Friday, October 2, 2015

Bluebells - are they Boys or Girls?

Wahlenbergia Species
FAMILY: CAMPANULACEAE
 Australian bluebells, with their sky-blue flowers, are one of the spring/summer delights of the Darling Downs. They particularly love the bit of extra moisture provided by road runoff, so they are lining many of our country highways at the moment.
One of the few bits of natural lore that my mother taught me was that there are boy bluebells (left, below) and girl bluebells (right).


My mum was not strong on knowledge about native plants. As I grew up I learned to be a little sceptical about her pronouncements in this area, so I was delighted when discovered she was right.

Well, almost.

Like so many flowers, each bluebell has both male and female parts. They are little hermaphrodites, with a central style(female) surrounded by anthers (male).
The style, as you would expect from its name, looks like a post in the middle of the flower.
You don’t really notice the anthers. They are tucked right down in the bottom of the cup, and perform their pollen producing role before the flower opens. (You may be able to see them if you click on this photo to enlarge it.)
 
As the style grows in the unopened bud, it passes the anthers. It collects pollen on the way, with its purpose-designed hairs. When the flower opens, the style does the job that is done in most other flowers by the anthers, presenting the pollen in a conspicuous position for pick-up by the insect courier service.  (The insects also pick up their "pay", in the form of a bit of nectar). The photo below shows a bluebell in the male phase, well loaded with pollen.

Once the pollen has aged to the point of being unviable, the style moves into the female phase. It splits into three and exposes the sticky surface of the stigma.

Another flush of nectar brings the insects back. If they are carrying pollen from male-phase flower, some adheres to the stigma. From there it makes its way down into the ovary, to grow into seed.

This sex change process is fairly usual in hermaphroditic flowers. They have both male and female parts, but do the jobs one at a time to ensure the spread of their genes around their species. Some, like bluebells, are protandrous - meaning that they are male first, becoming female after that. Flowers that do it the other way round, being female first, are protogynous.

I wish I could tell you which species these bluebells are, but Wahlenbergia ID drives me to despair.
If anyone out there has some helpful tips on how to tell one Darling Downs bluebell species from another, I’d love to hear it.

4 comments:

Judith Gray said...

This is really interesting Trish, and something I haven't actually noticed before. We have at least two different types of bluebells here, so will go and have a closer look today for the "males & females".

Patricia Gardner said...

Hello Judy,
I hope you can make a better fist than I can of telling what species is what. The little one, Wahlenbergia gracilis is easy just because it's little, but the others baffle me.
Trish

Anonymous said...

I've had the one with small flowers flowering at my place in Kingaroy, but a larger flowering species is in flower currently lining the road between Kingaroy and Memerambi.

Frank S.

Patricia Gardner said...

Hi Frank.
Nice to hear from you.
I wish someone could help me distinguish between the larger species. In particular, I notice that some have a hairy calyx and some don't. This is an obvious distinguishing feature but I can't find any description of the likely local species which includes this feature.
Trish