Bumping into old floral friends, and pollination with a hug.

Rare plants nurseries are like second hand bookshops. It’s always so tempting to browse on the off chance you find that little treasure. I recently visited a charming rare plants nursery in Mt Macedon (boutique-y town outside Melbourne, Australia) where I discovered these for sale:

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Hello old friend! (Hesperantha coccinea)

The last time I saw this elegant iris, it was flowering on stream banks 10,000 km away in the Drakensberg Mountain range in South Africa. There in its natural habitat, it is pollinated in some areas by a very special butterfly: the Mountain Pride (Aeropetes tulbhagia). In other places, it is pollinated by the amazing long-tongue fly (Prosoeca ganglbaueri). The two forms are a wonderful example of “pollination ecotypes”, where different populations are undergoing adaptation to their unique pollinators. The fly-serviced ones are a pink hue with narrow petals, while the butterfly-pollinated ones are much redder with broader petals.

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Hesperantha coccinea at home in South Africa with its pollinator (Prosoeca ganglbaueri).

Fast forward two weeks, and I’m home walking the dog in my quite unremarkable Melbourne suburb, when who should I see?

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Hello old friend! (Diascia sp.)

It’s winter here, with very little in flower, but these brilliant little pink blooms volunteering themselves from underneath a fence in suburban Melbourne really made my day. The last time I saw a Diascia, it was growing amongst the boulders on creek beds and on cliffs in the Drakensberg Mountains. These are Diascia, or “twinspur” and its this common name that alludes to their fascinating pollination story.

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Hug-pollination by oil-collecting bee (Rediviva sp.) in Diascia.

Diascia have two spurs on the back of the flower, which is distinct from the usual arrangement of a single nectar-spur. The difference is that these flowers don’t reward pollinators with sugary secretions, instead they provide oil to specialised oil-collecting bees in the genus Rediviva. The bees use this oil to line their nests and provision their young. In order to collect the nectar, they must reach deep into the twin spurs with their lanky forelimbs, and comb it out. In so doing, they effectively hug the reproductive parts of the Diascia flower and effect pollination.

In Spring, I plan to take some cuttings from this little Diascia. Keeping species with special personal significance is a deeply satisfying part of cultivating plants. A plant can be kept like a souvenir or memento marking a time in one’s life, just like a photo or trinket. But plants have an advantage over these inanimate reminders. Because biological reproduction requires the physical donation of part of the mother’s cells to the daughter cells, my keepsake plant can be viewed as a physical part of the plant that appears in my fond memory. If I could see in four dimensions, I could literally look down the line of cell-divisions all the way back to where the Hesperantha in the nursery physically intersects as the same individual with the Hesperantha I observed flowering in the Autumn sun of the Drakensberg Mountains in South Africa.

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The Drakensberg Mountains, South Africa, Autumn 2014.

 

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3 thoughts on “Bumping into old floral friends, and pollination with a hug.

  1. Hello friend

    Nice post. I bumped into some horticulturally modified Diascia on a German market square recently that were reminiscent of a friend that had changed almost beyond recognition- along the lines of too much wild youth and a bad dye job since one last saw them, but retaining the essential traits, of which colour was not one…. orange, red white Diascias? the bees would be befuddled. That pink Hespie with wide petals is odd, I suspect it of being a horticultural mongrel or product of LOTS of selfing. Does anything visit them in Oz? Bees? Butterflies? I trust you bought some plants to take home.

    Greetings to Sam

    Ruth

    On Thu, Jun 22, 2017 at 5:38 AM, Michael Whitehead wrote:

    > michaelrwhitehead posted: “Rare plants nurseries are like second hand > bookshops. It’s always so tempting to browse on the off chance you find > that little treasure. I recently visited a charming rare plants nursery in > Mt Macedon (boutique-y town outside Melbourne, Australia) where I” >

  2. Nice to see our plants appreciated that side! I love this one (i.e. H coccinea), have been cultivating it myself for some years now, by cuttings I took in the same Drakensberg mountains you mentioned ;-). In fact I was privileged to do part of my MSc there looking at emerging invasive species. Enjoy!

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