|Weeds in our Area (Part One Hundred and Nineteen)
By Bob and Ena McIntyre – Garden Route
Tradescantia fluminensis, T.pallida, T.zebrina - Wandering Jew
Many of our readers will immediately recognize our plant choice for this instalment. The Wandering Jew has been around for many years as a quick and easy solution to cover bare patches in the garden. Interestingly gardening books recommending its use as a groundcover also sounded a warning that the species, because of its quick spreading habit, would be troublesome unless trimmed back regularly. Not surprising then that is has become an emergent invasive alien species. As yet not formally listed as invasive in this country, it is undoubtedly one that threatens under-storey vegetation and especially the germination of young trees in our forested areas. Locally it is commonly found flourishing on the forest floor, particularly where construction work has disturbed the soil. In our experience we have also found it pretty persistent.
Tradescantia fluminensis is a species of spiderwort native to South America. Closely related varieties are T.pallida (with elongated, dull grey-green pointed leaves, fringed with red or purple - bearing small, sterile three-petalled flowers of white, pink or purple) and T.zebrina (with attractive striped leaves, the lower leaf surface presenting a deep uniform magenta). See pictures below.
Still often grown in the Unites States as a garden or house plant, T. fluminensis is considered an invasive species, noxious weed, or pest plant in many areas and therefore targeted for eradication. Seriously affected areas include the south-eastern United States, Australia, and New Zealand.
T. fluminensis has excellent shade tolerance and forms a dense mat under forest canopy. It smothers ground-level plants and prevents the natural regeneration of taller species. Left unchecked, this can lead to the destruction of natural forest. Even where adverse climatic conditions do not promote rooting, this will not prevent it from spreading by means of animals and humans. The succulent stems break easily at the nodes and establish themselves wherever they land on moist soil. While T. fluminensis responds to herbicides and other applied weed controls, each segment has the ability to regenerate, so it is able to make a rapid comeback, especially in soft soils where stems often remain below the surface. The most appropriate means of control is manual clearing on a very regular basis. Luckily this is not as formidable as it seems since an initial clearance performed by raking the area will have an impact. Repeated efforts, at regular intervals of a couple months are likely to be successful. Regular monitoring of re-infestation is necessary, as is responsible disposal of the plant material – preferably in a landfill site, where it is unlikely to spread.
Identification: Tradescantia fluminensis is a quick growing ground hugging plant with jointed succulent stems. The leaves are up to 4cm in length, clear green, oval shaped with a pointed tip. Clusters of small white three-petalled flowers are borne in spring.
Invasive Status: Not listed in RSA.
Control: Manual clearing.
Indigenous substitutes: Sutera sp., Falkia repens