Acaena
The burs, from New Zealand, form creeping mats of ground covering foliage, the stem rooting as it goes. Best in a well drained soil in full sun. Very useful and long lived front of border plants. We grow ours mainly in our dry garden.
The burs, consisting of seeds with long spines, are designed to adhere to animal fur etc for dispersal, so these plants have a high risk of inadvertently escaping the garden. They can become very invasive especially in dry habitats such as sand dunes, and exclude native plants in such sites because of their mat-forming dominance.