Common groundsel

Senecio vulgaris L.

Common groundsel seedling
Common groundsel seed head and flowers

Images above: Left: Common groundsel seedling (Antonio DiTommaso, Cornell University). Right: Common groundsel seed head and flowers (Scott Morris, Cornell University).

Identification

Other common names:  common groundsel, staggerwort, stinking Willie, groundsel, grimsel, simson, bird-seed, ragwort, chickenweed, common ragwort, garden groundsel, grand mouron, old-man-in-the-spring

Family:  aster family, Asteraceae

Habit:  Erect, branched, summer, or occasionally winter annual herb.

Description:  Cotyledons of the seedling are club to ellipse shaped, measuring 0.1-0.4” (0.25-1 cm) long by 0.1” (0.25 cm) wide, with a grooved, 0.4” (1 cm) long stalk.  First true leaves are purple tinged along their midrib and grooved along their narrow stalk.  The stalk may have thin flaps of blade tissue on its edges.  Leaves are club to egg shaped and shallowly toothed; teeth point towards the leaf tip.  A few hairs may be present along leaf bases, stalks, and midribs.  Mature plants are many-branched and 5-24” (13-61 cm) in height.  Hollow, hairless stems will root at leaf-stem junctions, especially if these junctions contact the ground.  Leaves are alternate, 6-10” (15-25 cm) long by 0.5-2” (1.3-5 cm) wide, hairless, and club shaped in outline, with a prominent white midvein.  Lower leaves are deeply lobed with forward-pointing lobe tips, stalked, wavy edged, and purple tinged on their undersides.  Upper leaves are irregularly toothed to pinnatifid and lacking stalks, instead clasping around the stem with blade tissue.  All aboveground portions are somewhat succulent and fleshy.  The root system consists of a small, inconspicuous taproot and supplemental fibrous roots.  Several flowerheads are grouped together at the ends of branches.  Flowerheads are 0.4” (1 cm) in diameter and made up of many smaller yellow, petal-less flowers.  Two sets of small, narrow, green bracts are present directly beneath the flowerhead.  Several spirals of shorter bracts at the top of the flower stalk are blackened on their upper quarter to third.  Longer bracts, running from the flower base to the upper reaches of the yellow flowers, make up the second set of black-tipped bracts.  The outer coat of the seed is actually a thin dry layer of fruit tissue.  Seeds are clustered in seedheads.  Seeds are gray or red-brown, 0.1-0.2” (0.25-0.5 cm) long, and cylindrical, with 5-10 longitudinal ridges; small, flat, overlapping hairs develop between these ridges.  An easily removed tuft of white bristles is attached to one end of each seed.

Similar species:  Other species in the Senecio genus can be distinguished from common groundsel by the presence of petals on their flowerheads.  Mugwort (Artemisia vulgaris L.) and common ragweed (Ambrosia artemisiifolia L.) seedlings have similar leaves.  Mugwort seedling leaves are more triangular, broad, and deeply divided; they also have wooly hairs on their undersides.  Common ragweed seedlings are very deeply lobed and more closely resemble a young marigold; their cotyledons are round to slightly oval.  Pineapple-weed (Matricaria discoidea DC.) also has small, yellow flowerheads without petals, however, pineapple-weed flowers are somewhat acorn-like and the leaves are very finely divided and emit a pineapple-like scent.

Management

Common groundsel is often present in field crops, but is rarely a problem due to its short stature and low competitive ability relative to most field crops (Lutman et al. 2008).  It is a pest in many vegetable and fruit crops due to its rapid reproduction and ability to thrive in all seasons of the year (Holm et al. 1997, Robinson et al. 2003).  Clean up field margins, waste ground, edges of parking areas etc. to prevent seeds from dispersing into fields.  Annual moldboard plowing will help control this species (Robinson et al. 2003), whereas rotary tillage is less effective (Roberts 1963).  Since the seeds are relatively short-lived in the soil, and must be close to the surface for seedlings to emerge, few seeds will survive long enough to get an opportunity for emergence if the soil column is mixed annually.  The fibrous root system and shallow emergence depth make the species highly sensitive to tine weeding.  Because young plants form a rosette of leaves before making a flowering stem, the species has little ability to push up through a dense mat of organic mulch material. 

Short season crops will help interrupt the life cycle of this rapidly maturing weed.  It is almost certain to set seeds in a full season crop.  If the species is a problem, use precision cultivation tools as long as possible and then clean up remaining plants by hoeing.  Note that to prevent seed set, the plants must be killed before flowers open.  Prompt clean up of fields after harvest is essential for controlling common groundsel.

Ecology

Origin and distribution:  Common groundsel is a native of Eurasia, where it is widespread.  It has been introduced into North and South America, Australia, New Zealand and South Africa.  In North America, its range extends from coast to coast and from Alaska and the Yukon to Mexico.  Although it occurs widely in North America, it is primarily a weed of cool, moist regions.  (Robinson et al. 2003)

Seed weight:  0.16 mg (Milberg et al. 2000), 0.19 mg (Holm et al.1997), 0.22 mg (EFBI), 0.25 mg (Thompson et al. 1993).

Dormancy and germination:  Most common groundsel seeds are capable of germination immediately after falling from the parent plant (Holm et al. 1997, Popay and Roberts 1970a,b).  One exception is seeds collected in early spring which were mostly dormant (Popay and Roberts 1970b).  Buried seeds become dormant in late spring and early summer, apparently induced by high temperatures (Holm et al. 1997).  Six months of burial in the soil is sufficient to break dormancy (Popay and Roberts 1970b).  Most seeds require light for germination (Lutman et al. 2008, Popay and Roberts 1970a) and, thus, non-dormant seeds do not germinate until exposed to light during tillage.  The optimal temperature for germination varies among populations, but generally ranges from 50-68 °F (10-20 °C) (Robinson et al. 2003).  The optimal temperature is also influenced by storage temperature; it has a narrower range of 50-59 °F (10-15 °C) when seeds are stored cold whereas it broadens to 50-77 °F (10-25 °C) when seeds are stored warm (Popay and Roberts 1970a).  Alternating daily temperatures do not increase germination over the optimum constant temperature (Popay and Roberts 1970a).

Seed longevity:  Common groundsel seed banks are relatively short lived.  Over a 5-year period, seeds in uncultivated soil declined by 45% per year (computed from Roberts and Feast 1972, Mohler et al. 2001).  In cultivated soil, no seeds were left after 5 years.  In another study, only 6% of deeply buried seeds survived for 2 years, and no viable seeds shed on the soil surface and subjected to multiple soil disturbances were left after 40 weeks (Figueroa et al. 2007).  However, seed buried in porous clay containers for 19 months did not lose viability (Popay and Roberts 1970b).

Season of emergence:  Peak emergence occurs from early spring to early summer, but some seedlings continue to emerge until late fall (Holm et al. 1997, Popay and Roberts 1970b, Robinson et al. 2003).  Emergence is likely to cease, however, during hot weather (Figueroa et al. 2003).  Flushes of emergence often follow rainfall events, or periods when plants are dispersing seeds (Robinson et al. 2003).

Emergence depth:  Most seedlings emerge from within the top 0.8” (2 cm), but a few emerge from as deep as 2” (5 cm) (Chancellor 1964, Popay and Roberts 1970a,b).

Photosynthetic pathway:  C3                          

Sensitivity to frost:  Late emerging common groundsel plants commonly overwinter in cold regions.  The weed can survive periods of frozen soil and can survive down to 21 °F (-6 °C), but plants wilt and tend to lose leaves (Paul and Ayres 1985).  Thus, snow cover is probably necessary for survival during severe cold periods.

Drought tolerance:  Common groundsel thrives best in cool to warm, moist conditions.  In hot, dry conditions it tends to quickly flower and die.  Drought stressed plants developed a higher ratio of root weight to shoot weight, and the root systems were more vertical and less spreading.  The actual depth of soil reached was not greater in drought stressed plants, however, because the total root system was smaller (Berntson and Woodward 1992).

Mycorrhiza:  Common groundsel is mycorrhizal (Harley and Harley 1987, Pendleton and Smith 1983, West 1995).

Response to fertility:  Common groundsel shows only a minimal growth response to increasing N application rates (Blackshaw et al. 2003).  The species has a low response to K and competes well at low K levels (Qasem and Hill 1995).  Application of a balanced nutrient solution to plants grown on a sandy loam soil increased seed production by 75% (Brown and Molyneux 1996).  In another experiment, application of N-P-K about doubled production of seed heads in agricultural fields (Leiss and Müller-Schärer 2001).  Nutrient stressed plants produce smaller seeds that have more sporadic germination (Robinson et al. 2003).  Seedlings from nutrient stressed parent plants had greater tolerance of low nutrient conditions (Robinson et al. 2003).

Soil physical requirements:  Common groundsel grows on a wide range of soil types (Holm et al. 1997).  Generally, the species does best on loose, moist, fertile agricultural soils, but genetically adapted races tolerate more stressful environments like sandy or rocky beaches and the edges of gravel parking areas. The species is salt tolerant.  (Robinson et al. 2003)

Response to shade:  Common groundsel can survive and grow even under 93% shade, but growth rate is much reduced relative to full sunlight (Fenner 1978).

Sensitivity to disturbance:  If plants are cut when flowering, 35% of the seeds will still mature (Gill 1938).  Flower buds form on short shoots in the axils of basal rosette leaves.  Normally, these do not develop but rather die after the main stem flowers.  If the shoot is cut or trampled, however, the short basal shoots quickly elongate and flower (Harper and Ogden 1970).

Time from emergence to reproduction:  In mild, moist conditions, plants flower 4-5 weeks after emergence and set seed 7-11 days later (Holm et al. 1997, Robinson et al. 2003).  Overwintering plants require several months, depending on how long freezing and near freezing temperatures last (Paul and Ayers 1986b).  In regions with mild winters, the species can flower in any month of the year, but even moderately hot conditions, such as 84/72 °F (29/22 °C) day/night temperatures, can inhibit seed set (Robinson et al. 2003).  An increase in daylength from 8 to 13 hours can decrease time to flowering and seed production (Robinson et al. 2003).  Populations subjected to a heavily weeded garden habitat have a shorter vegetative period before flowering, whereas populations from field margins and coastal areas have a longer vegetative phase (Robinson et al. 2003).                                                                                                        

Pollination:  Common groundsel mostly self-pollinates, but occasionally is cross pollinated by insects, particularly hover flies (Robinson et al. 2003).

Reproduction:  Typically, common groundsel seed production ranges from 1100-1800 seeds per plant (Paul and Ayers 1986b, Holm et. al 1997, Salisbury 1978), but can average as high as 38,000 per plant (Kempen and Graf 1981).  Seed production in pure stand was 8,000 to 13,000 seeds per plant, but was 900 to 2,200 in competition with wheat (Lutman et al. 2008).  Since the species can complete three generations per year (Holm et al. 1997) even in regions with long cold winters like central New York (Mohler and Asaro unpublished data), neglected populations can increase rapidly.

Dispersal:  The seeds have a plume that assists with wind dispersal.  Seeds also disperse in irrigation water, in contaminated crop and cover crop seed, and on vehicles and farm machinery.  The seeds occur in manure.  (Holm et al. 1997, Robinson et al. 2003)

Common natural enemies:  A rust (Puccinia lagenophorae) damages leaves and can reduce seed production by more than half (Leiss and Müller-Schärer 2001, Paul and Ayres 1986a,b).  Rust infection also reduced plant recovery from freezing temperatures (Paul and Ayers 1985).  Rust only occurred on plants fertilized with P (West 1995).  Infection is more severe in summer and autumn than in spring, probably because of lower inoculum levels in spring (Müller-Schärer and Frantzen 1996).

Palatability:  Common groundsel is not consumed by people because it contains toxic alkaloids that can damage liver and lungs (Holm et al. 1997, Robinson et al. 2003).  Consumption of 25-50% of body weight over several weeks causes poisoning of livestock.  Cattle and horses are more susceptible than sheep and goats (Burrows and Tyrl 2006).  Chickens also can be poisoned.  The onset of symptoms from poisoning is typically delayed by several weeks (Robinson et al. 2003).  Since the toxic alkaloids are contained in the flowers and more flowers are produced under good moisture and fertility conditions, these conditions can also increase toxicity potential to livestock (Brown and Molyneux 1996).  This species has value as a food source for birds and invertebrates, and therefore may promote biodiversity if retained at low population levels in agricultural fields (Lutman et al. 2008).

References:

  • Berntson, G. M., and F. I. Woodward.  1992.  The root system architecture and development of Senecio vulgaris in elevated CO2 and drought.  Functional Ecology 6:324-333.
  • Blackshaw, R. E., R. N. Brandt, H. H. Janzen, T. Entz, C. A. Grant, and D. A. Derksen.  2003.  Differential response of weed species to added nitrogen.  Weed Science 51:532-539.
  • Brown, M. S., and R. J. Molyneux.  1996.  Effects of water and mineral nutrient deficiencies on pyrrolizidine alkaloid content of Senecio vulgaris flowers.  Journal of the Science of Food and Agriculture 70: 209-211.
  • Burrows, G. E., and D. J. Tyrl.  2006.  Handbook of Toxic Plants of North America. Blackwell: Ames, IA.
  • Chancellor, B. J.  1964.  Depth of weed seed germination in the field.  Proceedings of the Seventh British Weed Control Conference pp. 607-613.
  • Cici, S. Z. H., and R. C. Van Acker.  2011.  Relative freezing tolerance of facultative winter annual weeds.  Canadian Journal of Plant Science 91:759-763.
  • EFBI.  Ecological Flora of the British Isles, accessed 1/16/17.  http://www.ecoflora.co.uk/
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  • Paul, N. D., and P. G. Ayers.  1986b.  The impact of a pathogen (Puccinia lagenophorae) on populations of groundsel (Senecio vulgaris) overwintering in the field. I. Mortality, vegetative growth and the development of size hierarchies.  Journal of Ecology 74:1069-1084.
  • Paul, N. D., and P. G. Ayres.  1985.  Water relations and growth of rust-infected groundsel (Puccinia lagenophorae Cooke; Senecio vulgaris L.) during and after exposure to freezing soil temperatures.  Physiological Plant Pathology 27:185-196.
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