Tree landscape design is an essential part of commercial or residential landscape gardening. As the Chinese proverb goes, “The best time to plant a tree was 20 years ago. The second best time is now”. With the cooler months, it is time to think about planting some trees.
Trees as an attractive focal point
Some attractive Trees and shrubs can provide an interesting focal point for your garden. Many Australian native trees will provide vibrant coloured flower creating both beauty and food and habitat for a wide range of Australian fauna. As an added bonus, the colourful flowers provide a source of nectar and pollen for honeybees and native bees, well away from the garden pesticides. Foliage colours can also be used to create a contrast.
Lemon-scented myrtle also known as the Sweet Verbena Tree (Backhousia citriodora) is a Queensland species that is both attractive to honeybees and a source of bush tucker. However, as it is a rainforest plant, it is not particularly drought tolerant. If you look after it, you will be rewarded with clusters of attractive white flowers.
Design Considerations. – Locating the tree
When designing the garden for trees, make sure you consider the final height of the tree and any garden maintenance requirements. Space between the tree and a fence might need to be big enough for mower access. Also the location of any overhead power lines should be considered. If you are planting a street tree, the local council will have guidelines for the minimum distance to services such as stormwater outlets and power poles.
Planting Trees like a professional commercial landscaper
If your new tree comes in a plastic pot, make sure you protect it from the searing sun. A few hours of intense sunlight on a black plastic pot can do a great deal of harm to your new tree. Make sure you give the root ball a good soaking. If possible, dip the pot into a bucket of water.
Dig your hole much bigger than the pot size of the tree. That means if you are planting a tree from a 300 mm pot, the hole should be dug around 900 mm. This is especially the case if you are planting in poor quality soils. Aim to have the new tree slightly higher than the natural ground level. If you are in a heavy clay soil, dig in some organic matter both below and around the plant. If you use a lot of organic matter, this will tend to shrink as it decomposes so take care not to overdo it. The organic material used should be well composted. Backfill with 50% high quality topsoil mixed with the site topsoil. If you have a reactive clay soil, which is common in Melbourne, a hand full od gypsum can be dug into the bottom of the hole.
Once you have placed your tree in the hole, give the roots a bit of a tickle if they appear to have been root bound by the planter pot. This will encourage the roots to grow outward into the new soil. If you are planting a Eucalyptus or Magnolia, the roots should be disturbed as little as possible.
Water the new tree and tamp down on the soil to remove any air pockets. Cover the root zone with around 75mm thick mulch ensuring there is a gap between the trunk and the mulch to prevent collar rot. In most cases staking of the tree is not necessary. If you have a larger or a top heavy tree, use 2 or 3 stakes placed away from the trunk and tied loosely with a rag.
To avoid drought stress with you newly planted trees, give the soil around the plant a good soaking. The best solution for saving water is a dripper irrigation system with a timer and a moisture sensor. An annual application of a soil wetting solution will save water by reducing run off.
Weeding and mulching
Keep Weeds, lawns and other vegetation away from the root zone of your new tree until it is well established. For trees, this means an area of around 1.5 metres diameter should be kept clear for the first 3 years. The mulch should be topped up annually as it slowly decomposes into the soil.
Feeding your new Tree
Native plants generally require very little fertiliser, so be careful when applying and always use low phosphorus fertilisers. Products like Neutrog Seamungus combine the trace elements of seaweed with the nitrogen of chook manure to get your plants off to a good start. Neutrog “Bush Tucker” has been developed specifically for Australian Native plants and is ideal for even the most phosphorus sensitive proteas, banksias or grevillias. As well as harming native trees, excess phosphorus will inhibit mycorrhizal fungi essential for root development with your new tree. Phosphorus run off into streams and waterways can also be a problem.
Exotic trees will require a little bit more feeding for the low phosphorus Melbourne soils. Also add a small amount of slow release fertiliser to the hole.
Even if your tree is an Australian Native, don’t be afraid of giving it a regular prune or trim to get it into the shape you want. This should be done both early and regularly. After a year or two it the tree should be strong enough to stay upright without the stakes. This is the reason why the young trees should not be staked too tightly. Always use a clean and sharp pruning saw to avoid spreading plant diseases.
The trees selected for your Melbourne garden should be reasonably drought tolerant, non invasive and easy to maintain. Consideration should be given to the full extent of the leaf canopy and the root zone when the plant is fully grown. In particular, the plants chosen need to have resistance to the weather conditions and the fungal diseases that go along with it. A visit to your local botanical gardens is a good way to select plants for your home garden and also pick up some landscaping ideas. Some councils Council have also published a guides to saving water. Some of the trees listed in the guide include Kurrajong, (Brachychiton populneus), Crape Myrtle (Lagerstroemia indica), Screw Pine (Pandanus Tectorius), Coastal Banksia (Banksia integrifolia), Tuckeroo (Cupaniopsis anacardioides) , Tulipwood (Harpullia pendula), Southern Magnolia (Magnolia grandiflora) Blue Lilly Pilly (Syzygium oleosum)
Lagerstroemia indica has purple, pink or white crinkly flowers that appear like crape (or crepe). It is a deciduous tree but it can be grown as a large shrub. The long dark leaves are bronze when the tree is growing rapidly.
Many of us love the look and the bird attracting ability of the Western Australian Flowering Gum. (Corymbia ficifolia) (Previously know as Eucalyptus ficifolia). In the past the problem has been its ability to withstand the humidity of the Gold Coast. The good news is that horticulturalist Stan Henry has developed a hybrid variety suitable for the humid conditions of South East Queensland. The hybrids, which combine Corymbia ficifolia, the red flowering gum from south-west Western Australia with the swamp bloodwood, Corymbia ptychocarpa from northern Australia are know as the Summer series – ‘Summer Red’, ‘Summer Beauty’ and ‘Summer Snow’. Look for these in your local plant nursery.
Local Council Street Tree Policies
Stonnington (Covers Prahan, Toorak, Malvern and Glen Iris.)