Trelissick Park Group: Weeds

The priority weeds for volunteers to target in Trelissick Park are discussed just below. More complete lists of weeds are available at the bottom of the page.

Wellington City Council carries out some weed control in Trelissick Park, but they need our help. There are some weed species which are best controlled by hand as long as the job is done properly. This guide lists weeds which you can help control, in priority order, and guidelines on the best way to do this.

There are other weeds in the park that are less prevalent. Some are being controlled by council contractors, for example, mile-a-minute, evergreen buckthorn, cotoneaster, pampas, Asiatic knotweed, gorse, daisy, boneseed, banana passionfruit, bay, and pasture grass. At the moment, Darwin's barberry appears infrequently, but it has invaded many of the hillsides around Wellington and should be removed when found in the park.

Remember if you see these weeds in the park and they look easy to control now, they soon won't be!

Priority weeds for volunteers to target in Trelissick Park

Tradescantia (Wandering Willie)

A spreading groundcover which does not seed in New Zealand. Instead this plant grows from stem fragments. This weed is an ecological nightmare because it spreads as a thick carpet, preventing seedlings emerging. It also causes eczema in some dogs. Trelissick Park is well used by dog walkers and we would like to keep it that way.

How to remove Tradescantia

To clear tradescantia pull it out by hand or rake it into a compacted heap in the shade on the ground (for bacterial action). Check the cleared area to remove all stem fragments or roots just below the surface. Try to get all broken fragments and watch that you don't lose any into the stream, as this will spread the problem. Form the heap into a plateau then compact by jumping up and down on the top. A black plastic covering stops spread from the heap. After 2 to 3 years the heap turns into compost. The Wellington City Council has huge weed bags which you can use instead of black plastic sheets. These ensure no escape, but the filled bags are unwieldy.

Revisit the area annually, extending to every 2 or 3 years, for a decade or more to remove any regrowth.

Wellington City Council information for community groups: Hierarchy of Tradescantia control (PDF, 53KB)

Old Man's Beard

This is becoming a serious problem in the park and adjoining areas. The flowers are easily spread by wind, so it is important to tackle this as soon as flowers appear, and before seeds are set early in the year. It is useful to have another person to act as a 'spotter', because while the flowers are easy to spot, the vine is sometimes hard to find in the thick bush.

How to remove Old Man's Beard

Cut the vines at ground level and apply a thin coat of Picloram gel (brands: Vigilant, Triumph, Cut'N'Paste) or Glimax (double strength glyphosate gel) to the stump. Wind the vines around nearby branches so they can't touch the ground. Make sure all the vines are cut - often hard to see in the surrounding scrub. Also look for tendrils at ground level that will take root at nodes.

The Old Man's Beard Free Wellington website has step-by-step guidance on control and help on how to map locations of Old Man's Beard, which is helpful for follow-up.

Climbing Asparagus

A nasty creeper which produces small white flowers in early summer, followed by orange berries which are spread by birds. Remove and bag the tubers for landfill disposal. You can leave the above ground plant material on site to rot.

Japanese Honeysuckle

Most outbreaks have been controlled by council contractors, but new outbreaks and re-growth still occur. Small plants can be pulled out, otherwise cut at ground level and apply Picloram gel to the cut surfaces.

Montbretia

Forms thick clumps which inhibit seedling growth. Pull out by hand, but make sure you get the corms, which can be quite deep. If they don't all come out you can use a trowel or an old chisel to dig them up. Remove the corms from the park for landfill disposal.

Buddleia

This shrub has attractive purple flowers and can take over areas, if not removed. Pull out any seedlings you come across. For larger trees, cut at ground level and apply Picloram gel to the cut surface.

Wattle

Wattle is an evergreen tree, which establishes quickly and displaces native plants. Small wattle seedlings are widespread in the lower part of the park. Pull these out by hand and expose to the sun. Wattle seeds stay dormant in the soil for years, so this will be an ongoing task. Larger wattle trees can be cut to kill them. They do not need poison.

Sycamore

Sycamore is a large deciduous tree which produces 'helicopter seeds' that are efficiently dispersed by wind. Pull out any seedlings you come across. For larger trees, cut at ground level and apply Picloram gel to the cut surface. They are easily spotted by their orange leaf display in autumn.

Flowering Cherry (Cherry)

Large deciduous trees quickly distributed by birds. Pull out any seedlings you come across. For larger trees, cut at ground level and apply Picloram gel to the cut surface. They are easily spotted by their orange leaf display in autumn.

Himalayan Balsam

After concerted efforts over recent years, this has largely been eliminated from Trelissick Park streamside areas. It can reinvade from seeds carried down from upstream. It is best pulled out before flowering or seeding.

Blackberry

Outbreaks can be grubbed out. Or, it can be lopped off at ground level to give other plants a chance to take over.

Broom and Gorse

These two yellow flowered shrubs are regular intruders into the park. Broom can be pulled out or cut and left on the ground to rot. Poison is not needed. Gorse is more prickly and also more difficult to eliminate. Use Picloram gel to poison the cut surfaces.

Ivy, Climbing Dock, Convolvulus (Bindweed)

These vines climb up and envelop young plants, every summer. Cut away the vines and free the plants. Climbing Dock and ivy should be bagged and taken out for the landfill. Climbing Dock is especially hard to control, with large tubers underground. Where time permits, remove these tubers from the ground and from the park.

Houpara, Coastal Five Finger (Pseudopanax lessonii)

There is concern about the spread of Houpara or Coastal five-finger. This is indigenous in northern New Zealand but hybridises with Lancewood (Pseudopanax crassifolius). We are trying to rid the park of these invasive hybrids. Pull out or cut out any that you find.

Karaka

A native tree which is probably not endemic to the Wellington region. It may replace the native vegetation of an area through aggressive regeneration, especially areas recently cleared of tradescantia. For this reason we encourage you to pull out karaka seedlings if they are beginning to form a dense grove. This plant does supply fruit for kereru and other birds so will not be completely removed.

Tree Lucerne

Planted in the park historically to attract birds. We are leaving the larger trees for this reason, but pull out or cut any spread of smaller tree lucerne.

African Club Moss (Selaginella kraussiana)

This is one to nip in the bud. Also called Spreading club moss, it looks like many native mosses and leafy liverworts, which makes it tricky to spot. It has neat rows of leaves (2-4mm), fine roots, and creeping, slender, irregularly branched stems that root at the nodes. Pull it out and put all parts of the plant directly into a bag to go to landfill. Wear gloves and remove the gloves when you've finished handling it to avoid transferring spores elsewhere. Infestation is quite small at present. Let's remove it before it becomes a big job!

Remember...

Keep piles of weeds clear of the track, and out of the flood zone. If weeds end up in the stream they spread downstream.

Like many of Wellington's parks and reserves, a common source of destructive weeds in Trelissick Park is people dumping their green-waste. Please don't contribute to the problem, and dispose of your green-waste thoughtfully.

The other main source of invasive weeds is plants escaping from gardens and growing wild over the back fence. If you live near a reserve such as Trelissick Park, please have a look in your garden and think about plants that may become potential weeds in the future. It doesn't take much for a fast-growing climber to spread seed and escape into the native bush beyond your garden.

More weeds

For a more complete listing of Trelissick Park weeds see Weed listing May 2023

The National Pest Plant Accord downloadable manual (2020) has descriptions of 135 pest plants (weeds) identified for NZ.

National Pest Plant Accord – Ministry of Primary Industry