Irish moss

Irish moss: how do you recognise it?

Habit

Dense, moss-like cushion only about 3 cm tall; spreads to 20–30 cm wide.

Foliage

Very small, needle-like leaves in rosettes; bright to fresh green. ‘Aurea’ has yellow-green foliage.

Flower

Very small white stars with five petals on thin stalks, from June to August.

Evergreen

Stays green all year and gives a green carpet even in winter.

Roots

Shallow and fibrous; the stems root into the ground themselves, so the cushion slowly gets bigger.

Flowering: June–August · Plants: March–May and September

Why grow it?

• Forms a soft green carpet that stays green all year.
• Ideal between paving, stepping stones and in the joints of a terrace.
• Tolerates light foot traffic, so you can walk over it from time to time.
• Covered in small white stars from June to August.
• Suppresses weeds and keeps the soil between the stones covered.
• Stays low: only 2–3 cm tall, ideal for edging a bed.

Irish moss: where does it grow best?

• Sun to partial shade; in full midday sun it scorches quickly, so lightly shaded in the afternoon is better.
• Free-draining, sandy to loamy soil, acid to neutral; it dislikes wet clay.
• Normally moist: the soil must not dry out, but must not stay waterlogged either.
• Tolerates occasional walking, but not heavy daily foot traffic.
• Allow 15–20 cm between plants; you need about 25–45 plants for 1 m².

Light

Sun and partial shade

Soil type

Sand or loam

Acidity

Acid or neutral

Moisture

Normal

Size

0.03 m tall, 0.3 m wide

Hardiness

Hardy (to -25 °C)

Goes well with

• Creeping thyme: A low cushion planted between stepping stones, wonderfully scented when you step on it.
• Saxifrage: Mossy cushions with spring flowers, in the same spot.
• Crocus: The little bulbs push up through the green carpet in early spring.
• Stonecrop: A low, drought-tolerant ground cover next to the carpet.

Irish moss: when and how to plant it?

Plant in March–May and September.

1. Plant in March–May or in September, when the soil is not frozen.
2. Clear the soil or joints of weeds thoroughly; they are hard to remove once the carpet is dense.
3. Work some sand into heavy soil or the joints for better drainage.
4. Space plants 15–20 cm apart and firm them lightly, with the top just above the soil.
5. Water in at once and keep the soil moist for the first few weeks.

Care

Water

Water in dry weather, especially in the first year and in sunny spots. The carpet turns brown if it dries out.

Feeding

Not needed on normal soil; a little compost or organic fertiliser in spring if wished.

Weeding

Pull weeds out by hand early; do not let them grow among the cushions.

Top-dressing

In spring, sprinkle a thin layer of sand over the carpet and brush it between the plants.

Mulching

Do not mulch: a layer of mulch smothers the carpet.

Tip: Plant it between paving and stepping stones, keep it moist in dry summers and choose a spot without full midday sun. Cut out brown patches in spring and fill with pieces from the edge.

Irish moss: when to prune it?

When: You do not really prune it; in March–April you tidy the carpet.

How:

• Cut out brown, dead patches with scissors or pull them out by hand.
• Trim the edges with scissors if the carpet spreads too far.
• Fill bare patches with pieces taken from the edge of the carpet and replant them.

Pruning calendar and basic rules

Propagation

Division

In spring or early September, lift pieces with roots from the edge of the carpet, divide them into plantlets of a few cm and plant them 10–15 cm apart. Keep moist.

Seed

The seed is very fine: in spring, scatter it on the surface of moist seed compost and do not cover it. It germinates slowly.

Irish moss: how does it get through the winter?

Hardy to −25 °C.

• Hardy down to about −25 °C: no protection is needed, even in hard Belgian winters.
• It stays green in winter; after a very wet or hard winter, brown patches may appear, which you cut out in spring.
• In a pot or trough: put it in a sheltered spot and do not let the compost dry out or become waterlogged.

Diseases and pests

• Brown patches: Drought or full midday sun turns the cushion brown. Water, give light shade and cut out dead parts.
• Winter rot: In wet, heavy soil the carpet rots away. Improve drainage and work in sand.
• Weeds: Grass and weeds grow quickly through the carpet. Weed early by hand.
• Bare centre: The centre of an old cushion sometimes dies off. Cut it out and fill with new pieces from the edge.

Through the year

• March: Plant. Tidy the carpet: cut out brown patches.
• April: Plant. Sprinkle a thin layer of sand. Weed.
• May: Plant. Water in dry weather.
• June: Flowering starts. Water in dry weather.
• July: Flowering. Water in dry weather, especially in sun.
• August: End of flowering. Water in dry weather.
• September: Plant or divide. Trim the edges.
• October: Weed. Fill bare patches.
• December: Rest. The carpet stays green.

Did you know?

• It is not a true moss: Irish moss is a flowering plant of the pink family, recognisable by its small white flowers.
• The name ‘Irish moss’ is also used in cooking and the food industry for a seaweed (Chondrus crispus), a completely different species.
• The species name subulata means ‘awl-shaped’ and refers to the small pointed leaves.