10.2.2. Single species dominance
In some areas, a long history of improving and fertilising exotic pastures has resulted in the dominance of single species such as phalaris. This is a hard and vigorous introduced grass species which can quickly dominate all other pasture species, native or exotic.
The following is an account of how to control phalaris enough to allow other plant species (in this instance, native trees) to be established in a paddock.
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Getting on top of phalaris
By Hilary Kent and John Merritt, Gearys Gap, ACT
Phalaris is too vigorous and dense to permit direct seeding native trees so we plant tubestock instead. Wherever possible we rip some months before planting. In our case this means calling upon an obliging neighbour, who attaches a single-tine plough to his tractor.
We then apply Roundup along both sides of the ripline to create a metre-wide phalaris-free strip.
The dead phalaris is left in the ground to help conserve moisture and inhibit grass growth. If it is removed, it is quickly replaced by wild sorrel, which has the capacity to choke young trees almost equal to that of the phalaris itself. Moreover, in time, the phalaris will always come back. Thus we also add mulch to the rip-lines. Often we use phalaris hay, cut after the seeds have fallen. It is durable and effective.
Growing tips
We grow our own tubestock or purchase it from local nurseries. Some more frost-tender trees, however, will not survive unless they are relatively well advanced before planting. Casuarinas, for example, need to be at least a metre in height.
We prefer to plant in spring after rain. The strategy has been to plant a mixture of eucalyptus species to minimise the effects of insect attack, and acacias to add nitrogen to the soil and provide wind protection for the slower growing species.
We water every three weeks during the first summer and weed and mulch until the trees are well established. The established trees reduce the phalaris growth themselves.
Phalaris must be eaten down or slashed if it is not to become a fire hazard.
The good and bad of sheep
We run sheep which eat down the grass, but they can be hard on trees. For some time we experimented with a variety of individual wire tree guards which we anchored with steel pickets. The guards worked well while the trees were young, but not so well once the trees began to acquire breadth and height. They restrict lateral growth and sheep learn to climb up the sides. There was no alternative but to fence our windbreaks and to build largish squares or circles of ringlock around solo trees.
When the foliage of our paddock trees is above sheep height, we remove the ringlock and use chicken wire sheaths to protect the trunks. (Light plastic mesh works just as well.) The sheath needs to be anchored, otherwise the sheep will push it upwards and nibble in the areas of the trunk thus exposed.
Persistence does pay off. Most of our five- to six-year-old paddock trees are now without protection of any sort and are strong enough not to be affected by sheep rubbing against them.
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