How to Grow Sandwort, Irish Moss, Scotch Moss and other Arenaria Plants

The common names for the Hardy perennial Arenaria include Irish Moss, Scotch Moss and Sandwort.

The plant that does not fair well in humid conditions.

It typically flowers from the late spring until the early summer months.

Arenaria
Arenaria franklinii by Matt Lavin.

Description of Irish moss (Arenaria)

Arenaria are low growing plants that reach a height of 30 cm at the most. Their leaves make an evergreen cushion that has multitudes of pink or white flowers when in bloom in the late spring. Due to their small size they make ideal plants for rockeries and to fill the gaps in between paving stones and in dry stone walling.

Wood Sandwort
Wood Sandwort by gmayfield10.

Arenaria Growing and Care Guide

Common Names: Sandwort, Wood Sandwort, Fendler's Sandwort, Also Sandwort: English, Marsh, Blunt-leaved, Large Leaved, Mountain, Ballhead, Bear Valley); Scotch moss; Irish Moss
Life Cycle: Hardy Perennial.
Height: 5 to 11 inches (12 to 28 cm).
Growing Region: Zones 3 to 8 (species dependent).
Flowers: Late Spring through to Early Summer.
Flower Details: Pink or White.
Foliage: Evergreen.
Sow Outdoors: Surface. Early Spring before last frost, or late Autumn. Spacing 3 to 4 inches (7 to 10 cm).
Sow Indoors: Use Peat pots . Germination time 1 week to 5 weeks. Temperature 55 to 65°F (13 to 18 °C), 7 or 8 weeks before expected last frost. Transplant outdoors following the last frost.
Requires: Full Sunlight (Partial shade in very hot areas), Good drainage, Soil pH 6 to 8, Gritty, Sandy soils. Regular watering, Light feed, best grown from seed but can be propagated by division at the start of spring or by taking cuttings in the summer.

How to Grow Arenaria

If sowing seeds directly outside it is best to sow Arenaria species such as Irish Moss and Sandwort seeds on the surface in the early spring, when there is still a possibility of a late spring frost; alternatively the seeds can be sowed out in the Autumn. However, as seeds are sown on the surface, they may be subject to predation from hungry birds through the winter.

If you prefer to grow Arenaria seedlings indoors first then they should be sown about 7 weeks before you plan to put them outside (after the last frost of spring). Germination typically takes from a week to a month and should be performed at a temperature of around 13 to 18 Celsius.

The seedlings should be planted in full sunlight, they will however still thrive in partial shade in very hot summers. They prefer a soil that is well drained, with a pH of between 6 and 8 and sandy or gritty in nature.

Caring for Arenaria

Arenaria is easy to look after, though it may require regular watering in the heart of a very hot summer. It may also be necessary to give them a light feeding if required. the best way of propagating the plants is by seed, though cuttings may be taken in the Summer.