Easily confused with : Wavy Bittercress, but, paradoxically, that can have hairy stems whereas Hairy Bittercress doesn't (but it does have hairy leaves). Also, the seed-pods of Hairy Bittercress usually over-top the flowers, whereas those in Wavy Bittercress are usually lower than the top-most flower. Wavy Bittercress has nominally six stamens whereas Hairy Bittercress has but four. The number of stem leaves also differs: Wavy Bittercress has between four and ten whereas Hairy Bittercress has only one to four stem leaves. Although the leaves of Wavy Bittercress are hairless, those of Hairy Bittercress only might possibly be hairy.
Not to be confused with : Hairy Rockcress,
Hairy St John's Wort,
Hairy Mock Orange,
Hairy Garlic or Hairy Tare, etc [plants with similar names].
Hybridizes with : Wavy Bittercress (Cardamine flexuosa) to produce
Cardamine × zahlbruckneriana (Cardamine flexuosa × hirsuta) but luckily this is present in but very few locations, and is not present where the above photographs were taken.
Some similarities to : Hairy Rockcress
Flowers over a longer time period than that of Wavy Bittercress, from February to November, and all year in mild winters.
Habitat: bare ground, usually damp, including dunes, or rocks, walls and especially garden beds. Ubiquitous almost, but not quite, throughout the UK.