Lobelia (syn. Pratia)

In a brutal scenario of ‘death by taxonomy’, the rather lyrical name of Charles Louis Prat-Bernon has been relegated to an echo. Although many of us will continue to refer to various members of this genus as ‘Pratia’ (in memory of the early 19th Century French naval officer, Prat-Bernon), it behoves us now to call these native groundcovers Lobelia¹ – as botanists have relatively recently ascertained that they should once again reside within the boundaries of that famed genus.

When one reflects upon this change, it should not come as a great surprise – as our native lobelias are similar in appearance to the mostly blue varieties of Lobelia that adorn countless hanging baskets, pots and garden edges in many countries.

The species that most regularly appears in New Zealand gardens is L. angulata – which is of course better known as Pratia angulata. This vigorous, free-flowering groundcover occurs naturally in a wide range of habitats throughout the country, from lowland forest through to montane grassland.

Amongst alpine enthusiasts and southern gardeners, the high altitude dweller Lobelia macrodon has long been admired for its large, fragrant flowers. A newly-described montane species that is closely related to L. macrodon, called Lobelia glaberrima, also shows considerable potential for gardens (even performing well in nursery trials within Auckland). Another species that hails from our southern mountains, Lobelia linnaeoides, is worthy of special mention, on account of its attractive bronzish foliage and pale pink flowers (that hover well above the leaves like dancing cobras).

Lobelia perpusilla is a valuable species for gardens in many parts of the country. We have found it to be the most useful of the genus (surpassing Lobelia angulata) for a wide variety of garden situations, including open, dry conditions (especially when growing in association with other creeping herbs). It inhabits a range of often challenging wetland habitats, such as the margin of the small tarn in the image below (at the Glenmore Tarns complex, on the western side of Lake Tekapo).

Due to the demise of Pratia and the description of new species (including L. carens and L. fugax), the ranks of Lobelia within New Zealand have swelled in the last few years from 3 (Lobelia anceps, Lobelia roughii and L. linnaeoides) to now include 12 members. Pratia is not the only genus to have been sunk back into Lobelia; the erstwhile NZ species of Hypsela and Isotoma have both become synonyms within the expanded Lobelia.

The plant formerly known here as Isotoma fluviatilis is a salutary lesson in the importance of accuracy when growing native plants. For years, a vibrant blue-flowered groundcover has been widely propagated and planted as a ‘native’. Unfortunately, this plant is not native, and gardeners wishing to plant a native groundcover should instead opt for one of our species of Lobelia.

The first time I saw this fine plant in flower within the wild was at the shameful vestige of the once-majestic Wairua Falls (near Whangarei), where it wound its way through stones that lie in the flood zone of the river. As a result, its pretty white flowers hold court with abandoned cars and fridges within my memory banks – an association that serves as a reminder of the adaptability of this mat-forming groundcover.

As part of the burgeoning interest in native plants that has taken place over the last three decades, Lobelia angulata has deservedly become one of the stars of native horticulture – a plant that is vigorous, has vibrant green foliage, and of course bears huge quantities of those white flowers. Following flowering, L. angulata develops attractive reddish berries that add significantly to its appeal as a garden plant.

Although it is almost universally welcome in gardens, its presence is not celebrated everywhere – such as in bowling greens in certain parts of the country, where it is treated as a weed. This is worthy of note, for the ability of some native groundcovers (such as Lobelia angulata, Dichondra brevifolia or Leptinella dioica) to compete as weeds within artificial habitats (like lawns or bowling greens) can be a good indicator of their gardenworthiness – as resilience is an important characteristic in groundcovers.

Provided it receives adequate protection from slug damage and is not subjected to particularly dry conditions, panakenake is a very useful groundcover for a range of conditions (as one would expect from a species that grows from lowland forest – as pictured above, in the Waitakeres – up to montane grasslands). It has a long flowering season, with flowers appearing at any time from late spring through the entire summer.

L. angulata was one of the earliest of our plants to be discovered to Western science, as it was collected in flower (By Joseph Banks and Daniel Solander) within the first weeks of Cook’s first voyage to New Zealand.

Where would we be without our Mums ? I had been planting this species for a long period of time before I finally saw it in the wild, despite concerted efforts on my behalf to look for it. It wasn’t until a drive out with my mother and aunty (to see black stilts in the wild), when my mother suggested we stop at an area between Lake Alexandrina and Lake Tekapo, that I finally encountered it. As we moved close to the water’s edge, a carpet of delicate white flowers became visible, in the marginal zone where a pair of black stilts were wading.

Lobelia perpusilla is naturally found in periodically damp, open sites, such as dune hollows and the margins of lakes and streams (like the one pictured above, by Lake Alexandrina). It is remarkably adaptable within cultivation, withstanding both dry conditions and high light exposure – a fact that should come as no suprise when one considers that it is a member of seasonally dry wetland turf communities in the Mackenzie Basin. It will even thrive for extended periods completely submerged under water.

L. perpusilla‘s foliage has a bronzish tint to it, which gives it a more recessive look than other species of Lobelia. The pure white flowers appear over the entire duration of summer and possess an appealing scent.

Although its current natural range only extends as far north as Lake Whangape in the Waikato, it thrives in Auckland, where we frequently specify it as a groundcover. This is one of many plants to which we have been introduced by Oratia Native Plant Nursery, as part of their pioneering work with natives; and it has subsequently become a regular feature within our gardens.

Despite the considerable extent of botanical exploration in New Zealand (dating back to Captain Cook’s first voyage, and earlier in the case of Māori), surprises do still occasionally occur. One such incident was the discovery of this distinctive little groundcover on Auckland’s western coastline (next to Woodhill Forest), by Ewen Cameron.

For those that like the full taxonomic picture, this beautiful little groundcover is officially titled Lobelia aff. angulata (AK 212143; Woodhill) – a name that unsurprisingly doesn’t appear in Oratia Native Plant Nursery’s marketing of this horticultural newcomer. At some stage in the future, decisions will be made around what exactly it is, and a more permanent name will probably be applied.

Following its discovery at Woodhill, another population was found further south on the Waitakere coastline – although these plants exhibit some differences from the original Woodhill plants, not least in terms of vigour. We use plants propagated off material originating from this more vigorous form in our gardens.

With its bright, light green foliage, compact growth habit and abundantly-produced white flowers, this form of Lobelia ‘Woodhill’ has proved itself to be an excellent groundcover that takes exposed conditions and seasonally dry soil. Like many coastal natives, it performs best with high fertility – a state that would have been delivered by the millions of seabirds that once occupied our coastlines (and which have declined majorly since man’s arrival).

The lack of fertility caused by the absence of birds from sites such as these goes some way to explaining the thin appearance of specimens within the wild – in stark contrast with the dense, vibrant mats that L. ‘Woodhill’ forms within gardens (especially where sufficient fertiliser is applied). Lobelia ‘Woodhill’ performs best within high light; and therefore, gardeners looking for a native lobelia for shaded conditions should look more towards L. angulata, a species that occupies considerably shaded sites in the wild.

Following flowering, it produces attractive pink fruits, as seen in the photograph above. Those fruits are rarely seen in the wild, as rabbits (a scourge on the Waitakere coastline, as in so much of the country) avidly consume both the flowers and fruits of L. ‘Woodhill’. This is obviously a matter of concern for the long-term viability of this distinctive plant in the wild. Bearing that in mind, it is a good thing that this extremely rare plant has found its way into cultivation (as an extra safeguard against the perils that it faces in the wild).