Ce
- Ceanothus — New Jersey teas
- Ceanothus americanus — New Jersey tea, redroot, white snowball, mountainsweet
- Ceanothus herbaceus — narrowleaf New Jersey tea, prairie redroot, inland ceanothus
- Celastrus — bittersweets
- Celastrus scandens — climbing bittersweet, American bittersweet
- Celtis — hackberries
- Celtis occidentalis — sugarberry, northern hackberry, false elm, common hackberry
- Celtis tenuifolia — dwarf hackberry Threatened
- Cenchrus — sandburs
- Cenchrus longispinus — longspine sandbur
- Cephalanthus — buttonbushes
- Cephalanthus occidentalis — common buttonbush
- Cerastium — mouse-ear chickweeds
- Cerastium alpinum — alpine mouse-ear chickweed, alpine chickweed, woolly alpine chickweed
- Cerastium arvense subsp. strictum — field mouse-ear chickweed, meadow mouse-ear chickweed, prairie mouse-ear chickweed (other subspecies, including the type subsp. arvense, are considered introduced)
- Cerastium brachypodum — shortstalk mouse-ear chickweed
- Cerastium nutans — nodding mouse-ear chickweed
- Cerastium velutinum — long-hairy chickweed
- Ceratophyllum — hornworts
- Ceratophyllum demersum — common hornwort, coontail
- Ceratophyllum echinatum — spineless hornwort
Read more about this topic: List Of Canadian Plants By Genus C