Ground-covers cool the earth in micro-forests

When you think of a forest, the first thing that pops into your mind is probably trees. While trees are an essential part of a forest and do much of the heavy lifting others have a role to play. Think shrubs, climbers, ground-covers, orchids and epiphytes.

At The Climate Factory, we design, build and teach about micro-forests. We are inspired by the industrial engineer, Shubhendu Sharma who applied Toyota’s production systems to forest-making and now coordinates native forest plantings across the world. Sharma in turn, was influenced by the Japanese botanist and plant ecologist, Akira Miyawaki, author of ‘The healing power of forests’.

The Climate Factory’s smallest forest is the size of a car space – 5.5 metres x 2.5 metres . We’d love to see micro-forests replacing car spaces in urban areas as we transition away from private vehicle use to a more regenerative way of living.

If you look closely at a forest, you will notice plants jumbled together. They tend not be evenly spaced and plants compete with one another for light, nutrients and water. And plants are a range of different heights, some have just germinated, some have died and some are in their prime.

At the bottom of the forest are the ground-covers. They have a special role to play. They keep the ground cooler while your micro-forest is establishing and provide habitat for beetles, skinks and lizards. Eventually the forest will become too shady for many of them and leaf litter may take their place.

Starting at the forest floor, here’s our recommendations for four native groundcovers (two which are edible) that would be beneficial in a native micro-forest.

Hardenbergia violacea

A stand out is the tough Hardenbergia violacea, also known as False Sarsparilla. It occurs as an understorey plant in native forests either as either a groundcover or twines its way up shrubs. It’s in the pea family and bears purple flowers at the same time as Wattles signalling winter is almost kaput.

It has leathery dark green leaves and once established is drought and frost hardy.

Hardenbergia can be grown from pre-treated seed. We collect the dried pods from  a plant thriving in our Moruya garden. Soak seeds overnight in hot water and plant them in a mix of 50:50 coarse river sand to native potting mix. The seeds germinated indoors in a warm sunny spot from 10 days to three weeks.

Picture of freshly germinated Hardenbergia seeds.
Hardenbergia seeds collected from the garden germinate after pre-treatment with boiling water. We used a mix of washed river sand mixed with native potting mix to make the seed raising mix.

Myoporum parvifolium

This is a rapidly growing bright green groundcover that comes in a couple of forms – either fine leaf or broader leaf. It can become woody if not left in check as it grows. Creeping Boobialla, bears small white or pink flowers and creates a living mulch over the ground.

It self-propagates by laying down roots across it stem as it sprawls over the ground. These can be removed and repotted to create new plants.

In our west facing front garden in Moruya (which we are infill planting to turn into a micro-forest) Creeping Boobialla makes a fast green mat with Pigface (see below).

Carpobrotus glaucescens

Many will be familiar with the iridescent pink flowers of the Pigface from the sand dunes of the east coast of Australia. As a kid I thought it was a weed and was unaware the flowers form edible scarlet fruits, a snack for coastal indigenous people. The fruits surprise with their salty tang.

It’s a rapidly growing plant, with sage green succulent leaves, and pieces can be broken off and potted to create new plants. As it’s a succulent it’s best to let the end of the broken portion heal over first (for a couple of days) before growing in a free draining propagation mix.

Pigface is drought and cold hardy to a point. We experience -4C frosts on our block in Moruya, NSW  and it has withstood those. It’s been used on the green roof at Thor’s Hammer in Fyshwick, Canberra and has survived.

Tetragonia tetragonoides

This leafy green sprawling groundcover, also known as Warrigal greens, is edible and is rumoured to have helped Captain Cook’s crew stave off scurvy.  It grows wild near the beach and along rivers underneath Casuarina glauca and prefers a slightly more sheltered position and more water than Pigface.

Like many other leafy edibles, its leaves are high in oxalic acid and should be blanched prior to eating. In Canberra, its best grown in a sheltered position with adequate irrigation. The leaves will tell you if its thriving. It will have large green leaves if happy or small leaves if it’s struggling.

It can be grown from seed or by cuttings.

Edwina Robinson

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