Plantago coronopus
(Buck's-horn plantain)

In its native range of Europe, northern Africa and Central and West Asia, P. coronopus is an inoffensive low-growing herb in coastal saline situations. It is rarely a weed of crops though Holm et al. (1979) list it as a ‘common’ weed in Spain. In recent years, however, it has been recorded as invasive in Australia and in California, forming dense mats which displace native vegetation, including endangered species in California (Weber, 2003; United States Fish and Wildlife Service, 2008a, b). Furthermore, it is reported as a weed problem in non-tilled orchards, irrigated pastures, and alfalfa and clover fields in California.

P. coronopus is native to Europe, northern Africa and Central and West Asia, but has been introduced to parts of North America, South America, South Africa, Australia and New Zealand.

There is some risk of introduction via trade in the seeds for cultivation as an ornamental but this is not extensive. The main risk would seem to be via the importation of grass seed from contaminated pastures.

In the UK, the species is found mainly in maritime habitats including the lower rocks immediately above high tide mark, rock crevices and ledges, the face of cliffs where detritus has collected, and grassy slopes leading up to, and above, the cliff face. It is also found on some fixed sand dunes and often in sandy soils when present inland (Dodds, 1953). Weber (2003) indicates occurrence in grassland, along rivers, in fresh and saline wetlands and on coastal dunes. Given its wide native range, however, the species is likely to inhabit a broader range of environments than reported here.  

In California, USA, P. coronopus is a weed problem in non-tilled orchards, irrigated pastures, and alfalfa (Medicago sativa) and clover (Trifolium spp.) fields. It is also reported as a threat to two endangered plant species in California; Trifolium amoenum (US Fish and Wildlife Service, 2008a) and Astragalus robbinsii var. jesupii (US Fish and Wildlife Service, 2008b).

Genetics

The genetics of P. coronopus are complex. The plant is normally diploid (2n=10), but in a detailed study, Böcher et al. (1955) found one strain with 2n=11 and a single hexaploid plant with 2n=30. They treat the tetraploid form (2n=20) as a separate species P. commutata, presumably corresponding to P. coronopus subsp. commutata. A range of sources quoted by Missourri Botanical Garden (2012) confirm most forms being diploid (2n = 10 +/-1 or 2) but subsp. commutata tetraploid (2n = 20). Mohsenzadeh et al. (2008) conversely found the coronopus species to be tetraploid and the commutatus species diploid, but admit that this does not agree with previous publications.

Paliwal and Hyde (1959) found that male sterility in P. coronopus was associated with a single extra chromosome which is largely heterochromatic, shorter, and not homologous with any of the other chromosomes. No male-fertile plants contained this B-chromosome. However, this finding was contradicted by Raghuvanshi and Kumar (1983) who found no relationship between B chromosomes and male sterility. Male sterility has been further studied by Koelewijn and Damme (1995b; 1996) and by Damme et al. (2004) who found that both nuclear and cytoplasmic genes are involved in the inheritance of the male sterile character. They describe the nuclear (restorer) genetics of two cytoplasmic types. In both types, at least five multiple interacting nuclear genes are demonstrated, three with dominant and two with recessive restorer allele action. Intermediate partially male sterile plants can also occur (Koelewijn and Damme, 1996).

Other studies on the genetics of P. coronopus include a genetic diversity analysis of Plantago species and their interspecific hybrids through RAPD markers (Samarth and Vala, 2012) and the interspecific hybridization and induction of variability in Plantago species (Samarth and Fougat, 2012).

Reproductive Biology

P. coronopus is self-compatible (Samarth et al., 2009) but protogynous, meaning that the ovaries are receptive before pollen shedding (Bos, 1992). This facilitates out-crossing.

The large seeds are shed in the autumn and germinate almost immediately. The small seeds are retained in the capsule and although they are capable of germinating immediately, their germination is generally delayed (Rowling, 1933; Braza and Garcia, 2011). The seeds differ also in the fact that the larger seeds develop mucilage on wetting while the small seeds do not. One consequence of this is that the larger seeds rapidly sink in water while the small ones float indefinitely (Rowling, 1933). There may be an initial dormant period, which is longer, up to two months, at higher temperatures. Germination occurs between 10 and 25°C. This may require light. Germination of P. coronopus subsp. crassipes was 96% after 72 h at 20°C in light, but only 2% in the dark (Shem-Tov et al., 1999). Rowling (1933) also showed that light was needed in May, but there was little difference between dark and light germination in September.

Male steriles produced more (41% to 148%) and heavier (12% to 22%) seeds than hermaphrodites (Koelewijn and Damme, 1996). In the field, the contributions of seed size variation (15%) and inbreeding (9%) combine with 48% higher seed production to give a total fitness advantage of 70% to male steriles relative to hermaphrodites. This is probably sufficient for maintenance of gynodioecy under the nuclear-cytoplasmic inheritance of male sterility (Koelewijn and Damme, 2005).

Germination is reduced under saline conditions and completely prevented in 0.2 M NaCl solutions (Luciani et al., 2001). The importance of mucilaginous seeds for the survival of the plant species under desert conditions is discussed by Gutterman and Shem-Tov (1996). The mucilage causes the seeds to stick to the crust of the desert soil and prevents the seeds being washed away by showers.

Physiology and Phenology

The relative growth rate (RGR) during the vegetative stage is 300 mg g^-1d^-1 and drops at the initiation of flowering buds to 60 mg g^-1d^-1, a fivefold reduction. The initiation of flowering is stage-dependent. After the formation of about 14 leaves, plants start to form flowering buds, independent of weight or leaf size (Koelewijn, 2004a). Seed size effects lasted until the end of the experiment and were reflected in all morphological measurements. The proportion of small verses large seeds is influenced to some degree by the environment (Braza et al., 2010). When grown intermixed, selfed offspring were always inferior to their out-crossed relatives (Koelwijn, 2004b).

In east Poland (Sotek, 2007) populations of P. coronopus are mainly composed of perennial plants with a significant proportion of biennial and a small contribution of annual plants. The shorter cycle was characteristic of the individuals growing in the conditions of lack of competition or strongly limited competition of the co-existing plants.

Under desert conditions P. coronopus showed plasticity according to the day length; plants under long days were larger and produced more seeds that germinated to higher percentages (Shem-Tov and Gutterman, 2003).

Longevity

Established plants may apparently survive for several years, while Dodds (1953) refers to high germination from 3-year-old seeds.

Associations

Dodds (1953) reported a number of associations in a range of habitats: in salt marsh - Armeria maritima, Glaux maritima, Plantago maritima, Cochlearia officnialis and Triglochin maritime; and in transitional salt marshes or dunes - Agrostis stolonifera, P. maritima and G. maritime; in less saline conditions a much wider range of species was recorded.

In the Swina valley, Poland, extensive grazing by horses and cattle on salted meadows contributes to the protection of 21 plant species growing there, including a rare stand of P. coronopus (Warda and Rogalski, 2004).

Environmental Requirements

P. coronopus favours situations with light sandy soils and high light intensity; withstanding high summer temperatures and moderately low rainfall. It is adapted to highly saline conditions (Apaydin et al., 2009). A study recorded the salinity threshold of P. coronopus being reached at 25% of sea water levels and growth was strongly depressed by higher salinities (Koyro, 2006).

Growth stimulation by carbon dioxide enrichment beyond close-to-current concentrations is only likely to be seen under nutrient-rich conditions in semi-arid and possibly other drought-stressed grasslands (Grünzweig and Körner, 2003).

Tánczos and Hasselt (1992) reported that P. coronopus was able to tolerate prolonged freezing at -4°C but given its presence in Norway and Greenland it may be able to tolerate even lower temperatures. The plant has also been shown to tolerate high levels of iron (Schmidt and Fühner, 1998) and compacted soils (Popay et al., 1995).

Natural enemies of P. coronopus include the fungal pathogen Cadophora luteo-olivacea, which occurs in Spain (Agustí-Brisach, et al., 2011) and the ants Messor barbarus in France (Detrain and Pasteels, 2000) and M. rugosus in Israel (Gutterman and Shem-Tov, 1997). These authors noted that the larger mucilaginous ombrohydrochoric seeds were less likely to be taken by the ants. Lepidopterans Metzneria littorella and Phthorimaea plantaginella, the coleopterans Ceuthorhynchidius dawsoni and Mecinus collari and the dipteran Phytomyza plantaginis are all listed by Dodds (1953) as affecting P. coronopus in the UK.

Dodds (1953) also recorded that rabbits (Oryctolagus cuniculus) graze on the plants, especially the more succulent forms in the regions of salt marshes. Soay sheep (Ovis aries), goats (Capra hircus) and ponies (Equus caballus) have also been recorded as grazing on the succulent form.

Animal feed, fodder, forage

• Forage

Human food and beverage

• Leaves (for beverage)
• salad
• Spices and culinary herbs
• Vegetable

Medicinal, pharmaceutical

• Source of medicine/pharmaceutical
• Traditional/folklore

P. ovata (important as a medicinal plant in India) and P. lanceolata differ in having somewhat more erect, entire leaves and shorter inflorescences. The widely common P. major and P. media have much broader leaves.

Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.

Physical/Mechanical Control

Control measures suggested for ornamental and perennial crops include cultivation, cover crops and the use of mulch (UC-IPM, 2012).

Chemical Control

Isoxaben, a relatively new broadleaf pre-emergent herbicide, has been effective in limiting germination of P. coronopus in turfgrass and some ornamental crops. Post-emergent 2,4-D, triclopyr, MCPA, and mecoprop can control seedlings, but control of established plants is much more difficult. For established plants, 2,4-D works best while triclopyr, MCPA, and mecoprop will only reduce vigour. Repeated applications to perennial plants with products containing 2,4-D or triclopyr can be helpful (UC-IPM, 2012). In lucerne or alfalfa, pre-emergence treatment with hexazinone has been successful. Glyphosate can be effective in plantation and orchard crops.

03/12/2012 Original text by:

Chris Parker, Bristol, UK