils, which are often the cause of pests, diseases, slow growth, and a low number of fruit and vegetables. In contrast, having rich and healthy soils can lead to healthy plants with vigorous growth that need little maintenance to achieve good results. It is often the soils that distinguish aspiring gardeners from those with a ‘green thumb’.
One of the most significant benefits of raised garden beds is that you have all of the control over the soil you will plant in. There are countless options for this, which will vary depending on your needs and context. In most cases, you can mix and match different materials to make the best soil from materials you may have readily available.
What To Use To Fill Your Beds
+ Native Soils: One of the most obvious resources for filling your garden bed are the soils native to your area. This can be a great option for budget-conscious gardeners or those with rich native soils in their area. However, be aware that not all native soils have the same nutrients and minerals, healthy soil biology or overall quality as a potting soil and may require extra work to achieve best results.
To improve texture, water retention or drainage, different types of soils can be mixed. For example, heavy clay soils can be mixed with sand or vice-versa. Infertile soils with light or red colours can be mixed 1:1 with compost or worm castings to improve fertility. Native soils are generally not sterile which means they may contain beneficial microorganisms, but they may also contain pests, disease, or many seeds of unwanted weeds. Also, you may want to be careful with native soils that may have a risk of contamination from pollutants such as heavy metals or agrochemicals.
+ Compost: High-quality compost is something essential to your soil health. It contains nutrients, beneficial biology, and helps improve the overall texture of any soil. Make sure to get your compost from a reliable source that guarantees it is free of disease or pests. Ideally, heavily amend (50% by volume) the top 10-15 cm of your raised bed with compost. If accessible, worm castings are an excellent alternative to compost.
+ Potting Soil: Premade potting soil can be a great and easy option for those looking for a simple solution. It is best to find something organic and avoid those with synthetic NPK fertilisers. The biggest downside is that this can get costly, especially for larger beds. You can also make your own potting soil by mixing 25% perlite (or vermiculite), 25% coco coir, and 50% compost.
+ Wood for “Hugelkultur”: Wood can be an excellent material to help fill a large bed cheaply while providing some beneficial properties. Hugelkultur is a technique that does just this. By placing large branches, trunks, and other woody materials at the bottom of a bed you get a natural sponge that holds water and nutrients. This wood soaks up moisture during the rainy season and makes it available when water is limited. As it decomposes, it also releases nutrients and feeds beneficial biology. It is recommended only to do this with large beds and to leave a minimum of 15 cm at the top without woody materials. This ensures the soil is easy to work with in the future.
+ Rocks, Gravel, and Stones: Rocky materials can be a great way to fill space and improve drainage. These materials are most recommended for large beds and should only be used 20cm below the soil surface. Near the surface rocks may interfere with mixing or planting.