Thursday, 29 December 2011

Urban forest remnants; the balance between planting and killing

Wellington abounds with small forest remnants in gullies and on hillsides, most of them second-growth.  Many of them have dedicated "friends" groups that plant and weed to encourage the natives and discourage the invaders.  My local patch is the Birdwood Reserve, which is continuous with its more glamorous neighbor the Karori Wildlife Sanctuary, now rebranded as Zelandia.

Kaka, Birdwood reserve.

Birdwood Reserve is kohekohe/titoki/mahoe forest, with some kotukutuku thrown in and a lot of kawakawa in the understory.  Tui and kaka are the common native birds, along with fantails and silvereyes.  Once I saw a tieke.  There are a few big cherries and sycamores that'll have to be removed some day, and some agressive introduced climbers, particularly old man's beard.  Around the edges it suffers the usual urban fates of rubbish dumping, landslides, clearing, and vandalism; there are road cones, a bicycle, a bathroom sink, roofing iron, and old election hoardings flung down the bank.

Sprayed understory, now collecting weeds and rubbish.
A few years ago I started planting out there a few natives (mahoe, ngaio, rangiora, matipo, makomako) that had come up in odd corners of my garden where wind or birds had dropped the seeds.  Each year I'd plant out a dozen or so, and a few of them are now quite big.  But each year someone would decide the area needed tidying up, and would organise for the weeds along the paths to be sprayed.  Whenever this happened I'd lose about half my plantings to spray drift.

Spraying has yellowed the leaves on this planted karamu (Coprosma robusta), but the orange-flowered Tropaeolum majus  appears unharmed.
Worse than that though, the spraying has eaten into the original bush edge, mostly by killing off the kawakawa, which is particularly sensitive, so that the area needing replanting keeps getting bigger.  The understory and bush margin dies, then the wind gets in and tears branches from the trees.  It's a steep bank, and prone to slips after heavy rain; there have been two quite big ones in recent years, both following vegetation clearance.  Before you know it, weeds, especially wandering willy, have invaded under the trees, so that next year's tidy-up has to go further from the path.  In places, where once there was a sharp and impenetrable bush edge at the path, there's now an ugly bare and dying area, and you can see 10–20m into the bush.

Spraying has isolated a titoki and a mahoe (left) by opening a gap right through the forest where once was dense undergrowth.
I've tried to discuss this with the Council.  They were concerned and helpful.  But my impression is that the team that manages reserves is different from the team that manages weeds.  In response, the council generously offered to provide me with more plants, free from their own nursery, if my group (i.e., me) would plant them.  But I don't see the point of planting more until the sprayers are brought under control.  And as a ratepayer, I also don't see the point of raising plants in a nursery, planting them out, and then killing them.

Sprayed Crocosmia xcrocosmiiflora.  Vandals repeatedly damage the fences, pushing over posts and ripping off the rails.

The plant names

Prunus spp.
Piper excelsum
Dysoxylum spectabile
Fuchsia excorticata
Melicytus ramiflorus
Aristotelia serrata
Myrsine australis
Myoporum laetum
old man’s beard
Clematis vitalba
Brachyglottis repanda
Acer pseudoplatanus
Alectryon excelsus
wandering willy
Tradescantia fluminensis


  1. Have you managed to get in touch with the weed-management team at the council at all? I wonder where their direction comes from, and what their goals are?

  2. I suspect they might contract out the spraying, so have little control. They need to apply some performance standards about damage to non-target species I guess.