Hawkweed IR

When I started in infrared (IR) photography, I went around snapping everything I could - partly for the fun of seeing common things in their IR guise, and partly to learn how to work in an IR world. One of the shots I took then, and posted here, was this image of a field of wild flowers that I tentatively identified as Hawksbeard. What is surprising about this shot is that while the flowerheads themselves show the typical IR response of foliage - their yellow colour turning to bright white, the sepals of the flowers appear to absorb IR radiation and are seen as more or less black. Almost all other plants have sepals that show the more typical IR response of white.



Recently, I had the opportunity to investigate this anomalous IR photographic response once again. The first point to note is that I was incorrect in calling these plants Hawksbeard. In fact, they are probably one of several hundred (!) varieties of Hawkweed - a member of the Compositae family of which the common dandelion is also a member. Any botanist looking in here is more than welcome to comment and correct me, as my botanical expertise is very limited. There Hawkweeds can be small and low growing, and range upwards to well over a meter in height. I came across such in one of my perambulations through the Scottish countryside and the first new image below shows as it appears (more or less) to the naked eye - yellow dandelion-like flowerheads with dark green sepals on long stems with few leaves. Contrast this to the second image of the same plant (slightly different angle) taken as a 720 nm IR shot with my converted Canon 40D camera fitted with an R72 filter. The flowers are "white" and the sepals "black".

   


The next shot is a close-up of the flowerheads and the IR light clearly brings out the tiny stamens of the flower, as little curly objects of slightly different tone. I had never been aware of these from the normal visible light view of the flowers. From a photographic aesthetic point of view those black sepals present a fantastic contrast in monochrome as seen in the next two shots.



    


Finally, given the close botanic relationship between Hawkweed and dandelions, I hunted around for a good old fashioned dandelion that we all know and love - just to check whether its sepals were also "black" in the IR image. The last shot shows that to be just about true! However, note that the dandelion flowerhead has a set of bracts (small petal-like structures) turning down at the bottom of the base of the flowerhead, and they are not "black". Intriguingly, maybe IR photography could be a means of identifying or classifying members of this branch of the Compositae family of plants.




Many Thanks for viewing and for any comments.
Cheers

David aka Okavanga