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Weeds in our Area (Part Sixty Three) By Bob and Ena McIntyre, Botanical Society of S.A. – Garden Route Branch The South African connection with the Australian Acacia species has a long history. This time we look at Port Jackson Willow (Acacia saligna). The Port Jackson Willow is native to south-western Australia and was imported into South Africa in the mid 1800’s. Baron von Ludwig refers to a batch of Australian Acacias imported in 1835 but does not name any individual species. It is however recorded that the Colonial Secretary, the Hon John Montagu, had imported Port Jackson by 1847. These, together with other Australian plants were used to bind the drift sands along the first road to be constructed across the Cape Flats - from Cape Town to Bellville and beyond. The stabilisation effort was very successful and still today, the area is dominated by Port Jackson Willow (Acacia saligna) and Rooikrans (A. Cyclops) wherever there is vacant land. The spread of Port Jackson (A. saligna) is predominant in coastal areas with a mean annual rainfall exceeding 250mm. Although mainly confined to the region between the Olifants River in the West and the Kei River in the Eastern Cape, infestations are found as far as Kosi Bay and the Gariep (Orange) River. The plants are found in mountain and Lowland Fynbos, forest areas, grasslands and Succulent Karoo. Identification: As with all Australian Acacias Port Jackson is an unarmed (no thorns) shrub or tree 3-10 m high with a willow like appearance. The introduction of a rust fungus as a bio-control agent has resulted in badly deformed stems, characterised by large, brown, irregularly shaped galls. The leaves are phyllodes (leaf-like petiole with no blade) blue-green turning green up to 200mm long and 10-50mm wide mainly pendulous, with a single mid-vein. They are broader and somewhat wavy on young plants. The flowers are a bright yellow with globular flower-heads from August to November. The seed pods are brown with hardened whitish margins. Control: Young Port Jackson Willow (up to 3m), can be sprayed with a glyphosate (RoundUp) at a 3% mix with water. Felled plants need a cut stump treatment with an effective herbicide to prevent coppicing. Freshly coppiced plants can be treated as for young plants (see above). A bio-control agent Uromycladium tepperianum that produces galls on any young tissue (see photo) was released in 1987. The effect of this agent is evident on most Port Jackson plants and is considered to be successful. A seed feeder, Melanterius compactus released in 2001 has had moderate impact. Substitutes: Many of our indigenous smaller trees and/or large shrubs will fit the bill. Buddleja saligna (False olive), Calpurnia aurea (Natal Laburnum), Rhus crenata, Allophylus decipiens (False currant), Brachylaena discolour (Coast silver oak), are a few indigenous alternatives. Illustrations: “AFRICA invaded”: Published by The Global Invasive Species Program 2004 BotSoc Forthcoming Events Knysna: Sunday, 11 June, 10.00 am: Collection and planting of fynbos plants for Pledge Nature Reserve. Bring forks, plastic bags and lunch. Meet in the parking lot at Pledge at 10h00. To participate please contact Chris or Ariane below. Plettenberg Bay: Saturday, 17 June - Hack at Lookout Park. Bitou municipality are on course to declare this a Nature Reserve. To participate please contact Jean or Maaike below. BotSoc Contacts in your area: George/Wilderness: McIntyre’s 044 877 1360 Knysna: Chris Gow 044 387 1978, Ariane Rohloff 044 382 7993 Mossel Bay: Lucretia van der Walt 044 691 3230 Plettenberg Bay (Bitou Twig): Jean Sparg 044 533 2625, Maaike Murphy 044 531 6857 Stilbaai: Janet Naude 028 754 1106