Procumbent Pearlwort (Sagina procumbens)
This weed can be very confusing because Pearlwort is a very generic term. Here we
focus on the weed with the Latin name
Other names include: Common Pearlwort, Prostrate Pearlwort, Beads pearlwort, Birdseye/Birdeye Pearlwort, or just plain Sagina.
Sagina procumbens is from the Caryophyllaceae Family, also known as Pink Family. This family also includes the carnation and dianthus flowers.
The Caryophyllaceae family has approximately 86 different genus types, with close to 2300 species within these genera. Sharing the name Pearlwort along with the genus Sagina is also the genus Colobanthus, which consists of about 30 species of flowering plants that produce a cushion-like bloom.
Many species of Pearlwort are sold as a groundcover and are very popular for walkways. Like commercial Pearlwort's that are sold as groundcover, Sagina procumbens will survive being walked on but will flourish without.
Sometimes these commercial species are the little pearly stems found in the moist potting mix from a plant you may purchase at a nursery. Unfortunately the weed, Procumbent Pearlwort, can also be found mixed into these small pots to. Difficult to differentiate species, if Sagina procumbens isn't spotted immediately it can become a widespread problem.
Procumbent Pearlwort is native to North and South America and technically is a broadleaf cool season annual. Depending on geographic conditions it can be a short-lived perennial. Procumbent Pearlwort resembles moss and can be found growing in poor, gravelly soils and other disturbed areas such as roadsides. It likes moist to wet soil conditions and can grow year-round in environments that include light shade to full sun. In spring when soil is extremely moist and temperatures are cool, dormant little weed seeds become very active. Click for more about soil and soil testing methods.
Weed stems are smooth, bright green and grow branched out off of each other forming a round to oval-like cluster. They grow up to 8" long and stems can be erect or flat. Stems root at nodes, or joints, and form a mat. Leaves are also smooth, narrow, hairless and grow about 1/2" long with pointed tips and grow opposite of one another.
Flowers of are very small and white with either no petals, usually 4, sometimes 5 flower petals.
Flower can stand alone or in cymule. A cymule is a small
cluster of flowers where the
central, or main flower opens first.
A cymule is a small cluster,
whereas a cyme, or cymes (pl.), would be larger cluster.
There are 4-5 green sepals that form the calyx. A sepal is the small leaf-like structure that is found beneath the flower. With this weed, Sagina procumbens, there are about 4-5 sepals that circle around the base of the flower forming calyx. Calyxes are designed to protect the developing flower buds.
All that said, many weeds do not develop flowering stems. If there are flowering stems it can be difficult to distinguish individual flower structures, including petals, and sometimes the flowers are not visible at all. Those that we are able to see often look like bead-like buds. The fruits are stored within and flowers self-pollinate automatically.
Procumbent Pearlwort can become invasive if left unattended. The best options for control is to keep up with weeding and it will unlikely become a major problem. New weeds can grow with fruits that contain 60 to 80 seeds that spread easily to shoots that become detached with nodes. Seeds can remain dormant for years.
If it is creeping into your garden use a pre-emergent to kill the weed seeds. Boiling water can also be used as a pre-emergent around garden edges, but I wouldn't recommend using it if there are established plant roots around that you want in the garden.
If it is in your lawn cut the grass at a higher level so sun doesn't reach seeds or new growth. This weed is susceptible to competition to taller plants and grasses grow not allowing the sun to reach weed. When cutting grass, height is important.
The flowering stage is April through September. Manual weeding methods of pulling weeds taproot out can help but hoeing can be more difficult option. If you ever purchase a potted plant where you see a foreign, small pearly growing plant - remove it thoroughly before planting.
Burning weed seeds with a propane torch is another option that works. Apply caution, overall this method won't be as damaging as boiling water for wanted vegetation.
Post-emergent herbicide options would include glyphosophate products. Sagina procumbens has become resistant to weed killers and this option may not always work. Germinated seedlings have root systems large enough to escape the effects of post-emergent's, including selective herbicides.
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