Other common names: staggerwort, stinking Willie, groundsel, grimsel, simson, bird seed, ragwort, chickenweed, common ragwort, garden groundsel, grand mouron, old-man-in-the-spring
Senecio vulgaris L.
Identification of Groundsel
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 inch long by 0.1 inch wide, with a grooved, 0.4 inch-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 inches in height. Hollow, hairless stems will root at leaf-stem junctions, especially if these junctions contact the ground. Leaves are alternate, 6–10 inches long by 0.5–2 inches 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 or with opposite lobes. Leaves lack stalks and instead clasp 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 flower heads are grouped together at the ends of branches. Flower heads are 0.4 inch in diameter and made up of many smaller yellow, petal-less flowers. Two sets of small, narrow, green bracts are present directly beneath the flower head. 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 inch long and cylindrical, with five to 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 flower heads. 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 flower heads without petals. However, pineapple weed flowers are somewhat acorn-like, and the leaves are very finely divided and emit a pineapple-like scent.
Management of Groundsel
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. 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. 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, whereas rotary tillage is less effective. 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 seed 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 cleanup of fields after harvest is essential for controlling common groundsel.
Ecology of Groundsel
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.
Seed weight: Population mean seed weights range from 0.16–0.25 mg.
Dormancy and germination: Most common groundsel seeds are capable of germination immediately after falling from the parent plant. One exception is seeds collected in early spring, which were mostly dormant. Buried seeds became dormant in late spring and early summer, apparently induced by high temperatures. Six months of burial in the soil is sufficient to break dormancy. Most seeds require light for germination 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. The optimal temperature is also influenced by storage temperature; it has a narrower range of 50–59°F when seed are stored cold whereas it broadens to 50–77°F when seeds are stored warm. Alternating daily temperatures do not increase germination over the optimum constant temperature.
Seed longevity: Common groundsel seed banks are relatively short lived. Over a five-year period, seeds in uncultivated soil declined by 45% per year. In cultivated soil, no seeds were left after five years. In another study, only 6% of deeply buried seeds survived for two years, and no viable seeds shed on the soil surface and subjected to multiple soil disturbances were left after 40 weeks. However, seed buried in porous clay containers for 19 months did not lose viability.
Season of emergence: Peak emergence occurs from early spring to early summer, but some seedlings continue to emerge until late fall. Emergence is likely to cease, however, during hot weather. Flushes of emergence often follow rainfall events or periods when plants are dispersing seeds.
Emergence depth: Most seedlings emerge from within the top 0.8 inch, but a few emerge from as deep as 2 inches.
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 22°F, but plants wilt and tend to lose leaves. 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. Deliberately 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.
Mycorrhiza: Common groundsel is mycorrhizal.
Response to fertility: Common groundsel shows only a minimal growth response to increasing N application rates. The species has a low response to K and competes well at low K levels. Application of a balanced nutrient solution to plants grown on a sandy loam soil increased seed production by 75%. In another experiment, application of N-P-K about doubled production of seed heads in agricultural fields. Nutrient stressed plants produce smaller seeds that have more sporadic germination. Seedlings from nutrient stressed parent plants show increased tolerance of low nutrient conditions.
Soil physical requirements: Common groundsel grows on a wide range of soil types. 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.
Response to shade: Common groundsel can survive and grow even under 93% shade, but its growth rate is much reduced relative to full sunlight.
Sensitivity to disturbance: If plants are cut when flowering, 35% of the seeds will still mature. 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.
Time from emergence to reproduction: In mild, moist conditions, plants flower four to five weeks after emergence and set seed seven to 11 days later. Overwintering plants require several months, depending on how long freezing and near freezing temperatures last. In regions with mild winters, the species can flower in any month of the year, but even moderately hot conditions such as day/night temperatures of 84/72°F can inhibit seed set. An increase in daylength from eight to 13 hours can decrease time to flowering and seed production. Populations subjected to a heavily weeded garden habitat exhibited a shorter vegetative period before flowering, whereas populations from field margins and coastal areas had a longer vegetative phase.
Pollination: Common groundsel mostly self-pollinates but occasionally is cross pollinated by insects, particularly hover flies.
Reproduction: Typically, common groundsel seed production ranges from 1,100–1,800 seeds per plant but can average as high as 38,000 per plant. Seed production in a pure stand was 8,000–13,000 seeds per plant but was 900–2,200 in competition with wheat. Since the species can complete three generations per year even in regions with long, cold winters like central New York, 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.
Common natural enemies: A rust (Puccinia lagenophorae) damages leaves and can reduce seed production by half or more. Rust infection also reduced plant recovery from freezing temperatures. Rust only occurred on plants fertilized with P. Infection is more severe in summer and autumn than in spring, probably because of lower inoculum levels in spring.
Palatability: Common groundsel is not consumed as food by people. It contains toxic alkaloids that can damage the liver and lungs. Consumption of 25–50% of bodyweight over several weeks causes poisoning in livestock. Cattle and horses are more susceptible than sheep and goats. Chickens can also be poisoned. The onset of symptoms from poisoning is typically delayed by several weeks. 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. 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.
Summary Table of Groundsel Characteristics
| Common groundsel | ||||||||
|---|---|---|---|---|---|---|---|---|
| Growth habit | Seed weight (mg) | Seed dormancy at shedding | Factors breaking dormancy | Optimum temperature for germination (F) | Seed mortality in untilled soil (%/year) | Seed mortality in tilled soil (%/year) | Typical emergence season | Optimum emergence depth (inches) |
| short, branched | 0.16–0.25 | No | li | 50–68 | 45 | 100 | early spring to early summer | 0–0.8 |
| Photosynthesis type | Frost tolerance | Drought tolerance | Mycorrhiza | Response to nutrients | Emergence to flowering (weeks) | Flowering to viable seed (weeks) | Pollination | Typical & high seed production (seeds per plant) |
| C3 | high | low | yes | low | 4–5 | 1–2 | self, can cross | 1,500 & 38,000 |
Table Key
General: The designation “–” signifies that data is not available or the category is not applicable.
Growth habit: A two-word description; the first word indicates relative height (tall, medium, short, prostrate) and second word indicates degree of branching (erect, branching, vining).
Seed weight: Range of reported values in units of “mg per seed.”
Seed dormancy at shedding: “Yes” if most seeds are dormant when shed, “Variable” if dormancy is highly variable, “No” if most seeds are not dormant.
Factors breaking dormancy: The principle factors that are reported to break dormancy and facilitate germination. The order of listing does not imply order of importance. Abbreviations are:
scd = seed coat deterioration
cms = a period subjected to cold, moist soil conditions
wst = warm soil temperatures
li = light
at = alternating day-night temperatures
ni = nitrates
Optimum temperature range for germination: Temperature (Fahrenheit) range that provides for optimum germination of non-dormant seeds. Germination at lower percentages can occur outside of this range. The dash refers to temperature range, and the slash refers to alternating day/night temperature amplitudes.
Seed mortality in untilled soil: Range of mortality estimates (percentage of seed mortality in one year) for buried seeds in untilled soil. Values were chosen where possible for seeds placed at depths below the emergence depth for the species and left undisturbed until assessment. Mortality primarily represents seed deterioration in soil.
Seed mortality in tilled soil: Range of mortality estimates (percentage of seed mortality in one year) for seeds in tilled soil. Values were chosen for seeds placed within the tillage depth and subjected to at least annual tillage events. Seed losses are the result of dormancy-breaking cues induced by tillage, germination and deterioration of un-germinated seeds.
Typical emergence season: Time of year when most emergence occurs in the typical regions of occurrence for each weed. Some emergence may occur outside of this range.
Optimum emergence depth: Soil depths (in inches below the soil surface) from which most seedlings emerge. Lower rates of emergence usually will occur at depths just above or just below this range.
Photosynthesis type: Codes “C3” or “C4” refer to the metabolic pathway for fixing carbon dioxide during photosynthesis. Generally, C3 plants function better in cooler seasons or environments and C4 plants function better in warmer seasons or environments.
Frost tolerance: Relative tolerance of plants to freezing temperatures (high, moderate, low).
Drought tolerance: Relative tolerance of plants to drought (high, moderate, low).
Mycorrhiza: Presence of mycorrhizal fungi. “Yes” if present; “no” if documented not to be present, “unclear” if there are reports of both presence and absence; “variable” if the weed can function either with or without, depending on the soil environment.
Response to nutrients: Relative plant growth response to the nutrient content of soil, primarily N, P, K (high, moderate, low).
Emergence to flowering: Length of time (weeks) after emergence for plants to begin flowering given typical emergence in the region of occurrence. For species emerging in fall, “emergence to flowering” means time from resumption of growth in spring to first flowering.
Flowering to viable seed: Length of time (weeks) after flowering for seeds to become viable.
Pollination: “Self” refers to species that exclusively self-pollinate, “cross” refers to species that exclusively cross-pollinate, “self, can cross” refer to species that primarily self-pollinate, but also cross-pollinate at a low rate, and “both” refers to species that both self-pollinate and cross-pollinate at relatively similar rates.
Typical and high seed production potential: The first value is seed production (seeds per plant) under typical conditions with crop and weed competition. The second value, high seed production, refers to conditions of low density without crop competition. Numbers are rounded off to a magnitude that is representative of often highly variable reported values.
Further Reading
Holm, L., J. Doll, E. Holm, J. Pancho and J. Herberger. 1997. Senecio vulgaris L. In World Weeds. Natural Histories and Distribution. pp. 740–750. Wiley and Sons: New York, New York.
Müller-Schärer, H. and J. Frantzen. 1996. An emerging system management approach for biological weed control in crops: Senecio vulgaris as a research model. Weed Research 36: 483–491.
Popay, A.I. and E.H. Roberts. 1970b. Ecology of Capsella-bursa-pastoris (L.) Medik. and Senecio vulgaris L. in relation to germination behavior. Journal of Ecology 58: 123–139.
Robinson, D.E., J.T. O'Donovan, M.P. Sharma, D.J. Doohan and S. Figueroa. 2003. The biology of Canadian weeds. 123. Senecio vulgaris L. Canadian Journal of Plant Science 83: 629–644.