Birdeye pearlwort (Sagina procumbens)

Synonyms: Sagina procumbens var. compacta, Alsine procumbens, Alsinella procumbens

Common Names: Procumbent pearlwort, matted pearlwort, birdseye pearlwort, arctic pearlwort

Description:

Birdeye pearlwort (Sagina procumbens) is a tiny, low, mat-forming plant in the pink family, native to Europe, western Asia, and North Africa [1]. It was introduced to North America ? first collected in Michigan in 1889 ? and is now a common weed of lawns, pavement cracks, nursery containers, and greenhouses, where its dense, moss-like mats spread in moist, compacted ground [1][3]. MISIN tracks it because it is easy to overlook and hard to remove once it carpets turf, paths, and growing beds [2][3].

Habit:

Birdeye pearlwort is a very small plant that is easy to mistake for moss [2]. It forms low, dense green mats of thread-thin stems that creep along the ground and root where they touch, with tiny, narrow, hairless leaves ending in a fine bristle-like point [1][2]. Tiny white flowers ? so small they are hard to see without a hand lens ? rise on slender upright stalks above the mat from mid- to late spring [2][3]. It stays green much of the year and is easiest to notice in spring and early summer, when it is growing fast and flowering in damp lawns, gravel, and the cracks of walks and driveways [2][3].

At-a-glance cues:

1. Low, dense, moss-like green mat of very fine stems that root as they spread [1][2]
2. Tiny, narrow, hairless leaves tipped with a fine bristle-like point [1]
3. Minute white flowers on thin upright stalks, mid- to late spring [2][3]
4. Grows in damp, compacted spots ? lawns, gravel, pavement cracks, and nursery pots [2][3]

Leaves:

1. Arrangement: opposite (paired), often crowded along the stem [1][2]
2. Shape: narrow and thread-like, only a few millimeters long, tipped with a fine bristle-like point [1]
3. Margin: smooth (toothless) [1]
4. Surface: hairless, sometimes slightly fleshy, bright green [1]

Stems:

1. Habit: low, mat-forming perennial; thread-thin sprawling stems that root at the joints (nodes) [1][2]
2. Spread: forms dense, moss-like mats that widen as the stems root [2]
3. Roots: a shallow, slender, much-branched taproot [3]
4. Height: flowering stalks rise only about 1 to 3 inches above the mat [2]

Flowers:

1. Color: white [2]
2. Size and shape: minute, with four or five small petals ? often hard to see without magnification [2]
3. Arrangement: single flowers on slender, upright stalks above the mat [2]
4. Bloom time: mid- to late spring [3]

Fruit and seeds:

1. Fruit: a tiny capsule that splits open at the top [2]
2. Seeds: very small, dark, and numerous [3]
3. Dispersal: seeds are splashed out by rain and irrigation water and carried on tools, footwear, and in potting soil; the mats also spread as the stems root at the joints [2][3]

Habitat:

Birdeye pearlwort is native to Europe, western Asia, and North Africa [1]. In North America it is introduced and now widespread, growing as a weed across much of the continent [1][4]. It favors moist, compacted, disturbed ground in sun or light shade: lawns and turf, pavement and sidewalk cracks, gravel, greenhouse benches, and nursery containers ? especially where overhead watering keeps the surface damp [2][3]. It does best on frequently watered or poorly drained soils [2].

Reproduction:

Birdeye pearlwort spreads in two ways [2]. Its sprawling stems root wherever a joint touches moist soil, so a single plant widens into a dense mat [2]. It also makes large numbers of tiny seeds in small capsules; rain and irrigation water splash the seeds out and around, and they also hitch rides in potting soil and on tools, pots, and footwear ? the main way it jumps between gardens, nurseries, and greenhouses [2][3].

It grows and flowers mostly from spring into summer but stays green much of the year [2]. For control timing: pull or scrape out the mats while they are small and before the spring flowers set seed, so they cannot reseed the area [2][3].

Impact and Damage:

Birdeye pearlwort is a nuisance weed rather than a health or safety hazard ? it is not toxic and does not irritate skin. The concern is simply where it grows [2][3]. In lawns it forms dense, moss-like patches that crowd out thin or damp turf, and in pavement cracks and gravel it spreads into an unwanted green mat [2].

Its biggest cost is in plant nurseries and greenhouses, where it carpets the surface of containers and benches, competes with young plants such as conifer seedlings for water and nutrients, and is slow, costly, and difficult to weed out by hand once established [3]. It is mainly a weed of lawns, pavement, and growing operations rather than a threat to natural areas [2][3].

Similar species:

Corn spurry (Spergula arvensis) is a weed in the same family that can be confused with birdeye pearlwort, since both have very narrow, thread-like leaves. Corn spurry is taller and more upright, with leaves in whorls and larger white flowers, while birdeye pearlwort stays low and mat-forming with paired leaves and minute flowers [2].

Monitoring and rapid response:

Signs to watch for:

1. A low, moss-like green mat of very fine stems in damp lawns, gravel, pavement cracks, or nursery pots [2]
2. Tiny white flowers on thin upright stalks in mid- to late spring [3]
3. Patches spreading where the ground stays wet or is watered from overhead [2][3]

What you can do:

1. Pull or scrape out the mats by hand while they are small, getting the rooted stems and shallow roots, and do it before the spring flowers set seed [2][3]
2. Let damp, compacted spots dry out and drain better, and ease off frequent overhead watering ? pearlwort thrives on constantly wet surfaces [2]
3. In beds and containers, top with fresh mulch or clean growing media, and keep tools, pots, and boots clean so seeds do not hitch a ride [3]
4. Bag and trash the mats and any seed capsules rather than composting them [3]
5. Nursery and greenhouse operators can switch from overhead to drip watering, improve bench and floor sanitation, and remove plants before they seed [3]

When to call a professional:

1. Large, well-established mats across turf, nursery stock, or growing areas where hand removal cannot keep up [3]
2. For chemical control options, contact a licensed applicator or your local cooperative extension office.

Report sightings to MISIN. Help track this species' spread by submitting observations through the MISIN web site or the MISIN mobile app (Android, iOS, Windows, and macOS). Photos at multiple angles paired with a precise GPS location are the most valuable data for confirming new occurrences and triggering rapid-response review.

Credits:

1. Plants of the World Online (POWO), Royal Botanic Gardens, Kew. Sagina procumbens L. powo.science.kew.org
2. University of California Statewide IPM Program (UC IPM). Birdseye Pearlwort (Sagina procumbens), Weed Gallery. ipm.ucanr.edu
3. Michigan State University Extension. Birdeye pearlwort in conifer seedling nurseries in Michigan. canr.msu.edu
4. USDA NRCS PLANTS Database. Sagina procumbens L. plants.usda.gov

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