Heath pearlwort, sagina subulata: a white-blooming grass substitute for lawns

Ground cover with heath pearlwort, in full bloom

Heath pearlwort facts

Botanical nameSagina subulata
Family – Caryophyllaceae
Type – Perennial

Height – 1 to 2 inches (3 to 5 cm)
Planting density – 25 to 30 plants per sq. yard (m²)
Exposure – part shade to full shade
Soil – cool, any type, even poor

Flowering – summer
Foliage – evergreen

Introduction to heath pearlwort

Considered an invasive by some, and an ornamental perennial by others, heath pearlwort is yet another of those controversial topics that involve weeds. Nonetheless, one thing is sure: it’s a magnificent ground cover plant.

Sagina subulata is a short grass-like perennial that spreads thanks to runners. These branch out constantly, helping it cover surface in all directions. The dark green clump is technically a cluster of long, thin leaves that, botanically speaking, are called “awl-shaped” since they taper to a point. When you look at them closely, they strongly resemble small conifer needles. Thanks to these peculiar leaves, heath pearlwort is very similar in appearance to moss.

In spring, hovering just above the leafage, white flowers appear. They bloom in incredible abundance, and if the weather is warm enough, you’ll even catch a whiff of its delicate fragrance. Heath pearlwort also comes in a special ‘Aurea’ variety that has beautiful gold-yellow foliage.

Planting heath pearlwort

When you purchase it, heath pearlwort is often sold in rolls or in nursery pots, each one with a small one-inch square growing already (2-3 cm). When planting, space these about 6 inches apart (15 cm).

It’s important to think a bit about where to place your heath pearlwort: it’s best to find a spot in part shade where the soil stays relatively cool. Even if the soil is poor, it isn’t a problem, quite the opposite. Indeed, if it finds too much food and nutrients, the plant won’t stay lush and compact.

Planting it isn’t difficult, but you do have to fully pull weeds out beforehand. This has two purposes: first, you’ll protect your plant from undue competition, and second, weeds would mess with the beautiful aesthetics of your heath pearlwort.

The ideal planting period is, as often, the beginning of fall in order for roots to settle in well. Once you’ve cleared the small plot, simply:

  • Dig a hole 2 to 4 inches (5 to 10 cm) deep.
  • Settle the pearlwort in the hole after having pulled a few roots out from the clump to spread them out.
  • Water and press the whole area down with a small board or plank.

Caring for heath pearlwort

Caring for pearlwort helps have healthier plants than this sickly oneOnce properly settled in, Sagina subulata doesn’t require much special care:

  • watch over soil moisture in summer, and water regularly (but in small quantities) during drought.
  • If you’ve planted your heath pearlwort from large lawn-like rolls, do go ahead and run a heavy roller across it so that it stays compact and so that the plant stays in close contact with the soil (otherwise it will turn yellow in some patches).
  • Remember to pull weeds out from time to time, with a cultivator or even simply a fork, so that your plant stays intact.

Propagation:

Heath pearlwort can be propagated through clump division: cut small squares out from the outer portions of the plant, and put them in the ground as described in the planting section above. This lawn replacement plant self-sows spontaneously and might quickly turn invasive.

This is precisely what some gardeners hate about it, and why they call it an undesirable weed. Nonetheless, it’s possible to let these sprouts grow up a bit, and then you can transplant them to a more auspicious part of your garden.

Diseases and pests:

Heath pearlwort doesn’t get sick. However, you might discover aphids and spider mites hiding among the leaves.

Uses in landscaping

Landscaping with heath pearlwortSagina subulata is perfect to fill in slits between tiles and spaces in rock gardens. It’s also possible to use them to line flower beds or along the edges of walkways, but the self-sowing seeds will quickly become a hassle to manage.

If your lot allows for it, why not try to integrate your Irish moss (as it’s also called) when re-sowing your lawn, planting it together with dwarf clover and the more traditional grassy species.


Image credits (edits Gaspard Lorthiois):
CC BY-SA 2.0: mrburnes99
CC BY 2.0: K M, Dr Mary Gillham Archive Project