All pest plants must go!

Otago Regional Council has recently announced new research into just how established the pest plant old man's beard is, which got us thinking about pest plants in general.

Arrowtown has a long history of environmental modification, beginning with Māori who cleared parts of the basin with fire. It accelerated with the arrival of miners and farmers in the 1860s, who brought with them plants from home that quickly took off in the Arrow. As with the introduction of rabbits, many caused unintended consequences.

The list of pest plants that have invaded is long, and only the worst offenders are described here. Many of them have made it into Arrowtown gardens, and it's here that you can do your bit to help wipe them out. You can find out the best way to deal to them on the Weedbusters website.

The Otago Regional Council Pest Management Strategy is under review at the moment, but you can read the current version here.

 

Woody weeds

Broom is one of the first woody shrubs to invade disturbed areas. It is well adapted to Arrowtown's dry weather, with the seed staying viable for decades. (The good news is that our lower rainfall also means that gorse, which is a huge problem elsewhere, struggles to establish itself except in the wettest of areas.) Other woody weeds include hawthorn, which was once used as a hedging plant, cotoneaster, flowering currant and briar rose. Also found around the trails are blackberry and barberry, a plant with viciously long thorns and yellow wood.

Another spreading pest is the common garden plant buddleia. Like many of the other woody weeds, it is well adapted to the challenging Arrow environment, and can form dense stands, altering water flow and causing flooding. A similar issue can be found with Russell lupins along the Arrow.

However, because the environment was once forested, many of these weeds will eventually be replaced in areas where trees can grow.

 

Trees

Pest species in the form of trees include all the wilding conifers, sycamore and rowan, which were favoured by settlers as they grew well. Unfortunately they have have grown too well and the distribution of their seed by wind and by birds has now seen these trees spread out from the town into the surrounding hillsides.

Sycamore, while a lovely autumnal colour, is shade tolerant and can quickly encroach into the few stands of native trees that remain. You can clearly see these trees spreading into the beech forest up Bush Creek. Sycamore, part of the maple family, requires more moisture than most conifers, so is more restricted in where it can grow. It likes south facing slopes which don’t dry out as much and valley floors next to streams.

A number of willow species have also become a major tree pest. Planted to keep rivers from meandering, these trees have significantly altered our riparian ecosystems, destroying habitats for a range of birds and invertebrates and causing sedimentation and flooding.

 

Smaller weeds

Some smaller pest plants can be hard to see. While many are lovely in the garden, their explosion into the surrounding areas is actively damaging our environment. They offer little or no food or shelter to our native species and in many instances they are destroying what little native vegetation we have left.

Old man’s beard, a type of clematis, is found in small patches near the river, where it smothers other plants. Its seed is spread by water and wind. Exotic pasture grasses are common in dense swards that prevent native seed regeneration. Another group of smaller weeds includes hawkweed/hieracium, which grows as a ground cover. It can be seen in large patches above the tree line, particularly around the Sawpit track, preventing tussockland regeneration and destroying more delicate native plants.

All photos except rowan and Douglas fir courtesy of Weedbusters.

Otago Regional Council has recently announced new research into just how established the pest plant old man's beard is, which got us thinking about pest plants in general.

Arrowtown has a long history of environmental modification, beginning with Māori who cleared parts of the basin with fire. It accelerated with the arrival of miners and farmers in the 1860s, who brought with them plants from home that quickly took off in the Arrow. As with the introduction of rabbits, many caused unintended consequences.

The list of pest plants that have invaded is long, and only the worst offenders are described here. Many of them have made it into Arrowtown gardens, and it's here that you can do your bit to help wipe them out. You can find out the best way to deal to them on the Weedbusters website.

The Otago Regional Council Pest Management Strategy is under review at the moment, but you can read the current version here.

 

Woody weeds

Broom is one of the first woody shrubs to invade disturbed areas. It is well adapted to Arrowtown's dry weather, with the seed staying viable for decades. (The good news is that our lower rainfall also means that gorse, which is a huge problem elsewhere, struggles to establish itself except in the wettest of areas.) Other woody weeds include hawthorn, which was once used as a hedging plant, cotoneaster, flowering currant and briar rose. Also found around the trails are blackberry and barberry, a plant with viciously long thorns and yellow wood.

Another spreading pest is the common garden plant buddleia. Like many of the other woody weeds, it is well adapted to the challenging Arrow environment, and can form dense stands, altering water flow and causing flooding. A similar issue can be found with Russell lupins along the Arrow.

However, because the environment was once forested, many of these weeds will eventually be replaced in areas where trees can grow.

 

Trees

Pest species in the form of trees include all the wilding conifers, sycamore and rowan, which were favoured by settlers as they grew well. Unfortunately they have have grown too well and the distribution of their seed by wind and by birds has now seen these trees spread out from the town into the surrounding hillsides.

Sycamore, while a lovely autumnal colour, is shade tolerant and can quickly encroach into the few stands of native trees that remain. You can clearly see these trees spreading into the beech forest up Bush Creek. Sycamore, part of the maple family, requires more moisture than most conifers, so is more restricted in where it can grow. It likes south facing slopes which don’t dry out as much and valley floors next to streams.

A number of willow species have also become a major tree pest. Planted to keep rivers from meandering, these trees have significantly altered our riparian ecosystems, destroying habitats for a range of birds and invertebrates and causing sedimentation and flooding.

 

Smaller weeds

Some smaller pest plants can be hard to see. While many are lovely in the garden, their explosion into the surrounding areas is actively damaging our environment. They offer little or no food or shelter to our native species and in many instances they are destroying what little native vegetation we have left.

Old man’s beard, a type of clematis, is found in small patches near the river, where it smothers other plants. Its seed is spread by water and wind. Exotic pasture grasses are common in dense swards that prevent native seed regeneration. Another group of smaller weeds includes hawkweed/hieracium, which grows as a ground cover. It can be seen in large patches above the tree line, particularly around the Sawpit track, preventing tussockland regeneration and destroying more delicate native plants.

Photo courtesy of Weedbusters.