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Header image: Uropetala chiltoni (New Zealand mountain giant dragonfly or kapokapowai) with a wingspan of over 100mm in the Springburn valley

News from the nursery and summer outlook

While mild temperatures and above average rainfall left us with good spring growth in Central Otago, predictions suggest we are now in the grip of a hot and dry summer. NIWA drought forecasting suggests the next month will continue to be dry with some risk of very dry conditions developing east of Cromwell, but no drought is forecast yet.

Seedlings in our propagation house, including Olearia fragrantissima (bottom left) eco sourced from Lake Hayes area, a fairly rare plant in Central Otago

We’re keeping busy watering and with propagation, and following our first seed collection of the growing season the seeds are now germinating and being pricked out for trays. We have changed our propagation methods to treat these seeds and have increased our germination percentages substantially with species like Olearia. We’re in our second phase of potting for the season, and almost everything we’re potting is propagated and grown on site. There’s always plenty of weeding to do this time of year, as they enjoy our irrigation and the heat stimulates flower setting which we need to anticipate to avoid weeds proliferating. Unfortunately, creating ideal conditions for our plants also creates ideal conditions for weeds.

A selection of Hebe/Veronica available in our catalogue. Clockwise from bottom right: Hebe pinguifolia, 'Emerald Gem', odora, topiaria

Ecosourcing

Samantha attended the New Zealand Plant Conservation Network’s Biennial Conference in Queenstown around this time last year, and we commented in our newsletter then on the presentation by Peter Heenan where he gave a sneak peak at the research his team has being doing on ecosourcing, a particularly relevant topic for us here at the nursery. This paper, cited and linked below, is now published in the New Zealand Journal of Botany.


While ecosourcing is a term that is frequently used in the context of local councils’ requirements for Resource Consents, it has lacked a proper definition, and guidelines from DOC and district councils only suggest seed should be sourced from the same area it is being planted. In the past, we’ve used a definition borrowed from the Royal Horticultural Society in the UK that applies a distance and altitude limit to seed provenance: ecosourced plants must be propagated from seed collected within 150km and 300m in elevation from the planting site.


However, these “local” ecosourcing approaches are not scientifically informed. Furthermore, based on Heenan et al’s research they are contrary to the goals of ecosourcing, which are to preserve and improve genetic diversity and population health of native plants, to reduce inbreeding and to preserve threatened species. These goals align well with ours here at Springburn Nursery and we also believe that ecosourced plants can in many cases deliver superior plant health and survivability especially in challenging locations.


Heenan et al’s paper suggests a more relaxed approach to ecosourcing that is based on nine broad ecosourcing regions set by phylogeographic patterns and biogeographic boundaries, as below:

This is particularly important in Central Otago, where the extreme deforestation and continually obstructed regeneration of the pre-human settlement plant populations has led to remnant pockets often being small in number of individuals and low in genetic diversity. Applying a local ecosourcing approach in these situations will inevitably create genetic bottlenecks, as even common and iconic species like mountain flax and fierce lancewoods that would once have been prolific now exist in many areas as a few scattered individuals or small populations - and large, robust and ideally naturally regenerating populations are necessary for proper seed sourcing. Furthermore, combine the thorough ecological destruction of the past with the dominance of novel ecosystems in the present and the result is that significant portions of the original ecosystems species are missing, and restoration of these species essentially requires sourcing from outside Central Otago.


The paper used Kunzea ericoides as a case study, and following a genetic analysis combined with examining the phenotypic differentiation (the differences in observable traits between populations) and ecotypic differentiation (the gradual differences across a large, continuous population) concludes that “where widespread species exhibit phenotypic and/or ecotypic variability, it is more important to ensure the site of the ecosourced plant material is similar to the restoration site rather than focusing on the geographically closest sites.” To put it simply, in order to grow hardy kanuka for an inland mountain site, you’d want to take kanuka seed from another inland mountain site within the same broad zone, and not from a closer population of kanuka in a mild valley. This “niche matching” approach does not necessarily apply to all species but it is intuitive and has supporting evidence.

The four phylogeographic regions for kanuka (Kunzea ericoides) suitable as ecosourcing seed zones based on population genetic data

Here at Springburn Nursery we intend to use the Heenan proposed regional model for ecosourcing moving forward, and will update this approach if any further research advances it. Our ecosourcing zone therefore includes all of Otago, Southland east of the Southern Alps, and some of the Waitaki and Mackenzie districts of Canterbury. Within this zone we will endeavour to take seed when possible from large healthy populations in similar geographic and climactic conditions to Central Otago to ensure we offer the best possible plants in quality and genetic lineage.


The citation for the paper is below and you can read the full paper here.


Peter B. Heenan, William G. Lee, Matt S. McGlone, James K. McCarthy, Caroline M. Mitchell, Matthew J. Larcombe & Gary J. Houliston (2023) Ecosourcing for resilience in a changing environment, New Zealand Journal of Botany, DOI: 10.1080/0028825X.2023.2210289


IPPS New Zealand Dunedin field trip

Kelvin poses on an ornamental bridge at the Lan Yuan Dunedin Chinese Garden.

During November Sam and Kelvin joined the International Plant Propagators Society NZ Region (IPPS NZ) field trip to Dunedin. The 3 day field trip had us visiting native nurseries, Dunedin Botanical Garden, Dunedin Chinese Garden, and public and private gardens, among other activities. Visiting other gardens and nurseries is invaluable for gaining ideas and insights on how to operate and grow plants.


Highlights from the trip include seeing seeing thousands of Kauri seedlings for an ambitious, highly experimental southern 'Kauri forest', our first wild Kaka in the south at Orokonui ecosanctuary and spotting Albatross and seals on the Dunedin peninsula. One stop we both enjoyed greatly was Anna and Peter's garden at Hereweka, this garden is a plant lover's dream with a great diversity of plants, many rare. Theirs is a garden to get lost in and feel dwarfed by the giant ferns, palms and magnolias that overhang the meandering paths.

Left: A collection of a few interesting plants among hundreds at Hereweka Garden

Right: A very old Acer dissectum Japanese maple trunk at Dunedin Botanic Garden

We were treated to a guided tour of Larnach Castle gardens by head gardener Fiona Eadie and Dunedin Botanic Garden by curator Alan Matchett. The in-depth knowledge of plant care was fascinating. Both discussed their experience and methods of adapting to the changing climate, expressing possible future changes in plant selection and using methods such as thick mulching to try to reduce water evaporation from soil during the increasingly frequent dry periods.


We concluded our adventures at Blueskin Nurseries where we were treated by Mark Brown to a delicious lunch and tour of his well established garden centre and nursery. Blueskin Nurseries has been operating for over 30 years so it's fair to say we picked up a few tips and tricks. We were struck by the passion and vast knowledge of all our hosts and it was a pleasure to indulge in a weekend of deep plant nerdery.

Some bonsai/penjing trees of kowhai (Sophora) at the Lan Yuan Dunedin Chinese Garden.

Plant spotlight

We’ve just marked as ready a new batch of Prunus lusitanica PB6.5, below next to some harakeke. These ever popular plants are fairly versatile, doing well in most areas where they can get enough water and are attractive and useful for hedges. Tolerates shade and heavy frost well.

Coprosma rugosa PB6.5

All our lavenderis looking good, including the Lavandula angustifolia 'Hidcote' PB6.5 below. This English lavender is compact and bushy with short stemmed flowers. Like all lavenders, full sun and good drainage is essential.

Euphorbia robbiae PB6.5

As always if you are planning any plantings or big jobs for the planting season in autumn let us know and we will prepare a quote. The more lead time you can give us, the better we can meet your needs.


Check out our Catalogue for more information or feel free to flick us an email or a call.


As always, if you want a quick overview of what we have in stock, you can check our order page.

Above: Newly mulched bed in the nursery’s mother plants area, Ozothamnus leptophyllus front and left and Muehlenbeckia astonii on the right.

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