Sunday, January 28, 2018

Plant Story--So Exotic, Bird of Paradise Flower

The bird of paradise flower, Strelitzia reginae, is so commonly planted in tropical and subtropical climates--southern California, Florida, Hawaii in the United States--as to seem boring.

Strelitzia reginae bird-of-paradise plant

At the same time, for newcomers to those and more tropical regions, it is the essence of an exotic flower: very large, bizarrely shaped and in incredible blue, orange, red and green.

Strelitzia reginae bird-of-paradise flower
bird-of-paradise flower
Bird of paradise is from South Africa, brought to western attention in the late 1700s. The flower is the group of bright blue petals, two of them fused together, and upright orange sepals.The blue petals hold a rich nectar (sugar water), lots of it, though not particularly concentrated. The orange sepals advertise. The whole flower is oddly turned to emerge from the red-and-green bract, so that it looks like a bird's head. In its native South Africa, it is called crane flower (in several languages).

The red-and-green bracts (called a spathe) under the flower contain up to six buds. In the picture below, the orange sepals to the left are from a dying flower, the open flower has the three orange sepals to the right and the blue petals. Each flower lasts several days, so the one flowering stalk produces flowers for several weeks. Gently treated, cut flower stalks of bird of paradise can last several weeks as successive flowers emerge.

bird-of-paradise flower, Strelitzia

In Africa the flower shape is functional. The chief pollinators are cape weaver birds (Ploceus capensis) (photos). They perch on the tip of the lateral, fused blue petals, which are quite strongly reinforced and will support the bird, and from there cape weavers probe for nectar. The stamens inside the blue petals spring outward in response to the bird's activity and deposit pollen on the bird's feet. When the bird visits another plant, the stigma is released to brush the bird's feet and pollination happens. The cape weavers also eat a lot of the pollen, which is unusual for birds, but just as for us, pollen is highly nutritious.

Across the world, where bird of paradise has been planted, there are no cape weavers and the plants have been sterile: growing, flowering but producing no seeds. Recently Hoffmann and colleagues spotted seeds on most of the bird of paradise plants in three different locations in Irvine California. They investigated and discovered that the American common yellowthroat (Geothlypis trichas) (photos) had worked out where to land and was efficiently taking nectar and pollinating bird of paradise flowers. Seed set was excellent. That was 2011 and the authors didn't know if the common yellowthroat had been taking bird of paradise nectar and pollinating for years or if this is the beginning of a bird-plant mutualism that will spread. Birds can learn new behaviors and can learn from other birds but often opportunities that seem obvious to us are missed. If you happen to live where bird of paradise is planted, watch for seeds (and common yellowthroats!). 

Strelitzia reginae bird-of-paradise plant

 On the surface this sounds like a great thing--a pollinator is found in the New World--but it might turn bird of paradise, which generally stayed where it was planted, into an aggressive, invasive weed.

The seeds of bird of paradise are dramatic, black with a red-orange aril and an oil body. The aril is probably tasty to birds and certainly eye-catching and the oil drop is nutritious, which makes the seeds very attractive to birds. In South Africa, quite a list of bird species eat and disperse bird of paradise seeds (see seeds in Kew Garden post: link). I have seen no reports of American birds eating bird of paradise seeds in California, but it is worth watching for.

Bird of paradise was brought to Kew Gardens in England in 1773 by Sir Joseph Banks (bio). A major figure in British botany for decades, Banks personally named only two plants, but Strelitzia was one of them. He named it to honor his queen. Strelitzia refers to the region of Strelitz in Germany, the birth place of Queen Charlotte, Queen to George III of England. and the species epithet "reginae" means "of the queen." (Partial biography link, more on Queen Charlotte link). 

The bird of paradise's common name comes from the resemblance of the flowers to a bird's head. Birds that are actually called bird of paradise are spectacular birds, but don't look particularly like the bird of paradise plant's flowers link. The African common name for it, crane flower, is more accurately descriptive. You can also find it called the paradise plant.

Strelitzia reginae bird of paradise plant

The genus Strelitzia was for a while included with Heliconia, plants of tropical America but the relationship is pretty distant and currently Strelitzia is classified in a tiny family named after it, the Strelitziaceae. There are five species in the genus Strelitzia all from South Africa, and two other genera, Phanakospermum (one species of massive plants, tropical America link) and Ravenala (one spectacular species, native to Madagascar link). 

Where they are happy, bird-of-paradise plants flower abundantly. They can be grown as houseplants and will flower in a sunny window (but can get 3' tall). They are very much tropical plants, however, and require bright sunlight and temperatures of 50 F or higher, though they do better outdoors in summer if lightly shaded. Tough once established, they like plenty of water in a well-drained soil, and cool nights (60s not 80s).

Strelitzia reginae bird of paradise plant

Widely beloved, they are the emblem of the South African National Biodiversity Institute (link), appear on the South African 50 cent coin (link), on the coat of arms of the Province of KwaZulu-Natal link, were chosen as the floral emblem of Los Angeles, California (link) and in very stylized form, are the emblem Aloha Air Cargo of Hawaii (link). There are probably many more.

The big leaves that make them attractive even when not flowering have a strange ridged surface that causes water to form elongated drops and quickly run off. The fact that you never see water on the leaves is not chance but very sophisticated bio-engineering involving both surface waxes and structure. Engineers have noticed and are imitating the structure for synthetic materials.

When you walk by flowerbed after flowerbed of bird-of-paradise, don't just think "oh, boring!" slow down to look for seeds and bird visitors. Or watch the leaves shed water when the sprinklers turn off. 

Comments and corrections welcome.

Coombs, G. S. Mitchell and C. Peter. Pollen as a reward for birds. The unique case of weaver bird pollination of Strelitzia reginaeSouth African Journal of Botany.2007.73: 283-283
Cron, G. V., C. Pirone, M. Bartlett, W. J. Kress and C. Specht. 2012. Phylogenetic relationships and evolution in the Strelitziaceae (Zingiberales). Systematic Botany. 37: 606-619.
Hoffman, F., F. Daniel, A. Fortier and S.S. Hoffmann-Stay. 2011. Efficient avian pollination of Strelitzia reginae outside of South Africa.South African Journal of Botany 77: 503-505.
Mele, E. S. Girardo and D. Pisignano. 2012. Strelitzia reginae leaf as a natural template for anisotropic wetting and superhydrophobicity. Langmuir. 28:5312-5317.
Kew Gardens. Strelitzia reginae Banks Plants of the World Online. link Accessed 1/24/18
Laszlo, P. Plant of the month. Genus Strelitzia link Accessed 1/24/18
Matt. 2017. Bird pollination of the bird of paradise. Oct 23, 2017. link Accessed Jan. 24, 2018 
Missouri Plant Finder. Missouri Botanical Garden. Strelitzia reginae. link  Accessed 1/25/18.

Kathy Keeler, A Wandering Botanist

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Heliconia - The Dramatic Heliconias link

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