Species account: Hairy Bittercress / Cardamine hirsuta

This species (as we have discovered ourselves) can very easily be confused with Wavy Bittercress and both species are common and widespread. For a start a well known flower guide states Hairy Bittercress has straight stems, whilst Wavy Bittercress has wavy ones. The species we have growing in our garden clearly has a wavy stem (see below)…

In addition the plant we have isn’t particularly hairy either. Whilst it does have some hairs on the upper surface of the leaf and stem, they are very sparse and need close examination to really notice them.

So with a wavy, almost non-hairy plant we naturally assumed we had Wavy and not Hairy Bittercress. So what made us change our mind…

In the search for the first plant to flower in our garden during 2022 we had only to wait until the 3rd of January to note our “Wavy Bittercress” was in flower…….

…but wait! our flower guide is very clear, whilst Hairy bittercress can flower throughout winter if conditions are mild (which they most certainly have been), Wavy Bittercress however will not flower before April.

Initially we believed the book may have had this wrong but it goes on to state two further characteristics that confirm the species we have is in fact Hairy Bittercress. First, the seed pods in Hairy Bittercress extend beyond the flower itself, not usually the case with Wavy, but certainly the case with our specimen.

A check online does suggest this seed pod characteristic cannot always be relied upon, but the number of stamens within the flower is a surer bet, with 4 present in Hairy and 6 in Wavy, although really numbers can vary and several flowers should be checked.

Our specimen clearly has four stamens. We checked other flowers in the garden and all had four.

So this was a case of misidentification based on assumptions made due to the flowers common name. Our wavy non-hairy plant is indeed Hairy and not Wavy Bittercress. We may well have both species and we will check later in the year for Wavy Bittercress. But for now it has been removed from the species list and replaced by Cardamine hirsuta.

Whilst confirming this plants identity, some online sources, in fact just about everything we read, warns this species can quickly take over the garden if not controlled. This is certainly something we need to be on the look out for. It has already formed dense patches around the Wildlife Hotel and Wetland areas created in the autumn where the ground was disturbed. And may have to join Large Bindweed, Clevers and Herb Robert on the naughty list of species to keep in check, along with the creeping buttercup we notice has been spreading in the lawn since the flooding last summer.

On the plus side you can bung this in a salad to give it a mustard edge.

DC 04/01/2022