The very smallest variety of Sedum, with the biggest territorial attitude.
Sedum acre is very aggressive, spreading by seed and dropped leaves, so only plant where this isn’t an issue.
Bright lemon yellow flowers completely cover it in summer, attracting many beneficial insects and bees.
Use in containers and weed it out if it roots into unwanted areas. It can spread by vegetative means (it roots from any broken off portion, even an individual leaf) and by seed.
It's very pretty, as you can see from the picture, despite its roaming nature.
Sedum acre is fairly invasive, and tends to root into lawns where it persists. Weeding it doesn't get rid of it as the tiny leaves fall off at the slightest touch - making even more of it as each piece roots.
Learn to live with this little thug, as it's invasive.