Parahebe

At the outset of this profile, it is important to note a significant change that has affected how this genus is known. After a period of considerable debate, Hebe has been transferred into Veronica (along with its related genera, including Parahebe) – the genus in which it was originally described. Regardless of the current stance on this matter, I personally favour continuing usage of the name Hebe, for the same reasons as the authors of the most comprehensive monograph on the genus¹. Within that work, M. Bayly and A. Kellow, contended that lumping all species back into a very large, wide-ranging genus, Veronica, would “create a classification that is information-poor, obscuring obvious diversity and some clear relationships.”

More important than my personal preference on this matter (which I obviously do not consider to be better-informed than the botanists who made the change) is the fact that it continues to be referred to almost universally within horticulture as Hebe (as well as within practically all literature about the genus).

Stories are an important part of developing people’s interest in native plants, and few stories rival that of Parahebe jovellanoides – a creeping herb with attractive pale pink flowers, that was discovered in late 2007. One of the most intriguing aspects of this mat-forming groundcover is its location (in forest northwest of Auckland), where it grows further north than all other members of the genus.

Geographically speaking, its nearest relative is P. lanceolata, a substantially larger plant that extends as far north as the Coromandel Peninsula and Mt Pirongia in the Waikato. In addition to its strange distribution, P. jovellanoides‘ distinctive appearance and rarity have made it a botanical enigma. A fuller account of its discovery is provided below, in the profile pertaining specifically to Parahebe jovellanoides.

As noted above, the subject of the whether these plants should be referred to as Parahebe (or Hebe or Leonohebe) has been argued about. From a horticultural perspective, Parahebe spp. were given a different name because (as a group) they look different to Hebe and Heliohebe; and that name therefore carries information that is useful to gardeners and landscapers. They are generally low-growing, have a spreading form, and bear relatively soft stems (compared to Hebe). The most widely-grown species have attractive, upright flowerheads that can be produced in great profusion – in shades of white, pink and purple-blue (often with attractive markings).

Most of the c. 16 species of Parahebe inhabit the South Island, with four occurring in the North Island. As can be inferred from this, they are mostly plants for gardens within cooler areas. Like their Hebe relatives, they generally occupy fairly open habitats, such as streamsides and rocky slopes – and are therefore most suited to a relatively open aspect within gardens.

As mentioned at the beginning of this profile on Parahebe, this intriguing species was one of the most significant (and mystifying) botanical discoveries of recent times. The reserve where it was found was acquired, in 1982, by the NZ Native Forests Restoration Trust (NZNFRT), an organisation that had only been formed in 1980. The Trust has since gone on to purchase extensive tracts of land with significant conservation values, throughout New Zealand.

In 2007, Geoff Davidson (pictured above) of Oratia Native Plant Nursery (one of the key driving figures behind the NZNFRT) went to survey this patch of remnant bush with the Trust’s field officer, Sharen Graham¹. They noted a number of species that are unusual for the region (as they are more characteristic of higher-altitude, colder habitats); and at one stage, Sharen asked Geoff what a particular groundcover was. Geoff guessed that it might be Jovellana repens, a creeping plant only known from much further south.

Intrigued as to its identity, Geoff collected a small section of plant, and grew it on. Some time passed, and various experts (including Peter de Lange and Phil Garnock-Jones) were consulted on the plant’s identity. During this time, the plant flowered at the nursery, thereby proving itself to be a Parahebe. It was subsequently described as a new species, under the name Veronica jovellanoides².

The unlikely location of its growing station (near Riverhead Forest, in the northwest of Auckland) caused a good deal of scepticism when its discovery⁴ was announced. Indeed, a further twist in the tale was provided in the early stages of its botanical recognition, when the original plant that Geoff and Sharen found could not be spotted (after much searching) – thereby fuelling the doubts of sceptics. However, a search by the Auckland Botanical Society succeeded in relocating a significant specimen of P. jovellanoides; on a slope in which a number of specimens have subsequently been found⁵. Any prior doubts regarding its legitimacy have since abated, as its obvious distinctiveness has been recognised, and a range of experts have surveyed it within the wild.

We became familiar with Parahebe jovellanoides from plants that were grown and distributed by Oratia Native Plant Nursery. It is a very free-flowering plant within cultivation, smothering itself with pretty, pale pink flowers in late spring and early summer, especially when it is planted in moderately high light. By comparison, the low light conditions of its forest remnant home cause comparatively sporadic flowering in the wild. Within cultivation, the foliage often looks considerably different to its appearance in the wild, due to the effect of higher light upon the leaves. Whilst leaves are dark green under the cover of forest within its natural habitat, they usually assume a lighter, more olive hue in cultivation, and are frequently smaller in size.

In gardens, it can be affected by powdery mildew (in late summer and autumn), and should therefore be planted in a cool location with good air movement. That notwithstanding, Parahebe jovellanoides forms a very vigorous groundcover under suitable conditions, such that the Pukekohe plantsman Terry Hatch refers to it as ‘Geoff’s weed’ (albeit a critically endangered and very beautiful ‘weed’).

In November of 2010, I had the privilege of viewing this plant in the wild with Geoff Davidson. One of the major impressions that I was left with was the overall beauty of the remnant of bush in which Parahebe jovellanoides is situated. The riverside communities of plants were particularly attractive, with a great diversity of species and a lightness of feeling that can be missing from northern bush.

P. jovellanoides grows in relatively dark forest on a slope running down to a small ditch, in close proximity to Cyathea smithii (one of the suite of species that is unusual for such a low-lying ecology). When not in flower, it could be easy to pass by P. jovellanoides‘ mats of mildly toothed foliage, or mistake it for another groundcover. It tumbles through the leaf litter and exposed roots of the forest floor, forming reasonably dense patches in some parts. Established plants were throwing up small numbers of distantly-placed flowers, which made for interesting comparison with plants in cultivation (that had been flowering prolifically for a month prior).

In subsequent visits, I found it reassuring to see that P. jovellanoides seemed to be holding its ground. With adequate protection, it is to be hoped that this enigmatic plant can continue to strengthen its hold in its only known home, whilst also gaining some degree of security from its introduction into our gardens.