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Planting for Weed Control
Poa labillardieri Eskdale and Lomandra longifolia Cassica planted at density, and making it near impossible for weeds to compete. Four years after planting it is still performing well.
Unfortunately many smaller native grasses are often planted, with generally the same result. After one or two years the weeds take over. Usually these smaller native grasses are also short lived, which ads to the failure. Here Danthonia have been thinned out by weed invasion. In the back ground some of the larger grasses are doing well.
Golden Rule
When planting natives grasses, there is only one golden rule to keep in mind! Will they work long term? To achieve long term success the native grasses must not only be long lived, they must be able to out compete exotic weeds.
To do this they must be large enough or vigorous enough to out grow the competitors.
Small native grasses such as Danthonia, Bothriochloa and Microlaena can not usually out compete weeds. To achieve long term success and weed control you must plant larger native grasses. Grasses such as Poa labillardieri Eskdale, Poa poiformis, Pennisetum alopecuroides, Themeda australis, and grass like plants such as Lomandra longifolia and Dianella. Often the improved varieties will grow larger (e.g. Eskdale) and provide better weed control.
Now that you have chosen the right plants, you must plant them at the correct density. If you plant Lomandra longifolia at 1 per square metre, it will soon become riddled with weeds, but if you plant them at 6 per square metre, they will outcompete weeds. See left for recommended planting rates on some varieties for outcompeting weeds.
Planting rate guide when weed control is important
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|
Variety |
Size |
Plants/sq m |
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Poa
labillardieri Eskdale |
VC, VT,
pot |
15 to 25 |
|
Poa
poiformis Kingsdale |
VT, pot |
15 to 25 |
|
Poa
poiformis Courtney |
VT, pot |
15 to 25 |
|
Lomandra longifolia
Cassica |
VC, VT,
pot |
6 to 15 |
|
Lomandra
longifolia Katrinus |
VC, VT, pot |
6 to 15 |
|
Lomandra longifolia
Tanika |
VT, pot |
8 to 15 |
|
Pennisetum alopecuroides
Nafray |
VT, pot |
10 to 15 |
|
Pennisetum alopecuroides Purple
lea |
VT, pot |
10 to 15 |
|
Themeda
australis Mingo |
VT, pot |
10 to 20 |
|
Eragrostis elongata Elvera |
VC, VT, pot |
25 to 35 |
|
Isolepis
nodosa Aranda |
VC, VT, pot |
15 to 25 |
|
Dianella
elongata
|
VT, pot |
6 to 15 |
For native grasses to make the list in the above table, they must be able to out compete weeds, they must look good, and they must have proven performance on projects for at least 4 years.
Note:
For specimen planting where weed maintenance is possible, lower planting
rates are possible. A good example of this is high maintenance garden
planting.
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