The poor soil promotes other survival strategies. Take, for example, the delicate, glistening carnivorous sundews (Drosera
). Sixty-eight of the more than 160 sundew species in the world thrive in Australia’s southwest. During the wet winter and spring, their sticky leaves are astonishingly effective at trapping insects. One species found near Perth (Drosera erythrorhiza
) eats an average of 80 tiny arthropods a day in spring. Another similar carnivore (Byblis gigantea
), which belongs to an entirely different plant family found only in Australia, can trap four flies per centimeter of each leaf’s length. Insects provide the plants with an essential supply of nitrogen, phosphorus, potassium, sodium, and zinc.
Still, most kwongan plants cannot trap insects. So they obtain a portion of their nutrients from mycorrhizal soil fungi, which live on the roots of plants and help import nutrients. The fungus
generally derives some benefit from the relationship by drawing on carbohydrates manufactured by its plant partner during photosynthesis. But a few plant species have managed to so thoroughly exploit the fungus that they no longer make any of their own food. For example, the underground orchid (Rhizanthella gardneri
) has given up photosynthesis; it flowers and fruits deep in the earth, where it must be pollinated and dispersed by burrowing invertebrates.
The orchid is not alone in its thievery. At least 42 other kwongan plant species get by as outright parasites. One is the Christmas tree (Nuytsia floribunda), which earns its name from the great masses of flame orange flowers that appear around it each summer. The blooms of this type of mistletoe look like great clusters of brilliant orange grapes and can seem hallucinatory in the summer heat. It lives by sucking the life out of grasses and lesser plants growing within its reach. The roots are armed with structures called haustoria, which throw a collar around the rootlets of neighbors. Spigotlike outgrowths from the collar pierce the roots
and drain off nutrients and moisture. Its discarded leaves, which contain considerable nitrogen and phosphorus, create a niche for herbs growing under the tree’s canopy.
Other plants rely on less predatory methods. The banksia and other members of the protea family extend roots across the soil surface to collect the tiny amount of nutrients that come with rainfall or decaying plant matter. To fund extravagant summer blossoms, an extraordinary taproot penetrates deep into the earth to reach sweet groundwater and less-weathered rock.
In spring, after a wet winter, the kwongan goes berserk. Some bushes obscure foliage with red, white, and blue flowers, while others produce compound flowers that look like pinecones, toothbrushes, even feather boas. At first, the astonishing floral exuberance seems puzzling, given the limited conditions. But plants actually expend little of their nutrient store to make flowers. All that is needed to produce nectar is sunlight and water, and during the Australian spring both are abundant in the southwest. The real challenge is spreading pollen. Without nutrients, potential pollinators such as insects and birds are scarce, and the appetites of carnivorous plants compound the problem. Each plant must therefore compete intensely to attract a pollinator. Only the most handsome and nectar-filled blooms win out.