Sagina subulata

Sagina subulata, known as Heath Pearlwort, forms a very low, dense carpet reminiscent of moss, spreading by rooting in place, and covering itself with tiny white flowers in late spring. This evergreen perennial works wonders in rock gardens, in the gaps between paving stones and walls, in moist but well-drained soil, in full sun or partial shade.

Sagina subulata belongs to the Caryophyllaceae family, like the twenty or so species that make up the genus. It is a small perennial plant native to Western Europe and temperate regions of the Northern Hemisphere. This plant with running roots forms a low, dark green, evergreen carpet, 3 to 5cm (1 to 2in) tall, colonizing the ground by rooting tiny, stoloniferous and branched stems that are 1 cm (1in) long, eventually forming dense cushions over 25cm (10in) in diameter. Its growth is quite slow. In late spring, from May to June, the carpet is covered in tiny white flowers, 4mm (1in) in diameter.

This 'carpet plant' has the advantage of being able to cover an area where grass does not grow well, thanks to its running roots. It grows to form a uniform carpet that does not need to be mowed, tolerates wet soils, and for these reasons, knawel is often used as a substitute for grass. However, it does not tolerate heavy foot traffic well. It is also a popular species for use in mosaic gardening, commonly used in rock gardens, like baby's tears, or to fill the gaps between large paving stones and walls. It is also welcome in Japanese-inspired gardens. Paired with hostas, ferns, or used as a backdrop for a bed of fuchsias, it will be truly charming. It should be noted that subulate pearlwort does not tolerate dry or hot conditions, so it is best reserved for cool and shaded areas.