Chamomile

This plant is usually just known as Anthemis cupaniana It's often confused with the slower growing, shrubbier Rhodanthemum hosmariense....Read Morer />
In the milder parts of the UK this plant makes one of the fastest evergreen ground-covering plants there is - although it can be a bit straggly. It's a good choice if you cannot grow osteospermums as ground cover.
It spreads by long trailing stems which constantly produce new shoots, and can easily reach 3 - 4 feet across in a year. The stems can be gently pegged down to encourage rooting, or cuttings can be root directly into the ground. It is not invasive and can easily be cut back within bounds. The stems are quite delicate and snap easily.
It's said to flower most of the summer, but I've found it only flowers in early summer. They are about one and a half inches across (4cm), white with a bright yellow centre. The silvery, divided leaves are quite attractive and evergreen.
It needs reasonably well-drained soil and a fairly sunny position.