- Group 1Lycophytes, Monilophytes
- Group 2Gymnosperms
- Group 3Monocots
- Group 4Woody angiosperms with opposite or whorled leaves
- Group 5Woody angiosperms with alternate leaves
- Group 6Herbaceous angiosperms with inferior ovaries
- Group 7Herbaceous angiosperms with superior ovaries and zygomorphic flowers
- Group 8Herbaceous angiosperms with superior ovaries, actinomorphic flowers, and 2 or more distinct carpels
- Group 9Herbaceous angiosperms with superior ovaries, actinomorphic flowers, connate petals, and a solitary carpel or 2 or more connate carpels
- Group 10Herbaceous angiosperms with superior ovaries, actinomorphic flowers, distinct petals or the petals lacking, and 2 or more connate carpels
Species of Populus display leaf blade heterophylly along the branchlet over the growing season. Those leaves that overwinter in the winter in bud and expand in the spring are called first leaves (or preformed) vs. those leaves that are produced later in the season as the growing shoot continues to expand, which are called new leaves (or neoformed). As these leaves can vary in size, shape, and number of marginal teeth, it is important to collect both types when possible. Greatly enlarged leaves produced on vigorous shoots are not accounted for in the identification key. Reference: Eckenwalder (2010).
Show photos of: Each photo represents one species in this genus.