NOTICE: Hard copies of the Australian New Crops Newsletter are available from the publisher, Dr Rob Fletcher. Details of availability are included in the
Advice on Publications Available.[Much of this information has been gleaned from IPGRI's excellent book on the crop, by JA Chweya and NA Mnzava (Promoting the conservation and use of underutilized and neglected crops 11); available on http://198.93.227.125/regional/cwana/pdf/catswhisk. pdf within the web site http://www.cgiar.org/ipgri/doc/download.htm]
Edible wild leafy vegetables play an important role in African agricultural and nutritional systems but they are regarded by scientists as minor crops and hence receive little attention in most R&D programs.
Some of these vegetables are regarded as weeds in other parts of the world.
The cat's whiskers (Cleome gynandra L./Gynandropsis gynandra (L.) Briq.) grows as a weed in most tropical countries.
It is not formally cultivated as a commercial crop anywhere in the world but for years has been a semi-domesticated volunteer crop in home gardens or on fertile land near homesteads in many parts of sub-Saharan Africa (Kenya, Uganda, Botswana, Zambia, South Africa, Zimbabwe, Malawi, Nigeria, Cameroon, Namibia, Swaziland, Tanzania and Ghana).
The species is native to Northern Africa (Egypt, Mauritania), Western Africa (Cameroon, Ghana, Guinea, Cote d'Ivoire, Mali, Niger, Nigeria, Sierra Leone), Central Africa (Angola, Burundi, Zaire), Eastern Africa (Ethiopia, Kenya, Somalia, Sudan, Tanzania, Uganda), the African Islands (Madagascar, Mauritius, Reunion, Seychelles), Middle East (Oman, North Yemen), Far East (Afghanistan), Asia (Borneo, India, Java, Malaysia, Moluccas, Philippines, Sri Lanka, Sumatra, Sulawesi, Thailand) and Fiji.
It has been introduced to the Caribbean islands (Bahamas, Bermuda), Cuba, south-eastern USA (Florida, Kentucky and Louisiana), southern, mid-western and south-western USA, Mexico, Puerto Rico, Colombia, Venezuela, Bolivia, Peru, Brazil, Paraguay, Argentina, Uruguay, Chile, the Iberian Peninsula, Italy, France, Central and Northern Europe (including Great Britain), the former USSR, China, Japan, Korea, Philippines, Australia, New Zealand and the Pacific islands.
In Zambia, a national seed company markets the seed, production packages have been developed and the company is vigorously promoting cat's whiskers as a cultivated crop.
The plant
Cat's whiskers is an erect herbaceous annual herb, which can grow up to 1.5 m in height. It has a long tap root and stems and leaf petioles are thickly glandular.
The inflorescence is quite showy and is up to 30 cm in length. The fruit is a long-stalked, dry, dehiscent siliqua, which is a spindle-shaped capsule measuring up to 12 cm long and 8-10 mm wide. Seeds measure 1.0-1.5 mm in diameter.
Plants are predominantly self-pollinating but cross-pollination can occur.
There are reports of protandry and protogyny in the genus, Cleome, and some species other than Cleome gynandra exhibit 'super dioecy' in which flowers on the same inflorescence can be male sterile, have pistil abortion, or become complete
Because of its tropical origin, Cleome is believed to be daylength-insensitive, but some Cleome species are facultative long day species.
Propagation is by seed. Seed germination is erratic, occurring over an extended period, because seeds have a rest period (latency) that extends to the 5th month after harvest collection. Active germination starts 6 months after harvest and is believed to peak after 12 months of storage.
Seeds from a previous crop are usually broadcast or drilled on well-loosened fertile soil or the plants are grown on raised or flat beds.
Seeds germinate within 4-5 days. Seedlings are thinned about 3 weeks later, and the thinnings are used as a vegetable.
When plants reach a height of about 15 cm, they can be harvested by uprooting whole plants, or by topping, cutting back to ground level, or picking individual leaves or leafy branches at frequent intervals.
Frequent picking and deflowering encourages lateral growth, thus extending the harvesting period. Harvesting starts 4-6 weeks after seedling emergence and may last 4-5 weeks.
Bi-weekly removal of tender leaves allows regeneration of branches. Accessions have shown varying regeneration ability.
Cumulative leaf yields of 30 t/ha per season have been recorded. Weekly leaf yields increase with plant age, until about the 7th week of growth.
After several successive leaf harvestings from a plants, it is left to flower and produce capsules. Fruit development and maturation take 3-4 months.
Seed yields are about 500 kg/ha at most.
As a weed, cat's whiskers is commonly found growing on fertile soils, especially in those previously mixed with animal manure, or with homestead refuse.
It grows well up to about 1000 metres above sea level in semi-arid, sub-humid and humid climates, and is adapted to many soil types so long as they are deep and well drained, with a pH range of 5.5-7.0.
The soil types range from sandy loam to clay loams.
Favourable growing conditions for cat's whiskers require adequate soil moisture, high light intensity and temperatures of 18-25 C.
The species has a C4 photosynthetic pathway, an adaptation mechanism that enables it to survive in drier and hot environments.
The leaves exhibit strong rhythmic circadian movements, following the direction of the sun. The plants do not grow well in shade and are unable to compete with weeds.
The species can grow in areas with short periods of useful rainfall but the plants are not drought resistant.
Water stress reduces leaf yield and quality. The plants cannot withstand flooding.
Seed yield is not responsive to nitrogen application because at higher rates, stems become too succulent and regeneration is reduced, a disadvantage where plants are periodically harvested.
The plants can be attacked by pentatomids, locusts, nematodes, flea beetles, green vegetable bugs, cabbage sawfly, cotton jassids and hurricane bugs.
The plant is also host to powdery mildew.
The nutritional composition of the raw leaves can vary with soil fertility, environment, plant type, plant age and the production techniques used.
The vegetable is a rich source of nutrients, especially vitamins (A and C) and minerals (calcium and iron). It also contains some protein, and the leaves contain over and above the normal recommended adult daily allowance of vitamins A and C and the minerals calcium and iron.
Boiling the leaves may reduce vitamin C content while drying reduces the vitamin content.
Deflowering significantly decreases plant height and increases number of branches per plant and leaf yield. Deflowering also significantly increases leaf ascorbic acid content, but has virtually no effect on leaf b-carotene and total phenolic contents.
Leaf ascorbic acid content significantly increases with plant age, while total leaf phenolics decrease.
These phenolic compounds give the vegetable an astringent taste. The phenolic compounds bind proteins and this may lower protein digestibility and quality. The leaves also contain glucosinolates.
The crude protein composition of the seed varies from 17.9% (in green-stemmed plants) to 31.4% (in purple-stemmed plants).
The lipid content varies from 25.1% (green-stemmed plants) to 29.6% (purple-stemmed plants). Oleic and linoleic acids account for about 81% of total fatty acids, but linoleic acid is the most abundant (accounting for 59% of total fatty acids).
Lipids have a high degree of unsaturation and different varieties exhibit slight variation in the proportion of fatty acids.
Amino acid analysis of defatted meal has indicated that the composition is comparable to that of leguminous oilseeds.
In Asia, cat's whiskers is cultivated for seed oil.
Uses
Cats' whiskers is predominantly used as a leafy vegetable.
Throughout Africa, the tender leaves or young shoots, and often the flowers as well, are eaten boiled as a pot herb, tasty relish, stew or side dish.
In India, it is eaten as a pot herb and a flavouring in sauces and in Thailand it is consumed fermented in a product called 'pak-sian-dong'.
The leaves are rather bitter, and for this reason are cooked with other leafy vegetables such as cowpea, amaranth and black nightshade. To reduce the bitterness, milk is added to the boiled leaves and the mixture left overnight.
In other areas, leaves are boiled briefly, the water is discarded, and they are then combined with other ingredients in a stew.
In many cultures, the boiled leaves of cat's whiskers are also regarded as a medicinal meal. As well, sap from the leaves is used as an analgesic, particularly for headaches and earaches and the leaves also have anti-inflammatory properties. A decoction or infusion of boiled leaves and/or roots is administered to facilitate childbirth, treat stomach-ache, constipation, conjunctivitis or thread-worm infection. The seeds and roots also have these anthelmintic properties.
Plants of cat's whiskers also have insecticidal, antifeedant and repellent characteristics.
The leaves have anti-tick properties, an ethanol extract is toxic to insect pests of cruciferous vegetables and the volatile oils repel diamond back moth larvae from cabbage leaves.
The plant has an anti-feedant action against the tobacco caterpillar and the extract from the mature seeds is toxic to brinjal aphid and Heliothis larvae (Heliothis armigera).
Development
Small germplasm collections of Cleome gynandra exist in Botswana, Kenya, South Africa, Tanzania and Zambia.
Long-term seed storage is at -20 or -10 C, and seeds are kept in hermetically sealed packs (aluminium foil or air-tight containers). For active collections, seeds are kept at temperatures of 12-15 C, at 40% relative humidity.
Studies in Kenya on germplasm collected from farmers' fields have indicated there were no significant differences between plant characteristics, leaf yield and the nutritive quality of plants from seedlots collected from various areas although there was variability in most morphological characters between the seedlots.
Characters likely to be of interest to any genetic improvement work would be:
Yield could be improved indirectly via yield components (days to flowering, plant height, number of leaves, leaf length, fresh leaf weight and dry leaf weight).
All components of vegetative yield, except days to flowering have shown a positive correlation with dry leaf yield. Number of leaves is the most consistent determinant of dry leaf weight.
Limitations
The status of the crop as a wild and weedy volunteer renders it unattractive for attention, especially as it is often seen as a poor person's crop.
The palatability of the crop is low, especially without appropriate preparation.
Prospects
Cat's whiskers is a highly nutritious leafy vegetable, with a rich source of vitamins A and C, calcium, iron and protein. The seeds also have potential for use as edible oil and animal feed. The plant also possesses insecticidal properties.
Crop improvement could select for:
There is also a need to:
For contacts with experience with Cleome gynandra, refer to pages 45-54 of the publication by JA Chweya and NA Mnzava:
http://198.93.227.125/regional/cwana/pdf/catswhisk.pdf
Any claims made by authors in the Australian New Crops Newsletter are presented by the Editors in good faith. Readers would be wise to critically examine the circumstances associated with any claims to determine the applicability of such claims to their specific set of circumstances. This material can be reproduced, with the provision that the source and the author (or editors, if applicable) are acknowledged and the use is for information or educational purposes. Contact with the original author is probably wise since the material may require updating or amendment if used in other publications. Material sourced from the Australian New Crops Newsletter cannot be used out of context or for commercial purposes not related to its original purpose in the newsletter
Contact: Dr Rob Fletcher, School of Land and Food, The University of Queensland Gatton College, 4345; Telephone: 07 5460 1311 or 07 5460 1301; Facsimile: 07 5460 1112; International facsimile: 61 7 5460 1112; Email:
r.fletcher@mailbox.uq.edu.au[
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GK; latest update 6 June 1999 by: RF