The nursery industry calls it Green Carpet and well they should. This lovely bright green creeper spreads effortlessly in all directions filling up to two feet per plant. A fairly flat plant with a maximum height of about two inches, it has one long tap root (as opposed to many surface roots like a Creeping Thyme) which helps with water conservation. It likes full sun but it can take partial shade. Related to Carnations and Dianthus (or Pinks), the lowly Green Carpet must be the black sheep of the Caryophyllaceae family because the tiny flowers are so small that they are easy to miss. They are also close to the same color of the leaves which makes it hard to see them.
The vibrant green of Herniaria perks up gray leaved plants (like Lavenders) and offsets darker green plants like Hyssop, Myrtle and Germander. It is soft to walk on and can take quite a bit of foot traffic, as long as it is not continual. Trailing down the side of a container, it adds interest and color to container plantings.
Sunset Western Garden Book rates this plant as hardy in all Sunset Zones. We have seen it rated from USDA Zone 5, but most literature suggests Zone 7.
Herniaria, a native of Europe, was used in the past for (I know you guessed, already) hernias. But, not hernias like we think of them today, but, rather hernias of the skin (like a cut). In this capacity, it was known as Rupturewort.
These are plug trays of Herniaria ready for sale. These trays hold 128 of all the same plant. They are a great low cost way to fill a lot of space. Each cell is 3/4 of inch by an inch. Check here to see if Herniara Plug Trays are available.