Sydney golden wattle, the sinister yellow of spring

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In many places in New Zealand spring is heralded by the dancing yellow of daffodils in pastures. In Mangawhai the harbinger of spring is a much more sinister ‘yellow’ – the weedy Sydney golden wattle.

This invasive tree was introduced back in the late 1800s from Australia as a garden shrub for its yellow, fluffy blooms in early spring. The early flowers and the long, blunt-ended leaves with three prominent veins running lengthwise are key features to identifying Sydney golden wattle.

Little did our forefathers (and mothers) realise just how invasive this tree would become. Neither did they realise the length of time the seeds would last. As a ‘pea family’ member or legume (like gorse), the seeds can last for up to 50 years in the soil. Members of this family can get their nitrogen for growth from the air so can survive in very poor soils, such as our special gumland soils.

Sydney golden wattle leaves and dead branches, however, release a lot of nitrogen when they rot down and can change these special soils and habitats. The plants that naturally grow in these special soils are at risk of being squeezed out by new and invading plants that love the extra nitrogen. Sydney golden wattle also loves sandy soils and can quickly colonise dunes and other coastal areas, sometimes adding to coastal erosion problems.

If your property is harbouring one of these invaders, make sure you cut it very low to the ground when removing it and paint the stump with undiluted glyphosate.

You can pull or dig small plants all year round but try to minimise soil disturbance and mulch the area to prevent more growing. Trees that will not damage property when they fall can be killed standing by drilling 10-12mm holes, 200mm around the trunk and filling with undiluted glyphosate. When your property is clear of these pests, keep an eye out for seedlings and don’t let the invasion back.

„ Weed Action can help with other methods and herbicides. Email Sara at weedactionpb@gmail.com or phone 022 010 4092.