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Native grasses in horticulture
Sowing native grass under an apple orchard
Intensive horticulture is rapidly switching on to the use of living cover between the rows of trees or vines as an aid in soil and moisture management. A number of people are also looking to utilize the attributes of native grasses in this application. The following text explains why this is a valuable approach, what grasses can be used and how to go about maintaining them once established.
Why use a living grass cover?
The choice for many is between a zero cover (achieved through cultivation or spraying), a cover of introduced mulch or a living vegetation cover. Many studies have shown that the use of living cover is beneficial through better utilisation of water during winter, retention of nitrogen within the profile, the maintenance of cooler temperatures in the soil surface which keeps the crop cooler and reducing dust around the crops.
In some areas the use of living cover crops has led to significant lowering in saline water tables by the utilisation of excess water from within the top 1 to 2 metres of the soil profile. This has been a tremendous relief for some horticultural operators as these areas were almost unusable owing to the high salt content of the topsoil.
Why use native grasses?
Whilst a living cover crop is advantageous, it does have a significant management downside being the extra labour required to keep the inter-row under control. If the grass and weeds get too high, access becomes difficult. Weeds will provide habitat for pests such as the light brown apple moth and irrigation will be compromised. For many people this means mowing all the inter-row areas as regularly as every 8 to 10 days – a considerable expense and inconvenience.
The low growing habit of many native grasses means they can offer both the advantage of a living grass cover, but without the disadvantage of requiring all too regular mowing. Selected native grasses will not grow higher than 200 mm (8 inches) and will require mowing only once every two to three months. They will also survive if not irrigated.
Which grass to use?
The table at the bottom of the page provides some suggestions for horticulturalists in southern Australia. There are several sets of choices that influence the decision on what grass to use. There are three considerations:
1. The form of irrigation being used for the trees or vines: if it is dripper irrigation in the line of trees or vines, if it is narrow band sprinklers (say 2 m wide) focussed on the line of trees, or if it is broadcast over the entire area from tree line to tree line.
2. The water use desired. This may be a requirement for use of water deeper into the profile to reduce surface salinity or it may simply be a need to provide ground coverage with no real care about the potential water use of the grasses.
3. The season of growth that is preferred. For some situations a summer water use is preferred as it will reduce waterlogging from summer rainfall or irrigation. In other situations winter growth, and hence higher winter water-use, is desired to prevent accumulating water in the profile when the trees or vines are dormant.
Management of a native grass sward between rows of trees or vines
Once they are established native grasses are very easy to manage as they require little, if any, watering and will not become too tall and rank. The problems that do arise are with the control of weeds, including other grasses, over the first two to three years until the native grasses become dominant.
The best advice is to get to know the native grass used and be able to recognise its seedhead and seed maturity state. The aim is to maximize the seed production of the desired native grass and to minimize the seed production of the weeds. This usually means regular mowing of the sown area over the spring to reduce seed production of the weeds. This will also reduce seed production of the natives but they are likely to produce a second crop later in the season and this can be the one to aim for.
Within trees and vines the use of herbicides is limited and we encourage people to adopt methods that do not rely on the use of broad-spectrum herbicides. Selected and well targeted spot spraying can be a good method of killing exotic weeds and leaving the native grasses to flourish.
We do not recommend the use of any fertilizer on the grasses as this will usually advantage the exotics in favour of the natives. |
| Drippers or narrow band sprinklers |
Broadcast sprinklers |
| Ground cover only | Hume Wallaby grass
Shannon Weeping grass |
Griffin or Tasman Weeping grass | | Profile reduction | Bidgee or Bunderra Wallaby grass | Bidgee or Bunderra Wallaby grass | | Winter water use | All Wallaby grasses and weeping grasses | All Wallaby grasses and weeping grasses | | Summer water use | Barwon Windmill grass
Curly Windmill grass | Barwon Windmill grass
Curly Windmill grass |
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