Plants make ideal filters

The benefits of keeping stock out of waterways with fencing can be boosted by a planted margin, which will help improve water quality.

Long dense grass, flax, sedges and rushes serve as a filter to help remove sediment, bacteria and nutrients (mostly phosphorus) from surface run-off. The planting provides shade in waterways less than 2m wide and improves the habitat for fish.

There are locations where low planting will be most effective at improving water quality, such as along drains and small lowland streams that feed main rivers, areas with significant run-off and beside waterways which are strip-grazed in autumn and winter.

Other ideal locations are beside vegetated drains in areas with poor soil drainage or pugging and moderate slopes, and where paddocks are cultivated.

The steeper and longer the slope feeding into the waterway, or the more poorly drained the soil, the wider the planted area needs to be.

For gently rolling land, a margin width of 1m to 3m per 100m of slope feeding into the waterway is ideal.

In areas with steeper slopes or poorly draining soils, a grassy margin of 10m to 15m per 100m of adjacent slope is recommended.

Getting plants in the ground

Here are some simple reminders to help get plants off to a good start:

Preferably plant on an overcast, wet or windless day.

Handle plants carefully to avoid damaging the roots.

Set plants out to check for correct spacing.

Dig a good size hole and loosen the soil.

Set the plant in the hole and fill three-quarters. Give the plant a very gentle lift to set the roots in a natural position and continue filling with soil, firming as you go.

Stake plants to help find them again at weeding time.

Weed growth - especially gorse, broom and blackberry - can be a real problem in low planting areas, so it's important to ensure that you manage it from the outset.

This article is adapted from the fourth in a series of nine DairyNZ Farmfacts on managing waterways on farms. They can be viewed in the farmfacts environment section at

- Hamilton News

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