Once botanical research has identified species that might be in peril, political, social, and economic decisions are made to determine which species will receive conservation attention. This excellent guide is available without charge from any of the contributing agencies. Plants categorized as threatened under the ESA include two cacti, three mustards, and an orchid. Specimens of all of these protected plants can be found in the CSU Herbarium. The families above are also well-represented in the common state flora, but such is not always the case.
Some families have a disproportionate number of rare members.
All Colorado members of the fern-like family Ophioglossaceae, for instance, are rare and endangered. Generalizations about rarity at levels below family are also difficult to make. California, with its diverse ecosystems, has by far the greatest number of rare plant species outside of Hawaii, with Florida next in line. Scientists are discovering that rare plants fit many different descriptions. Colorado's rare flora affords a fascinating opportunity to explore a wide diversity of plant families.