Stellaria media (L.) Vill., Common Chickweed
Account Summary
Native, very common and widespread. Eurasian wide-temperate, but naturalised to become circumpolar wide-temperate. It is almost cosmopolitan as a weed, absent from arctic and very arid areas.
1881; Stewart, S.A.; Co Fermanagh.
Throughout the year.
Growth form and preferred habitats
In the temperate zone, Common Chickweed is wintergreen and it can germinate in any month of the year. It can therefore behave either as a winter or a summer annual, or as a short-lived perennial. S. media is regarded by many as one of the most common ruderal, sprawling, diffusely branching, mat-forming weeds in Fermanagh, and otherwise as one of the most common plants in Britain & Ireland. It is also notorious world-wide as an economically important weed of arable farmland and gardens. S. media can become a major contaminant in some crops, including soft fruit, potatoes and barley. It sometimes is so abundant, it can overgrow and smother young seedlings of other species and successfully compete for nitrogen in the soil, thus depriving its neighbours of an adequate supply of this essential nutrient (Holm et al. 1977; Turkington et al. 1980).
The decumbent or ascending, much-branched plant up to 40 cm in height is distinguished by having a single row of hairs down its stem internodes and leaf stalks (petioles). It prefers cool, moist, semi-shaded places and quickly colonises almost any piece of disturbed lowland soil and semi-open habitat offering a damp, preferably fertile or nutrient-enriched substrate (Salisbury 1974). Examples of where it is most abundant include on loose piles of moved earth in gardens or on building sites, on rubbish dumps, around farmyards, and along the junction of roadside pavements and hedges, in neglected or in young pasture areas, in arable crops and in waste ground (Holm et al. 1977).
The flowering cycle of around five weeks is also very rapid, and in optimal conditions it allows the production of three generations per year. It should be stressed, however, that in weedy species like this, not every individual is capable of behaving in the same way. There now exists a growing body of information revealing habitat-correlated intra-specific genetic variation in life-history traits as well as a capacity for developmental plasticity (Briggs et al. 1991). The soil seed bank population of S. media is potentially enormous and buried seed can persist for many years.
These properties, underpinned by the great physiological versatility of the species, often allow Common Chickweed to become a hugely abundant, sometimes dominant weed in suitably fertile, open waste ground or in unmanaged, ± open habitats (Sobey 1981). This is due in part to its abilities to grow and reproduce even during the winter months whenever temperature rises temporarily, to survive subsequent frosts, and then to produce very rapid growth in the early spring. S. media is able to continue growing at 2°C, when most other plants stop growing below 6°C.
Detailed ecological accounts are given by Sobey (1981) and by Grime et al. (1988, 2007). Ecology, weed behaviour and other very interesting lore is reviewed by Holm et al. (1977), Turkington et al. (1980) and Defelice (2004).
Variation
Being an extremely common and widespread, almost ubiquitous weed species, unsurprisingly S. media displays a high degree of phenotypic plasticity, varying in size, habit, hairiness, petal length, stamen number, and number, size and surface details on the exquisite sculptured, tuberculate seeds (Turkington et al. 1980; Jonsell et al. 2001). The variation is so extensive that in the past 32 varieties or micro-races have been described (Béguinot (1921), cited by Matzke (1932); Peterson (1936)). Also in the past, two subspecies were delimited: S. media subsp. neglecta (Weihe) Gremli and S. media subsp. pallida (Dumort.) Asch. & Graebn., but while these are similar to S. media, both are now regarded as separate species (Jonsell et al. 2001; Stace 2010).
The second edition of Flora Europaea 1 (Tutin et al. 1993) suggests that S. media sensu stricto contains two additional subspecies: subsp. media (throughout the whole species range) and subsp. cupaniana (Jordan & Fourr.) Nyman, the latter being restricted to C & E Mediterranean regions. There is another form subsp. media described as var. apetala Gaudin which has petals minute or absent. This latter form has often been confused with S. pallida (Lesser Chickweed).
Flowering reproduction
This is essentially by seed only, although prostrate branches can root and spread the individual in loose soil surfaces, giving the plant additional resources for growth and seed production. The small, star-like flowers are formed either solitary in the axils of upper leaves or few to many borne in loose cyme inflorescences. Each flower normally opens for just one day, and the five petals are so deeply bilobed they look like ten, and are shorter than the sepals. The number of stamens varies from three to eight depending upon the degree of illumination (Salisbury 1964).
Pollination and fertilisation
The flowers are scented and are visited by bees, ichneumon wasps and members of the Diptera, Hymenoptera and Thysanoptera (Turkington et al. 1980). If insects fail to visit, the flowers self-pollinate and self-fertilise (ie they are autogamous). Indeed, autogamy may predominate in this species, and some reports suggest the flowers are cleistogamous, self-pollination occurring while still in bud (Salisbury 1974; Jonsell et al. 2001).
Since its sexual reproductive cycle is unfettered by either seasonality (ie day-length) or a need for pollinators, in moist, temperate climates plants of S. media flower and seed right throughout the year except in very severe weather. During the winter months, flowers tend to be without petals and are entirely autogamous. In general, the influence of day-length, the length of the photoperiod upon the reproductive capacity of flowering plants is to restrict the area of the species distribution. Species of wide geographical range that are indifferent to photoperiodic stimulation, and which flower and fruit irrespective of long or short days, include ubiquitous weeds such as S. media and the annual grass Poa annua (Annual Meadow-grass) (Salisbury 1942, p. 49).
Fruit production
According to Salisbury (1964, p. 191), the average fruit production per Common Chickweed plant is about 240 capsules, but one very large plant that he examined produced a total of 1153 capsules! The fruit capsule is oblong in shape and when ripe, like all members of the genus Stellaria, it splits at the tip into six triangular valves or teeth to release the seed. The capsule valves open and shut depending on whether the weather is dry or wet, thus protecting the 5–16 (the mean is ten) contained seeds.
Seed dispersal
The seeds are shaken out of open capsules by wind and appear to be secondarily dispersed in mud attached to the feet of animals, including man. They are also common in the dung of animals including cattle, horses, pigs and birds. The English common name 'Chickweed' refers to the fact (or the belief) that birds peck around and feed on the plant, ingesting the seed as they do so. S. media seeds are also dispersed as contaminants in seed of many crop plants including cereals, rape, swede, fodder-beet, sugar-beet and kale (Fryer & Makepeace 1977).
Seed dormancy and soil seed bank survival
The seeds are light, disc-like, with a sculptured, knobbly surface, 0.8-1.4 mm in diameter. They vary in colour from yellowish grey to reddish or dark purplish brown.
In temperate and maritime regions, there is no seed dormancy in the population: germination can occur immediately after release (Peterson 1936; Salisbury 1964). In arctic, subarctic and continental populations, however, germination is delayed (presumably to allow after-ripening of the embryo), with subsequent rapid development and sparse vegetative growth materialising (Peterson 1936).
While a portion of the seed produced may germinate within a few days of release, the remainder can survive in soil for some time. With up to three generations of seed produced in a calendar year, the soil seed bank population of S. media is potentially enormous, and some buried seed can persist for years. Seed survival estimates vary, but viable seeds are known to persist for between 25 and 60 years or more (Salisbury 1964; Fryer & Makepeace 1977).
Fossil history
Fossil evidence indicates S. media is native in Britain and Europe, seeds having been identified in pre-glacial and Mesolithic deposits in Britain. Godwin (1975) regarded it as persistently native in Britain up to and throughout the Weichselian glaciation. In the early post-glacial Flandrian, it was present in the middle of what is now the North Sea, but there are no fossil records of it from the Boreal and Atlantic periods when more or less uninterrupted deciduous forest predominated across the land. It reappeared in the fossil record once farmers arrived and cultivation began in the Late Bronze age and from then onwards it is always present. The numerous interglacial records prove the species is perfectly capable of existing in Britain and Ireland independent of human influence (Godwin 1975, p. 149).
Fermanagh occurrence
Despite its widespread reputation for commonness, in terms of record frequency S. media actually ranks 148th in the Fermanagh Flora Database, showing yet again just how unreliable casual impressions of relative abundance can be (Crawley 2005). Despite this, Common Chickweed is very common in Fermanagh, having been recorded in 306 tetrads, 58% of those in the VC.
British and Irish occurrence
A ubiquitous naturalised archaeophyte weed in disturbed, often enriched habitats, the hectad map in the New Atlas shows S. media is widespread and abundant throughout both islands, except on the highest mountains and on the driest soils (Preston et al. 2002).
European and world occurrence
Native to Europe and Asia, S. media has been spread everywhere man has introduced cultivation and is now naturalised, cosmopolitan and circumpolar in its geographical distribution. The only ground it eschews are totally inhospitable habitats involving heavily disturbed soils and the high arctic and arid deserts. In the tropics, it is confined to higher altitudes where more temperate conditions allow it to flourish (Hultén & Fries 1986, Map 724). Fossil records from Greenland show it was present there from around 1400 to 1721 AD, before European settlement began (Pedersen 1972). It was first recorded in N America in 1672 in New England (Turkington et al. 1980), and it has spread with agriculture worldwide.
Weediness
S. media was ranked as the 72nd worst weed in the world by Holm et al. (1977) because it is a problem in more than 20 crops in 50 countries. It can also be a serious weed in lawn turf in N America, because its prostrate growth habit and rapid growth rate allow it to survive frequent mowing (Uva et al. 1997). In addition to its direct weediness and power to significantly reduce crop yields, S. media is a host plant for several insect and disease pests of economic crops, including viruses such as Tomato Spotted Wilt Virus (Defelice 2004).
The very rapid growth rate of S. media and its ability to overgrow and smother seedlings and young plants of other species has led to its use in weed control. In Switzerland, Common Chickweed is used to combat infestations of Convolvulus arvensis (Field Bindweed) and Calystegia sepium (Hedge Bindweed) in vineyards. In such circumstances, the Chickweed itself is not a problem weed (Stalder et al. 1973).
Uses and toxicity
Young leaves of the plant when boiled were eaten like Spinach from which it is described by Grieve (1931) as "hard to distinguish". They were also used fresh along with young Dandelion leaves (Taraxacum vulgare agg. (Dandelion)), as salad. However, like other members of the family Caryophyllaceae, S. media contains saponins, and it accumulates sufficient nitrogen to actually render it toxic if eaten in large quantity. Having said this, there is no evidence of stock animals being seriously poisoned or killed by it in recent years (Cooper & Johnson 1998). There is a long history of Chickweed being fed to cage birds and hens. Both wild and cage birds eat the seeds, the young shoots and the leaves, as do rabbits, cows and horses (Grieve 1931).
In herbal medicine, S. media has long been used for a wide diversity of ailments. The main use has been for a mat of the plant, boiled and applied as a hot, relaxing poultice to treat inflammation, bruises, and reduce swelling. It has been applied in this way for boils, abscesses and ulcers, rheumatism, chilblains and rashes. An ointment made from the plant has also been used for sore eyes, and for eczema in some parts of Britain. These and many other uses are listed by Allen & Hatfield (2004), along with localities where they are practiced.
Names
The genus name 'Stellaria' is of medieval origin from the Latin 'stella', meaning 'a star', referring to the shape of the five-petalled flower (Gilbert-Carter 1964). The Latin specific epithet 'media', means 'middle-sized' or 'intermediate' and refers to size (Gledhill 1985).
The English common name 'Chickweed' refers to the fact that it has long been used to feed birds. Grigson (1955, 1987) lists no less than 16 variant names for S. media from around Britain and Ireland, amongst which 'Skirt Buttons' from Devon, seems one of the most interesting. Having said this, I cannot find this name mentioned in any other reference, and have no suggestion as to its origin, even if one tries misspelling either part of the name. Another name is 'Chick Wittles' (ie vituals), which originates from Suffolk, and yet another is 'Tongue-grass' from Ireland (Threlkeld (1727)). German and French names that Grigson mentions translate as 'Hen's guts' or 'Hen's bite', again making reference to chicken feed.
Threats
None.