I've so far spotted two of these mysterious blue botanical plaques on my regular commute, but two implies that there may be a multitude, appended to convenient railings beside scraps of land where flowers grow wild:
It's an interesting question, whether the unloved weeds of interstitial urban spaces constitute heritage. I suppose the seeds pass on from generation to generation (both Herb Robert and Goldenrod, here respectfully allowed their Latin names, are colossally prolific self-seeders) but in neither place does the particular plant named grow in massive proliferation (the creek by Oxford City College being more notable for its reeds than its Goldenrod, and the churchyard being rather more noticeable for its lovely mass of snowdrops) leading me to wonder if the plaque might celebrate a single plant, in which case the point might be about evanescence, and the delight of affording something as ephemeral as the flowering of a weed with full municipal celebration. And now maybe I'll notice the Herb Robert and the Goldenrod, when it comes back this year.
I finished the last of this, my second attempt to find a good gardening moisturiser, last week. It looked very promising: "multi-defence ... protects against the five major daily aggressors" but when it goes on you can feel a certain thinness, and it fades into your skin almost at once. The five main aggressors that damage your skin (according to the packaging) are sun, heat, cold, pollution and wind. Presumably if it's raining, you're just supposed to stay indoors! On the whole, I'm not sure it's really solving the right problems, even for an urban gardener like myself. I'd list seven aggressors: sun, wind, rain, mud, cold, slugs and scratches. Pollution is more of an issue for my lungs than my skin, and I don't think I need to moisturise my lungs.