Thanks for contacting Toronto Master Gardeners to help with your plant identification. This appears to be creeping spurge (Euphorbia myrsinites), also known as donkey-tail spurge, myrtle spurge or blue spurge. It’s a low-growing, succulent species of spurge that tolerates drought and poor, rocky soils.
Euphorbia myrsinites produces a milky sap that can irritate skin and eyes in both humans and pets, so you should always use gloves if you are going to handle it. If it’s currently located near a child’s play area, consider moving it to another location in the garden.
For more information on this attractive addition to borders and rock gardens, please visit the plant profile at the Missouri Botanical Garden.