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.