Native agent

Help save our native bush – get out there and kill those weeds!

So, when is a plant a weed? According to the national weeds awareness and education programme Weedbusters (, it’s when a plant is “growing where it is not wanted and having a harmful effect on the environment”.

oany of our common environmental weeds are “garden escapees” – pretty in the backyard but perilous in the wild. You can help protect New Zealand’s unique environment by preventing further spread of these plants.

**Bulbs and corms

**oontbretia (Crocosmia x crocosmiiflora) was once a favourite spring bulb. Since its escape into the wild, it reigns supreme over vast areas of grassland, streamsides, wetland and open forest where it competes against other low growing plants. In the garden, it’s easy to control by pulling out newly sprouted corms or sieving soil to remove corms. Large colonies are best sprayed with Escort, Roundup and Sprayfix in spring.

Yellow flag iris (Iris pseudacorus) is widely planted around large pond areas, especially in rural gardens. It has now escaped, via waterways and machinery, into the wild where it often displaces native species.Well-established clumps can even cause flooding and changes to water levels in swampy areas. Control as for oontbretia.

Grasses and groundcover Two species of South American pampas (Cortaderia selloana and C jubata) are serious environmental weeds. They can be differentiated from native toetoe by their upright (as opposed to drooping) flower heads and their dead leaf bases, which look like spiralled wood shavings. oasses of windborne seeds quickly invade cleared areas and take over. Dig out small seedlings, chainsaw mid-sized plants and bulldoze major colonies. Burn the flower heads and spray recurring growth with Roundup and Pulse Penetrant.

Wandering Willie (Tradescantia fluminensis) is a plant that is familiar to many of us for its thick, impenetrable mat of shiny dark-green foliage, which smothers shady areas of the garden. Every fragment has the potential to grow into another rampaging plant. Rake and roll up foliage into small bundles for disposal. Remove or apply Vigilant Gel to all remaining fragments. Follow up regularly.

**Shrubby pests

**Chinese privet (Ligustrum sinense) and tree privet (L ovalifolium) are widely used as hedging and boneseed (Chrysanthemoides monolifera) was once a popular coastal shrub. These all produce vast quantities of seed and are aggressive colonisers. Pull or dig out small plants. Chainsaw large ones and swab stumps with Vigilant Gel.

Kahili ginger (Hedychium gardnerianum) produces pretty, highly scented flowers, but each flower produces up to 100 seeds. The thick rhizomes (creeping stems) gradually spread into the bush, preventing native species from growing. Yellow ginger (Hedychium flavescens) is similar but doesn’t spread by seed. Grub out all rhizomes, or spray with Escort or Roundup and Sprayfix from spring to autumn, or paint Vigilant Gel on cut stems.


**Around 80% of vines that have been introduced to New Zealand as garden ornamentals are now causing problems in the wild. These include moth plant (Araujia sericifera), old man’s beard (Clematis vitalba), ivy (Hedera helix) and Japanese honeysuckle (Lonicera japonica). These are all capable of smothering desirable species and may lead to canopy collapse. Cut vines close to the ground, swab stumps with Woody Weedkiller or Vigilant Gel and dispose of all top growth in a managed landfill.

Agapanthus Agapanthus praecox has recently received a lot of bad press for its weedy tendencies. If you like it, opt for eco-friendly sterile or low-sterility varieties, including ‘Finn’, ‘Sarah’ and ‘Peter Pan’ or variegated ‘Tinkerbell’. A stunning new addition to this group is miniature Agapanthus ‘Lapis’, which produces gorgeous dark violet flowers up to four times every year.

**Lawn weeds

**Daisies and dandelions look pretty in the lawn and my girls love making daisy chains, so I let them be. But for the lawn connoisseur, they are a scourge! The good thing is, they’re easy to get rid of. Spray with any proprietary brand of lawn weed spray during the active growth periods of spring and autumn for a perfectly smooth weed-free lawn of grass only.

**How to dispose of problem weeds

**Weeds which grow from fragments:

  • Don’t leave any plant pieces behind.

  • Dispose of at a green waste landfill or compost as below:

  • In warm conditions: lay plant material on concrete in the sun to dry out.

  • In cool conditions: place plant material in plastic bags, cover with water and leave to rot.

  • once waste is completely dried or rotted, leave material on site to compost.

Weeds which grow from tubers or corms:

  • Tubers or roots (eg wild ginger) that can re-sprout will not be killed in a compost heap.

  • Remove tubers, rhizomes, corms etc to a managed landfill for deep burial.

  • Compost other parts of plants.

Spraying weeds

  • Add a wetting agent (Pulse, Sprayfix or a little detergent) to weed sprays to help them stick.

  • Always allow sprayed foliage to die down – don’t pull it out as this compromises herbicide action.

  • oost weeds require follow-up applications of re-sprouted stems or newly germinated seedlings.

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