The gully system
The Mangakotukutuku is one of four major Hamilton City gully systems that are currently the focus of efforts to re-establish significant areas of native biodiversity in the urban environment (Clarkson & McQueen 2004). Collectively, Hamilton's gullies make up 8% of the city area and they have been described as the "best kept ecological secret of Hamilton City".
The Mangakotukutuku Gully and its favourable growing conditions were ripe for newcomers, and pretty garden ornamentals found themselves in seventh heaven, having being tossed over the fence. Trandescatia (wandering jew/willie), pretty morning glory, privets, nightshades and lilies spread throughout the Mangakotukutuku Gully, meeting limited resistance from a few pasture weeds (blackberry, willow, gorse).
It can be argued that native plants would eventually re-establish, in the absence of further disturbance (for example, periodic clearing tends to favour many introduced weeds). Already pockets of tree ferns (mamaku, wheki) can be seen re-establishing in the Mangakotukutuku Gully. However, it is difficult to imagine the more shade tolerant exotics, such as privet and Trandescantia, stepping aside if not pushed. Restoring the Mangakotukutuku Gully’s unique and lush forest will require a careful and staged attack on the pests and weeds - bit at a time, focusing on the worst offenders first. It will also require planting initiatives to replace the weeds with our missing native plants. It is crucial to select the right native plants. There are books, people and events available to us with exactly this type of information. Read your gully guide (see link below), speak to your nurseryman, and find out what you need to know.
Information on the restoration of gully vegetation is available from the Hamilton City Council website. Some flowering trees provide food for native birds - check your gully guide or with your local nursery to see which species are appropriate for gully planting.
In terms of stream health, planting trees that provide shade, stabilise eroding banks, and create habitat diversity (e.g., stable streambank overhangs) are the most important considerations. Plants differ in their abilities to stabilise streambanks or provide cover for native fish. Secretive species such as the banded kokopu are often found under bank overhangs created by tree ferns.
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