Composition: I like the positioning of the cactus. I think the crop might be a little close on the bottom, but it's hard to say without seeing what was further down (it may have looked worse). In general though the composition is quite good.
Technical Quality: I like the sharpness of the main subject and the blurred background, although the blur looks more like camera shake than just a natural lack of focus. The clarity of the cactus is very good and you've done well to get some contrast between the main subject and the background.
Meeting the Challenge: It definitely meets the challenge - there is nothing non-flora in the photo to distract the viewing, and your chosen subject is quite obvious thanks to the shallow depth of field.
Creativity: It's a very interesting subject, although there is nothing specifically creative about the technique you have used. That's not to say I don't like the photo though.
Border / Title: The border is alright, but just on the edge of being too large. The title is witty and interesting.
Overall: I like the image and to be honest I'm slightly surprised at the position it finished in - obviously there was some strong competition.
The colors seem a bit muted to me. I don't really know what the natural colors of this are, but it does seem a bit bland. The angle and framing/cropping are good, I like how the subject comes in from the left. The focus seems a bit soft. with a very sharp subject like this, I would prefer a really sharp focus. ~Heather~
I've never seen this kind of cactus before. Nice composition, maybe a little teak on the saturation could have richened those greens more, otherwise a top pic.
Don't take this the wrong way, but the way the colors of this photo are and the way its almost sharp makes me think that the marlboro man from the '70s is firing up a red sitting by the campfire 10 feet away from this exact cactus. Good texture on the thorns and I like the DOF. It really reminds me of that 70's look of color photography though.
Very interesting use of subject placement in this picture. I'm not sure I'm all that crazy about it. Since I'm not sure if I've seen a plant like this, I would like to see more of it. Also, it just seems a bit dark and maybe slightly out of focus. Although, it shows nice depth the way it is, I think the branches, or whatever you call them, could stand out even more and show better detail. I like the colors in the background of what appears to be a very brushy landscape.