The Layman’s Guide to Invasive Alien Vegetation in our region Southern Cape Weeds Forum By Ena & Bob McIntyre, Botanical Society of S.A. – Garden Route Arundo donax (Spanish Reed, Spaans(e)riet)

Of Mediterranean origin, A.donax has been introduced worldwide. Research evidence shows that the species can grow up to 5cm a day and reach its mature height within one year. Ironically, during the 1980’s it was recommended as a “striking evergreen for the large garden……..”!

Identification: The robust growth habit of Arundo donax makes this invasive reed easily identifiable. Two colour variants exist; the variegated cream/bright green and plain green. Distinguishing between Spanish reed and our indigenous common reed – fluitjiesriet is easy - Phragmites australis (common reed/fluitjiesriet) is a tall delicate suited to a wet environment and without the large leaf lobes of A.donax. Mature A.donax are very tall (10+ meters). Classified as poaceae (grass family), leaves are up to 700mm long and 80mm wide with persistent leaf sheaths on the stem. The inflorescence (flower) is spear-shaped and cream or brown. The plant reproduces by means of rhizomes.

Invasive Status: A.donax’s Cat1b invasive status identifies it as one of those established invasive species that are most destructive. The need here is to run coherent control programmes and that gains are maintained. Spanish Reed readily out-competes other vegetation - invades watercourses, road verges and moist sites away from water.

Control: Herbicide application to mature plants is ineffective. A donax’s dense growth and thick root masses complicate manual or mechanical removal of the above-ground plant-mass, yet these methods remains most effective. Deeply buried rhizome pieces may re-sprout and soil-disturbance from physical/mechanical removal may be severe. Follow-up after manual removal is essential. Cut back and allow re-growth to reach about one meter and spray with a glyphosate herbicide. Regular follow-up is the key to successful eradication.

Indigenous substitutes: Typha capensis (Bulrush), insignis ( Dekriet), capensis (Fonteinriet).

References: “ALIEN WEEDS AND INVASIVE PLANTS”: Lesley Henderson. Copyright © 2001 Agricultural Research Council. Problem Plants of South Africa: Clive Bromilow. Wikipedia. GG No 37886 01/08/2014 effective 01/10/2014.