Creating a garden bed – soil, mulch and materials

Mark the bed and inspect the site

Allow for the plants’ mature size and access around the bed. Look at light, wind and where rainwater collects or flows. A dry, exposed position and a wet hollow do not automatically need the same growing medium.

Remove turf and perennial weeds from the area being prepared. Look below the surface for building debris or a layer that prevents roots using the soil beneath. Do not hide an unresolved problem under new soil.

Decide what to retain, improve or replace

Compare the soil with the chosen plants’ requirements.

• The existing soil appears usable and water can leave: retain it as part of the rooting area. Do not automatically buy the whole desired rooting depth as new material.
• One property needs changing: identify it, such as moisture retention or a compacted layer. Get a treatment appropriate to the plants and medium before adding amendments.
• Water stands or the ground remains wet: check where it comes from and where it can go. Adding better soil on top does not itself solve drainage.
• Unsuitable material occupies the root space: identify what must be removed and the medium that will replace it before filling.

This is not a universal clay- or sandy-soil amendment recipe. Choose a growing medium for the plants and site, not its appearance. Products called topsoil, compost and potting mix are not automatically interchangeable.

Calculate the material you will add

Separate the total usable rooting layer from the new medium. The growing-medium-depth guide explains the distinction; the plant and product requirements determine your own bed.

For this example, assume the entire 12 m² bed needs a new 25 cm finished layer:

12 m² × 0.25 m = 3 m³.

The depth is a calculation assumption, not a recommendation for every plant. Where usable existing soil remains, calculate only the additional layer. Ask the supplier what delivered quantity will produce it and how settling is included.

Stop at a genuinely planting-ready bed

Spread the selected medium to the planned level. Do not bury the root collars of retained plants or unintentionally change water flow.

Before planting, have the boundary, surface level, water route and usable rooting arrangement resolved. New soil does not make the bed ready while a persistent water problem remains.

Calculate mulch separately and apply it after planting according to the product’s instructions. Keep plant bases and stems clear. Mulch does not replace the growing medium.

Use the plants’ instructions for the planting itself. A shared GB/AU guide cannot give one planting depth or seasonal calendar for every species and location.