Arenaria species - Thyme-leaf Sandworts
Arenaria are patch-forming plants. They have almost stalkless leaves which can be grey-green and are roughly hairy with cillate borders. The petals are shorter than the acute sepals.
Arenaria serpyllifolia - Thyme-leaved Sandwort
This is the commoner plant and is larger - flowers 5 - 8 mm in diameter. The sepals are broader, ovate-lanceolate and the capsules are flask-shaped with curving sides. The seeds are brown-black.
Arenaria leptoclados - Lesser Thyme-leaved Sandwort
This is less common and more slender. The flowers are only 3 - 5 mm in diameter and the sepals are lanceolate. The capsules are conical with straight sides and the seeds are lighter brown.