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 Class C noxious weeds 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 The Nature Conservancy Archive, The Nature Conservancy, Bugwood.org
Cortaderia selloana & C. jubata Crowds out native species along coast Reduces growth in forests 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) Cortaderia selloana: not listed Cortaderia jubata: listed as a noxious weed in California, Oregon (B), and Hawaii
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 Asotin: 2 roadside plants Olympia Tacoma C. jubata C. selloana Grayland
1. Deve) Control Methods 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 Ravenna grass Pampas grass Jubata grass
Arundo donax Control Methods 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.
Chemical 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 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
Chemical 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 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