The Marlborough Rock Daisy is justifiably one of our most well-known, and desirable, native garden plants. Its appeal is not only derived from the remarkable white flower heads that it bears in mid-summer; but also its compact, spreading form and attractive fleshy leaves.
At present, 3 species are recognised in the genus – Pachystegia insignis, P. rufa and P. minor. When it was first discovered, P. insignis was originally classified as a member of New Zealand’s most widespread genus of shrubby daisies, Olearia.
All three species grow in seemingly inhospitable conditions on cliffs (especially those formed from limestone) in Eastern Marlborough and North Canterbury, from the coast up to higher altitudes. They are often found growing in association with another spectacular eastern South Island endemic, Heliohebe hulkeana (and its close relatives).
Eastern Marlborough is an interesting region for plants that bears a range of unique species, including Pachystegia, Heliohebe and several attractive species of brooms (Carmichaelia). This is in part due to the distinctive, and active, underlying geology of the area. It is also related to the extreme seasonal climate that characterises much of the eastern side of the South Island.
This is the species that is most commonly grown, and to which most people refer when they speak of Marlborough Rock Daisies. It makes an arresting sight when in full flower on the coastal cliffs around Kaikoura in mid-summer. As stated previously, it also grows inland, extending into the Kaikoura Ranges.
In addition to the striking overall form of the flowerhead, it is worth observing the flowerheads from side on, for the beautiful overlapping arangements of woolly bracts that sit beneath the main white disc. These bracts give the buds a very distinguished appearance, extending the period of appeal of the flowers by at least a month. ‘Distinguished’ is indeed an apt term to use in association with this species, as that is the meaning of the Latin epithet, ‘insignis‘.
As may be guessed from its natural growing station (cliffs and rocky places – such as the steep bank upon which the seedling above, left, is establishing), Pachystegia insignis requires well-drained conditions within the garden. A good amount of air movement is also advantageous, especially if one is attempting to cultivate it in the warmer, humid north of New Zealand.
Many gardeners consider it to be a difficult species to grow in Auckland, but I have seen it grown successfully in many locations – where it is provided with sufficient drainage and exposure. That notwithstanding, we have found Pachystegia rufa (or hybrids between these two species) to be a superior performer in our conditions. Where the species are brought into close association, P. insignis hybridises readily with Pachystegia rufa, creating a variety of intermediate forms.
Although older plants of P. insignis can occasionally attain a somewhat straggly form in nature, it keeps a tidier habit within cultivation, without need for significant pruning.
Interestingly, there is a degree of variation between forms from different areas within Marlborough, as might be expected from an area in which geographical isolation has played a role in forming a unique flora. It is also worth noting that many other species of New Zealand’s shrubby daisies show a preference for cliff, and other rocky, habitats (such as, amongst many others, Olearia furfuracea, O. pachyphylla and Helichrysum coralloides).