Indigenous garden design with heavy clay soils

Post building works, many gardens in Melbourne have been left with poor soil structure and heavy clay close to the surface. This soil condition creates significant problems for many plants, and if you don’t recognize it before you being planting you will most probably lose many plants without knowing why.

In the following example, I am working with the scenario that I am planting directly into a heavy clay soil. If you are careful with your plant choices, there are many indigenous plants that can succeed in this challenging situation and when I put together a planting design for a site like this my key considerations are rapid site coverage, soil structure improvement, ecosystem development and habitat creation.

Indigenous Design: Heavy clay soil

The site has been densely covered with rapidly growing, self seeding indigenous plants. Higher proportions of large shrubs and bushes will add structure to the soil and provide habitat for insects, birds and other fauna. Very little consideration has been given to the aesthetic qualities of the plants. This is not to say the garden will not look good!

Landscape design for heavy, clay based Melbourne soil

My pathway mix for heavy clay includes plants that will tolerate some very light foot traffic. I would try Atriplex semibaccata, Calocephalus lactus, Linum marginale and Gonocarpus tetragynus and observe what seems to like the site. You would still want to be careful with where you step to avoid damaging branches as none of these are plants are true ground covers. Linum is included as seasonal plant burning off each summer. You could also try Carpobronus modestus at the edges if you have enough rainwater runoff.

For my herb rich grassland mixes area I have selected a range of plants that can either handle the conditions year round, or which overcome adversity by rapid reproduction. My year round group includes Themeda triandra, Calocephalus citreus and Dianella Admixa, whislt my prolific self seeding group would include Senscio quadridentalis, Rytidosperma setaceum and Chloris trunica. Chrysocephalum apiculatum & semipappossum would also be given a try. With challenging soil experimenting is a great way to get to know the conditions before you roll out a whole planting design.

For my smaller shrub layer, I would look to Rhagodia parabolica, Cassinia arculata and Goodenia ovata. With my larger shrubs, I would look to create bird habitat with plants such as Myoporum viscosum, Solanum aviculare and Cassinia longifolia. Along fence lines I would trial Clematis microphylla.

Remember that the plants that grow from seed in your garden will be much better adjusted to the harsh conditions than the tube stock plants you bring in. In difficult conditions, tube stock plants will require a long period of nurturance in order to establish. Assisting your plants to seed within your garden is a worthwhile approach. When you see your plants dropping seed, help them by spreading the seed within the garden.

Happy planting  and good luck,

Ben

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