Bushland Weeds Manual - Environmental Weeds Action Network

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12 Chapter 3 Grass Weeds Box 3.3 Grass growth forms Caespitose or tussock grasses are the dominant grass growth form around the world. Examples include the bushland weeds Perennial Veldgrass (Ehrharta calycina), Pampas Grass (Cortaderia selloana), Tambookie Grass (Hyparrhenia hirta) and Lovegrass (Eragrostis curvula). Reproducing by seed and/or tillers they form dense, usually erect, clumps. As clumps age, each year’s old leaf material accumulates, creating large fuel loads (Briske and Derner 1998, Hannaway et al. 2000). Caespitose grasses typically occupy resource-poor habitats. By accumulating soil organic carbon and nitrogen directly beneath clumps, they monopolise resources (Gibbs Russell et al. 1991). African Lovegrass (Eragrostis curvula) Stoloniferous grasses are creeping or mat-forming grasses that spread locally by stolons and include Para Grass (Urochloa mutica) and Queensland Blue Grass (Digitaria didactyla). A stolon is a segmented, horizontal stem, which runs predominantly along the soil surface. Adventitious roots and aerial shoots arise from stolon nodes. Stolons themselves arise from adventitious buds in the crown tissue. Propagation is both vegetative, from stolon fragments, and from seed. Although commonly occupying moist, high nutrient areas, some foredune species such as Spinifex (Spinifex sericeus) and Saltwater Couch (Paspalum vaginatum) are stoloniferous. Many stoloniferous grasses are considered invasive species (Hannaway et al. 2000). Para Grass (Urochloa mutica) Rhizomatous grasses form dense mats, extending their coverage by producing below-ground lateral rhizomes. A rhizome is a modified underground stem capable of rooting and shooting at nodes to develop daughter plants. They can serve as storage tissue for vegetative propagation and, being underground, are protected from fire. These grasses, including species like Reed Sweet Grass (Glyceria maxima), Pyp Grass (Ehrharta villosa) and Johnson Grass (Sorghum halepense), propagate vegetatively, but may also spread by seed. Rhizomatous grasses dominate moister, more nutrient-rich habitats and are often invasive (Hannaway et al. 2000). Many grasses can be both rhizomatous and stoloniferous, Couch (Cynodon dactylon) and Kikuyu (Pennisetum clandestinum) being just two examples. Reed Sweet Grass (Glyceria maxima) rhizome node adventitious shoot node stolon tiller buds adventitious shoot adventitious root
• Animals can carry grass seeds on their skin and fur. Seed bracts and/or awns may have sticky hairs, hooks or spines that aid adhesion. Ingestion also plays a role in grass dispersal. Grasses evolved with grazing and several authors have noted seeds are voided intact (Davidse 1986). Dogs, horses, native animals and humans (among others) readily disperse seeds along bush tracks. Horses can spread grass weeds from paddocks into bushland, depositing seed with their manure. • Human activities including inappropriate management practices, provide additional mechanisms for grass weed dispersal: Grading drags seed (and tillers) along road verges. Slashing during flowering spreads seed with an explosive action. Lawn clippings dumped in bushland often contain grass seed. Soil seedbanks: Seedbanks consist of dormant seed, which is ready to germinate given the appropriate environmental cues. Dormancy allows seed to persist in the soil in the absence of further seed rain. As a general rule grass seeds are not considered to be persistent within the soil. However, there are exceptions. Numerous grasses have a soil seed life greater than five years and not surprisingly many of these are widespread weeds (eg. Fountain Grass and Barnyard Grass). Poa pratensis and a number of Setaria species are known to remain viable for at least 39 years (Baskin and Baskin 1998). Environmental factors, including temperature, moisture and light intensity can induce dormancy in seeds. For example, deep burial induces dormancy in Wild Oat seed, increasing its longevity from six months to anything up to ten years (Baskin and Baskin 1998, Nugent et al. 1999). Dormancy is broken when the seed is returned to the surface through soil disturbance. For many species, seed longevity is not understood and yet it is invaluable information when making management decisions. The length of a control program is largely determined by seedbank persistence. The shorter lived the seed, the more rapidly a grass infestation can be controlled (provided the source is no longer present or is also managed). Chapter 3 Grass Weeds Vegetative reproduction Vegetative reproduction as a strategy in grasses is most successful in moist, nutrient-rich conditions (Briske and Derner 1998). Under these conditions rhizomatous and stoloniferous grasses can easily establish roots and rapidly disperse rhizome and stolon fragments in soil and down streams. In Reed Sweet Grass (and possibly other species), shoots of young plants can be vegetative or flowering. However, once established, the majority of new shoots produced are vegetative. This strategy allows the plant to quickly colonise new areas by seed, whilst increasing the density of established plants (Department of Primary Industries Water and Environment 2001). Tussock-forming grasses may also propagate vegetatively. Tillering is responsible for each season’s new growth and the expansion in tussock area (Hannaway et al. 2000). Tillers are also referred to as sprouts, shoots and daughters and may break off when disturbed. If resources are scarce, management should focus on controlling the invading edge(s) and new or isolated populations. Grass growth stages As with all weeds the timing of grass control measures is important. Active growth is required for herbicide uptake and slashing can enhance leafy growth or result in defoliation, depending on the growth stage. In most grasses (sterile grasses are the exception) there are three main stages of active grass growth: Vegetative, transition and flowering. • Vegetative growth involves the production of shoots, mostly leaf blades but also stolons and rhizomes. Herbicides are best applied at this stage, while slashing usually results in increased production of leafy material. vegetative transition boot stage flowering 13
Page 1 and 2: Bushland Weeds A practical guide to
Page 3: Acknowledgments This manual is the
Page 6 and 7: iv Introduction The Banksia, Tuart
Page 8 and 9: 2 Chapter 1 The Project Blue Gum La
Page 10 and 11: 4 Chapter 1 The Project Both Arum L
Page 12 and 13: 6 Chapter 2 Managing Weeds in Bushl
Page 14 and 15: 8 Chapter 2 Managing Weeds in Bushl
Page 16 and 17: 10 Chapter 3 Grass Weeds Many grass
Page 20 and 21: 14 Chapter 3 Grass Weeds • Transi
Page 22 and 23: 16 Chapter 3 Grass Weeds Control te
Page 24 and 25: 18 Chapter 3 Grass Weeds Rhizomatou
Page 26 and 27: 20 Chapter 3 Grass Weeds Case Studi
Page 34 and 35: Chapter 3 Grass Weeds Management Ta
Page 36 and 37: Chapter 3 Grass Weeds Management Ta
Page 38 and 39: 32 Chapter 4 Corms, Bulbs and Tuber
Page 58 and 59: Chapter 4 Corms, Bulbs and Tubers W
Page 60 and 61: Iridaceae Moraea miniata Two Leaf C
Page 62 and 63: Chapter 5 Broadleaf Herbs, Sedges a
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62 Chapter 5 Broadleaf Herbs, Sedge
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64 Chapter 5 Broadleaf Herbs, Sedge
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Chapter 5 Annual Broadleaf Herbs, S
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Chapter 5 Annual Broadleaf Herbs, S
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Chapter 5 Perennial Broadleaf Herbs
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Chapter 5 Perennial Broadleaf Herbs
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74 Chapter 6 Trees, Shrubs and Clim
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Chapter 6 Trees, Shrubs and Climber
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Chapter 6 Trees, Shrubs and Climber
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90 Chapter 7 Weed Mapping in Remnan
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92 Chapter 7 Weed Mapping in Remnan
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94 Chapter 8 Herbicide Use in Bushl
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100 Final Note In the end, environm
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102 References 1 Aarssen, L.W., Hal
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104 References 101 Dixon, B. (2002)
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106 References 204 Mann, R. (1998)
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108 307 The Nature Conservancy (200
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