Green alkanet: that mystery plant, revealed

Is it borage? Is it forget-me-not? No, it's green alkanet!

Is it borage? Is it forget-me-not? No, it's green alkanet!

If you're a member of more or less any Facebook gardening group, you've probably seen a post in the past month that reads something like this:

"I've seen this plant in my garden/on my allotment/on a grass verge, can anyone tell me what it is/whether it's a weed?"

The comments below will go something like this:

"It's borage."

"Forget-me-not, I think."

"No, it's green alkanet, it's a dye plant."

"Green alkanet, it's a horrendous weed."

"Borage. Or maybe comfrey."

"I think it's Brunnera."

"Forget-me-not."

"Can you eat it?"

The plant in question is almost always green alkanet (Pentaglottis sempervirens). It does have piercing blue flowers not dissimilar to forget-me-nots and borage and hair leaves that look a bit like both these plants but also comfrey, and indeed they are all part of the Boraginacae family, but once you get to know this plant it's easy to spot: the blue is sharper than a forgot-me-not - really really bright, the leaves are too big for forget-me-nots and the flowers don't have the same star shape as borage.
Why is this plant appearing so often in social media? I think it's the blue flowers that do it: it really does stand out, even to people who are usually "plant blind"*. It's bemoaned as a weed by many: its deep, brittle tap root makes it tricky to eradicate completely, a bit like dock, and doesn't really even serve as a wild edible, although the flowers are edible they don't add much other than a beautiful garnish.

Green alkanet taking over a front garden... what's not to like?

Green alkanet taking over a front garden... what's not to like?

Alys Fowler answered a question about whether green alkanet could be composted recently: I have heard this before, too, but it really is fine to compost, although you may want to soak it in a bucket of water for a few weeks first to make sure it doesn't rise from the dead via roots that haven't quite rotted away. But what about its worth as a dye plant? Another red herring, sort of. It's dyer's alkanet (Alkanna tinctoria) that's used to produce a purple/red dye, although I understand a weaker dye can be obtained from green alkanet's roots.
So what is green alkanet good for? For some it's a weed - I let it grow around my pear tree but try not to let it spread about. It will grow where little else will, and the flowers are pretty and come in a long succession from spring to Autumn: if you hack it back to the ground it will return, unperturbed. Finally, and most importantly, the flowers are popular with pollinators, just like its tamer relative lungwort (Pulmonaria).

*I think it's great that people can now use Facebook groups to expand their knowledge of plants, but I find some of the questions asked breathtaking In the knowledge gaps they expose - like the young woman who was weeding around the onions on her family allotment and wondered what the little red and white things she was digging up were - a glance at the picture showed radishes: and this is someone who is engaged enough with plants to be working on an allotment. Social media can be a real boon for beginner gardeners, particularly younger people who may not feel comfortable asking advice from the "old hands" on the plot. Mostly people commenting are doing their best, and are happy to help identify plants, but sometimes (often) they get it wrong: a lot of people confidently yet wrongly identify green alkanet as borage or forget-me-not. The "wisdom ofo the crowds" does eventually prevail, however, but it's certainly worth waiting until a dozen or more people have commented to see what consensus has been reached.