What we do in the shadows
By David McDermott
Plantsman David McDermott examines shade-tolerant plants.
PHOTOSYNTHESIS 101 GOES something like this: “Plants absorb sunlight and water to convert atmospheric carbon dioxide into oxygen and sugars which the plant cells can use as energy.” Sunlight gives life to plants — their very existence depends upon it. Therefore, when there is very little light available to plants — for example, under a dense forest canopy or beneath a south-facing cliff — one observes botanical life pushed to its absolute limit of environmental adaptation. These species have evolved to thrive in places deprived of one of life’s key building blocks, they are true freaks of the plant world. Shade tolerant plants also present compelling opportunities for use in urban landscapes, environments where built structures and lack of air-flow can present major challenges to the planting designer.
New Zealand possesses a plethora of ferns, many of which are extraordinarily shade-tolerant. Adiantum cunninghamii is a rigorous, creeping fern that forms ‘fields’ of blue-green foliage; an elegant alternative to mass-planting of individual crown-forming fern species. Lastreopsis velutina features wonderfully soft foliage with fine, rusty hairs; great as a single specimen or small group in deep shade. Ptisana salicina lives up to its common name ‘king fern’ in bold glory, it’s massive fronds of glossy deep-green providing a taste of the tropics in sheltered northern forests.
Another giant is the largest of our native asteliads — Astelia trinervia. This fine, flax-like northerner grows to 2 metres, appearing in ‘fields’ beneath the kauri (Agathis australis) forest canopy. Microlaena polynoda is a native grass with dense, bamboo-like stems which seem to cascade through the understorey; plant as a ‘screen’ through which other bolder species (such as ferns) can be viewed. Ourisia macrophylla is our ‘mountain foxglove’ and another shade-lover. Its rosettes of lush green foliage and distinctive pure white blooms make it a prize garden specimen in cooler climates.
Brachyglottis sciadophila is a vine-form of the beloved New Zealand tree daisy and is classified as ‘at risk’ in the wild; its scrambling habit and bright yellow flowers make it a fascinating addition to southern gardens. Jovellana sinclairii brings a ‘northern-hemisphere woodland’ aesthetic to shaded NZ landscapes with soft, pale-green foliage and bell-shaped flowers; despite wide distribution however, this beauty is classified as ‘declining’ in its natural habitat. Rhabdothamnus solandri is a common, yet graceful, shrub often found on steep or sloping ground. Its ability to flower so brightly in shade renders it an attractive option for both its winged pollinators (tui, bellbirds, and stitchbirds) and landscape designers alike. Myrsine australis is a rather familiar small tree which inhabits almost all parts of New Zealand yet
is often overlooked as a landscape design plant. This fast-growing and reliable species features red stems and mottled, yellow-green leaves; it is of value as a single bushy specimen or can be grown in rows and clipped into a formal/informal hedge.
Just as native shade-dwellers are highly adept at colonising the darkest reaches of our landscapes, so unfortunately are exotic invaders. Invasive species often penetrate deep into native forests and other hard-to-reach spaces, resulting in massive challenges for those who work with the land. As always, it is best to treat all exotic plant species with some caution. When used responsibly however, exotics can bring immense interest and value to designed landscapes.
Helleborus foetidus hails from the mountain regions of Europe and produces massed heads of light green, cupped flowers in winter and early spring to perfectly complement its dark green foliage; plant in drifts or allow to self-seed through shaded gardens areas. Ligularia reniformus is a lush perennial herb with large, glossy leaves on erect stems and bright yellow, daisy-like flowers which, despite its tropical looks, can be grown in most areas of NZ that are free from heavy frosts.
Cyclamen hederifolium is a deciduous, tuberous perennial with rounded, mottled leaves and distinctive ‘nodding’ pink flowers which appear in Autumn; it is an excellent container plant for seasonal colour and for introducing an exotic woodland aesthetic to de- signed landscapes. These and many other shade-loving species remind us that despite being deprived of life-giving light, the darker corners of our landscapes need not be deprived of beauty.