Micro-forest vs Food forest – what’s the difference?

On a 2000 square metre block in Moruya, NSW, I’ve been exploring growing different types of vegetation. As well as traditional shrub beds, mown grass, vegetable gardens, water harvesting ponds and a large outdoor courtyard I’ve planted a micro-forest and a Food forest.

Micro-forests cool the landscape

In 2019, I created pilot urban landscape project, called the Downer micro-forest. The pilot used dense planting, climate-ready trees and provides a cool space for the public to enjoy.

The Federal Labor Member for Canberra, Alicia Payne cottoned on to the idea. She invited the Molonglo Conservation Group and The Climate Factory to submit a grant application to build a micro-forest in her electorate. The Sullivans Ck micro-forest was borne.

Australia’s National Forest Inventory

The Federal Department of Agriculture describes forests as areas dominated by trees, usually with a single stem and a mature height exceeding two metres. The crowns of trees have the potential to cover 20% of the area.

They say,”Native forests are categorised in Australia’s National Forest Inventory​ into eight national forest types named after their key genus or structural form: Acacia, Callitris, Casuarina, Eucalypt, Mangrove, Melaleuca, Rainforest, and Other native forest (which includes a range of minor native forest types that are named after their dominant genera, including Agonis, Atalaya, Banksia, Hakea, Grevillea, Heterodendron, Leptospermum, Lophostemon and Syncarpia).”


“Across the wide range of rainfall and soil conditions that support forest, most of Australia’s ‘Native forest’ category of forest is dominated by eucalypts (77%) and acacias (8%).”

A home micro-forest

In our home garden, I’ve planted our front garden into a dense native micro-forest. My aim was to mimic the look and feel of the heavily vegetated local sand dunes at Moruya Heads. And to create a windbreak from hot westerly winds, provide privacy and make wildlife habitat.

The micro-forest grew quickly to provide a dense windbreak, privacy screen and wildlife refuge in 3 years.

To establish a dense privacy screen and windbreak I planted the fast growing local coastal wattle, Acacia longifolia subsp sophorae. Amongst these wattles, I peppered local tree species like Casuarina glauca, Allocasuarina, Callitris rhomboidea, Acacia mearnsii (Black Wattle) and Acacia fimbriata. The coastal wattle and Black Wattle grew to four metres high in three years. And some of the Casuarina outstripped the wattles.


Understorey shrubs include, Banksia integrifolia (Coastal Banksia), Leptospermum petersonii (Lemon-scented Tea Tree), Correa alba, Westringia ‘Wynyabbie Gem‘ and strappy plants like Dianella and Lomandra. Groundcovers include Myoporum parvifolium (Creeping boobialla), Carpobrotus (Pig Face) and Hardenbergia. Hardenbergia also known as Native sarsparilla, can grow as a sprawling groundcover or twine up trees and shrubs.

The native groundcover, Dichondra repens (Kidney Weed) grows naturally in the damp and shaded parts of the micro-forest.

Wildlife habitat

With the micro-forest or tiny forest, the aim is to make it as dense as possible and to avoid bare ground. We plant at a ratio of between three to four plants per square metre.

Local Blue-tongues took up residence in 2018. They provide an excellent service, munching on unwelcome snails.

This Blue-tongue lizard lives in the dense undergrowth of our micro-forest. I was quite surprised when I threw some snails near it and it started eating them and was lucky enough to capture it on video!

In November 2019, I spotted my first pair of bumbling metallic green Carpenter Bees (Xylocopa) gathering pollen from Dianella and Westringia flowers. The dense shrubs are visited by small birds like Silver Eyes.

Soil improvement and irrigation

With soil excavated from our building site, our contractor, manipulated the ground to look like sand dunes. In each plant hole, I added organic material to give plants the best possible start to life.

In its first three years, the micro-forest survived on rainfall and occasional hand watering. Then, the summer of 2019 hit. By the year’s end Moruya received a paltry 508mm of rain (about 5/8ths) of the ‘average’ annual rainfall. Over summer 2019/2020 firestorms devastasted the Eurobodalla area, burning almost 80% of the landscape.

As a smokey January 2020 unravelled I questioned whether I’d made the right choice in planting a native micro-forest so close to our house. Our micro-forest faces west and if the fire reached us, the front garden would go up like kerosene on a barbie.

My partner and I, discussed hacking the trees off. But where would we place the prunings?

Late in January 2020, the fire burned to Moruya’s fringes. Luckily it didn’t penetrate into town. Since then, I’ve installed a 50m length of drip irrigation pipe to keep the micro-forest moist in hot weather. In addition, we are installing a second large water tank to protect the garden and house in case of fire.

Resources

Since penning this article, I’ve created a 54 minute video addressing frequently asked questions on how to make a home micro-forest.

Home food forest

As the name implies, the main aim of a food forest is to grow a diverse range of food in a forest-like environment. So while an orchard is a simplified forest, consisting of an over-storey that bears fruit, a food forest includes multiple vegetation layers. Like a micro-forest it includes groundcover layers that cool the soil (and provide habitat), shrubs, grasses, climbers and trees.

Improving the soil with organic material

In 2019 I chose a spot with alluvial soil, near Racecourse Creek, an ephemeral creek. Sometimes the creek is dry for months at a time, like in 2019 and sometimes it floods.

I marked out a 5m x 5m area for the food forest. Then I relocated the chooks to this space for a couple of months to scratch and fertilise the soil. I also added compost, seaweed and coffee grounds (from a local cafe). Our next door neighbour, a market gardener, formed five mounds with his cultivator.

Like the micro-forest I planted Wattles like Acacia floribunda that would grow quickly and protect sensitive plants. An added benefit of wattles is they drop leaves forming a fine mulch layer and add nitrogen to the soil.

Edible plants

I planted tubestock of edible exotic trees into the mounds: five carobs, three figs and one Mulberry. Shrubs include the Hawaiian Guava (Psidium guajava), Tamarillo (grown from a neighbour’s seed) and Peppino. Understorey plants include Comfrey (non-edible but a compost accelerant), Raspberry and Lemon Grass and rambling pumpkins and sweet potato.

The Food Forest was just above the flood on Racecourse Creek in February 2020. We received around 200mm of rain over 10 days. The flood took down fences and washed away vegetables in the next door market garden.

Bush foods

I added tough local Warrigal greens, Tetragonia tetragonoides to the food forest. These plants grow exposed to salt laden winds at the beach and as a groundcover in Casuarina glauca forests. Warrigal greens need to be cooked prior to eating to remove oxalates. I combine them with silver beet and kale when I want to add some greens to a dish.

I also added one Davidson’s Plum, Davidsonia. These trees grow in Australian rainforests and require frost protection. They bare edible fruit which is apparently best stewed.

Maintenance

The biggest maintenance issue, for both the micro-forest and the food forest is keeping grasses like Kikuyu and Couch at bay. I’ve almost won the battle with our micro-forest. I find hand weeding enveloped by greenery meditative.

Cool haven

Once the trees canopies overlap in our food forest, a small spot for a comfy chair will be the perfect antidote to oppressive summer heat.

Holt Micro-forest and food forest

In 2021, I started working with a group of residents from Holt in the ACT. The group are on target to build a 1500 plant micro-forest and a food forest in 2022.

Postscript

January 2020 was followed by two years of La Nina bringing extreme rainfall. Our micro-forest is thriving while the back garden and food forest is soggy. These climatic extremes illustrate the need to prepare for the future – for drought, bushfire and flood.

Climate ready trees in tiny forests

2019 was Australia’s hottest and driest year on record.

Studies show trees significantly reduce temperatures. So by planting more trees in our cities and towns we can adapt to climate change.

Urban areas get hot

Urban areas are typically hotter than the countryside. That’s because when we build cities we remove trees and pave over waterways. And the building materials we use, like concrete and asphalt, absorb heat and release it slowly at night.

A study by the CSIRO found in summer Canberra’s urban areas were up to eight degrees hotter than surrounding rural areas.

Tiny forests battle climate change

In 2020, The Climate Factory built its first tiny forest or micro-forest in Downer in the Australian Capital Territory. This weeny forest occupies just 450m2 of suburban parkland.

The tiny forest is modelled on the Miyawaki method. The Miyawaki method plants native plants densely which leads to fast growth. The layers of native plants improve local biodiversity.

Young leaves of a Kurrajong in the Downer tiny forest in Canberra.

However, Edwina Robinson founder of The Climate Factory, realised she needed to take a different approach to climate change. Robinson decided not to use local native trees in the tiny forest. Instead she experimented with growing trees from hotter and drier climates. Plus she integrated simple water harvesting methods to direct water deep into the soil.

Australian National University tree study

In 2019, the Australian National University released a study showing the trees most likely to survive a hotter, drier Canberra. Top of that list was the Kurrajong, Brachyciton populneus.

The signature tree of Canberra’s tiny forests

In 2020, Robinson worked with local community to build a second micro-forest – the Watson Micro-forest. The Kurrajong has become the signature tree in both the Downer and Watson tiny forests.

These Kurrajongs are planted at
the Banksia St, O’Connor wetland and are around 10 years old.

The Kurrajong is a sturdy evergreen Australian native tree with green glossy foliage. It grows slowly and may only reach four metres high in 10 years. Although this tree grows naturally in the Canberra region, The Climate Factory sourced plants from a nursery six hours north of Canberra. This nursery experiences temperature extremes of 49°C in summer and -9°C in winter. So these trees are likely to thrive in hot and dry urban environments.

As well as planting Kurrajongs, a number of other native trees are being trialled. The list includes the Queensland Bottle Tree, She-Oak, Allocasuarina and Silky Oak.

Ngunnawal use of the Kurrajong

The Ngunnawal people have lived in the Canberra region for tens of thousands of years. They used the bark of the Kurrajong to make string and rope. Kurrajongs have hard dark brown seed pods. The pods were turned into children’s toys. And inside the pods are seeds which are edible when roasted over a fire.

Does planting densely cool the landscape?

Robinson says she ordered temperature and humidity loggers to install into the micro-forests in 2022. Data from the loggers will be retrieved with smart phones. She will test if the dense planting of a micro-forest cools local temperatures.

To compare different planting approaches, one logger will be placed within the micro-forest and another one in a mature park tree with grass underneath. Time will tell if the dense planting cools the landscape. Robinson, says the inclusion of water harvesting should help keep temperatures down.

Resources

How to build climate-cooling micro-forest in 8 steps – video