Megaherbs make use of what light they can get on the cloudy subantarctic islands.

The white-faced heron is common in the subantarctic islands of New Zealand. Photo: Shutterstock

New Zealand is far enough south in the southern hemisphere that some of its islands are in subantarctic territory. These cold and windy islands get little light, particularly in the southern winter (which corresponds to the northern hemisphere’s summer), and what light they do get is intermittent thanks to intensely cloudy and cool conditions.

But some plants do survive in this harsh climate—the so-called megaherbs of the subantarctic New Zealand islands. They are very large, with big, dark flowers and broad, hairy leaves, which are pollinated by insects.

A team form the University of Otago in New Zealand has made some interesting discoveries about those plants, asking the basic question of how, and why, are the so big?

It turns out that the dark pigment of the flowers, as well as the large size of the leaves, helps to soak up what light there is as quickly as possible. This heats he plants up, and they can be noticeably warmer than the surrounding air.

“Their dark floral pigments are able to more efficiently harvest the unpredictable, intermittent sunshine to speed up metabolism and attract insects seeking warmth and their large rosette leaves can provide mini-glasshouse effects,” says Dr. Janice Lord, co-author of the study.

The insects protected by the megaherbs visit other plants and spread pollen from plant to plant, allowing them to reproduce. The large, multileveled organization of the leaves also helps to trap heat, creating a sort of miniature greenhouse. Essentially, the plants wear layers of dark colors in order to trap and hold as much heat as they can.

The adaptations of these plants mirror those of tropical plants that live in cool, alpine climates. “Plants in those climates face similar challenges in terms of cloudiness and the cold, especially at night,” says Dr. Lord.

These subarctic megaherbs are excellent examples of how diverse and adaptable life can be on the planet, and there is always something new to learn about that diversity of life.