Trip Report – 13 February 2016 :   Otari-Wilton’s Bush

1.   Plant propagation, Leonard Cockayne Centre and Plant nursery

Rewi Elliot - Curator: Introduction to Otari

Botanist Dr Leonard Cockayne started developing the collection that now forms the Otari Native Botanic Garden here in 1926.   He had four aims:
•   Conserve and restore the native forest
•   Cultivate NZ plants, grow as many as he could
•   Represent NZ plant communities in the gardens
•   Represent NZ horticulture and teach people about their use

Otari Native Botanic Garden and Wilton’s Bush Reserve are owned and managed by Wellington City Council, it has four main functions:
1.   Conservation - many threatened species are kept here (insurance populations), also return plants to the wild for restoration
2.   Research - use the plants for research, classification
3.   Education - help visitors learn by displaying plant names, running tours
4.   Recreation - great place to visit, today a good example with lots happening, even a wedding here today

Otari-Wilton’s Bush staff go on trips around Wellington and further afield to collect plants.

*At this point we admired a flock of over 20 (!) kereru, followed by a trio of kaka and we all praised pest control which has happened here since 1993.

Propagation

Propagation occurs at any time of the year at Otari, because of the special nursery set up.   Most propagation to rejuvenate plants in the collections involves cuttings, owing to the risk of hybridisation from seed.

Barbara noted that she had spotted a large patch of Asplenium x lucrosum in Otari.   Everyone now disses Asplenium x lucrosum which is a hybrid of a native (Asplenium bulbiferum) and a Norfolk Island species (Asplenium dimorphum).

Practical propagation tips

If you are taking cuttings for storage (not immediate planting):
•   trim big leaves cut straight across ⅓ of size to preserve energy
•   wrap in paper towel (like a nappy!)
•   dunk in water
•   place in zip lock bag with water
•   place in chilly bin (with freeze bags at bottom covered with newspaper)

Some species can last up to two weeks like this.

When Rewi gets them back to Otari, he uses a 150 mm nail to create a hole, pushes the cutting in, and firms up soil.   Otari has a heated bench and misters.

Rewi’s DIY version is: circular pot, stakes, bread bag to maintain humidity, well-lit site, but not in direct sun so cuttings don’t overheat.

Otari staff use a mix of pumice, and coconut fibre from the Pacific, for their cuttings.   They used to use peat, but found it came from Estonia, so wanted a more sustainable product produced closer to home.   The product is available at Daltons or Caranz.   If you use sand as your mix, use river sand, not beach sand which is salty.   Don’t use fertiliser, the idea being to encourage the cutting to grow roots in search of food.   It takes between 1 week to 2 years (!) for a cutting to root, depending on the species.   Once the cutting has rooted, transfer it to potting mix in a 10cm pot, keep it well-watered, then once outgrown, transfer it to a PB2 planter bag.

Practical seed-growing tips

Use a commercial seed sowing mix with a short-term release fertiliser, then firm it down.   Avoid having the seeds touching each other.   Your seedlings need good air circulation to prevent ‘damping off’ - collective term for fungal diseases that kill plants.   Do not provide too much water.

If you have small seed that is difficult to handle: fold some paper, place the seed in the folded ‘V’, then mix the seed with sand and sprinkle potting mix over it.   Cover your seeds with loose potting mix or pumice, ensure the covering is level and even, and well watered (water will drain from the bottom when it is).

Keep the pot flat and the soil level, so that when you water the seeds they don’t all bunch up, which could cause ‘damping off’.   Once your seedlings have sprouted, wait until you have the true leaves, not the first leaves / cotyledons.   Then prick out the seedlings - hold them gently by a leaf, not by the stem which is easy to crush.

Nursery tour

Rewi then showed us the impressive nursery complete with heated bench and electronic leaf irrigation.

Many special plants are being raised here, including Brachyglottis kirkii var. kirkii a plant that used to occur in the Karori and Wadestown region.   It was probably browsed out.   Rewi obtained seed from a mix of five populations from the wider Wellington region.   B. kirkii is usually epiphytic.   If they are grown straight in the ground they usually die within two weeks, but they transfer well after growing in pots made from dead mamaku.   N.B.   If anyone has any dead mamaku, Rewi would love to have it.

References

Rewi recommends: Metcalf, L J.   The Propagation of NZ Native Plants.   It easy to obtain second-hand.

Amelia recommends: the website of Te Motu Kairangi Miramar ecological restoration, which has excellent plant lists.   http://www.temotukairangi.co.nz/

2.   Botanising in Otari

In the collections area, we saw Raukaua edgerleyi, uncommon in Otari, and the Nationally Critical Metrosideros bartlettii / rata moehau, from the Far North.   We then botanised intensively along the lower Yellow Trail in the valley of ‘Bledisloe Gorge’.   The efficacy of over 20 years of pest control by WCC staff, Greater Wellington Regional Council (GWRC), and by Otari-Wilton’s Bush Trust’s ‘Rambo’ volunteers, is clear.   The numerous kohekohe, tawa, rewarewa and titoki seedlings, now have the chance to repopulate the depleted understorey tiers, and in time, the canopy.   The previously abundant possum and rodent populations would have severely restricted the regeneration of these species, the possums eating the leaves, flowers and fruit, and the rodents eating the seeds.   Weed control is required, because we saw numerous Hoheria populnea, the lacebark which occurs naturally from Waikato northwards, and abundant Corynocarpus laevigatus / karaka.   The latter is spread by kereru whose numbers are being boosted by pest control.

With Rewi’s approval, we botanised up an old track towards the skyline, then down another one into a gully with a mature nikau, numerous nikau seedlings, a large pukatea, and velvet fern / Lastreopsis velutina.   Beyond, we admired one of the city’s few mature matai / Prumnopitys taxifolia, and nearby a small-leaved milk tree / Streblus heterophyllus.

Glen Falconer, GWRC, reports that Otari is part of a large Key Native Ecosystem (KNE) called Wellington Western Forests.   See http://www.gw.govt.nz/assets/council-publications/Key-Native-Ecosystem-Plan-for-Western-Wellington-Forests-2015-18.pdf.

GWRC maintains 82 bait stations in the KNE at 3-monthly intervals, and the volunteer group, RAMBO, maintains c. 44 mustelid traps.

Participants : Bev Abbott, Rachel Anderson-Smith (notetaker during Rewi Elliot’s talk), Sam Buckley, Michele Dickson, Rewi Elliot (leader - plant propagation), Amelia Geary, Richard Grasse, Chris Hopkins, Chris Horne (leader - botanising), Mark Jones, Winifred Maindonald, Barbara Mitcalfe, Chris Moore, Karen Palmer, Sunita Singh.