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Discover how effective and strategic riparian planting fosters a balanced relationship between the land, waterways and biodiversity. Plants act as natural sieves, filtering sediment and nutrients. Using the right plants and techniques will not only combat land erosion and enhance habitats for native wildlife, but will also prove to be cost-effective
When deciding what to plant and how wide the riparian margin should be, it's crucial to consider the orientation of the waterway. This consideration is key because riparian planting offers a significant benefit: providing shade to the river.
This shade serves two important purposes. It helps reduce water temperature and prevents excessive plant growth. For these benefits to be fully achieved, rivers require a minimum of 70% shade coverage.
The table below suggests heights of vegetation for different stream orientations.
|Both banks planted:|
|North-south flowing stream||East-west flowing stream||Meandering stream|
|Plant height needs to be at least 80 percent of the stream width||Plant height needs to be at least 150% stream width.||Plant height needs to be at least 75% stream width.|
|One bank planted:|
|North-South flowing stream||East-west flowing stream||To create more shade|
|One bank planted North-South does not achieve 70% shade for aquatic weed control, but is likely to slow aquatic weed growth, improve temperature and water quality||Plant height= 3x stream width and overhanging canopy.Taller vegetation on the North bank.||Have taller plants, plants overhanging the channel, and/or meandering channels.|
In riparian margins, there are three distinct planting zones, each serving a unique purpose. Planting vegetation on the upper and lower banks enhances waterway conditions for aquatic animals and boosts terrestrial biodiversity. Additionally, allowing rank grass to flourish near laneways, bridges, culverts, and swales helps filter out sediment and phosphorus, particularly during periods of excess rainfall, preserving the health of our waterways.
Grass strips should be left between any riparian planting and fences to avoid plants tripping electric wires. Also leave rank grass in areas where swales enter waterways.
Upper bank zone
The upper bank zone is on higher ground but may still be partially flooded every couple of years. Use flaxes, grasses, shrubs or trees which provide shade and shelter.
Lower bank zone
The lower bank zone is prone to flooding so plants need to be tolerant of waterlogging. Use plants such as sedges and rushes, which are well rooted and can survive many days under water.
1. Remove grass and weeds.
Four to six weeks before planting, spray 1m diameter circles with a glyphosate-based herbicide at the location each plant will be planted
2. Dig a hole that is big enough to accommodate plant roots without them being curled up or bent in the hole.
On drier soils, ensure the base of the stem is 1-2cm below the soil surface.
Mulch around plants will help keep soils damp, reduce weeds and provide nutrients.
Good mulches include straw, staked down cardboard or wool.
3. Put a stake beside plants (unattached) so they can be easily seen when weeding and identified if they have died and need replacing.
Keeping on top of weeds and pests is crucial in the first five years for a healthy riparian area to become established.
The most effective maintenance option is to combine the protective and active maintenance methods below.
Surround each plant with at least a 30-40cm diameter of biodegradable weed mat, mulch or old woollen carpet to suppress weed growth.
Avoid using plain wood chip around the plant as it will strip all the nitrogen out of the soil causing the plant to yellow off and die.
Stake each plant for easy location and brush cut, hand weed or carefully spray with a glyphosate-based herbicide twice a year.
If spraying, follow product guidelines - desired plants are usually sensitive to herbicides so caution must be taken to protect against spray drift.
Video: Three plant releasing techniques to make your riparian planting a success
Getting Riparian Planting Right guides were developed in consultation with farmers, dairy companies and regional councils, to support farmers with meeting their riparian planting requirements in The Sustainable Dairying: Water Accord.