Picture matches will only get the right genus, and not the right species, for a handful of species! Examples:
Brodiaeas. You have to look carefully inside the flower to tell our three species apart.
Owl's clover. We have two nearly identical species that are separated by looking at whether a small part of the flower is fuzzy or not. This will not show up in most pictures. Fortunately, our species separate by location.
Tarweeds. We have three very similar species, which are distinguished by counting the number of petals. San Diego tarweed, Hemizonia paniculata always has 8 petals; slender tarweed, Hemizonia fasciculata always has 6 petals; and sticky tarweed, Holocarpha virgata ssp. elongata has 3-6 petals.
http://tchester.org/srp/plants/how_to_id/31.html
Comments and feedback: Tom Chester
Last update: 16 October 2003.