Habit Foliage Flower Seed pods Seedlings Roots Host for aphids
Bittercress (Cardamine hirsuta) has unique foliage
that makes it is easy to identify among other container weeds. The
leaflets on the foliage have a club shape, evident here on even small
seedlings. Leaves of bittercress seedlings are often simple, while
leaves that develop later are generally compound.
Bittercress leaves are pinnately compound, with each leaflet
having 3 to 5 obtuse lobes. Each leaf generally has 4 to 8 leaflets
alternately arranged along the rachis.
The image above is typical of lower foliage, or foliage that makes
up the rosette. The image below is more typical of foliage that emerges
higher up the stems and closer to flowers. Foliage higher on the
stem has the same pattern of lobes, however, the leaflets are longer and
more narrow compared to foliage of the rosettes.
Hairy bittercress gets its name from the fact that the stem and foliage
are pubescent (or hairy). However, in my experience, the hairs are
difficult to see with the naked eye. But if you look closely, you
can see them, particularly on the stem. The image below (when enlarged)
shows the small hairs fairly clearly.
It is my experience that Little Western bittercress (Cardamine oligosperma)
is often confused with hairy bittercress. In talking with a plant
taxonomist, I learned that the difference between C. hirsuta and
C. oligiosperma is in the size of the seed, and this is the only
way to distinguish the two. Suffice it to say that they are very similar
in appearance, and that control (cultural and herbicidal) for one species
will be the same for the other.
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