Waikato region tussles with tutsan
Tutsan is a major pest plant with potential to be the ‘‘new gorse’’ in the Waikato. It is spreading rapidly.
Under new rules in Waikato Regional Council’s pest management plan, landowners are required to control it wherever it occurs on their property.
Tutsan, which originated in southern and western Europe, is related to ornamental hypericums (St John’s wort) and looks very similar.
It forms a semi-woody, 1.5 metre tall shrub with reddish stems and small, pleasantsmelling, oval leaves that often turn red in autumn.
Clusters of small, bright yellow, five-petalled flowers with prominent stamens appear from November to February.
These are followed by fleshy, round, red berries, which ripen to black and disintegrate, spreading large amounts of long-lived, dustlike seed far and wide.
You will find tutsan growing along roadsides and waterways, and on scrubland and farmland. It is difficult to control once established.
A great survivor, this tough plant is tolerant of shade and all temperatures, poor soils and physical damage.
That dust-like seed is widely dispersed into natural areas by wind, birds and agricultural machinery.
Tutsan can take hold in areas of hill country farm land and disturbed forest where it forms dense stands and prevents the establishment of pasture and native seedlings.
Herbicides are most effective on tutsan during spring and early summer while the plants are still fresh and haven’t formed a wax coating.
Shaded areas can be sprayed later if the plant is still fresh and hasn’t formed a wax coating to the same extent.
Use herbicide designed to kill gorse.
Once tutsan is eradicated, the area it has occupied can be at levels replanted with native coprosmas or corokia, exotic Chinese sacred bamboo and other suitable shrubs to help stop it getting reestablished.
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Another major pest plant locally is yellow flag iris - a pretty, eye catching but destructive plant.
Yellow flag iris is prevalent in gardens throughout the Waikato.
This native to Europe, Asia and North America was introduced to New Zealand as an ornamental garden plant.
It has also been deliberately planted around waterways and wetlands in many areas.
The plant’s seeds and rhizomes are spread by water movement and machinery to infest new areas.
Yellow flag iris is tolerant of many climatic extremes and grows happily in any open, sunny swampy ground, fresh or brackish water margins, lakes, salt marsh, and wet sandy areas – even in paddocks near waterways or wetlands.
The rhizomes form dense floating mats, displacing native plants and potentially causing flooding and water level changes in swamps. Poisonous seeds may also affect native birdlife.
Identifying features include yellow flowers up to 120 millimetres across, typically in an iris like form, flowering in spring and early summer. Leaves are broad (20-30mm wide), flat and sword shaped.
Because seeds float in water, yellow flag has spread seed down the banks of the Waikato River, with small infestations from Hamilton to Ngaruawahia, and large infestations from Ngaruawahia to Port Waikato.
One plant can produce 1000 seeds, creating a large seed bank.
Tutsan originated in southern and western Europe.