silver saltbush on the left contrasts with Warrigal greens

Ground covers cool the earth in micro-forests

When you think of a forest, you probably think of trees. Whilst trees are essential to a forest, other plants layers are important too. These layers include shrubs, climbers and groundcovers.

If you look closely at a forest, you will notice plants jumbled together. These plants are randomly spaced and compete 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.

Tiny forests popping up in Canberra

The Climate Factory works with community leaders to build climate cooling micro or tiny forests. Over 2020-2021 we built the Downer and Watson Micro-forests and in May 2022 construction starts on the Holt Micro-forest. Since 2020 we have been trialling a range of native groundcovers in our forests.

Groundcovers a living mulch in the tiny forest

At the forest bottom are the groundcovers. They have a special role to play. They cool the ground and provide habitat for beetles, skinks and lizards. Eventually the forest will become too shady for some of them and leaf litter may take their place.

Below are three groundcovers we trialled at the Downer and Watson micro-forests.

Hardy Hardenbergia

Hardenbergia violacea (also known as False sarsparilla) is an understorey plant of native forests and woodlands. It grows as a groundcover or twines through shrubs. We like to plant Hardenbergia in the same hole as a wattle to mimic nature.

This hardy plant is in the pea family and bears purple flowers. You will often see it flowering at the same time as wattle. This signals spring is on its way.

Purple flowering Hardenbergia growing amongst wattle.

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

ACT for Bees says, its flowers provide food for butterflies, European Honey bees and native Leaf-cutter bees.

This groundcover can be grown from pre-treated seed. To pre-treat seeds, soak overnight in hot water. This should break the seed dormancy. Then plant the seeds in a mix of 50:50 coarse river sand to native potting mix. Depending on conditions, seed should germinate within 10 days to three weeks.

Marvellous Myoporum

This is a fast growing groundcover that comes in two forms. Plants can have either a fine leaf or broader leaf. Myoporum parvifolium is also known as Creeping boobialla. The plant bears small white or pink flowers and creates a living mulch over the ground. It prefers full sun to part shade.

At the Watson Micro-forest we planted it at the forest edges and in pollinator patches. This is so it gets enough sun to grow happily.

Myoporum parvifolium is easy to grow from cuttings. It prefers full sun to part shade.

Creeping boobialla can be grown readily from cuttings.

Tasty Tetragonia

This sprawling groundcover, Tetragonia tetragonoides is also known as Warrigal greens. It is has edible leaves. Captain Cook is rumoured to have used its leaves to stop his crew getting scurvy. 

silver saltbush on the left contrasts with Warrigal greens
Warrigal greens on the right combined with the silvery Saltbush (Rhagodia spinescens) in the Edible Micro-forest, Lonsdale St, Braddon. Prefers full sun to part shade.

It’s leaves are high in oxalic acid and should be blanched prior to eating. In Canberra, its best grown in a sheltered position with adequate water. Warrigal Greens were planted as a groundcover in the Edible Micro-forest display in Braddon.

Warrigal greens can be grown from seed or by cuttings.

In Canberra and other cool climate areas it’s best treated as an annual. Hopefully it will set enough seed in the micro-forests so it self propagates.

Home propagation

In our home propagation area we are trialling some hardy shade tolerant groundcovers for future micro-forests. These include: Ajuga australis, Hydrocytle laxiflora (gloriously known as Stinking pennwort) and Acaena novae-zelandiae (Bidgee widgee).

Hydrocotyle laxiflora or Stinking pennywort is useful for moist shady sites. According to ‘Australian Plants for Canberra region gardens and other cool climate areas’ it can be invasive in garden beds. It grows readily across the soil, rooting at nodes. Greenish globular flowers with a strong odour are held on upright stems. This plant isn’t commonly grown by nurseries, maybe due to its invasive nature and smelliness.

At the Holt Micro-forest we will plant Stinking pennwort and Bidgee widgee. We will also plant Dichondra repens (Kidney weed) which likes shade and moist soils and Viola hederaceae (Native violet) at the dry creek bed edges.

If you’d like to start a community micro-forest or build a micro-forest at home we’ve created videos on these topics.

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