Portulaca quadrifida
(chickenweed)

P. quadrifida is a succulent, annual, mat-forming species. The native range of this species is not clearly defined and many describe it as pantropical. P. quadrifida has been introduced into a number of new countries around the world. There are no records of P. quadrifida behaving as an invasive weed outside its native range, where it acts as an agricultural weed. This species is not particularly competitive but, as a halophyte, it is resistant to drought and areas of low soil fertility and therefore readily becomes dominant under such circumstances. There is also a large amount of variation within this species enabling it to adapt to new environments. As a plant with food and herbal properties, there are possibilities for deliberate introduction of this species into new areas where it could be problematic.

The distribution of P. quadrifida is not clearly defined. USDA-ARS (2014) describe the distribution of P. quadrifida as ‘pantropical, except Australia’ but the Flora of China Editorial Committee (2014) considers it as ‘probably native to Africa, now pantropical’. Wagner and Lorence (2015) in the Flora of West Indies also treat this species as native to much of the Caribbean.

For the purposes of this datasheet, P. quadrifida is treated as native to Africa and Western Asia and introduced elsewhere. See distribution table for countries in which this species is recorded.

The risk of P. quadrifida being accidentally introduced into new areas is low as it is a slow-growing species with minimal risk of contamination of crop seed. As a plant of interest medicinally, however, there is some risk of deliberate introduction.

P. quadrifida is found in the wild on bare patches of ground and among rocks, on sandy or stony soils, from sea-level up to 2000 m altitude. It is often involuntarily introduced by the agency of man and readily occupies newly disturbed areas, compost and rubbish heaps and fields. It is tolerant of a wide range of soils but prefers sand or sandy loams (PROTA, 2014). Singh (2005) notes that P. quadrifida may occur on alkaline soils but is not so common on saline soils. African Plant Database (2014) describe P. quadrifida as a plant of sandy river banks, open stony dry, or sub-desert grassland and shrubland, Acacia savanna; trampled areas, roadside and edges of cultivated fields. 

In its native range of India, P. quadrifida is a significant weed in maize (Zea mays) (Subbulakshmi, 2009) and onions (Allium cepa) (Kachare et al., 2005). It is also a major weed of green gram (Vigna radiata) in the ‘summer’ season in India but less in black gram (V. mungo) in the monsoon season (Singh et al., 1991). It also occurs in pigeon pea (Cajanus cajan), cabbage (Brassica oleracea var. capitata), cauliflower (Brassica oleracea var. botrytis), cucurbits (Cucurbitaceae family) and teosinte (Zea species) in India and in coffee (Coffea species) in Kenya and sorghum (Sorghum bicolor) in Sudan.

Genetics

The Chromosome number for P. quadrifida is variously reported as 2n= 18, 36 and 48 (Sharma and Bhattachyya, 1956; Missouri Botanic Garden, 2014; PROTA, 2014), with 2n= 48 being the most frequently quoted.

The wide distribution and large variation, seen in P. quadrifida, points to great genetic variability which enables the species to adapt to new environments (PROTA, 2014).

Reproductive Biology

P. quadrifida reproduces by producing seeds which are largely dormant due to their hard seed coats. Scarification with sulphuric acid, dry storage for more than three months or high temperature pretreatment (58°C) for about one month can overcome dormancy. Germination is controlled by external factors such as light, the water content of the soil and temperature. Alternation between 12 and 35^°C gives higher rates of germination than a constant intermediate temperature. The temperature requirement appears to be the main regulator of germination and seeds can germinate over wide ranges of moisture content and photoperiods (Shukla, 1972). Fresh seeds need light for germination, but this requirement disappears in older seeds.

It is also possible for P. quadrifida to regenerate vegetatively from small stem fragments (PROTA, 2014).

Physiology and Phenology

P. quadrifida has C₄ metabolism (PROTA, 2014) and is therefore well adapted to benefit from high temperature conditions. The C₄ metabolism helps to optimize photosynthesis in conditions of high heat and bright sunlight while enduring periods of limited water availability (Koch and Kennedy, 1982). As a prostrate herb, it is not otherwise especially competitive, but with extreme resistance to drought, it can become dominant in hot, arid conditions. The author collected a herbarium specimen of this species in Ethiopia and found that it was still alive and growing from between dry newspaper 12 months later (Chris Parker, Consultant, personal observation, 2015).

Generative development seems not to be influenced by photoperiod. Flowering in Pakistan is from August to March but flowering and fruiting can occur at any time of year when conditions are hot. This may be year-round in some areas. Under conditions of sub-lethal desiccation, the weed may propagate through shoot fragments. As only the most extreme desiccation is lethal, this is a very common phenomenon.

Longevity

P. quadrifida is an annual species and the established plants are not believed to perennate. The longevity of seeds in the soil is presumed to be at least a few years but no estimates have been seen.

Environmental Requirements

Although P. quadrifida is frequently referred to as a halophyte, therefore adapted to saline soils (Kokad and Ahmad, 2010), Singh (2005) suggests it is more tolerant of alkalinity than of salinity. Ecocrop (2014) indicates a low or moderate tolerance, not exceeding an electrical conductivity of 4 dS/m (equivalent to 40mM NaCl). Although Ecocrop (2014) indicates that P. quadrifida benefits from moderate or high soil fertility, it may thrive in extremely infertile conditions.

There is no information available on the natural enemies of P. quadrifida. It is however likely that it is affected by many of those listed for P. oleracea.

Animal feed, fodder, forage

• Fodder/animal feed

Human food and beverage

• Vegetable

Medicinal, pharmaceutical

• Source of medicine/pharmaceutical
• Traditional/folklore
• Veterinary

The mat-forming habit and prostrate stems which can root from the nodes easily distinguish P. quadrifida from other members of the genus (Gilbert and Phillips, 2000).

In Africa P. pilosa has a similar habit to P. quadrifida and Geesink (1972) reported that a number of specimens from New Caledonia and the Pacific recorded as P. pilosa were often actually P. quadrifida. They can be distinguished from each other as P. pilosa has alternate leaves, five petals and more numerous stamens whereas P. quadrifida has four petals and the leaves are opposite (PROTA, 2014). Additionally P. hereroensis has often been confused with P. quadrifida but this species is an annual which does not root adventitiously (Gilbert and Phillips, 2000).

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

Normal hoeing is relatively ineffective against P. quadrifida as the plant can survive extremely desiccating conditions and can re-grow from small fragments of stem. It is recommended either to burn or bury all removed material to prevent re-establishment.

Solarization for 30 and 45 days provided 100% control in North India (Nasr-Esfahani, 1993).

Movement Control

Due to its ability to survive desiccation and re-growth from small fragments of stem, it is especially important to prevent movement of weeded material via cultivation equipment.

Chemical Control

There are reports of P. quadrifida being controlled by herbicides and it is reported as being susceptible to MCPA and 2,4-D (Pfeiffer and Burleigh, 1958). In India, selective control was achieved with metoxuron, metribuzin, methabenzthiazuron, terbutryn, methabenzthiazuron + fluchloralin and fluchloralin + metribuzin (Randhawa et al., 1981). Additionally, directed applications of glyphosate + 2, 4-D have also been used in cropped fields (Tnau Agritech Portal, 2014).

16/07/2014 Original text by:

Chris Parker, Consultant, Bristol, UK.