There are three species of Skullcap which grow in the UK, however one called Somerset Skullcap is incredibly rare and only grows in a couple of locations, one is a wall in Wells!!, so I will deal with the other two and even these are not that common.
First of all the commoner of the two which is simply known as Skullcap, Scutellaria galericulata, sometimes it is called Common Skullcap, Marsh Skullcap or even Hooded Skullcap, take your pick. I recently came across some in woods in Worcestershire where I was looking for some Violet Helleborines. I found lots of Broad-leaved Helleborines which I initially thought were the Violet species and I also found some Skullcap growing in a wet ditch like place at the side of a path. I did not take too many photographs of it which was a shame as I was on a mission to find the Violet Helleborine, which I never did.
Skullcap flowers from June to September and it has a typical Labiate style of flower shape, quite similar to Bugle except that the flowers are normally produced in pairs at each node whereas with Bugle there is normally a ring of about six so pointing out in every direction. The flowers are also a similar blue colour.
It is a low creeping or spreading plant and usually found in wet areas along the edge of ponds and ditches, it seems to be also tolerant of some shade so is found in woodlands. Predominantly it is found up through the central regions of the UK and becomes less common on the East and West coast areas.
You might wonder why it is called Skullcap…. It comes from the scientific name and scutella means a small dish. The flower shape if you invert it has a vague resemblance to a small dish. I suppose the traditional skullcap as worn by the Jewish is also like a small dish. So there you have it for what its worth. It is also used a lot in traditional herbal medicines, used for a variety of ailments including rabies !
The other species of Skullcap is called Lesser Skullcap, Scutellaria minor and this also lives in wet areas but is perhaps more often found in woodlands, and it does not like lime. In the area where I live I have read that it is often found in regions where there was open cast coal mining. I visit lots of such areas in the Forest of Dean, many of them are now quite beautiful and rich wild life resources in complete contrast to what they were 50 or so years ago. However I have only once come across a Skullcap species in the forest and it was not growing in such an area. It was simply growing at the side of one of the cycle paths in a central region close to Speech House.
Lesser and Common Skullcap do evidently hybridise. The pure species has pink flowers as opposed to the Blue of the Common species.
Here is a photo of Lesser Skullcap which was posted on the British Wildflower FB page, unfortunately I do not have the owners name and thus cannot credit the photo. If it is yours and you are looking at it do contact me and hopefully you will be OK with me using it??