Psychology and botany students took the plant blindness test, in which they were shown fourteen images of plants and fourteen images of animals of equal nameability, and then later asked to recall what those plants and animals were.
As you can see in this graph, the students were able to recall more animals than plants. It didn't matter if they students of botany or not, but there was a significant difference between male and females. Females were way better at recalling plants than males were, but the effect seems to be explained primarily by the substandard ability of males to recall plants compared to females, in addition to being slightly better at recalling animals than females.
The study included 124 introductory psychology students (58 female and 66 male) and 203 non-major botany students (90 female and 113 male).
This being a paper in a journal of education, the authors conclude that teachers should put more emphasis on naming plants in college:
To help identify which images are most helpful for instruction about plants, more teachers need to ask students which plants they know by name at the beginning of semester, and which examples they remember from class at the end of the semester. Teachers also need to be aware that there is a potential for gender differences in the recall of examples they use in class, particularly for cut flowers and carnivorous plants. Most importantly, biology teachers need to realise that students are coming to class with an inherent disparity in their plant and animal knowledge, and they need assistance to consciously attend to the green side of life in a world full of distracting animals.However, I would be more interested in a conclusion along the lines of how human males and females are naturally differently attuned to recognizing animals than plants. One hypothesis could be that during some period of our evolutionary past when differences in the male and female brains evolved, males were hunters and females were gatherers, and thus had different priorities. It's a hypothesis, nothing more.
Also, take a look at the individual plants that were presented and how well females and males recalled each:
I have highlighted in red those plants females remembered at least 20% more often than males, and in blue the same for males. Most striking here is that males are so much worse at remembering flowers (rose, daisy, and carnation). Perhaps women should start giving men venus fly traps on Valentine's Day. Or carrots.
Elisabeth E Schussler and Lynn A Olzak (2008). It’s not easy being green: student recall of plant and animal images Journal of Biological Education, 42 (3), 112-118