Using half topsoil and half organic compost is a solid starting point. Alternatively, you can build a base mix from equal parts peat moss (or a peat-free alternative), coarse horticultural vermiculite, and good quality organic compost.

It’s a bit like being a chef in the kitchen – you have the freedom to experiment. One important component is a balanced, slow-release organic fertiliser.

For most applications, a reliable raised bed mix breaks down roughly as follows:

• 50% high-quality topsoil – supplies mineral content and holds structure
• 30% compost – feeds soil biota and provides slow-release nutrients
• 20% drainage agents – coarse sand, perlite, or decomposed bark to prevent waterlogging

The most cost-effective ways to fill a raised bed include bulk-bought topsoil, homemade compost, sand, and recycled cardboard. Plant debris, logs, and landscape fabric are also useful for building up volume without spending a fortune.

“It’s always worth having a good rummage around your garden and garden shed first to see what you can find. There are so many everyday items that can be used to fill up raised beds, helping to reduce the amount of compost you’ll need."

Rather than simply filling with one uniform mix, layering creates a nutrient-rich environment that improves over time. Known as lasagne gardening, this mimics natural decomposition found in forest soils.

• Bottom layer: Coarse materials – small branches, twigs, pea gravel, or broken pots for aeration and drainage
• Landscape fabric: Laid over the drainage layer to prevent soil filtering down into the gravel
• Brown matter: Dry leaves, straw, cardboard, or newspaper to suppress weeds and add structure
• Green matter: Grass clippings, coffee grounds, or vegetable scraps for nitrogen
• Compost: A 2–4 inch layer of matured compost as a hub of microbial activity
• Top layer: 6–8 inches of your soil mix for immediate root development

Soil depth depends on what you plan to grow. “Not all raised beds are created equal,” advises Andrew White, “so before you purchase, consider what you’d like to grow and what surface you’ll be placing your raised beds on, as this may well have an impact on what you can grow.” As a rough guide:

• 6 inches: Herbs, lettuce, and plants with very shallow roots
• 12 inches: Carrots, radishes, peppers
• 18 inches: Tomatoes, cucumbers, courgettes, kale