Charles Sturt University
Charles Sturt University

Austral Trefoil

Austral Trefoil - Lotus australis

By Suzanne Prober & Kevin Thiele, 2002.

The common name Lotus conjures images of chanting Indian mystics and fat buddha-figures. The Lotus in question is a tropical water lily Nelumbo nucifera. But by a taxonomic accident, the true Lotus is an unrelated genus of legumes, one species of which, the Austral Trefoil (Lotus australis), is an uncommon inhabitant of grassy box woodlands.

Austral TrefoilThe Austral Trefoil is a perennial herbaceous legume with a growth habit quite similar to cultivated lucerne. In fact in some parts of New South Wales it's called Barwon Lucerne. Like lucerne, a woody crown helps it survive harsh periods of drought or winter cold when the above-ground parts die back. Its leaves are soft and lucerne-like also, with three elongate leaflets on a short stalk. It can be easily distinguished from lucerne by its leaves having two other leaflets at the base of the leaf-stalk, quite different from the small, transparent stipules at the base of a lucerne leaf. And unlike the small, purple flowers of lucerne, Austral Trefoil flowers are large and usually white to shell-pink (see picture).

Like many other grassy woodland plants, Austral Trefoil was once common and is still widespread. It ranges almost throughout Australia except the desert inland, but is mostly found in temperate and subtropical areas. In the region of the grassy woodlands, it's now somewhat more frequent on the Northern Tablelands and Slopes of New South Wales than it is further south. But nowhere is it common. It's sensitive to set-stocked grazing, and in many areas only persists in country cemeteries, roadsides, rail lines and Travelling Stock Reserves, or in parts of paddocks where grazing is light.

Being a legume, Austral Trefoil fixes nitrogen from the air. Along with other native legumes such as the psoraleas (Cullen species), it has promise as a component of native perennial pastures. There are reports of stock poisoning caused by high levels of cyanide compounds at times, but this trait is variable in wild plants and could probably be bred out (many pasture species also produce cyanide). Similarly, wild plants differ in their vigour and competitiveness. Very little work has been done to assess the potential of native legumes in sustainable grazing systems, but this is a growing field with much potential.

For these reasons, retaining many different natural populations of Austral Trefoil is important - one of them may hold a key to agricultural sustainability. That's another reason why saving Grassy Box Woodland remnants, with their precious cargo of native plants and animals, is so important.

Growing Lotus australis

Austral TrefoilAustral Trefoil should be easy to grow, and perhaps to reintroduce into Grassy Box Woodland remnants. Collect seeds in mid to late summer as the pods begin to split. Timing of seed collection may be difficult, as the pods will split explosively on a hot day as soon as the seeds are ripe - if you know where there is a patch, keep checking frequently as the seed pods harden. The seeds have hard coats like wattles and other legumes, so don't germinate readily. About 20% germination can be achieved by moistening seeds and leaving them in the dark. Better results will be achieved from hot- water treatment - put some seeds in a jar and cover with just- boiling water. Leave to cool, then examine the seeds - some will have swelled to double their size, others will be unchanged. Sow the swollen ones m ordinary potting mix. Germination will be rapid.

Re-introducing Austral Trefoil into your remnant

The simplest way to reintroduce Austral Trefoil to a remnant is to collect seed from the closest wild population, then scatter the seed in a small area and watch to see what happens. This is fairly hit-and-miss though - the seeds may be eaten by seed predators such as insects or pigeons, or the young seedlings may die from damping off or competition with weeds or other native plants. A more reliable method would be to grow plants in pots then plant out when well-grown. There is no published information on how successfully Austral Trefoil can be transplanted, but it should be fairly tough if conditions are suitable. If you intend to reintroduce Austral Trefoil, remember the following points:

  • You need to apply for a licence under the Threatened Species Conservation Act is you are collecting from a remnant of White Box Yellow Box Blakely's Red Gum as it is an Endangered Ecological Community.
  • Reintroduction onto a remnant on public land may only proceed with permission - consult NPWS for advice.
  • Always collect seed from the closest population, and never collect more than 10% of the seed from any population.
  • Again, always seek permission from the owner.
  • Keep records, of the location of the original seed, and the success of the re-introduction attempt. This is important for two reasons - so that others can learn from your success or failure, and so that future workers will know the provenance of your plants.
References
  • Clarke PI, Davison EA, Fulloon L (2000) Germination and dormancy of grassy woodland and forest species: effects of smoke, heat, darkness and cold. Australian Journal of Botany 48, 687-700.

This article was first published in Woodland Wanderings, WInter 2002.