One of the most common weeds in Tasmanian gardens is one of the hardest to get rid of!
A key area of study in our horticulture certificate II and III courses is weed identification. But anyone interested in gardening in Tasmania knows the dreaded Oxalis!
Oxalis is one of the most common weeds in the home garden. It is a perennial weed and can last and divide in the soil for many, many years. It has a reputation for being an extremely hard weed to get rid of. Oxalis pes-caprae is from the family Oxalidaceae. It has many other names including Soursop, Yellow Sorrel, Variable Wood Sorrel and Sour Grass. Most gardeners in Australia know it as Oxalis or Soursop.
Oxalis showing the lush growth above ground. An almost hairless plant with long-stalked, trifoliate leaves that often have dark spots. The radiating clusters of drooping yellow, 5 petalled flowers are in clusters of 3-16 flowers on long slender stalks held well above the leaves from June to November. There are 10 stamens and 5 styles. The fruit is a narrow capsule. Oxalis has annual tops with a perennial root system with a vertical rhizome, bulbils and a bulb.
Reproduction in Oxalis is the key to it’s success as a perennial weed. Just below the ground is a carrot like, vertical rhizome that produces leaves from the top and bulbils on its sides. Below the rhizome a thread like root connects it to the parent bulb. Within the exhausted parent bulb the new season bulb forms on top of a long, fleshy, vertical contractile tuber or ‘root’. One to several small bulbils form in the axil of each rhizome bract. On average a total of 20 bulbils are produced. When disturbed, these bulbils are spread into the soil and form new plants.
In small areas, dig out the whole area surrounding the plant, taking the soil and all bulbs. Larger areas require repeated spraying with diuron and sulfonyl urea herbicides over several years. Another method is to cover the whole area with clear plastic to “solarise” the bed. This heats the soil temperature and helps eradicate the weeds. It may take successive treatments to completely eradicate oxalis and it requires the bed to be completely free of any plants you wish to keep! If you want to expand your weed general knowledge, have a look at one of our short horticulture courses in Hobart or a GlobalNet Academy horticulture certificate I, II or III in Hobart and various locations around the state. References: http://www.herbiguide.com.au/Descriptions/hg_Soursob.htm http://en.wikipedia.org/wiki/Oxalis