Companion planting is a form of intercropping, typically practiced in small-scale gardens, in which two or more species of plants are grown near each other for shared benefit. For example, shade-loving vegetables like lettuce can be grown under taller crops like maize or sunflower. Mixed plantings are established to boost crop productivity, diversify options for food and income generation, and improve gardens’ resilience under difficult growing conditions.
Flowering plants can benefit garden or field crops in some interesting ways. In Issue 18 of ECHO Asia Notes, Dr. Abram Bicksler shared that certain flowering plants can:
- repel or confuse harmful insects
- attract insects, birds, frogs and other creatures that eat harmful pests
- attract pests to themselves, thereby minimizing damage to a main crop
- add beauty to a garden or field
ECHO’s Florida Seed Bank has obtained two marigold varieties, ‘Crackerjack Mix’ (African marigold; Tagetes erecta) and ‘Sparky Mix’ (French marigold; Tagetes patula). Both “African” and “French” marigolds actually come from Mexico and Central America (see Taylor 2011 for a historical account of the naming of marigold species). African marigold plants grow to 90 cm (3 ft) in height, producing large flowers that range in color from yellow to deep orange. By comparison, French marigolds are shorter (15-45 cm [6-18 in]) and have smaller orange/red flowers.
Marigolds have a strong odor that both repels pests and makes it more difficult for insects to find the plants they would normally feed on. Marigolds have been reported to reduce a number of pests in various crops. Examples include:
- leafhopper (Amrasca biguttula biguttula) and whitefly (Bemisia tabaci) in eggplant (Solanum melongena) (Sujayanand et al. 2015)
- aphids (Hyperomyzus lactucae and Macrosiphum euphorbiae) in lettuce (Lactuca sativa) (Russo et al. 2005)
- root knot nematodes (Meloidogyne sp.) or symptoms in tomato (Solanum lycopersicum) (Abid and Maqbool 1990), cowpea (Vigna unguiculata) (Olabiyi and Oyedunmade 2007), sweet potato (Ipomoea batatas) (Kumar et al. 2005), and soybean (Glycine max) (El-Hamawi et al. 2004)
Not all nematode species are controlled by marigolds. Suppression of root knot nematodes is most likely to be effective when marigolds are established as a dense cover (with plants no more than 18 cm [7 in] apart) in advance of a main crop (Krueger et al. 2010).
More information about African marigold is found in an ECHO Asia Seed Fact Sheet. Plants and seed may already be available in the country in which you are working. Alternatively, see www.ECHOcommunity.org for information on how to register as an active development worker to request complementary trial packets of seed.
Abid, M., and M. A. Maqbool. 1990. “Effects of Inter-Cropping of Tagetes erecta on Root-Knot Disease and Growth of Tomato.” International Nematology Network Newsletter 7 (3): 41–42.
Bello, T. T., B. Fawole, and A. Claudius-Cole. 2014. “Management of Root-Knot Nematodes (Meloidogyne Spp) on Tomato Using Antagonistic Plants.” Journal of Biology 4 (24): 97–100.
El-Gindi, A. Y., H. A. Osman, M. M. A. Youseef, H. H. Ameen, and A. M. Lashein. 2005. “Evaluation of the Nematicidal Effects of Some Organic Amendments, Biofertilizers and Intercropped Marigold, Tagetes erecta Plant on the Root-Knot Nematode, Meloidogyne incognita-Infected Cowpea Plants.” Bulletin of the National Research Centre (Cairo) 30 (3): 307–15.
El-Hamawi, M. H., M. M. A. Youssef, and H. S. Zawam. 2004. “Management of Meloidogyne incognita, the Root-Knot Nematode, on Soybean as Affected by Marigold and Sea Ambrosia (Damsisa) Plants.” Journal of Pest Science 77 (2): 95–98.
Krueger, R., K. E. Dover, R. McSorley, and K.-H. Wang. 2010. “Marigolds (Tagetes spp.) for Nematode Management.” http://edis.ifas.ufl.edu/ng045
Kumar, N. U. S., K. Krishnappa, B. M. R. Reddy, N. G. Ravichandra, and K. Karuna. 2005. “Intercropping for the Management of Root-Knot Nematode, Meloidogyne incognita in Vegetable-Based Cropping Systems.” Journal of Nematology 35 (1): 46–49.
Olabiyi, T. I., and E. E. A. Oyedunmade. 2007. “Marigold (Tagetes erecta L.) as Interplant with Cowpea for the Control of Nematode Pests.” Edited by K. Z. Ahmed. 8th African Crop Science Society Conference, El-Minia, Egypt, 27-31, October, 1075–78.
Russo, S., S. M. Rodriguez, S. Delfino, and M. Badiola. 2005. “Effect of Tagetes spp. on two pests aphids of Lactuca sativa (L.). [Spanish].” Revista de la Facultad de Ciencias Agrarias, Universidad Nacional de Cuyo 37 (1): 55–59.
Sujayanand, G. K., R. K. Sharma, K. Shankarganesh, Supradip Saha, and R. S. Tomar. 2015. “Crop Diversification for Sustainable Insect Pest Management in Eggplant (Solanales: Solanaceae).” Florida Entomologist 98 (1): 305–14.
Taylor, J.M. 2011. “The Marigold: History and Horticulture.” Chronica Horticulturae 51:24-28.