Common lambsquarters

Chenopodium album L.

Common lambsquarters plant
Common lambsquarters plant in flower
Common lambsquarter seedling

Images above: Upper left: Common lambsquarters plant (Antonio DiTommaso, Cornell University). Upper right: Common lambsquarters plant in flower (Scott Morris, Cornell University). Bottom: Common lambsquarters seedling (Antonio DiTommaso, Cornell University).

Identification

Other common names: lamb's-quarters, white pigweed, white goosefoot, pigweed, lambs-quarters, fat-hen, mealweed, frost-blite, frost-bite, bacon-weed, lamb's-quarters goosefoot, netseed lamb's-quarters, wild spinach, green pigweed

Family:  goosefoot family, Chenopodiaceae

Habit:  Tall, erect, summer annual herb.

Description:  Seedlings have thumb to long ellipse shaped, 0.16-0.6” (0.4-1.5 cm) long by 0.04” (0.1 cm) wide cotyledons.  Upper sides of cotyledons are dull green; seedling stems and undersides of cotyledons are maroon-green.  The first two leaves are egg shaped and opposite; all subsequent leaves are alternate although first few leaves may appear opposite.  Young leaves have a silvery or pink grainy or mealy coating.  The diamond to egg shaped young leaves arise from a silvery to light green, mealy stem; leaf edges are either entire or lightly toothed.  Stems of mature plants are upright, pyramidal, highly branching, hairless, ridged, maroon-speckled, and can reach 3-5 ft (0.9-1.5 m) tall.  Leaves are alternate, 1.2-4” (3-10 cm) long by less than 3.5” (9 cm) wide, green, and diamond or egg to triangle shaped, with mealy undersides.  Lower leaves broader, longer, and usually toothed and stalked.  Upper leaves are sometimes lance shaped, stalkless, and toothless.  The taproot is short and branched.  Individual flowers are very small, inconspicuous, and silvery to green; they are clumped together in dense clusters located in stem-leaf junctions and at branch tips.  Seeds are round, black, and 0.06” (0.15 cm) wide or they can be brown and slightly larger with a flatter oval shape.  Papery flower tissue closely coats most of the seed surface at dispersal.

Similar species:  Halberdleaf orach (Atriplex patula L.) is similar to common lambsquarters and has a white mealy bloom on young growth.  Halberdleaf orach is shorter and bushier than common lambsquarters, and its leaves are generally more lance shaped, less toothed, and often have a pair of narrow lobes near the base of the leaf blade.  Common lambsquarters seedlings are sometimes confused with several young pigweed species (Amaranthus spp.).  Young, true leaves of common lambsquarters seedlings have grainy or fuzzy, silver to pink bloom when they first emerge, pigweed seedlings do not.  Mature common lambsquarters leaves generally have toothed, sculpted edges while pigweeds have generally oval shaped, untoothed leaves.  Other Chenopodium spp. do not have mealy young tissues, diamond to egg shaped leaves and light colored, succulent looking stems.

Management

Common lambsquarters germinates readily in response to tillage and cultivation.  More than most weed species, a one- to two-week lag between initial and final seedbed preparation is effective at flushing out and destroying seedlings.  A short fallow in the spring with repeated surface cultivation causes even greater depletion of the surface seed bank.  The key is to use progressively shallower tillage, with the final seedbed prepared to a depth of no more than 1.5” (3.8 cm).  The species rarely emerges from deeper than that, and deeper tillage will raise seeds into the near-surface zone favorable for germination.  Continue killing seedlings after crop planting by tine weeding with blind tillage.  Once the crop is large enough to tolerate inter-row cultivation, hill up slightly when the lambsquarters seedlings are still in the early seed-leaf stage.  Even crops like cabbage and tomato that are not normally hilled will tolerate 1” (2.5 cm) of soil against the base and this is sufficient to bury the tiny seedlings.  Continue hilling with subsequent cultivations if the crop will tolerate it.

In spring and fall planted grains, a dense, uniform and vigorous stand is critical for maximizing the crop's initial competitive advantage.  Light harrowing just as the lambsquarters seedlings begin to emerge can substantially reduce density of the weed, but any substantial reduction in stand density of the grain is likely to prove counter-productive.

Straw mulch and other mulch materials are highly effective for suppressing this species since its small seeds provide few resources for pushing the seed leaves up out of the mulch mat (Mohler and Teasdale 1993).  Because the seed-leaves stay together in a vertical position until they reach the light, however, a few seedlings will usually penetrate at least 2” (5 cm) of loose straw, so either use a deeper mulch layer or compact the mulch after application (Teasdale and Mohler 2000).

Common lambsquarters is highly responsive to N fertility.  Avoid excess fertilization and, in particular, avoid heavy fertilization before the crop is well established.  On the other hand, incorporation of a legume cover crop can enhance seedbank decline of this species by triggering fatal germination of buried seeds (Mohler et al. 2018b).

Because common lambsquarters is a prolific producer of long-lived seeds, consistent efforts to limit seed production will greatly assist long term management.  Since most seeds remain on the plant long after they mature (Schwartz-Lazaro et al. 2021), they can be captured or destroyed during combine harvest.  Clean up fields promptly after harvest if this weed is present.  If possible, remove plants that have flowered, as they can continue to form seeds even after mowing or light tillage that leaves the flowering stalks on the soil surface.  Hand rogue at least the larger plants out of intensive vegetable systems.  Many of the seeds remain on the plant until early winter, so fall cleanup after harvest can reduce lambsquarters density the following year.  In a long-term vegetable crop rotation, seed banks of common lambsquarters tended to decrease with deep plowing to 14-16” (36-41 cm) but increased with rotary tillage or shallow plowing to 6-7” (15-18 cm) (Roberts 1963).  Despite the potential longevity of common lambsquarters seed banks, the species can be virtually eliminated from a field through proper crop rotation coupled with other good management practices (Mohler et al. 2018a).

Ecology

Origin and distribution:  Common lambsquarters was introduced from Europe.   It is present in all 50 states and all Canadian provinces and territories except for Nunavut (USDA Plants).  It has been introduced throughout the world and is widespread from 70° N to 50° S except in extreme deserts (Holm et al. 1977).

Seed weight: 0.4-0.7 mg depending on the population and type of seed; the same plant may produce several types of seeds with different size and dormancy characteristics (Stevens 1932, Harrison 1990, Lutman et al. 2002, Mahoney and Swanton 2008, Anderson et al. 2023).  Germination percentage increases linearly with increasing seed weight (Anderson et al. 2023).

 Actual data: 0.50 mg (Lutman et al. 2002), 0.56 ± 0.08 mg (Harrison 1990), 0.58 mg (Mohler et al. 2016), 0.65 to 0.74 mg (Mahoney and Swanton 2008), 0.70 mg (Stevens 1932), 0.72 mg (Gaba et al. 2019).

Dormancy and germination:  Common lambsquarters frequently produces two or more visually distinct types of seeds on the same plant, and these differ in their dormancy properties (Williams and Harper 1965, Yao et al. 2010).Many seeds are usually dormant immediately after falling from the parent plant, but some are not. A period of cold, wet conditions breaks dormancy (Williams 1963, Vincent and Roberts 1977, Bouwmeister and Karssen 1993, Hu et al. 2018),and warm weather (68/50to 86/68 °F or 20/10to 30/20°C) in early spring promotes subsequent emergence (Forcella 1992, Huet al. 2018). Seeds produced under short day-length conditions are less dormant than those produced during long days (Bassett and Crompton 1978).Common lambsquarters germination is substantially increased by white light (Henson 1970, Vincent and Roberts 1977, Roberts and Benjamin1979, Eslami 2011) but is inhibited by light depleted in red wavelengths, such as light that has passed through a plant leaf canopy (Taylorson and Borthwick 1969). Germination is increased by the presence of nitrate and by large day/night temperature fluctuations (Henson 1970, Vincent and Roberts 1977, Roberts and Benjamin 1979 ,Williams 1963).The germination promoting effects of light, nitrate and fluctuating temperature act together such that more seeds germinate with two of these cues than with one, and maximum  germination is usually reached when the seeds receive all three cues (Henson 1970, Vincent and Roberts 1977, Roberts and Benjamin 1979).All of these cues tend to occur during or shortly after tillage. Seeds from plants grown in high nitrate conditions have higher N concentrations and higher germination rates than seeds from unfertilized soil (Fawcett and Slife 1978). Seeds germinate best with daytime temperatures of 64-77°F (18-25°C) (Weaver et al. 1988, Harvey and Forcella 1993, Roman et al.1999, Eslami 2011, Hu et al. 2018).The process of germination begins at temperatures as low as 43°F (6°C)(Wiese and Binning 1987, Roman et al.1999) but relatively few seeds germinate below 55°F (13°C) or above 91°F (33°C) (Harvey and Forcella 1993, Roman et al.1999, Tang et al. 2022). A few weeks exposure to temperatures over 59°F (15°C) causes some seeds to enter secondary dormancy (Bouwmeister and Karssen 1993), and thus, warm weather in summer induces dormancy in a substantial fraction of seeds (Karssen 1980). Germination is reduced by increasing salinity and moisture deficit, but unaffected by soil pH (Tang et al. 2022).

Seed longevity: Common lambsquarters seeds can remain viable in the soil for many decades (Toole and Brown 1946).  As an extreme example, viable seeds have been recovered from under medieval ruins in Europe (Ødum 1965).  Most seeds, however, do not last so long.  In undisturbed soil, mortality rates of 8-35% per year have been observed (computed from Chepil 1946, Roberts and Feast 1972, Conn and Werdin-Pfisterer 2010, Gardarin et al. 2010).  In the U.S. corn belt, annual mortality rates averaged 40-48% but with considerable variation among locations (Davis et al. 2005).  In New York, annual seed mortality was variable with an average rate of 21% in one experiment, but an unusually high rate of 78% in another (Mohler et al. 2018b).  In long-term conventional and organic plots in the mid-Atlantic states, annual seed mortality averaged 51% (Ullrich et al. 2011).  In annually tilled fields, decline in common lambsquarters seed bank varied from 14 to 42% per year (computed from Barralis et al. 1988, Schweizer and Zimdahl 1994, Lutman et al. 2002), with most loss rates nearer the higher value.  In soil stirred six or more times per year, seed loss was 31-52% per year (Roberts 1963, Popay et al. 1994).

Season of emergence:  Common lambsquarters emerges throughout the growing season, but with a strong peak in spring (Chepil 1946, Williams 1963).It is categorized as an early emerging species that begins emergence in early spring, but it has one of the longest emergence durations of all weeds studied (Myers et al. 2004, Werle et al. 2014). Common lambsquarters was most commonly present when average air temperature was less than 68 °F (20 °C) during the first four weeks after planting (Teasdale et al. 2019).

Emergence depth: Optimum depth for emergence is near the soil surface, 0.1-0.2” (0.25 to 0.5cm), and few seedlings emerge from deeper than 1.2” (3cm) (Barralis et al. 1988, Grundy et al. 1996, Benvenuti et al. 2001, Eslami 2011, Mohler and Galford 1997, Tang et al. 2022).

Photosynthetic pathway: C3 (Pearcy et al. 1981).

Sensitivity to frost:  Common lambsquarters is sensitive to frost (Stevens 1924, Williams 1963).

Drought tolerance:  The species is relatively drought tolerant (Williams 1963, Maganti et al. 2005).

Mycorrhiza: The species is non-mycorrhizal (Bassett and Crompton 1978, Dhillion and Friese 1994, Williams 1963).

Response to fertility:  Common lambsquarters is a heavy feeder of plant nutrients.  It has a strong growth response to increasing N applications up to at least 480 lb N/A (540 kg/ha) (Blackshaw et al. 2003) and a moderate response to P up to about 46 lb P2O5/A (52 kg/ha) (Blackshaw et al. 2004).  Plants grew substantially larger with 5,830 lb/A (6,530 kg/ha) of composted chicken manure as compared to 2,920 lb/A (3,270 kg/ha) (Little et al. 2015).  The species concentrates N in excess of its needs (Andreasen et al. 2006, Lindsey et al. 2013), and increasing N can favor this weed relative to crops (Holm et al 1977).  Common lambsquarters also has a strong growth response to increasing K and it is strongly competitive when K levels are high (Qasem and Hill 1995).  The species tolerates a wide range of soil pH but tends to grow poorly on very acidic soils (Williams 1963).

Soil physical requirements:  Common lambsquarters is regularly found on all soil textures from sand to clay and peat, but it grows most vigorously on fine textured soils (Williams 1963).  It emerges best in a moderately rough seed bed (Harper et al. 1965).  It tolerates some soil compaction and waterlogging, but with reduced emergence and growth (Harper et al. 1965, Maganti et al. 2005).  The species tolerates salinity (Yao et al. 2010).

Response to shade:  Common lambsquarters is intolerant of heavy shade, especially shortly after emergence.  Plants react to shade by growing taller and allocating a larger proportion of tissue to stem and leaves and a smaller proportion to the inflorescence (Mahoney and Swanton 2008).  Nevertheless, plants will still flower in dense shade (Williams 1963), and shading that begins after the plant flowers has no affect on seed production (Gramig and Stoltenberg 2009).

Sensitivity to disturbance: Young plants are unable to survive mowing or trampling (Williams 1963, Bassett and Crompton 1978, Donald 2001), and older plants may re-grow poorly (Meiss et al. 2008).  Mowing common lambsquarters plants that extend above the crop leaf canopy can reduce biomass and seed production in dry years, but can increase biomass and seed production in moist years that permit abundant regrowth from lower nodes on the remaining plant stem (Anderson et al. 2023).  Plants dry out quickly, however, when uprooted (Mohler, personal observation). 

Time from emergence to reproduction:  Plants flower more quickly with short day lengths than with long days (Williams 1963).  Flowering occurred 5-6 weeks after emergence in Canada (Shrestha and Swanton 2007) and 81 days after emergence in Wisconsin (Doll 2002).  Some seeds become viable within two weeks of flowering and most are viable within three weeks.  Early maturation may be triggered by protracted drought (Mohler, personal observation).

Pollination:  Common lambsquarters is self-pollinated or wind pollinated (Bassett and Crompton 1978).

Reproduction:  Plants set seeds over a relatively short period as they mature.  A small plant (about 1 ft) can produce several hundred seeds and large plants can produce more than 100,000 seeds (Mohler and Callaway 1995).  Plants growing at low density with cabbage, onion, or without a crop produced 30,000-370,000 seeds/plant (Grundy et al. 2004), plants in soybeans produced 30,000 to 175,000 seeds/plant (Harrison 1990, Perron and Légère 2000), plants in corn produced 8,000-117,000 seeds/plant (Perron and Légère 2000) and plants in rapeseed produced 175-2,250 seeds/plant (Blackshaw et al. 1987).  Within each of these crops, most variation was due to differences in growing conditions between years.  Plant size at maturity decreases as the date of emergence is delayed (Shrestha and Swanton 2007) and seed production is closely correlated with total plant weight (Harrison 1990, Grundy et al. 2004).  Seed shattering at the time of soybean harvest ranged from low (1-29%) in eight site/years to moderate (45-65%) in two site/years (Schwartz-Lazaro et al. 2021).

Dispersal:  Because seeds of common lambsquarters often reach high densities in soil, they are easily spread between sites by soil clinging to large animals, shoes, tires and machinery following soil disturbance from farm operations, road construction, and even in ship’s ballast (Bassett and Crompton 1978).  The seeds survive well in the digestive tracts of cows, sheep, and pigs, and manure is commonly contaminated with common lambsquarters seeds (Bassett and Crompton 1978, Mt. Pleasant and Schlather 1994).  Some seeds will pass through chickens, sparrows, and ducks (Williams 1963, Mueller and van der Valk 2002).  Seeds also disperse in streams (Gurnell et al. 2006) and irrigation water (Wilson 1980)

Common natural enemies:  In wet weather, damping-off fungi can kill large numbers of lambsquarters seedlings, particularly if they are shaded by a crop or mulch.  Leaf miner damage (curved tracks on the leaves) is commonly observed but is rarely severe enough to check the weed’s growth.  (Mohler, personal observations)

Palatability:  Young lambsquarters are highly palatable and can be used as a salad green or pot herb.  The foliage is high in vitamin C, carotinoids, and essential minerals (Guerrera and Toriia Isasa 1997, Williams 1963).  Seeds and dried flower heads can be ground and added to soups and breads.  The cleaned seeds can be cooked as a grain or ground for flour (Bassett and Crompton 1978).  In pastures, crude protein and digestibility of common lambsquarters are similar to that of a tall fescue/legume forage (Bunton et al. 2020).  Plants can, however, contain oxalic acid and nitrate (Bassett and Crompton 1978, Williams 1963) and can be toxic to sheep and pigs if large amounts are consumed rapidly (Burrows and Tyrl 2006).

References:

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