Weedy Grasses Why and how we need to deal with them
Sarah Spear Cooke Seattle, Washington www.Cookescientific.com Why do we care?
Weedy grasses reduce crop yields because they invade pastures and rangeland at the detriment of crops. Some are “bad” for livestock. They can be hosts for diseases- fungiii and viruses They take over natural areas and habitat restorations and stop natural succession The worst
In Wetlands: Reed canarygrass- Phalaris arundinaceae Common reed- Phragmites australis, Class B Spartina- Spartina alterniflora, S.densiflora, S. anglica- covered another time
In uplands: Ravenna grass- Saccharum ravennae, Class Pampas grass- Cortaderia selloana, Class C Jubata grass- Cortaderia jubata, Class C Giant reed- Arundo donax (none found in Wa yet) A bit about ID’s
Vegetative- can be very helpful for the 5 big species that all look VERY similar. I will go through a few characteristics that may help you figure out what you have
Flowering- Don’t always have the flowers and 5 of the problem species have “plume-like” inflorescences
But here goes………. Grass Sedge
Rush Stem (culm) cross section
(but be careful that you don’t squash stem when checking!) Annual Perennial, rhizomatous Perennial, stoloniferous Perennial, caespitose Perennial, bulbous or tuberous Parts of a Grass Leaf Leaf blade tips Leaf blade width Sheath opening Open sheath Open sheath Closed sheath
Be careful not to rip while checking! Closed sheath Hairy sheath Hairy blade Hairy node Hairy collar Hairy throat Let’s talk ligules No ligule at all Ligule: fringe of hairs Ligule: acute, membranous Ligule: ciliate, membranous Ligule: erose (chewed up) Ligule: lacerate (shredded) Ligule: obtuse Ligule: truncate Auricles present Auricles absent The suspects- uplands Jubata grass
Pampas grass Ravenna grass Giant reed Ravenna grass, Saccharum ravennae
As a Class A noxious weed Native to Asia, Europe and North Africa Tall, perennial, ornamental grass; forms clumps, mound of leaves up to 4 ft high, flower stems up to 14 ft Hairs on leaf blades and sheaths Leaf < 12mm wide w/ a single white stripe down the middle. Plumes 10-24" long appear in late summer to early autumn, on upright, leafy stalks Stalks often red tinted in late summer Plumes bloom purplish-bronze turning to silver-gray in fall and persist well into winter. Spreads by seed Ligule is a fringe of hairs< 1 mm long.
Pampas grass, Cortaderia selloana and
Jubata grass, Cortaderia jubata Nature Conservancy, Bugwood.org Class C noxious weeds The Nature ConservancyArchive, The Native to parts of S. America Monitor list 2008 Large, densely tufted perennials, to 15-20 yrs old Long basal leaves (3 ft)- dropping lvs in jubata, erect in selloana Tall, showy, plume-like inflorescence above leaves in jubata C. selloana: Plants female are hermaphroditic (acting primarily as males) C. jubata: all female, apomitic Spread by seed Leave margins of selloana are serrated Ligule is a fringe of hairs
Cortaderia selloana & C. jubata Cortaderia selloana: not listed • Crowds out native species along coast Cortaderia jubata: listed as a noxious weed in California, • Reduces growth in forests Oregon (B), and Hawaii • Access to fires and present a fire hazard themselves • Saw-toothed leaves can cause injury • Historically just females were introduced (more attractive); recent years, some nursery stock propagated by seed, and both sexes have been widely planted Disturbed areas, dunes, bluffs, roadsides, logged forests, coastal shrub and grassland and adjacent inland areas moderated by maritime influences, inland riparian areas, other interior sites where sufficient moisture (may tolerate standing water for prolonged periods)
Tacoma In WA: C. selloana Olympia site: 484 plants in all states of growth, seedling, vegetative, vegetative with flower stalks, and mature. Bellingham: water front 1 escaped blooming plant Tacoma: Port property ~100 seedlings Grayland: few escaped plants Olympia Asotin: 2 roadside plants Grayland C. jubata C. selloana Control Methods 1. Deve) NOT boating, fishing, walking on the peat and Educate and encourage neighbors to stop using fertilizers, pesticides, and discharging point source pollution into the bog. Remove a section of the road to better connect the lobe with the rest of the wetland
Arundo donax- giant reed
Listed as monitor species, Wa quarantine list Native to Asia* Large, creeping (1 cm tick!) rhizomatous perennials 36” long, 7.5 cm wide cauline leaves on woody stems, 20-30feet tall! Leaf margins scabrous Stems commonly branch after first year/5 to 1.5 “ thick Tall, showy, plume-like inflorescence Auricles present and collar brown with hairs No reported escaped populations in WA
Giant reed is taller with thicker stems, rhizomes than common reed and the leaves are 2-ranked. *seeds possibly sterile The suspects- uplands
Pampas grass Ravenna grass Jubata grass Control Methods Arundo donax Hand pulling ok with just a few plants- when they are small and young. Mowing is difficult because of robustness of stems. Must remove rhizomes.
Best method Heat girdle the stem with a burner device, allow plants to resprout and treat with herbicide.
Chemicals suitable Most commonly used: Glyphosate (2-5% foliar spray), Imazapyr (.5-1 lb a.e.), and triclopyr (%?).
Surfactant must be non-ionic and State approved.
Spraying most effective in summer (beginning of
July) after the seed head has formed. Estuary Imazapyr use in the fall Spray should be applied to wet the leaves and flower plumes- damp BUT NOT DRIPPING
Chemical Cut stem can be used. Cut to 4” tall and wiper apply herbicide, or squirt solution down the stem. A mixture of glyphosate (.25 lba.e/aacre) and imazapyr (1 lb a.e/acre) worked well in some studies. Phragmites australis- common reed Listed as a Class B noxious weed* Wetland plant Native to parts of Europe, Asia, and Australia Large, creeping rhizomatous perennials; 12-16 feet tall! 20-40 cm long cauline leaves on woody stems Ligule hairy showy, plume-like inflorescence *Native genotypes are less dense, the stems are thin and shiny. The flowers are also less dense. Control Methods 1. Phragmites australis Particularly a problem in Eastern Washington in alkalai wetlands but also found along the coast. Mowing typically difficult because of “humocky” nature of growth, but best when done late summer. Burning alone NOT recommended. Thought to stimulate growth! Covering with a plastic shade cloth for 3 seasons somewhat effective. Cut to 4” height first. Re-introduce salty water (> 18 part/thousand) Best method Herbicide, wait 1 month, mow. Repeat each year for 3 years
Reed canarygrass
Listed as a Class B noxious weed* Wetland plant Native to parts of S. Europe Large, creeping rhizomatous perennials; 3-5 feet tall 20-40 cm long cauline leaves on somewhat woody stems- no hairs Reddish panicle but not plume-like Ligule large- 1 cm membranous No auricles
Control Methods Phalaris arundinaceae What works: Burn, disk, mow, shade, flood, and herbicide- all work Best to use a few methods in tandeum. Mow (May) –herbicide July –disk repeat x 2 years Mow (May) –burn (July/August) – herbicide Disk – herbicide – disk – herbicide Flood/shade for 2 years –herbicide Dig pits for tree plantings
Chemicals suitable Most commonly used: Glyphosate (1.2-2.5 lb ae/A) Surfactant must be non-ionic and State approved.
Imazapyr (.5-1lb ae/A), Aquatic sites must use
Habitat. Rangeland, non-crop land Arsenal
Estuary Spraying most effective in summer (beginning of July) as early seed head has formed, through first frost
Early spraying use imazapyr Chemical Spray should be applied to wet the leaves and flower plumes- damp BUT NOT DRIPPING Cut stem can be used. Cut to 4” tall and wiper apply herbicide, or squirt solution down the stem. Boom work great! Kills off RCG and lets other herbs grow up afterward. Species that compete with Reed canarygrass
In Native Restoration Areas:
Glyceria- both G. grandis and G. elata, especially in forested areas Carex comosa- in open flooded pastures. Any tree or shrub that grows quickly and can shade, especially if planted densely- e.g. willows! Replacement Species
Calamagrostis acutiflora
Stipa gigantea