Alpine plants are unique because they can grow and reproduce in low temperatures. Many of the adaptations underpinning this ability are features admired by gardeners. The plants are miniature and compact, yet often have disproportionately large flowers – even small plants need to attract pollinating insects or birds (few, except grasses, sedges and rushes, risk relying on the wind).
Adaptive features of alpine plants
As well as large flowers, alpine plants have other features that assist their survival:
- Leaves are often woolly to help trap heat, reduce transpiration, and protect against wind, abrasion, and ultraviolet radiation.
- Their optimum rates for photosynthesis and respiration are at lower temperatures than for low-altitude plants.
- They are long-lived. There are very few alpine annuals. Perennials can store more energy and are not obliged to reproduce every year.
- Flower buds are typically formed in the preceding summer, if it has been warm enough. Whether or not the bud flowers or is aborted is determined by the temperature of the current summer.
- Some produce anti-freeze chemicals (soluble carbohydrates) that prevent their cells from freezing when temperatures drop below 0°C.
New Zealand's alpine flowers are notable for their lack of colour. After white, yellow is the most frequent hue, although much less common. The proportion of white flowering alpine plants in New Zealand is 77% – about twice the world average. Genera and families with colourfully-flowered species in other parts of the world (for example, Gentianaceae, Asteraceae, Myosotis and Ourisia) are represented mainly or exclusively by white-flowered species in New Zealand.
‘My darling specimens’
On his first trip to the alpine herb fields of the Ruahine Range in 1845, missionary botanist William Colenso was astonished at the richness and beauty of the flowering plants that grew there. He collected many specimens and stowed them in his jacket, shirt and hat for safekeeping. He recorded, ‘I was wholly occupied with my darling specimens … only getting about 2 hours sleep towards morning’. 1
The prevalence of white flowers seems to be related to New Zealand’s lack of specialised insect pollinators. Flower colour attracts certain pollinators – for example, long-tongued bees respond especially to blue and ultraviolet. New Zealand has no native species of long-tongued bees – the chief pollinators are flies, moths and short-tongued bees, which visit a wide range of flowers. Colour is a cost to the plant in terms of resources and genetic coding, and if colour has no advantage, then in severe alpine environments evolution tends to select against it. White, bowl-shaped flowers attract as many insect pollinators as possible in areas where pollinators are scarce.