Living with the bush
Reader Meg Blackman’s email asking for more tips on caring for soils has sparked a new series of grower’s guides by Don Burke. This month, it’s all about keeping native bushland plants alive in your own garden.
Reader’s email: Don, I was thrilled to see your article on ‘How Water Works in Australia’ in the May issue of BBY magazine. Your dry soil theory and Peter Andrews’ principles in his book, ‘Back from the Brink’, show how to care for the land by allowing it to heal and revitalise naturally. They make sense, and obviously work. I would love to see more articles on how these principles might be applied to a suburban backyard, which often has a mix of natives and exotics. We all want to heal our own bit of Australia.
Meg Blackman, Canberra, ACT
Most of us live near to or in the bush. How lucky we are in Australia to have remnant native plants and animals in and around our blocks of land.
Since my article on ‘How Water Works in Australia’ in the May issue of BBY magazine, a number of people, like Meg, have emailed, asking “how do we apply these new insights into our own gardens?” That is, how can people keep native bushland plants alive in the garden?
Often people build houses in bushland and retain many of the bush plants including the gum trees. Sadly, many of these die over the next 10 to 20 years and often they fall on the house, on fences or on electricity or phone lines.
There is still a huge amount of work to do to answer these questions. For the moment, the best I can do is to tell you what I am trying. All of the techniques listed in this article seem to be working, but since trees can take over 20 years to die, it is all still a bit experimental.
This seems to be the best of all methods. That is, quarantining areas around existing gum trees to keep excess water and nutrients away from their roots. This means keeping water runoff away, keeping fertilisers away, and therefore keeping most foreign garden plants away.
Runoff kills many native plants. Your roof collects huge amounts of water. If this is piped towards native trees and shrubs in dry forest areas these plants will die. So roof water needs to be piped off your block or just away from quarantined bushland areas. Septic tank water is the worst of all runoff in damaging bushland.
Most people know that phosphorus is poisonous to many native plants, especially grevilleas, banksias and hakeas. What is not so well understood is that any large amount of fertiliser is also toxic to most native plants, including grasses. So keep fertilisers away from natives as much as possible. Often over-fertilising natives causes them to grow very rapidly then to fall over or die rapidly too (within 5-10 years).
Plants to grow
The best trick around existing bush trees or shrubs is to plant attractive plants that actually like fairly dry soils lacking in fertiliser. The following plants are worth a try:
most grevilleas (especially local species)
croweas (especially Crowea saligna)
PLUS, non-natives such as:
Most of the rain that falls on your block lands on lawns, paving and other surface areas. In my garden I use a concept called ‘the swale’ to manage surface water.
Swales are areas of land designed to carry and/or deal with runoff. Usually they are grassed strips or zones which collect and direct surface water. Well constructed, they also soak up the water and absorb and use any fertiliser in it as well.
Swales can effectively more than double your rainfall each year by moving around, retaining and soaking up surface water. In doing so, you can direct water to zones that need lots: for example ferns, palms and most fruit trees and plants from other countries.
The key bit here is to make the water bypass zones of pre-existing native plants. By doing this, you can maintain the exact growing conditions that the plants had before the house was built.
All of my lawn areas are swales. The sides are around 75-100mm higher than the middle (see diagram below). My roof water is directed out onto the swales or into fish ponds. You can retro-fit your lawn by lifting the edges up by the same amount (ie, 75-100mm) as I have done. Then they become swales.
You can add an amount of lawn underlay on top of your grass then re-turf your lawn edges or you can spade under the edges, flap them over and add the soil underneath and unflap the grass on top.
These simply must not be used around dry forest or desert native plants. Here I am particularly talking about retained native plants from the original bushland or native plants from dry areas like WA. A high proportion of the native plants sold in nurseries these days are members of a small group that can tolerate moister conditions.
Wetting agents effectively break down the dust-dry, water-repelling nature of bushland soils. This is death to many Australian plants, but not to those from moist areas – for example rainforests.
It is interesting to note that many of the native plants introduced to gardens during the 1960s and 1970s quickly disappeared from nurseries. The reason? They died in gardens or became ill and straggly. Eucalyptus scoparia, Grevillea rosmarinifolia and Hakea salicifolia are classic examples. I believe that they died out since they need dry, water-repelling soils for survival. The death of vast numbers of native plants in gardens gave this group of plants a very bad name indeed. For that reason, very few native plant nurseries exist any more.
The good news is that the native plants sold in nurseries today are much more reliable. Perhaps the least reliable group sold today are kangaroo paws – but even in this group there are some that are quite hardy (those closest to Anigozanathos flavidus – eg, the Bush Gems series of kangaroo paws).