Cleome (Cleome gynandra) is a widespread herb that occurs in Southern Africa from Limpopo to Namibia. It is not formally cultivated in South Africa, but rather found growing naturally in disturbed soil, especially in the homestead backyard.
Cleome is an herbaceous, erect annual plant that grows to a height of between 0,5m and 1,5m, depending on the environment.
It is branched, sometimes becoming woody with age, and has a long taproot with a few secondary roots with root hairs. The stem is sticky, with glandular hairs, and is marked with longitudinal parallel lines.
Pigmentation on the stems varies from green to pink and purple. The leaf stalk is between 20mm and 50mm long and has glandular hairs. The leaves are between 2cm and 10cm long and 2cm to 4cm wide.
The flower stalk is 10mm to 20mm long and has glandular hairs. Petals are white, sometimes fading to rose pink.
The tender leaves or young shoots, and often the flowers, are boiled as a pot herb, relish, stew or side dish. In India, cleome is eaten as a pot herb and used as a flavouring in sauces; in Thailand it is eaten fermented in pak-sian-dong.
Cleome also has insecticidal and repellent characteristics.
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).
For optimal growth, cleome requires a temperature of 18°C to 25°C and high light intensity, as it is sensitive to cold. It grows well up to about 1 000m above sea level in semi-arid, subhumid and humid climates. The plant performs poorly when shaded and is unable to compete with weeds.
Cleome tolerates a degree of water stress, but prolonged water stress hastens flowering and senescence. It can therefore grow in areas with short periods of useful rainfall. Water stress reduces leaf yield and quality. The plant cannot withstand flooding.
Cleome prefers well-drained, medium-textured soil and struggles to grow in poorly drained or heavy clay soil. The soil should have a pH range of between 5,5 and 7 and should ideally be of the sandy loam to clay loam type.
As cleome is cultivated from seed, harrow the soil to a fine tilth and ensure it is well drained. Level the seedbed before planting.
Sow the seeds densely at 30cm inter-row spacing and thin them out later to 10cm to 15cm between plants. Plant the seeds at a shallow depth to ensure emergence and a good stand.
Applying a fertiliser containing a high level of nitrogen will delay flowering and increase the number and size of leaves. Soil fertility may affect the nutritional composition of the raw leaves; you will therefore need to apply farmyard manure, compost or inorganic fertiliser.
Diammonium phosphate is reported to give better results than double or triple superphosphate, as the nitrogen gives the plant an early start.
In rural areas, cleome is known as a self-seeding herb of cultivated land and other disturbed areas, requiring little attention. For this reason, it is rarely irrigated. However, during inadequate rainfall, frequent watering is necessary, especially during the vegetative growth period. Irrigation frequency is determined by the water-holding capacity of the soil.
Weeds and pests
Cleome does not have dense foliage and therefore cannot smother weeds, which renders it vulnerable to competition from weeds. The critical stage for weed control is during the first six weeks of development. The weeds can be hand-picked.
At planting, carry out a close inspection for slugs and snails, as these can devour entire seedlings.
Other pests that attack cleome are pentatomids (Acrosternum gramineum and Agonoscelis nubilis) and their parasitoids, locusts (Schistocerca gregaria), nematodes (Meloidogyne spp) flea beetles (Podagrica spp), green vegetable bugs (Nezara spp), cabbage sawfly (Athalia spp), cotton jassids (Empoasca spp) and hurricane bugs (Bagrada spp).
Apply insecticide to control these pests.
Harvest cleome in summer during the first rain. Thereafter, it can be harvested until autumn. Leaf harvesting starts four to six weeks after seedling emergence and may last four to five weeks.
You can also pick the leaves when the plants have reached a height of about 15cm. Fruit development and maturation take three to four months.
Harvest by uprooting the entire plant, 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, thereby extending the harvesting period. Biweekly removal of tender leaves enables the branches to regenerate.
After harvesting the leaves several times, leave the plant to flower and produce capsules.
Source: Cleome production guideline