There are four and in order of abundance we have Hairy Bittercress C. hirsuta, then Wavy Bittercress C. flexuosa, Large Bitercress C. amara and the least common is Narrow-leaved Bittercress C. impatiens.
Hairy Bittercress is a very common garden weed… as the saying goes, if I had a pound for every one I have pulled up etc etc. They are as it happens fairly easy to pull up as opposed to some weeds. However if you don’t get them early then as you pull them up the seed pod bursts and a shower of little seeds are dispersed thus ensuring that you will have the pleasure of removing another generation of Bittercress in a month or so time. The key characteristics of this species which helps to differentiate it from the others is a straight stem and seed pods which develop and grow so that they extend well above the flowers which are still blooming. The little flowers have 4 stamens, but you will probably need a hand lens to see them. It can flower almost throughout the year. The plant is quite small growing to about 15 cm high..
Wavy Bittercress is quite similar to Hairy Bittercress except that the stem grows in a zig-zag fashion,thus the name wavy. Also the seed pods tend not to grow up so high above the remaining flowers. The flowers look very similar to Hairy Bittercress but they have six stamens. Flowering is more restricted being from April through to September. This is less of a garden weed and is more likely to be found in woodland, it does like wet muddy or boggy ground. However the Bittercress I have in my present garden is Wavy Bittercress. It is slightly hairy, you can see hairs on the stems sometimes it can be quite hairy. Yes the other one is called Hairy Bittercress and this is the one that is is hairy…..do not ask me why. It has a fairly strong smell of watercress. You notice the smell when you have pulled up several plants, it is from the damaged leaves. I don’t think the flowers produce any scent. This can grow up to almost 30 cm
Large Bittercress. I have no experience of this, I am on the look out for some but no luck so far. It has larger flowers, looking more like Cuckoo flower. also the anthers are purple. This is a bigger plant growing to 60cm and you do find it in woodlands.
Narrow-leaved Bittercress, this is by far the least common of the four being only found in parts of central England and a few other locations but not in Scotland and quite restricted in Wales and Ireland. It has very small petals, sometimes they are absent, the anthers are yellow sow the effect is that the tiny flowers look yellow. It is hairless and has deeply toothed leaves This is also a woodland species
I first saw this on a visit to Lady Park Wood…. well the perimeter of Lady Park Wood as it is a fenced off reserve which you can only visit with special permission. Recently I have found several plants in Blakes Wood near Staunton.