Ac
- Acalypha
- N Acalypha virginica — Virginia copperleaf, Virginia threeseed mercury
- Acanthospermum
- X Acanthospermum hispidum — hispid greenstripe
- Acer
- X Acer campestre — hedge maple, field maple
- X Acer ginnala — Amur maple, ginnala maple
- N Acer negundo — Manitoba maple, box-elder, ashleaf maple
- N Acer nigrum — black maple, black sugar maple, rock maple
- N Acer pensylvanicum — striped maple, moose maple, goosefoot maple
- X Acer platanoides — Norway maple, Schwedler maple, crimson king maple
- X Acer pseudoplatanus — sycamore maple, Scottish maple, great maple
- N Acer rubrum — red maple, swamp maple, scarlet maple
- N Acer saccharinum — silver maple, soft maple, white maple, silverleaf maple, river maple
- N Acer saccharum — sugar maple, hard maple
- N Acer spicatum — mountain maple
- N Acer × freemanii (A. rubrum × A. saccharinum) — Freeman's maple
- Achillea
- X Achillea filipendulina — fernleaf yarrow
- N Achillea millefolium subsp. borealis — northern yarrow
- N Achillea millefolium subsp. lanulosa — woolly yarrow
- X Achillea millefolium subsp. millefolium — common yarrow, milfoil
- X Achillea ptarmica — false sneezewort, white tansy, sneezewort yarrow, pearl yarrow
- N Achillea sibirica — Siberian yarrow, many-flowered yarrow
- Acinos
- X Acinos arvensis — mother-of-thyme, spring savoury, basil thyme
- Aconitum
- X Aconitum napellus — garden monk's-hood, helmet flower, Venus' chariot, aconite
- X Aconitum variegatum — Manchurian monk's-hood
- X Aconitum × bicolor (A. napellus × A. variegatum) — hybrid monk's-hood, two-coloured wolf's-bane
- Acorus
- N Acorus americanus — sweetflag
- X Acorus calamus — European sweetflag
- Acroptilon
- X Acroptilon repens — Russian knapweed
- Actaea
- N Actaea pachypoda — white baneberry, doll's-eyes
- N Actaea rubra — red baneberry
- N Actaea × ludovici (A. pachypoda × A. rubra) — hybrid baneberry
Read more about this topic: List Of Canadian Plants By Genus