Recreating the Country blog |
Acacia implexaAbout thirty years ago, I set off to collect my first Lightwood seed on a roadside near Lethbridge. I had been tipped-off by a local farmer, who said that it grew alongside a shrubby form of Blackwood. I remember driving up and down the gravel road several times, wondering if I had been sent on a wild goose chase. The trees on the roadside all looked like Blackwoods through my open window. At this stage of my nursery career, I had only read about Lightwood and didn’t know about the subtle features that distinguished it from it's very close relative, Blackwood. Though, a walk amongst the roadside trees soon revealed that there were indeed two different species growing side by side. With a more experienced eye, I can now comfortably identify Lightwoods while driving along a country road or highway, and it has become one of my favourite medium-sized wattles. Commonly pronounced – im-plex-a (no surprises there) Its species name, ‘implexa’ hints at another distinguishing feature of the tree. Its spiralling seed pods form tangled clumps and look very like untidy bird’s nests hanging from the branches. Implexus is Latin for tangled. Where does it grow? & what does it look like? The Lightwood is well suited to the soils and rainfall of the Geelong region. It can also be found growing on the basalt plains west of Geelong on stony barriers, in the eastern parts of Victoria, NSW and southern Queensland where the rainfall above 450 mm. In areas with high rainfall like the Otway Ranges, it’s unlikely to be seen, but this is where Blackwood’s excel and grow into forest giants. The Lightwood is an attractive, hardy, drought, frost-tolerant, upright small tree that grows 5-10 m tall. Though very like the Blackwood, its leaves are greener and distinctly sickle shaped. Another important difference between Lightwood and Blackwood is the seed. The glossy black seed of the Lightwood has a small bone coloured aril (the aril connects the seed to the pod) at the end of the seed, whereas the Blackwood has a large orange aril that surrounds the whole seed. The Lightwood has a rough bark and an attractive grey trunk. (click on the image to enlarge) The Lightwood is quite long-lived, thriving for 30 – 50 years. It still can be found on roadsides and on stony barriers, though it is becoming rarer. It’s more adaptable than the Blackwood and does well in dry, windy, exposed locations. The Lightwood is suited to all well drained soils. It's a fast-growing tree and will commonly reach two meters tall in the first twelve months after planting. The Lightwood is therefore very useful for erosion control, and its potential to sucker when its roots are disturbed is another benefit in eroded landscapes. Its tendency to sucker makes me cautious about recommending it for small gardens. Because it is a handsome tree, it is often planted as a street tree. An added benefit is its tolerance to pollution, and its shallow roots don’t raise footpaths. For a more detailed description of the leaves, flowers and seed pods, click to this Flora bank link Practical uses for the tree and its timber Its dense foliage makes it an ideal tree to plant for shelter on farms and as an understorey planting near remnant tall eucalypts like Yellow Gum and River Red Gum. Like all wattles, Lightwoods fix atmospheric nitrogen in the soil. This benefits all plants growing nearby. In Biorich plantations (designed for biodiversity and for income) it can be planted in clumps of 20 or more to allow for future maintenance and harvesting timber. Straight trees can be selected and ‘form-pruned’ to improve the future value of their harvested wood. ‘Form-pruning’ removes small branches from the main trunk, producing knot-free timber called clear-wood. Clear-wood is stronger and more valuable to furniture makers and wood turners because of its continuous, uninterrupted wood grain. Lightwood timber is hard, close-grained and dark brown with some pale stripes. The smaller branches and waste timber are also good firewood and are hot burning. Its lemon coloured pompom flowers in late summer provide good quality protein rich pollen for bees (crude protein is 23% - 27%). Traditional owner uses The very hard timber would have been useful for making Clapsticks and for carving small wooden bowls like the Coolamon. Traditional Owners boiled the bark of the Lightwood to produce a lotion that was applied to wounds to aid healing. This lotion could also relieve painful muscles and bruising. The leaves and bark are rich in soap forming chemicals called saponins. These produce a foam when crushed and mixed with water and were used to stun and catch fish. Nature notes The upright branching habit of the Lightwood provides excellent roosting sites for birds. Parrots and native pigeon’s eat the seed pods and seeds. Smaller birds like Silvereyes, feed on the many insects that are attracted to the late summer pollen rich flowers. Other insect eating birds like the Black-faced Cuckoo Shrike feed on grubs found under the bark. Like many wattle species, Lightwood is prone to attack from borers and gall forming wasps. The galls appear as brown, rounded woody growths on the branches. They can indicate that the tree is unhealthy (heavy clay soil or poor drainage can cause stress) or getting old. The galls can be cut off and burnt if they become unsightly. Propagation from seed The most convenient method to separate the acacia pods from the seed is to shake and rub the opened pods through a common garden sieve, a few handfuls at a time. Winnowing in a light breeze will remove the fine trash that passes through the sieve with the seed. After the Lightwood seeds are collected and cleaned. They can then be stored indefinitely in a jar or a zip lock plastic bag. Always record the date and place of collection. To germinate the seed, place the seed in a cup and pour boiled water over the seeds until they are well covered. Any seeds that float can be discarded because they are infertile. Allow the water to cool, pour off the water and pat the seeds dry. Sow in a shallow tray and cover the seed with potting mix. They should start to germinate within two weeks. Transplant into cells or forestry tubes when they are small and easy to handle. Add a pinch of slow release native plant fertiliser. Inoculating with rhizobia will increase the vigour and health of your trees when they are planted on in the field. Click here and scroll down for an easy acacia inoculation method. Grow plants on until they are about twice the height of the tube/cell and well hardened-off (toughened).
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Silver Wattle, Acacia dealbata A tree or a thicket In the early days of the nursery when we were exploring the district, we came across a great swimming hole on the Yarrowee River near Mt Mercer. On the steep walk down to the river bank I noticed a young Silver Wattle growing on the side of the track. When we returned each year to collect seed, the single stem had multiplied until ten years later it was a dense thicket. It had become popular haunt for Grey Fantails, Superb Fairy Wrens and Willie Wagtails. I discovered that the fifty or so stems of this copse all shared the one root system. They were suckers of the original tree that had grown from a single seed a decade before. This observation supported by research became very useful knowledge in later years. When a customer asked for suitable a tree to bind an eroding gully or river bank, my confident recommendation was Silver Wattle planted with a ground layer of Silver Tussock Grass. Both species named silver for their silver foliage and both gold class for their effectiveness at controlling erosion. Note. Its suckering habit and size make it unsuitable for small gardens. Commonly pronounced – deal-ba-ta Dealbatus is Latin for whitened. A white powder on the leaves and stems gives the tree a silvery appearance. This can vary from location to location and season to season. So much so that sometimes distinguishing Silver Wattle from Black Wattle, A. mearnsii can be difficult. This is easily sorted by examining the pattern of glands on the central rib or rachis of the leaf (the glands resemble tiny green doughnuts); To quote Leon Costermans, ‘Native trees and shrubs of south-eastern Australia’, A. mearnsii – glands are numerous, hairy and irregularly spaced along the length of the minutely velvety rachis A. dealbata – glands are at the base of each pair of pinnae (the rows of leaflets extending out from the central rachis The Australian Native plants Society has a more detailed but concise description of Silver Wattle. Also the SA Botanical Gardens website has some great photos. (Click on the front page circular image to see more photos). Practical uses Silver Wattle is indigenous to New South Wales, Victoria and Tasmania and naturalised in South Australia and Western Australia. It grows to a height of 8-12 metres. They are typically found along the edge of waterways and are well adapted to short periods of flooding. It therefore grows quite well in poorly drained soils, though its normal lifespan of around 20 + years is often reduced by as much as 50%. Like the Black Wattle, it is fast growing and produces an excellent hot burning firewood. If grown for firewood it would be ideal to choose a non-suckering provenance. These are more likely to be found in the higher rainfall districts. The honey coloured timber is useful for bespoke furniture and interior lining boards, but its uses are mainly limited craft furniture and turning. The oil extract or essence from the Silver Wattle flowers is in demand and a popular ingredient of perfumes. (It is known to contain enanthic (heptanoic) acid, palmic aldehyde, anisic acid, acetic acid, and phenols) A marketing description on an essence bottle sums up its potential. ‘Wonderfully rich, honey sweet, floral woody aroma which is uplifting, relaxing, calming, anti-depressive, aids happiness and calms noisy children. It sounds like the perfect antidote to modern living The bright yellow pompom flowers and tip shoots are harvested for use as cut flowers, known in the florist trade as "mimosa. The flowers are also a good source of protein rich pollen for bees, yielding an average of 21.4% crude protein. The peak flowering months are September and October The aromatic pollen rich flowers can also be used in fritters. The gum or kino collected from the trunk is edible and is used as a substitute for Gum Arabic. Traditional Owner uses Tools Silver Wattle’s suckering habit produces long straight strong stems which were ideal for making spears. Boomerangs, spear throwers, clubs, shields, handles for axes and chisels, coolamons, digging sticks, clap sticks and fire drills could also be made from its very hard wood. Silver wattle wood was also used to make handles for stone axes. The bark was used for implements and dishes. Ref: Victorian Koorie Plants by Beth Gott and John Conran Gums Both Black Wattle and Silver Wattle were important sources of gum. To ensure good flow of gum indigenous people notched the trunk in autumn. Balls of gum were then collected and eaten as a snack or dissolved in water with aromatic nectar collected from the flowers to make sweet drinks and Jelly. Heating makes it soft and chewable. Pale coloured gums are more likely to be sweet and pleasant to chew. The dark gum is rich in tannins and is more astringent. When the gum is mixed with burnt mussel shells or wood ash it becomes a cement for water buckets made from the bark of the tree. The bark also provided fibre to make a coarse string and was infused in hot water as a remedy for indigestion. Nature notes The Silver Wattles has bright yellow flowers (varying from lemon to golden) in early spring (July – October). This makes a stunning display against its grey-green ‘ferny’ leaves. All wattles fix atmospheric nitrogen in the soil. This benefits neighbouring plants particularly in leached and low nutrient soils. Choose drought tolerant understorey plants Survival for other plants growing near mature Silver Wattles can become a struggle. The roots of the Silver Wattle tenaciously suck-out all the available soil moisture around the tree, particularity in dry seasons. This eventually can become a bare zone where only the toughest shade tolerant native shrubs, grasses and lilies will grow. Its suckering habit makes this dry zone spread and reducing available light Silver Wattle in biorich design In 50+ meter wide sustainable biodiversity (biorich) plantings, Silver Wattles are planted in small clumps of 5-10 trees/clump. These clumps numbers can be increased to 50 if the wattles are grown to harvest for poles, lining boards or tan bark. This clump planting provides a concentrated source of food for wildlife and results in excellent pollination and seed production. It also makes it convenient to thin or harvest firewood. ‘Natural Selection’ will determine the strongest and fittest trees for the plantation as it matures. Propagating from seed As with other wattles the trick to germinating Silver Wattle seed is to soften or scratch (scarify) the hard seed coat. Softening is conveniently done by pouring recently boiled water over the seed. Allow this to cool, pour off the excess water then sow into a well-drained seed raising mix. Cover the seed. After the boiled water treatment the seeds can be patted dry for direct seeding into a plantation. The seedlings are transplanted when they lift their heads above the seed bed. This is my preferred method because it is fast and causes no damage to the root system which at this early stage is just a single shoot.
The Myrtles - eucalypts, callistemons, melaleucas, leptospermums and more. |
Stephen Murphy is an author, an ecologist and a nurseryman. He has been a designer of natural landscapes for over 30 years. He loves the bush, supports Landcare and is a volunteer helping to conserve local reserves. |