Wednesday, July 7, 2010

Give Me Pearlwort

"Some people are flower lovers.
I'm a weed lover," wrote English poet Norman Nicholson.

Weeds don't need planting in well-drained soil;
They don't ask for fertilizer or bits of rag to scare away birds.
They come without invitation;
And they don't take the hint when you want them to go.
Weeds are nobody's guests;
More like squatters.

Coltsfoot laying claim to every new-dug clump of clay;
Pearlwort scraping up a living from a ha'porth of mortar;
Dandelions you daren't pick or you know what will happen;
Sour docks that make a first-rate poultice for nettle-stings;
And flat-foot plantain in the back street,
gathering more dust than the dustmen.

...You can keep your flowers.
Give me weeds!

Nicholson's argument is compelling.  Just yesterday I spied a tidy clump of pearlwort growing beside an asphalt walk as a fellow was shoving a lawn mower over the grass around it.  It occurred to me that he might be better off if he planted his entire yard in pearlwort.

Pearlwort is of the genus Sagina which includes about 90 species native to Europe and North America.  It's a member of the Caryophyllaceae family which includes dianthus, carnations and campions.

Though most of the pearlworts are attractive, Sagina subulata is the one most commonly grown as an ornamental.  The green form is also known as Irish Moss while the yellow cultivar, Sagina subulata 'Aurea', is often called Scotch Moss.  Neither are native only to Ireland or Scotland.

Pearlwort is most often grown as a perennial, evergreen ground cover.  Mature height is only about 1".  It spreads to 12".  Leaves are needle-shaped and about .4" long.  Tiny white flowers, produced spring through summer, are about .25" diameter and borne on stems less than 1.5" long.  Its habit is dense, so it chokes out weeds once established.  Pearlwort also tolerates moderate foot traffic.  You can see it makes a perfect lawn substitute, especially for small to medium lawns.  Plant pearlwort between stepping stones, beside walks, in rock gardens and at the fronts of borders.  Eco-conscious gardeners should consider it for their green roofs.  Container gardeners will find it useful as a planting beneath taller perennials and shrubs, maybe even under larger bonsai.

Sagina subulata is hardy in USDA climate zones 4 - 10.  It prefers well-drained soil, but is not particularly drought tolerant.  Soil pH should range from 5.6 to 7.5.  Plant in full sun to partial shade.  Take a soil sample to your nearest Cooperative Extension Service office for proper analysis.  Follow the recommendations.

You wouldn't think a plant that can grow "from a ha'porth of mortar" would need to have the soil prepared before planting, but I recommend it.  Cultivate at least 6" deep, removing all traces of weeds. Compacted soil should be cultivated to 10" deep.  Compost may be incorporated into the soil.  Fertilize sparingly.  Incorporate 10-10-10 fertilizer at a rate of no more 1 lb. per 100 square feet into the top 4" to 6" of soil. Avoid synthetic fertilizers contacting any part of your plants.

Space plants 8" to 12" apart.  Dig planting holes into the cultivated soil a little less deep than the depth of the growing container.  Water the plants in the pots, then drain.  Place the plants into the holes and back-fill, watering as you go. Press soil around the root balls. Do not cover entirely the root balls with soil. The tops should be slightly exposed. Add a top-dressing of mulch around the plants, not on top of them, about 1" deep.

Plant your pearlwort with other species having similar cultural requirements.  It has few insect or disease problems.  Pearlwort is deer resistant.  The greatest cause of failure is over-watering.  Allow soil to dry slightly between watering.

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