Some plants, usually imported from other countries, have become
serious pests. The worst ones are very aggressive, crowding out
native species and causing many other problems.
- Boneseed (Chrysanthemoides monilifera) is a busy that
grows about 3 metres high. The seeds are very hard and bony. In
September and October, it produces bright yellow flowers. It grows
on stabilized dunes and can become so thick that nothing else
can grow there. It grows so fast and thick that it even makes
access to the beach difficult.
- Pampas looks like the native toetoe, with tall upright stems
with bushy white or purple flowers on the tops. It is a grass
that grows in large clumps up to three metres high. Pampas grass
has upright heads that are purple or yellow-green while the native
toetoe flowers droop downwards and are a rich creamy yellow.
- Boxthorn (Lycium ferocissimum) has nasty long, sharp,
poisonous spines along it's stems. It grows in thick clumps, and
restricts access to beaches while pushing out native plants.
- Shore wattle (Racosperma sophorae) was introduced to
New Zealand from Australia to help revegetate sand dunes. Unfortunately,
it did so well it became thick masses up to three metres tall,
rapidly displacing all native dune vegetation along with native
birds, insects, and snails. It is very difficult to remove, but
in the Waikato, the Whiritoa Beach Care group has removed large
areas of this invasive weed.
- Marram grass (Ammophila arenaria) was another plant
introduced to revegetate sand dunes (will the government never
learn?). It forms steep, stable dunes too close to the water and
these often blow out during bad storms. It also pushes out pingao
and spinifex, reducing the populations of these valuable plants.