Common chickweed

Stellaria media (L.) Vill.

Common chickweed seedling
Common chickweed flower
Common chickweed plant

Images above: Upper left: Common chickweed seedling (Scott Morris, Cornell University). Upper right: Common chickweed flower (Scott Morris, Cornell University). Bottom: Common chickweed plant (Scott Morris, Cornell University).

Identification

Other common names:  chickweed, starwort, starweed, bindweed, winter-weed, satin flower, tongue-grass, chickwhirtles, cluckenweed, mischievous Jack, skirt buttons, cyrillo, white bird's eye, common starwort

Family:  pink family, Caryophyllaceae

Habit:  Mat forming winter or summer annual herb.

Description:  Seedling cotyledons are oval, 0.4” (1.0 cm) long by 0.1” (0.25 cm) wide, pointed at the tip, and borne on a 0.4” (1.0 cm) long hairy stalk.  True leaves are opposite, round to tear drop shaped, and twice the length of the stalk.  Seedlings are light green, upright, and about the width of a penny at the 4 true leaf stage.  Branching starts at the 5 leaf-pair stage.  Mature plants form dense, light green carpets of foliage with creeping stems up to 20” (51 cm) long.  Stem tips are angled upward helping the stems crawl over and onto other plants.  Stems branch often, root at the nodes when in contact with the soil, and are smooth except for 1-2 rows of small hairs.  Leaves are oppositely arranged and located on 0.25-0.75” (0.64-1.91 cm) long stalks, which may be absent near branch tips.  One line of white hairs is present on stalks.  Leaves are broadly teardrop to elliptically shaped, pointed at the tip, and 0.4-1.25” (1.0-3.2 cm) long by 0.6” (1.52 cm) wide.  Upper leaves are no wider than 0.4” (1.0 cm).  Shallow, fibrous roots easily break from the shoots.  Mats may reach 0.3-3.3 ft (10-100 cm) in diameter.  Flowers have 5 deeply lobed, white petals set inside 5 larger, green, 0.2” (0.51 cm) long, triangular sepals.  The 0.1-0.3” (0.25-0.76 cm) diameter flowers are clustered at branch ends.  Each flower produces an oval, single chambered capsule containing 8-10 light yellow-brown to red-brown, irregularly round, flat, 0.06” (0.15 cm) diameter seeds with a pebbly surface.  The capsule splits to form 6 teeth when releasing seeds, and is retained on the plant.

Similar species:  Leaves of mouseear chickweed (Cerastium fontanum Baumg. ssp. fontanum) are densely covered in fine hairs at all growth stages.  Thymeleaf speedwell (Veronica serpyllifolia L.) has rounded, lightly toothed, dark green leaves with notched tips and no hairs on its stems or leaf stalks; its flowers have four white petals with blue streaks.  Thymeleaf sandwort (Arenaria serpyllifolia L.) has hairy leaves and 5 non-divided petals.  Little starwort (Stellaria graminea L.) has flowers similar to common chickweed but they are borne on long stalks and plants have long, tapering leaves.  

Management

Because common chickweed can grow and set seeds during any season of the year, control throughout all crop rotation phases should be practiced.  Otherwise, high densities of seeds may build up in the soil and overwhelm control efforts in crops that are sensitive to common chickweed competition.  For example, flame weeding sweet corn very effectively controls common chickweed, and may be worthwhile to prevent competition with subsequent crops, even though common chickweed causes little yield loss in corn.  If common chickweed is a problem, sowing density of winter cover crops should be increased.  Increased sowing density of both winter and spring grain crops may help reduce yield losses to common chickweed and will also reduce seed production (Mertens and Jansen 2002).   Because chickweed continues to grow and set seed until it dies, tilling fields immediately after harvest is important in controlling this species.  If the species is green and growing, one or two weeks of delay can increase seed production by several fold (Van Delden et al. 2002).

Because common chickweed seedlings are very small and fragile, stirring of the top 1-2” (2.5 - 5 cm) of soil 2-4 times during the first month following tillage is highly effective at removing many of the individuals that will emerge during the season.  Since stems root readily in moist soil, cultivation is often ineffective once the plant mat reaches several inches in diameter.  Thus, frequent but shallow weeding is more effective at controlling the species (Turkington et al. 1980).  Harrowing in the spring is more effective than fall harrowing for controlling this species in winter wheat (Wilson et al. 1993).  Since most common chickweed seeds that have been incorporated into the soil remain dormant unless exposed to light, flame weeding to create a stale seedbed before planting small seeded or slow growing vegetables is advantageous.  Organic mulch materials are effective for suppressing common chickweed due to the species' small seed reserves and prostrate growth form.   Common chickweed is highly shade tolerant, however, and can scramble up through loose straw.  Thus, plastic mulch, baled straw or a paper barrier under loose straw will be more effective than loose straw alone.  

Ecology

Origin and distribution:  Common chickweed is native to Europe.  It has been widely introduced throughout the world, including parts of the far north and sub-antarctic islands.  In the tropics it occurs primarily at high elevations (Sobey 1981).  It occurs in all fifty states and all Canadian provinces (USDA Plants), but it is generally absent from dry areas (DeFelice 2004).

Seed weight:  Seed weight varies between populations.   Averages of 0.36 mg (Whitehead and Sinha 1967 in Turkington et al. 1980), 0.37 mg (Benvenuti et al. 2001), 0.38 mg (Milberg et al. 2000), 0.40 mg (Gardarin et al. 2010, Gaba et al. 2019, Grundy et al. 2003), and 0.51 mg (King 1966 in Turkington et al. 1980) have been reported.

Dormancy and germination:  Freshly shed seeds are typically dormant (Roberts and Lockett 1975, Baskin and Baskin 1976, Hill et al. 2014), but some may germinate immediately (Mohler unpublished, Sobey 1981).  A period of after-ripening at warm soil temperatures (for example, 68 °F = 20 °C) breaks dormancy.  Thus, most seeds shed in the spring wait until fall to germinate.  In addition, a low temperature requirement for after-ripening has been reported (Cici and Van Acker 2009).  Seeds germinate best at moderate temperatures of 54-68 °F (12-20 °C) (DeFelice 2004, Grundy et al. 2000, Turkington et al. 1980) and will not germinate at temperatures above 86 °F (30 °C) (Turkington et al. 1980).  Once seeds have after-ripened, light (Cussans et al. 1996, Milberg et al. 2000), fluctuating temperature, and nitrate all promote germination (Sobey 1981, Turkington et al. 1980), but light is the most important germination cue.  Different populations can possess different after-ripening and environmental requirements for germination, presumably permitting the species to germinate in response to varying conditions (Sobey 1981).

Seed longevity:  Viable seeds of common chickweed have been found beneath medieval ruins in Europe (Ødum 1965).  Deep burial in high moisture, low oxygen conditions are highly favorable for seed survival (Kivilaan and Bandurski 1981).  Seeds stored under dry, cool laboratory conditions remained viable for 5.5 years (Egley and Chandler 1983).  In cool Alaskan conditions, buried common chickweed had a 17% annual mortality rate, but a few seeds were still viable after 24.7 years (Conn and Werdin-Pfisterer 2010).  Most common chickweed seeds die off quickly, however, in regularly tilled soil (Froud-Williams et al. 1984).  Seed viability declined annually by 19-30% in undisturbed soil, but by 34-56% under cultivated conditions (Roberts and Feast 1973).  In several studies in annually tilled fields, common chickweed seeds declined at 33-60% per year (Lutman et al. 2002, Popay et al. 1994).  Seeds buried in Mississippi lost all viability in 18 months (Egley and Chandler 1978). 

Season of emergence:  Although common chickweed can emerge any time of year in moist soil at moderate temperatures, most emergence occurs during the spring and fall (DeFelice 2004, Froud-Williams et al. 1984, Hill et al. 2014, Sobey 1981, Turkington et al. 1981).  

Emergence depth:  Optimum depth for emergence is from just below the surface at 0.4” (1 cm) (Chancellor 1964, Froud-Williams et al. 1984, Turkington et al. 1980).  Seedlings can emerge from seeds as deep as 2” (5 cm), but emergence from deeper is rare (Benvenuti et al. 2001, Cussans et al. 1996, DeFelice 2004, Grundy et al. 1996, Grundy et al. 2003).

Photosynthetic pathway:  C3

Sensitivity to frost:  Common chickweed can tolerate temperatures down to 7 °F (-14 °C) though with some damage (Cici and Van Acker 2011).  Photosynthesis can occur at temperatures below freezing (Sobey 1981), and the base temperature for growth of this species was computed to be 26 °F (-3.3 °C) (Storkey and Cussans 2000).  In the Northeast, fall germinating seedlings commonly persist through the winter. 

Drought tolerance:  The species is drought sensitive, and plants quickly wilt and die during dry conditions (Sobey 1981). 

Mycorrhiza:  Most studies have found no mycorrhiza (Harley and Harley 1987, Sobey 1981, Turkington et al. 1980), but one report indicated slight mycorrhizal presence (Harley and Harley 1987).

Response to fertility:  Common chickweed prefers highly fertile soils and its dense root system is well adapted to access nutrients (Sobey 1981).  Biomass, seed production and seed weight increase with increasing nitrogen (Van Delden et al. 2002).  Common chickweed is highly responsive to addition of P when N is adequate (Buchanan et al. 1976).  In excessively fertile conditions like manure piles, it concentrates nitrate to toxic levels (DeFelice 2004, Turkington et al. 1980).  Even in agricultural fields, nutrient levels in common chickweed tissues can be high.  For example, plants from a Massachusetts onion field had elemental N-P-K levels of 3.4-0.53-7.5 whereas levels in the onions were 2.0-0.28-2.2 (Vengris et al. 1953).  The species grows well on soil with a pH from 5.2 to 8.2, but growth is severely depressed below pH 5.2 (Buchanan et al. 1975).

Soil physical requirements:  The species tolerates a wide range of soil types, but grows best on moist, fine textured soils (DeFelice 2004, Sobey 1981).

Response to shade:  Common chickweed is shade tolerant.  It grows well in partial shade and can flower and set seeds in as little as 1.5% daylight (Sobey 1981).

Sensitivity to disturbance:  Small seedlings are easily killed by cultivation.  Larger plants may re-root following cultivation or hoeing if the plant is partially covered with soil (Sobey 1980). Stems root when in contact with moist soil which makes large plants difficult to completely remove by pulling.  Its low, prostrate growth habit allows it to survive repeated mowings as occurs with hay or green manure crops (Sobey 1981).

Time from emergence to reproduction:  Common chickweed flowering is independent of daylength (Sobey 1981, Turkington et al. 1980) and this species can flower and set seed at any time of the year provided moisture is available and temperatures are above freezing.  Flowering and seed set occur continuously as the plant grows.  Plants usually flower within 6 weeks of emergence and seeds set about 2 weeks later (Sobey 1981, Turkington et al. 1980).  Since some freshly shed seeds are not dormant or can after-ripen rapidly (DeFelice 2004), the species can complete 3 to 4 generations per year (Sobey 1981, Turkington et al. 1980).  The timing of 50% seed production in Michigan occurs between mid-May and mid-June (Hill et al. 2014).

Pollination:  Common chickweed usually self-pollinates (DeFelice 2004, Turkington et al. 1980), and under cold conditions, pollination may occur without opening of the flowers (Sobey 1981, Turkington et al. 1980).

Reproduction:  Mature plants typically produce between 500 and 3000 seeds each (DeFelice 2004, Salisbury 1978, Turkington et al. 1980), but very large plants may produce 13,000-15,000 seeds (Lutman 2002, Sobey 1981).

Dispersal:  The seeds have no special adaptations for dispersal, but it has been spread worldwide primarily by humans because of its adaptability to disturbed habitats (DeFelice 2004).  Most dispersal probably occurs in soil clinging to shoes, tires, farm implements and animal hooves.  Some seeds retain viability when passing through the digestive tracts of cattle (Mt. Pleasant and Schlather 1994), sheep (Kuiters and Huiskes 2010), horses, deer (Myers et al. 2004), rabbits (Pakeman, R. J. 1999), pigs and some birds including sparrows and gulls (Sobey 1981).  Seeds are also dispersed as a contaminant of pasture seed and other crops.  (Sobey 1981, Turkington et al. 1980)

Common natural enemies:  Several species of wildlife graze common chickweed, and several species of insects, nematodes, and disease organisms are found associated with this species, but the level of damage is usually trivial (Sobey 1981).

Palatability:  Common chickweed has a mild flavor that makes it palatable as a salad herb.  It is nutritious fodder for cows, sheep, horses, pigs, and chickens, but may contain toxic levels of nitrate when grown on nitrogen rich soils.  (DeFelice 2004, Turkington et al. 1980)

References:

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