Chances are that you have several pockets of shallow soil on your property, which have specific planting needs. Soil is generally shallow in front of retaining walls and above footings, underneath large trees, and on top of shale and rock beds, which we are quite familiar with in Brisbane. Read on for how to prep shallow soil, the kind of plantings that will thrive, and maintenance for shallow soil plantings.
If possible, build the garden bed up as high as you can. Mounds can look great – contours are beautiful and create diversity in a landscape. Try 200-300mm of soil mounded. Alternatively, use raised planters.
Large shrubs are not a good choice for shallow soil zones as they don’t have stability; they will only reach a small size.
Instead, choose shallow-rooted plants, such as grasses and ground covers for stability, rhizomal plants, vines and succulents (which are appropriate for hot, dry zones).
Grasses and ground covers
Try turf and spreading plants such as native violets (Viola hederacea), Johnny Jump Up violets, and Zoysia grass. Spreading plants are self-sustaining; when the older plants die, the new plants can keep growing. A mat of spreading plants will keep moisture in.
Rhizomal plants that cope well with shallow soil include Clivias (for shaded areas), Agapanthas, Lomandras, Dianellas, and Poa.
Vinges are aggressive growers (requiring a lot of fertiliser), but shallow rooted. They are great to train up retaining walls or to espalier.
Succulents thrive in difficult conditions such as dry, hot zones and shallow soil. See the SEED Landscape Designs project in Hamilton for a great example of use of succulents in the property’s front plant beds.
Shallow soil will need to have extra soil added regularly to replenish nutrients. Beds will need to be fertilised more frequently and treated like a potted garden.
Plants grown in shallow soil can’t grow deep roots, and without sub-soil moisture they are thirsty and dry up quickly. Keep shallow soil plantings well-watered.
For more advice on planting in shallow soil, particularly in South-East Queensland, contact us at Seed Landscape Designs.
Images: Seed Landscape Designs