Growing New Zealand Threatened Plants
Some general advice for gardeners wanting to grow the plants included on the New Zealand Threatened Plants Poster.
Many of New Zealand's threatened plants are available from garden centres, but some are only available from specialist nurseries. NEVER take plant material, cuttings or seed from these plants in the wild.
Threatened native plants generally have similar cultivation requirements to other native plants, particularly those of the same or closely related genera. Most native shrubs and herbs grow well in average garden conditions provided they have adequate moisture, and they will benefit from a mulch. Some of the threatened plants on the poster are easily cultivated and others have specific requirements. Some have good horticultural attributes while others have only intrinsic or botanical interest value.
Tecomanthe speciosa, Elingamita johnsonii, and Colensoa physaloides all occur on the Three Kings Islands and are easily grown in many lowland and frost-free northern areas. In areas such as Wellington, Christchurch, or Dunedin, these plants will require a relatively frost free and sheltered site.
Hebe breviracemosa, Carmichaelia williamsii, Clianthus puniceus, Hebe speciosa, and Metrosideros bartlettii are from northern or lowland parts of North Island but are readily cultivated in most lowland areas of New Zealand. Carmichaelia williamsii and Clianthus puniceus are well established garden plants with attractive and conspicuous flowers, and are easily propagated from semi-hardwood cuttings or seed.
Hebe speciosa, Carmichaelia williamsii, and Clianthus puniceus grow in an open position, or they can be deliberately planted in partial-shade for frost protection. C. puniceus should be pruned lightly after flowering, and it is generally beneficial to remove spent flowers from hebe bushes.
The other shrubs on the poster, Chordospartium muritai, Hebe armstrongii, Pittosporum dallii, and P. obcordatum are hardy and easily cultivated in all parts of New Zealand.
P. dallii is the most distinctive of the native pittosporums with its large, serrated leaves, but in cultivation it flowers only rarely. It is difficult to grow from cuttings, but can be grafted on to another species such as P. tenuifolium. Seed germinates easily.
The leafless and erect growing C. muritai has the smallest flowers of our native legumes, but these are attractive as they are numerous and densely placed on erect inflorescences.
The conifer-like H. armstrongii is exceptionally hardy and once established can be grown in most gardens. Large or woody plants of H. armstrongii can be rejuvenated by hard pruning as new growth readily shoots from old wood. The climbing daisy, Helichrysum dimorphum, has limited horticultural appeal, but is easily propagated by cuttings. It likes to scramble among twiggy shrubs, and it will eventually form a dense mat of stems on the top of such plants.
Euphorbia glauca and Myosotidium hortensia are very attractive and easily cultivated evergreen herbaceous perennials. M. hortensia, the Chatham Island forget-me-not, is well known as a garden plant, but the secret to growing it successfully is to maintain a high level of rich organic matter in the soil. The organic matter needs to be regularly replenished.
The waxy blue-grey leaved Euphorbia is less well known. It soon forms a dense sward of erect stems from underground rhizomes, and once established it is particularly suited to dry and/or loose soils.
Four of the threatened species on the poster are small herbs ideally suited to cultivation in rock gardens or alpine houses.
Myosotis colensoi occurs naturally on limestone soils but grows easily in a sunny position and in a freely drained garden soil. It forms compact, spreading clumps with white star-like flowers resting on the foliage.
Myosotis albosericea has silvery leaves and attractive yellow flowers which are held just above the foliage; it is exceptionally difficult to grow, and probably requires a free draining potting mix and to be grown in the protection of an alpine house.
Scutellaria novae-zelandiae forms a small subshrub up to 30 cm high and can be grown in the open or in semi-shaded sites, and once established it can grow in dry sites. It produces small white flowers throughout summer and is easily grown from cuttings.
Gunnera hamiltonii is an ideal ground cover as it forms a dense mat of closely clustered rosettes of brown-grey leaves. It requires a moist soil or a semi-shaded site as the leaves can dry out and wither easily. The remaining species have only limited appeal as general garden plants, requiring specific cultivation conditions, and are best attempted only by experts or specialists.
The two orchids, Chiloglottis valida and Cryptostylis subulata, are both best grown in pots in an alpine or shade house. They prefer a free draining potting mix rich in organic matter, such as rotted pine needles.
Australopyrum calcis is only in limited cultivation but is easily maintained and self-seeds around the parent plants. The aquatic herb Myriophyllum robustum can only be successfully cultivated in an aquarium.
Phylloglossum drummondii is very difficult to cultivate and has rarely been tried in cultivation. Lepidium banksii is not often cultivated but is easily grown from seed and it prefers a sunny open position and a moist soil rich in organic matter.
Written by Peter Heenan,
Landcare Research Lincoln, May 1996.
This information is Copyright to Landcare Research. You may print it out, and distribute it freely, as long as this copyright statement is left intact and no fee is charged for the information.
Further information:
- New Zealand Threatened Plants
- Full-colour, laminated poster, incl P&P, $15.00
Both available from: Manaaki Whenua Press