Eucalyptus tetraptera

Another entry from Tamara Bonnemaison today, who writes:

Thank you to Mike Bush (aka aviac@Flickr) for submitting this intriguing photo of one of the strangest flowers that I have ever seen. Mike managed to capture two Eucalyptus tetraptera flowers at different stages of development, with a flower having stamens curled up in a “doughnut” shape on the left and then elegantly unfurled on the right.

Living in Vancouver, I rarely come into contact with Eucalyptus, as so few of these species are hardy enough to withstand the occasional extreme cold the area receives. So it was with surprise that I came across this photo of the lush flowers of square-fruited mallee and learned that they come from a species of Eucalyptus. Eucalyptus is a large and diverse genus, and an article in Pacific Horticulture makes a strong case for greater inclusion of the mallees, or small and multi-stemmed species of eucalyptus, in western American horticulture (the article claims that Eucalyptus had fallen out of favour in the region due to invasiveness of some of the tree species). Of the many potential candidates, Eucalyptus tetraptera does not have the stateliest growth form – today’s photographer Mike Bush describes it as “a messy straggle of branches in a messy pile” – but its bright and unusual buds, flowers and fruit make this species well worth planting wherever it will grow (sadly, not likely to survive this far north).

Square-fruited mallee has a limited distribution in Western Australia, growing only on coastal sandplains at the southern margin of the continent. Its scraggly branches reach a height of about 2.5 meters, and it has very thick, leathery elliptical to lanceolate leaves. Like most eucalyptus, square-fruited mallee has an operculum or bud cap that falls off to reveal a flower composed largely of stamens. You may notice from Mike’s photo that the flower lacks petals: the petals in nearly all eucalyptus (with the exception of Angophora species) join at an early stage of bud development to form the inner operculum and the sepals join to form the outer operculum. Today’s photo shows a flower which has just lost its operculum. The square hypanthium forms the base of the flower. This hypanthium will mature into a 5cm wide fruit that will remain bright red or pink for most of the year. The woody fruits of Eucalyptus are commonly called gumnuts.

If you are interested in learning more about Eucalyptus, the Euclid website is a fabulous resource. For those of you looking for a lighter take on Australian plants, here is an article on the children’s author May Gibbs, who created characters of common Australian seeds & fruits, including the banksia man and the famous gumnut babies.

Eucalyptus tetraptera

8 responses to “Eucalyptus tetraptera”

  1. Bonnie

    Golly, those totally look like they come from outer space.

  2. michael aman

    Square–what a strange idea that a living organism would take on this form. So eucalyptus employs square,mint stems are square, I suppose some diatoms are square, and of course Sponge Bob Square Pants…..

  3. Eric Hunt

    Such a beautiful species!
    I photographed the fading stamens and the clear 4-sided hypanthium in the parking lot of a winery in southwestern Victoria State, a couple hours outside of Melbourne:

  4. Julie

    Amazing flowers! What a great photo. Does anyone know what US zones this might grow in?

  5. Bonnie

    How wonderful to see something as I sit in my office that I would not see in person. I did a double take with this square flower. 🙂

  6. Tamara Bonnemaison

    The B&T World Seeds website lists it as USDA Zone 9.

  7. Cora

    Woah, never seen anything like that! So cool, Tamara!!

  8. Deb Musselman

    Square flowers! ~~ at least, the ‘frame’ is square. Is this as rare as I believe it to be?? I’ve always assumed that nature abhors straight lines and right angles, except, I guess, in crystalline forms such as snowflakes? Surely there are not many plants which demonstrate thus – I hope??! It’s beautiful – I guess!

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