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Lobelia excelsa

Lobelia excelsa

Written by Daniel: Eric in San Francisco (Eric in SF@Flickr) shared today's image via the BPotD Flickr Group Pool | original image). Eric is very fortunate in being able to frequently visit the San Francisco Botanical Garden at Strybing Arboretum where he takes these great photos. Thanks yet again, Eric.

Written by Douglas Justice: Lobelias nearly always provoke interesting conversations amongst botanists and horticulturists. Many of the larger lobelia flowers (such as in Lobelia excelsa) are red, tubular, and bird-pollinated. In all lobelias, the flowers are upside down (i.e., twisted through 180 degrees as they develop), although this is hardly apparent to the casual observer. Lobelias are protandrous (compare protogynous), which helps prevent self pollination. The anthers form a tube through which the piston-like style picks up pollen. The protruding style is not receptive at the time the pollen is ripe and thusly presented to pollinators at the tip of the closed styles (as seen in Eric's excellent photo). Eventually (presumably after the self pollen is removed or no longer viable), the style branches split open and expose their pollen-receptive surfaces.

4 Comments

The 'plunger pollination' described above is one of the traits uniting the Asterales, including all composites as well as other members of the Campanulaceae ... or so the experts say :) In any case, it's a fun thing to look for.

Thanks, Daniel! The thing that really drew me to the plant and then to the composition was the height of the flowerhead - at my eye level or just a little lower. A magnificent sight.

Thanks for this!
I homeschool 2 boys and we were looking at plant classification today. Why was my eldest son's plant classified in the order Asterales? One reason given was "plunger pollination". Your photo and description enabled us to understand this reason:-)

Doesn't something very similar happen in some of the Proteaceae? I seem to remember being absolutely fascinated whilst in Australia some years back, to read that in, was it Grevillea, Hakea, Banksia or Lomatia (?), the stigma picked up pollen from the hidden anthers as it emerged and became ripe for pollination only later on.

It's hard to think of a family less closely related to Lobelia (without being a monocot or palaeodicot) so a nice case of convergent evolution. The flowers are very similar to look at too.

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