Text and photographs: Abelino Pitty, Ph.D.
Full Professor at ZAMORANO University
Agricultural Science and Production Department
Perennial Peanut (Arachis pintoi) is a plant native to South America (Brazil, Argentina, Paraguay and Uruguay). It was introduced in Honduras in 1989 for the feeding of cattle, Costa Rica in 1987 and Panama in 1985. It is perennial, of creeping growth and propagates by seeds or stolons. It adapts to different environmental conditions, tolerates ponding, prolonged droughts and grows well in the sun or shade. It grows well from sea level up to 1,800 msnm and with rain between 2000 and 3500 mm annually.
It is used for cattle feeding (initial use) because it has a high protein content and thus increases the nutritional quality of the pasture; it also resists grazing and it is persistent. It increases the fertility of the soil because it fixes nitrogen. However, its initial purpose changed; it began to be used as an ornamental plant for its attractiveness, it now is an invasive weed and very difficult to control.
It has been in ZAMORANO for about 10 years as ornament. It is popular because visitors enjoy the color of its leaves and the visibility of its yellow flower (Photo 1). In addition, because it covers the soil very well, it blossoms throughout the year, recovers easily from prolonged droughts. It is easy to propagate. It is also cheap and requires little maintenance. Some are replacing the St. Augustine grass and Indian grass with perennial peanut. As ornament, it is used in pots or directly on the ground.
Perennial peanut is a weed that is now invading sports fields, gardens, lawns and roadsides (Photo 2). It has already spread, in other words, it is a plant that was introduced with one purpose (cattle feed), now, it is a weed. It became a weed as it is difficult to remove by hand or with herbicides. The ability to propagate by stolons and seeds contributes to its rapid dissemination. The seeds have been found up to 30 cm deep in the soil, and not all germinate at the same time (they have latency or dormancy) and continue to germinate for several years.
A research in ZAMORANO (Gladys Amanda López López thesis, 2011) determined that the best herbicides to control perennial peanut were: Basta 15 SL® (ammonium glufosinate), at 4 weeks after application reduced 94% the size of the plant, Pastar 360 SL® (pyridine + 2,4-D) 95% and Roundup® (glyphosate) 94%. Other evaluated herbicides were less effective, Gramoxone Super® 20 SL (paraquat) reduced it by 80%, Atranex® 90 WDG (atrazine) 77%, Basagran® 480 SL (bentazon) 65%, Flex® 25 SL (fomesafen) 63% Sempra® 75 GD (halosulfuron methyl) 45%, Merlin® 75 WG (isoxaflutole) 45%, Command® 3 ME (clomazone) 34% and Accent® 75 WG (nicosulfuron) 29%. We usually try to eliminate this weed when it invades the lawn, but herbicides damage the lawn. The herbicide Pastar® 360 SL has the advantage that controls perennial peanut and does not damage the lawn, but Roundup® and Basta® 15 SL® damage it.
The use of this plant as ornament should be in pots or confined places (Photo 3) to avoid it spreads or invades areas we do not want it to grow. Avoid throwing out any stolons that are cut because they settle where they fall if there is moisture on the ground and then it is difficult to remove it. This is the main means perennial peanut invades new areas. Remember, be better safe than sorry.