Tagetes minuta L.
Common names: khaki bush, khaki weed, African marigold (Eng.); kakiebos, khakibos, langkakiebos, stinkbos, stinkkhakibos, transvaalse kakiebos (Afr.); mbanje (isiNdebele)
Khaki bush planted around your house will provide you with a very good early-warning security system. The strong odor of the bush when crushed will immediately give away any person or animal setting foot on your property. For some people the smell may bring back nostalgic memories from life on a farm or walking in the veld, whereas others cannot stand the stench. Whether you love it or hate it, it will not leave you untouched.
An erect, woody, annual, herbaceous weed, up to 2 m tall. Stems are unbranched or branching repeatedly in the upper parts, grooved or ridged. Stems are green at first, but changes to brownish or yellowish after flowering. The leaves are pinnately dissected into 4 to 6 pairs of pinnae.
Plants produce clusters of up to 80 cylindrical flower heads in a panicle-like inflorescence. The heads are 10–15 mm long, enclosed by 4 or 5, fused involucral bracts. Each head generally contains about 3 ray florets with short, broad, lemon-coloured lamina and 3 disc florets.
Fruits are narrow, cylindrical and usually dark brown.
It flowers and fruits in summer.
Tagetes minuta as naturalized exotic weed in South Africa, and therefore has not been evaluated for the Red List of South African plants.
Distribution and habitat
Tagetes minuta is an invasive weed that prefers growing in disturbed areas, such as old lands on farms, abandoned gardens, roadsides and waste places. It grows on dry or moist soil. It is originally from South and North America, but is now widespread everywhere in South Africa and neighboring areas.
Derivation of name and historical aspects
The common name of Tagetes minuta in English, khaki-weed, is derived from its supposed introduction by English khaki-clad soldiers during the Anglo Boer War (1899–1902). The weed was introduced with the imported fodder for the British Army’s horses. The earliest record in South Africa appears to be in 1905 at Vlakfontein. In 1909, it was recorded at Grahamstown as a troublesome weed. The first record for KwaZulu-Natal was noticed in Newcastle in 1910. By 1920 it was widespread in South Africa.
After the Anglo Boer war in South Africa, Australian troops took plants home to their native land, where it now also grows profusely.
Tagetes minuta is a pioneer plant and its roots assist in stabilizing disturbed soils. The flowers are mostly pollinated by insects and honeybees. Seeds are dispersed through different mechanisms, such as harvesting with crops and fodder, blown away by wind, carried away by small animals, birds or insects, or washed away by rain water.
Tagetes minuta is adapted to high temperatures and can tolerate low rainfall, but is not frost-hardy.
Although khaki bush can be harvested from the veld and provides an income to collectors, it is also grown commercially in South Africa, France and North America for its essential oil. The oil has a wild-citrus-like smell and has a yellowish to reddish amber colour.
Highland Essential Oils on the farm Vlakbult (near Clocolan) cultivate around 500 ha of Tagetes (about half of their production need) annually, for an output of about 1 ton of oil.
Leaves, stalks and flowers are picked when plants are in seed, mechanically chopped and the oil is then steam-distilled. Initially the oil has a wild unpleasant smell, but after 12 months of maturity, it achieves a pleasant sweet-fruity (mango-like) smell and attains a stable composition. During maturation, the oil thickens and the colour darkens. The aroma of the oil develops further in the following 5 years, after which the oil quality deteriorates.
Although Tagetes Oil is not a popular fragrance oil, it is used in some perfumes. It can be blended with massage oil or used in the bath where it can assist with wounds, cuts, coughs, chest infections, parasitic and fungal infestations.
The oil is very effectively used for wounds and a wide variety of infections.
The boiled leaves of the Tagetes minuta are used to treat infections in the respiratory system or stomach problems, by drinking the boiled mixture. In a 5% dilution, Tagetes Oil has been used to kill maggots in open wounds. When used in a cream or lotion, it can have a beneficial effect on fungal and microbial infections and especially helpful when treating weeping wounds or athletes foot.
In burners, vaporizers or steamers, the vapour from the leaves can treat headaches, coughs, bronchitis, chest infections or be an insect repellent for a wide variety of insects. The vapour also acts as an antiseptic in a room.
The leaves and flowers are a good insect repellent and are often seen hanging in dwellings to deter swarms of flies and mosquitoes. The oil is also used as a repellent to the bowfly and is useful as a bowfly dressing.
Caution should be taken when using Tagetes Oil. It is very powerful and should be used sparingly on the skin (less than 0.5% dilution), not used on a sensitive skin, and avoided during pregnancy. It is photo toxic and may cause photosensitivity.
Several other species of Tagetes, commonly known as marigolds with their rich and vibrant orange, yellow and brownish colours, are very popular as garden plants and in many cultures it plays an important role in traditional ceremonies. In Mexico, it is regarded as a flower of the dead during the 1st November celebrations of the Day of the Dead, where they use it to honor the lives of the family and friends who have passed away. It is believed that its strong odour attracts dead souls towards the flowers, therefore burial sites are adorned with marigolds. It was used by the Aztecs in many religious ceremonies and also as a medicine. In India, it is widely cultivated to make garlands, for decorative purpose in marriages and festivals.
Growing Tagetes minuta
Tagetes minuta grows on light (sandy), medium (loamy) or heavy (clay) soils, which are well drained, acidic, neutral or alkaline. It prefers sunny positions. Tagetes minuta can be propagated by seeds after the danger of frost is well passed. To encourage the seed germination, soil temperature should be 18.3°C or warmer.
Select a location in your garden that receives full sun and loosen the soil. Sow the seeds in early spring directly into the beds. Seeds should be sown approximately 1 cm deep and covered lightly with the garden soil. Water the area thoroughly and then water on a regular basis throughout the growing season. Plants will start to germinate within 2 weeks and will then reach maturity within 120 days of planting. Collect the seeds from drying plants to use them again or allow the plant to self-seed.
- Baser, K.H.L. & Malyer, H. 1996. Essential oil of Tagetes minuta L. from Turkey. Journal of Essential Oil Research 8: 337, 338.
- Forsyth, C. & Van Staden, J. 1993. Germination of Tagetes minuta L. Temperature effects. Annals of Botany 52(5): 659–666.
- Discover Life: http://www.discoverlife.org/mp/20q?search=Tagetes+minuta Accessed 3 February 2017
- Esoteric Oils: Tagetes essential oil information. http://essentialoils.co.za/essential-oils/tagetes.htm, Accessed 3 February 2017
- Highland Essential Oils: Tagetes Oil. http://www.highlandessentialoils.co.za/html/tagetes.html, Accessed 3 February 2017
- Leung, A. (1980). Encyclopedia of common natural ingredients. John Wiley, New York.
- SANBI. 2015. Tagetes minuta L. National Assessment: Red List of South African Plants version 2015.1. Accessed on 2017/02/24
- Soule, J.A. 1993. Tagetes minuta: A potential new herb from South America. In: J. Janick & J.E. Simon (eds.), New crops. Wiley, New York.
Millicent Ndou & Marinda Koekemoer
National Herbarium, Pretoria
Plant Type: Bi/Annual
SA Distribution: Eastern Cape, Free State, Gauteng, KwaZulu-Natal, Limpopo, Mpumalanga, North West, Northern Cape, Western Cape
Soil type: Sandy, Clay, Loam
Flowering season: Early Summer, Late Summer, Autumn
PH: Acid, Alkaline, Neutral
Flower colour: White, Cream
Aspect: Full Sun, Shade, Morning Sun (Semi Shade), Afternoon Sun (Semi Shade)
Gardening skill: Easy