Impolite conservation

Far from being a glaring typo, the title of this journal entry describes a form of conservation that is of considerable importance, yet which rarely registers within general discourse about plants and nature within New Zealand - the conservation of exotic plants within this country.

Anyone with a passing knowledge of our practice will be aware of the central role that conservation of our native flora (especially threatened species) plays within our work. However, we also hold a substantial interest in the preservation of the astonishing diversity of exotic plants that have become part of our horticultural traditions within New Zealand.

This is a somewhat selective interest, as weedy species or species that we consider to have considerable potential as weeds (of which Dietes grandiflora is at the top of the list) are excluded from our focus, as are examples of imbalanced approaches to plant breeding - such as many large-flowered daylilies or hybrid tea roses.

Amongst the many things that I (and many other horticulturists) have to thank Bev McConnell for, I am grateful to Bev for stimulating my interest in a particularly worthwhile group of exotic Clematis, whose potential for gardens (especially in the north of the country) has remained largely unexplored within landscape design. Many of these varieties are partially derived from a Mediterranean species, Clematis viticella, such as the variety pictured above, 'Betty Corning' (of one of its wonderfully fragrant, pendent blooms) or 'Venosa Violacea' (pictured below).

If Bev piqued my interest in these varieties, Peer Sorensen kicked the door in on a veritable Pandora's Box, with his boundless enthusiasm and knowledge for the genus Clematis. For almost twenty years, I have continued to cultivate varieties of these relatively small-flowered Clematis, which are far better suited to warmer climes than the large-flowered cultivars that garden centres and nurseries normally favour.

That said, they have become increasingly difficult to acquire, in a similar pattern to many exotic species grown by specialist nurseries. As with the multitude of rare bulbs or perennials that are grown by nurseries of the calibre of Joy Plants, Hokonui Alpines or Marshwood Gardens, it is important that gardeners and landscape designers take some interest in this diversity. Otherwise, much of it disappears from this collective resource.

In addition to the group known as Viticellas, several varieties descended from an American species, Clematis texensis, have been grown in New Zealand. The variety shown above and below, 'Gravetye Beauty', is the only one that I have found to be reliably persistent; about which I am very pleased, given the blood red, tulip-shaped flowers that open out to a broader shape midway through their season.

Part of our interest in these varieties of Clematis lies in their indifference towards self-propagating. Exotic climbers are one of the worst categories of plants for furnishing New Zealand with new weeds  - amongst which, another Mediterranean native, Clematis vitalba, is one of the worst offenders. Using exotic species should involve making educated decisions about the potential of a species or variety to become a problem. However, as proven by the widespread sale and use of Dietes grandiflora or queen palms, this kind of decision-making is not commonly undertaken.

Despite the fact that a tiny percentage of exotics become problematic (and should rightly be assessed for weed potential), a huge range of 'ten-pound weaklings' like the glorious Nerine pudica, Narcissus cyclamineus or Fritillaria davisii will never be environmental problems. There is a sound argument to be made for taking a particular interest in exotic species that require some effort to maintain their tenure within gardens, for the promotion of  certain exotics that are capable of perpetuating their presence in the absence of intervention (Agapanthus is an apt example) is an ideal recipe for the advent of serious environmental weeds.

In recent years, I have come across certain wonderful species only once or twice, including Anthericum liliago, Kniphofia typhoides and Enkianthus perulatus. Without interest and dialogue about such plants, they fade from gardens and nurseries.

The same processes that lead to diminished interest in exotics (notably decreasing engagement with plants by landscape architects and the landscape industry, as well as commercial conservatism) also lead to diminished interest in native species. The two are linked. Accordingly, as the range of Crocus species available within NZ decreases, the likelihood of seeing rare natives like Myosotis saxosa or Pseudowintera insperata (or cultivars like Clematis 'Hokonui', pictured below) within nurseries also decreases.

Obsession with the wonder of the natural world is a large part of what drives us in our work, and the same healthy obsession surfaced in a more adventurous form with generations of plantspeople like Os Blumhardt, Terry Hatch or Peter Cave - who travelled to a range of lands (including Vietnam, Papua New Guinea, South Africa, Korea and China) to establish a remarkable collective resource of garden plants. Similarly, adventurous journeys in New Zealand's varied landscapes established the basis of New Zealand's native nurseries and garden traditions.

The world is a large and fascinating place, to which gardens can relate as a myriad of microcosms. In this context, we hope that enough people take an interest in conserving some of that resource, so that the wonder of imagined places is still alive in our gardens and urban plantings.

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