Buddleia

(Buddleja davidii)

Boundary Control Pest

Buddleia is a large perennial shrub, whose showy inflorescence has made it a popular garden plant. It grows rapidly for about the first 10 years, with height growth rates of 0.5 metre a year. Plants eventually collapse after about 20 years, as stem rot, insect attack and the brittle nature of the wood cause the shrub to break down. The plant has a preference for low to moderately fertile sites, is highly tolerant of drought, intolerant of shade and slightly tolerant of frost. Vast quantities of seed can be spread by machinery, by transport of gravel, and by wind and water. Seed viability is initially high and probably drops off rapidly.

Reasons for the Strategy

A green bush with purple flowers.

Buddleia is a serious pest for plantation forests. Locally, forest companies acknowledge the threat and they destroy all known plants on their own land. It is also a conservation pest, as it can suppress early indigenous successional species (grasses, herbs and shrubs) in and beside waterways, impacting on conservation values.

Buddleia is assessed at “5” on the infestation curve. It is widespread throughout the Tasman-Nelson region. requiring boundary control of Buddleia is the only practical control option. This will assist in protecting land that is clear, or being cleared of Buddleia, from invasion from adjacent land by Buddleia. Extensive areas of suitable habitat, and the potential for it to cause significant adverse effects, mean the benefits of boundary control far outweigh the costs. Hybrids of Buddleia are not included in this Strategy.

Objective

To control the spread of Buddleia from adjacent properties to land that is clear, or being cleared of Buddleia, in the Tasman-Nelson region during the term of the Strategy.

Alternative Measures

The alternative option of “do nothing” or relying on voluntary control will not achieve the objective of the prevention of the spread of Buddleia to adjacent properties where there is no Buddleia, or where control is being carried out. The Strategy rule for Buddleia provides some protection for occupiers controlling Buddleia. The cost to the Management Agency of implementing this requirement over the past four years has been minimal. Requiring a greater level of control, instead of just boundary control, is not appropriate given the widespread distribution of Buddleia, and that the occupier is the main beneficiary.

Strategy Rule for Buddleia

The occupier shall destroy all adult and juvenile forms of Buddleia located up to 50 metres from the boundary of the land that they occupy where the adjacent property is clear, or being cleared of Buddleia. A breach of Strategy Rule 7.3.5 is an offence under Section 154(r) of the Biosecurity Act 1993.

Explanation of Strategy Rule

The Management Agency will limit its intervention to enforce compliance of the rule to occasions when a reasonable complaint is received from an adjoining forest occupier, irrespective of whether it contains either indigenous or introduced trees. This would require the complainant’s land to be already clear, or being cleared of Buddleia, and that any invasion of the pest plant through the boundary has the potential to cause economic or environmental harm to the complainant’s land.

Biosecurity Act Requirement

No person shall knowingly sell, propagate, breed, release, or commercially display Buddleia, under Sections 52 and 53 of the Act.