Common purslane

Portulaca oleracea L.

Common purslane seedling
Common purslane flowers
Stand of common purslane

Images above: Upper left: Common purslane seeding (Scott Morris, Cornell University). Upper right: Common purslane flowers (Antonio DiTommaso, Cornell University). Bottom: Stand of common purslane (Antonio DiTommaso, Cornell University).

Identification

Other common names:  pusley, purslane, pursley, wild portulaca, low pigweed, common portulaca, wild portulac, little hooweed

Family:  purslane family, Portulacaceae

Habit:  Succulent, prostrate, taprooted, summer annual herb.

Description:  Young seedling stems begin upright, reaching 0.5” (1.3 cm) in height, then become prostrate.  Stems and cotyledons are maroon tinged and fleshy.  Cotyledons are 0.08-0.4” (0.2-1 cm) long by 0.04-0.08” (0.1-0.2 cm) wide, and oblong.  First true leaves are 0.5-1” (1.3-2.5 cm) long, fleshy, smooth, and green with maroon hued undersides.  The first 6-10 true leaves are opposite.  Mature plants are succulent, crawling and grow prostrate in 2-3 ft (0.6-0.9 m) diameter circles.  Stems are highly branched, round, fleshy, and turn maroon with age.  Leaves are club shaped, round-tipped, fleshy, green, hairless, and smooth.  Leaves may be alternate or opposite and sometimes have red margins.  The root system consists of a thick taproot with secondary fibrous roots.  Yellow, 5-petaled flowers, 0.13-0.4” (0.3-1.0 cm) in diameter, are present individually in leaf axils and branch junctions and in clusters on terminal branch ends.  Flowers open only in sunny weather.  Seeds are black, flat, round to kidney shaped, and small, less than 0.04” (0.1 cm) in diameter, with a bumpy surface.  Seeds develop in 0.25” (0.6 cm) diameter globe shaped capsules that split horizontally to release the seeds upon maturity. 

Similar species:  Horse purslane (Trianthema portulacastrum L.) is also a prostrate succulent, but it has stalked leaves and pinkish purple flowers.  Common purslane is sometimes confused with prostrate pigweed (Amaranthus blitoides S. Watson), prostrate knotweed (Polygonum aviculare L.), and various spurges (Euphorbia spp.).  Prostrate pigweed has non-fleshy leaves, distinguishing it from common purslane.  Prostrate knotweed can be distinguished by the presence of papery appendages (ocreas) wrapping the stem above each leaf. Spurges release a milky, white sap when cut.

Management

Because newly emerged common purslane seedlings are very small and fragile, stirring the top 1-2” (2.5 - 5 cm) of soil with tillage implements 2-4 times after the soil warms is highly effective at removing most of the individuals that will emerge during the season.  Cultivation of large plants is often ineffective because the plants re-root or set seed without re-rooting.  Thus, cultivation of plants beyond the cotyledon stage should aim at burial rather than breakage or uprooting (Proctor et al. 2011).  Although stem fragments can develop new root systems, this requires several weeks and the resulting individuals are less vigorous and produce fewer seeds than new seedlings that germinate in response to the cultivation (Miyanishi and Cavers 1980).  Flame weeding kills seedlings, but large plants recover unless unusually long exposure times are used.

Organic mulch materials are highly effective for suppressing common purslane (Chauhan and Johnson 2009).  Because the species is susceptible to rotting under continuously shady, humid conditions, and because of its prostrate growth form, less mulch is required to control common purslane than for most other annual weeds.  Due to its shade intolerance and prostrate growth form, dense planting helps control this weed in crops that will tolerate high density and that grow quickly (Wang et al. 2006).  Rapid coverage of the ground is critical, however, because even small, dying plants can set seed (Miyanishi and Cavers 1980).

Common purslane requires high nutrient levels for rapid growth.  In particular, it is more responsive to P than some vegetable crops like lettuce.  Continuous reliance on manure derived compost as an N source for vegetable production leads to P accumulation and this appears to foster problems with common purslane (Hopen 1972).

Because the seeds are highly persistent in the soil, removal of escapes before they set seeds is useful for long-term control, but difficult due to the plant's substantial taproot.  Since flowers can self-pollinate without opening, plants can ripen seeds while still appearing to be immature.

Ecology

Origin and distribution:  Common purslane probably originated in South America and spread into North America with Native American agriculture.  It may, however, have originated in North Africa and spread to eastern North America with European colonization.  It currently occurs throughout the U.S.A. and southern Canada and has a world-wide distribution, except at latitudes above 60° N.  (Mitich 1997, Miyanishi and Cavers 1980, USDA Plants)

Seed weight:  0.078-0.093 mg (Chauhan and Johnson 2009), 0.13 mg (Stevens 1932), 0.15 mg (Zhao et al. 2011).

Dormancy and germination:  Some seeds are capable of germination immediately after falling from the capsule, although dormancy develops as seeds mature (Egley 1974).  Light is usually required for germination of freshly shed seeds (Chauhan and Johnson 2009, Egley 1974, El-Keblawy and Al-Ansari 2000), but germination in the dark becomes more likely as the seeds age (Baskin and Baskin 1988, Kruk and Benech-Arnold 1998, Singh 1973).  Initially, the species germinates best when soil temperatures exceed 86 °F (30 °C) (Baskin and Baskin 1988, El-Keblawy and Al-Ansari 2000, Kruk and Benech-Arnold 1998, Miyanishi and Cavers 1980, Singh 1973).  This temperature requirement lowers to 68 °F (20 °C), however, as spring progresses (Baskin and Baskin 1988, Kruk and Benech-Arnold 1998).  Germination of aged seeds is better at alternating than constant temperatures (Kruk and Benech-Arnold 1998).  Light filtered through a leaf canopy inhibits germination (Van der Veen 1970 in Baskin and Baskin 1988).  Nitrate promotes germination of seeds in the dark (Miyanishi and Cavers 1980, Vengris et al. 1972).  Germination is not affected across a pH range of 5 to 9 (Chauhan and Johnson 2009).

Seed longevity:  Common purslane seeds have germinated after 30 years (Toole and Brown 1946) and 40 years of burial (Kivilaan and Bandurski 1981, Miyanishi and Cavers 1980).  In several annually tilled soils in New Zealand seed viability declined by 29% per year (Popay et. al. 1994).  On three soil types in a tilled small grain-fallow rotation in Saskatchewan, the common purslane seed bank declined by 17-27% per year (computed from Chepil 1946).  Seed decline in a Mississippi soil was approximately 60% per year in untilled soil and 76-87% per year in tilled soil (computed from Egley and Williams 1990).  Seeds of common purslane remained viable after soil was solarized with a daily maximum of 149 °F (65 °C) (Egley 1983) and 30% survived continuous cooking of moist soil at 140 °F (60 °C) (Egley 1990).

Season of emergence:  Most seedlings begin emerging in late spring when maximum air temperature exceeds 86 °F (30 °C) and rain is adequate.  They continue to emerge during the heat of the summer.  (Baskin and Baskin 1988, Chepil 1946, Mitich 1997, Miyanishi and Cavers 1980)                         

Emergence depth:  Common purslane emerges best when the seeds are at the soil surface provided the soil is moist.  Emergence declines rapidly as depth in the soil increases, and seedlings do not emerge from seeds deeper than 1” (2.5 cm).  (Chauhan and Johnson 2007, Hopen 1972, Vengris et al. 1972)

Photosynthetic pathway:  C4 (Elmore and Paul 1983, Miyanishi and Cavers 1980)

Sensitivity to frost:  Common purslane is very sensitive to frost and sometimes even dies from chilling prior to the first frost (Miyanishi and Cavers 1980, Stevens 1924).

Drought tolerance:  This species is extremely drought tolerant due partially to water storage in the succulent leaves and stems.  It also has small stomates and a waxy outer layer on the leaves, both of which reduce water loss from the leaves.  Under extreme drought conditions, the plants shed their leaves and grow new ones when water again becomes available.  (Mitich 1997, Miyanishi and Cavers 1980, Vengris et al. 1972)

Mycorrhiza:  Common purslane is not mycorrhizal (Pendleton and Smith 1983, Vatovec et al. 2005).

Response to fertility:  Common purslane is most problematic on highly fertile soils (Miyanishi and Cavers 1980).  The species shows a linear increase in growth up to nitrogen levels of 133 lb/a (150 kg/ha) (Miyanishi and Cavers 1980).  It responds to N, P, and K, but responds most to P (Hopen 1972).  The species shows a strong response to available phosphorus, and competition for phosphorus is the apparent cause for competitive suppression of lettuce by this species (Santos et al. 2004).  The species is found on soils with a pH of 5.6-7.8 (Miyanishi and Cavers 1980).

Soil physical requirements:  Common purslane grows best on sandy soils but tolerates a wide range of soil textures on well-drained soils (Miyanishi and Cavers 1980).  It establishes best on finely prepared seedbeds (Vengris et al. 1972).  It is relatively tolerant of saline soils, partially because of its capacity to produce antioxidant compounds (Kafi and Rahimi 2011, Yazici et al. 2007).

Response to shade:  Common purslane grows slowly in shade, and since the plant has a prostrate growth form, it is a poor competitor for light (Miyanishi and Cavers 1980, Vengris et al. 1972).  Under moist shady conditions, the species is prone to fungal diseases.  Even senescing plants can set seed, however (Miyanishi and Cavers 1980).

Sensitivity to disturbance:  Common purslane germinates in response to environmental cues that are associated with tillage (light, warm soil, nitrate), and consequently, soil disturbance during summer generally results in a flush of new seedlings (Miyanishi and Cavers 1980) and it’s common occurrence in vegetable fields and gardens (Mitich 1997).  Because it is succulent, common purslane does not die easily following uprooting.  It may then re-root, or continue to mature and set seeds even without contact with the soil (Vengris et al. 1972).  The plant fragments easily, and the pieces can develop new root systems from stem fragments, but only stem fragments with nodes produce new leaves, and it is the presence of leaves on the fragment that improves survival and new growth (Proctor et al. 2011).

Time from emergence to reproduction:  Plants flower 4-8 weeks after emergence and set seeds 7-16 days later (Doll 2002, Egley 1974, Miyanishi and Cavers 1980, Vengris et al. 1972).  Plants emerging in mid-summer can flower within 2-3 weeks of emergence (Vengris et al. 1972).  Consequently, the species can complete two or more generations per year (Miyanishi and Cavers 1980).  Seeds mature on main branches first and subsequently on secondary branches, giving a sequential production of seeds from individual plants throughout the season (Vengris et al. 1972).

Pollination:  The species is primarily self-pollinated.  Flowers open in the morning on bright, hot days, and if conditions are not suitable for opening, the flowers can successfully self-pollinate and turn to mature capsules without opening.  (Miyanishi and Cavers 1980, Vengris et al. 1972)

Reproduction:  Flower buds form in the axils of leaves.  The capsules look very much like the flower buds (Miyanishi and Cavers 1980).  Consequently, plants commonly appear to go from a pre-reproductive state to seed shed overnight.  One foot (30 cm) diameter plants produce about 7,000 seeds (Vengris et al. 1972), but a large plant may produce over 100,000 seeds (Miyanishi and Cavers 1980).  Undisturbed common purslane does not spread vegetatively, but plant fragments created during cultivation can re-root (Proctor et al. 2011).

Dispersal:  The seeds have no apparent adaptations that aid dispersal and fall directly onto the ground around the capsule.  The principal mode of dispersal is probably in soil clinging to shoes, tires, and machinery.  Seeds have been recovered from cattle manure (Colbach et al. 2013), deer feces (Myers et al. 2004), and bird feces and occasional dispersal to new sites by animals may occur.  (Miyanishi and Cavers 1980)

Common natural enemies:  A sawfly, Sofus pilicornis, mines the leaves (Vengris et al. 1972).  A white rust, Albugo portulacae, commonly attacks common purslane and can destroy plants under favorable conditions.  (Miyanishi and Cavers 1980)

Palatability:  Common purslane is edible as a salad vegetable or pot herb (Mitich 1997, Miyanishi and Cavers 1980).  The digestibility, protein content and mineral content is higher than that in most other weed species (Bosworth et al. 1980).  The plant is particularly rich in omega-3-fatty acids, vitamin E, and vitamin C (Yazici et al. 2007).  An upright growing cultivar has been developed (Miyanishi and Cavers 1980).  However, livestock fed large amounts of common purslane can develop nitrate and oxalate poisoning (Mitich 1997).

References:

  • Baskin, J. M., and C. C. Baskin.  1988.  Role of temperature in regulating the timing of germination in Portulaca oleracea.  Canadian Journal of Botany 66:563-567.
  • Bosworth, S. C., C. S. Hoveland, G. A. Buchanan, and W. B. Anthony.  1980.  Forage quality of selected warm-season weed species.  Agronomy Journal 72:1050-1054.
  • Colbach, N., C. Tschudy, D. Meunier, S. Houot, and B. Nicolardot.  2013.  Weed seeds in exogenous organic matter and their contribution to weed dynamics in cropping systems. A simulation approach.  European Journal of Agronomy 45:7-19.
  • Chauhan, B. S., and D. S. Johnson.  2009.  Seed germination ecology of Portulaca oleracea L.: an important weed of rice and upland crops.  Annals of Applied Biology 155:61-69.
  • Chepil, W. S.  1946.  Germination of weed seeds. I. Longevity, periodicity of germination, and vitality of seeds in cultivated soil.  Scientific Agriculture 26: 307-346.
  • Doll, J.  2002.  Knowing when to look for what: Weed emergence and flowering sequences in Wisconsin. http://128.104.239.6/UW_weeds/extension/articles/weedemerge.htm.
  • Egley, G. H.  1974.  Variations in common purslane seeds.  Weed Science 22:535-540.
  • Egley, G. H.  1983.  Weed seed and seedling reductions by soil solarization with transparent polyethylene sheets.  Weed Science 31:404-409.
  • Egley, G. H.  1990.  High-temperature effects on germination and survival of weed seeds in soil.  Weed Science 38:429-435.
  • Egley, G. H., and R. D. Williams.  1990.  Decline of weed seeds and seedling emergence over five years as affected by soil disturbance.  Weed Science 38:504-510.
  • El-Keblawy, A., and F. Al-Ansari.  2000.  Effects of site of origin, time of seed maturation, and seed age on germination behavior of Portulaca oleracea from the Old and New Worlds.  Canadian Journal of Botany 78:279-287.
  • Elmore, C. D., and R. N. Paul.  1983.  Composite list of C4 weeds.  Weed Science 31:686-692.
  • Hopen, H. J.  1972.  Growth of common purslane as influencing control and importance as a weed.  Weed Science 20:20-23.
  • Kafi, M., and Z. Rahimi.  2011.  Effect of salinity and silicon on root characteristics, growth, water status, proline content and ion accumulation of purslane (Portulaca oleracea L.).  Soil Science and Plant Nutrition 57:341-347.
  • Kivilaan, A., and R. S. Bandurski.  1981.  The one-hundred year period for Dr. Beal's seed viability experiment.  American Journal of Botany 68:1290-1292.
  • Kruk, B. C., and R. L. Benech-Arnold.  1998.  Functional and quantitative analysis of seed thermal responses in prostrate knotweed (Polygonum aviculare) and common purslane (Portulaca oleracea).  Weed Science 46:83-90.
  • Mitich, L. W.  1997.  Common purslane (Portulaca oleracea).  Weed Technology 11:394-397.
  • Miyanishi, K. and P. B. Cavers.  1980.  The biology of Canadian weeds. 40. Portulaca oleracea L.  Canadian Journal of Plant Science 60:953-963.
  • Myers, J. A., M. Vellend, S. Gardescu, and P. L. Marks.  2004.  Seed dispersal by white-tailed deer: implications for long-distance dispersal, invasion, and migration of plants in eastern North America.  Oecologia 139:35-44.
  • Pendleton, R. L., and B. N. Smith.  1983.  Vesicular-arbuscular mycorrhizae of weedy and colonizer plant species at disturbed sites in Utah.  Oecologia 59:296-301.
  • Popay, A. I., T. I. Cox, A. Ingle, and R. Kerr.  1994.  Effects of soil disturbance on weed seedling emergence and its long-term decline.  Weed Research 34:403-412.
  • Proctor, C. A., R. E. Gaussoin, and Z. J. Reicher.  2011.  Vegetative reproduction potential of common purslane (Portulaca oleracea).  Weed Technology 25:694-697.
  • Santos, B. M., J. A. Dusky, W. M. Stall, T. A. Bewick, D. G. Shilling, and J. P. Gilreath.  2004.  Phosphorus absorption in lettuce, smooth pigweed (Amaranthus hybridus) and common purslane (Portulaca oleracea) mixtures.  Weed Science 52:389-394.
  • Singh, K. P.  1973.  Effect of temperature and light on seed germination of two ecotypes of Portulaca oleracea L.  New Phytologist 72:289-295.
  • Stevens, O. A.  1924.  Effects of the first fall frost.  The American Midland Naturalist 9:14-17.
  • Stevens, O. A.  1932.  The number and weight of seeds produced by weeds.  American Journal of Botany 19:784-794.
  • Toole, E. H., and E. Brown.  1946.  Final results of the Duvel buried seed experiment.  Journal of Agricultural Research 72:201-210.
  • USDA Plants Database, Natural Resources Conservation Service.  http://plants.usda.gov
  • Vatovec, C., N. Jordan, and S. Huerd.  2005.  Responsiveness of certain agronomic weed species to arbuscular mycorrhizal fungi.  Renewable Agriculture and Food Systems 20:181-189.
  • Vengris, J., S. Dunn, and M. Stacewicz-Sapuncakis.  1972.  Life history studies as related to weed control in the Northeast. 7--common purslane.  Research Bulletin 598.  Agricultural Experiment Station, College of Food and Natural Resources, The University of Massachusetts: Amherst, MA.
  • Wang, G., M. E. McGiffen, Jr., and J. D. Ehlers.  2006.  Competition and growth of six cowpea (Vigna unguiculata) genotypes, sunflower (Helianthus annuus), and common purslane (Portulaca oleracea).  Weed Science 54:954-960.
  • Yazici, I., I. Türkan, A. Hediye Sekmen, and T. Demiral.  2007.  Salinity tolerance of purslane (Portulaca oleracea L.) is achieved by enhanced antioxidative system, lower level of lipid peroxidation and proline accumulation.  Environmental and Experimental Botany 61:49-57.
  • Zhao, L-P, G.-L. Wu, and J.-M. Cheng.  2011.  Seed mass and shape are related to persistence in a sandy soil in northern China.  Seed Science Research 21:47-53.