Weeds Commonly Found in Sugarcane Everglades Research & Education Center

What are weeds? Plant out place

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Using this definition, almost any plant can be a weed Melaleuca--native tree in Australia, but weed in south Florida ➔ Corn--crop when it is planted, but weed when volunteer plants come up the next year ➔ Most “weeds” are non-cultivated native or non-native plants ➔

Why weed ID? Weeds are prominent pests in crops

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Control methods almost always required Mechanical ➔ Cultural ➔ Chemical (herbicides) ➔

Also important pests of natural areas

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Invasive weeds ➔

Brazilian pepper, old world climbing fern, Australian pine, etc.

Impact of weeds Economic

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Reduced yields of crops ➔ Reduced quality of turf ➔

Ecosystems

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Crowd out native species ➔ Reduced habitat quality for all species ➔

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Both plants and animals

How do weed cause harm? Competition for:

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Light Nutrients Water Space

Identification

Vegetative parts of grasses often used to aid in identification: ➔ ➔ ➔ ➔

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leaf blade, blade margin collar margin midrib ligule - structure which occurs in grasses at point where the leaf sheath and blade meet auricle - projections where sheath and blade meet sheath margins - split with overlapping margins or united

Diagnostic grass structure ➔

Primary leaf structures used to ID grass ➔ ➔ ➔ ➔

ligule auricle collar sheath

Vegetative characteristics • • • • • •

Blade Midrib Ligule Collar Sheath Auricle

Auricle variations

Ligule variations

Sheath variations

Steps 1 to grass ID • Overall characteristics – Relative length and width of first leaf – Seed characteristics

Step 2 to grass ID • Stem Type – Round – Flat – Triangular

Step 3 to grass ID • Ligule Type – Absent – Hairy – Membranous

Step 4 to grass ID • Blade Type – Hairy or not (glabrous) – Midrib prominence and color – Margin characteristics – Presence of auricles

Step 5 to grass ID • Sheath margins – Split with overlapping margins – United – Margin with hairs or not

Step 6 to grass ID • Root systems – Perennial with creeping rhizomes – Annual

Differences between grasses and sedges • Sedges have a solid, triangular in cross section, stem. Leaves are arranged in threes (extend in three directions). • Grass stems may be round or flattened.

Purple vs yellow nutsedge leaf characteristics • Purple – A - boat shaped tip – B - without constriction at tip – C - midrib groove continues to leaf tip

• Yellow – D - sharp or needle like tip – E - Constriction 1/2 to 1 1/2 inches from tip – F - Midrib groove absent or barely visible beyond constriction point (E)

Purple vs yellow nutsedge

Purple vs yellow nutsedge

Vegetative parts of broadleaf weeds often used to aid in identification:

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cotyledons - seed leaves first true leaf older leaves midvein leaf apex margin terminal bud

Dicots: broadleaved plants – 1. Two cotyledons – 2. Primary root often persists to become a strong tap root with smaller secondary roots. – 3. Leaves are usually net veined and are usually broad at the base with a petiole or stalk usually present

Diagnostic broadleaf structure • Cotyledon • Leaf – – – –

midvein margin shape arrangement

Steps 1 & 2 in broadleaf ID • Overall appearance • Shape of cotyledons

Steps 3 & 4 in broadleaf ID • Leaf shape • Leaf arrangement – opposite – alternate – whorled

• Root system

Common Sugarcane Weeds

Fall panicum (Panicum dichotomiflorum) • Most common grass in the area – Relatively easy to identify • • • •

Stem can be hairy or smooth (hairy when young) Ligule fringe of hairs Round stem Widely dispersed seedhead

Fall panicum (Panicum dichotomiflorum)

Wild oats (Sorghum almum) • Not really an oat – Closely related to johnsongrass • No rhizomes • Large, membranous ligule • Robust plant – Can look like sugarcane seedling when small – Do we identify it correctly early?

Wild Oats (Sorghum almum)

Broadleaf panicum • Panicum adspersum (Urochloa adspersa) – Relatively prostrate growth • • • •

Wide leaves with wavy margins Round stems Usually dark green in color Very similar to alexandergrass

Broadleaf panicum

Alexandergrass (Brachiaria plantaginea) – Relatively prostrate growth • • • •

Somewhat wide leaves with straight margins Round stems Usually light green in color Very similar to broadleaf panicum – leaves narrower (usually) – margins straight rather than wavy (usually)

Alexandergrass (Brachiaria plantaginea)

Alexandergrass vs broadleaf panicum

Guineagrass (Panicum maximum) • Very problematic if you have it – Small plants have narrow leaves • Stems, sometimes leaves very hairy

– Becomes very large – Highly branched seedhead – Round stem – Can look similar to Sorghum almum • Sorhum almum shouldn’t be hairy

Guineagrass (Panicum maximum)

Napiergrass (Pennisetum pupureum) • Very robust plant – Forms dense clumps in fields – Long, wide leaves with finely toothed margin – Up to 12 feet tall – Seedhead has “bottle brush” appearance

Napiergrass (Pennisetum pupureum)

Paragrass (Brachiaria mutica) • Prostrate growing, medium size grass – Long stems covered with hairs • Short hairs on leaf surface

– Swollen nodes – Grows in very wet areas • Often moves out of ditches

– Pasture grass in Africa

Paragrass (Brachiaria mutica)

Bermudagrass (Cynodon dactylon) • Very common – Easy to identify • • • •

Small leaves Rhizomes and stolons Matt forming Ligule fringe of short hairs (hard to see)

Bermudagrass (Cynodon dactylon)

Goosegrass (Elusine indica) • Found in many fields • Low growing – Very white, flattened stems – Looks like it has been stepped on – Probably not competitive

Goosegrass (Elusine indica)

Crabgrass (Digitaria spp.) • Very wide first leaf • Initial clumping growth progressing to prostrate, tillering • Visible membranous ligule • Can be very hairy, or hairless, depending on species

Torpedograss (Panicum repens L.) • Perennial with robust, creeping, sharply pointed rhizomes. • Leaf blade stiff and erect. • Hairs on upper and lower leaf surface. • Seedheads with stiff, ascending branches. • Occurs in wet areas.

Spiny pigweed (Amaranthus spinosus) • Most common pigweed species – Stickerweed

• Large, upright growth habit, entire leaves • Very evident spines located at nodes

Spiny pigweed (Amaranthus spinosus)

Alligatorweed (Alternanthera philoxeroides) • Common in many areas of the EAA – Prefers wet areas – Often spread by cultivation – Low growing • Hollow stems when growing in wet spots • Opposite leaves • Small white blooms

Alligatorweed (Alternanthera philoxeroides)

Common lambsquarters (Chenopodium album) • Common some years – Usually during the cooler months (Dec, Jan) – Can be difficult to control • Waxy leaf surface – Small “dots” of wax are useful for ID – Gives leaves a white-gray color

• Alternate leaves • Medium size lobes on leaves

Common lambsquarters (Chenopodium album)

Common purslane (Portulaca oleracea) • Very common – Probably not competitive – Prostrate growing – Succulent – Leaves small, smooth, opposite or alternate – Small, yellow flowers – Red stems

Common purslane (Portulaca oleracea)

Common ragweed (Ambrosia artemisiifolia) • Often found on ditch banks and field edges – Deeply dissected leaves – Many hairs on upper and lower surfaces – Long seedhead at top of plant • Yellow flowers

– Similar in appearance to ragweed parthenium • Different flower type

Common ragweed (Ambrosia artemisiifolia)

Ragweed parthenium (Parthenium hysterophorus) • Primarily ditchbanks – Less common than common ragweed – Leaves less deeply dissected • Divisions don’t go all the way to the stem

– White flowers • Single, not multiples

Ragweed parthenium (Parthenium hysterophorus)

Dayflower (Commelina spp.) • Common in open areas, field edges – Small, probably not competitive – Prostrate growth habit – Parallel veins on leaves • Actually a monocot, not a dicot

– Blue flowers

Dayflower (Commelina spp.)

American black nightshade (Solanum americanum) • Occasional weed in EAA – Problematic in vegetables (tomato, pepper) • Same family (Solanaceae) • Resistant to paraquat in some areas

– Alternate leaves • Usually entire to somewhat lobed

– Purple fruit – Seems quite competitive

American black nightshade (Solanum americanum)

Sources of Weed ID Information • Picture books: – Wildflower books • Good for plants with prominent flowers

– Area-specific books • Many exist – Varying quality of information

– Southern Weed Science Society ID Guide • Excellent resource – Very thorough (almost to many plants)

Sources of Weed ID Information – “Simple” keys – Many for specific crops or areas – Helpful in crops where common weeds are limited – Not so helpful in natural/disturbed areas

Sources of Weed ID Information • Web Picture/Taxonomic Sites – Aquatic, Wetland and Invasive Plant Particulars and Photographs (U. of Florida) • Excellent pictures and information • http://aquat1.ifas.ufl.edu/photos.html

– Weed Identification and Control in Southern Turfgrasses (U. of Georgia) • Pictures, descriptions • http://www.griffin.peachnet.edu/cssci/TURF/turf.htm

Sources of Weed ID Information • Web Picture/Taxonomic Sites –Many, many more sites • Many reputable sites – Many universities – Other public agencies

• Buyer beware – Some incorrect information on the web!

So You’re Stumped! • If you need help: – Actual plants are best • Store in plastic bag with damp paper towel – 8-10 hours

• Press between two pieces of paper – Change paper often while drying – Will last indefinitely

• Store on truck dashboard – Please don’t!

• Bring several plants – Flowers and seeds if possible – Different growth stages if possible

So You’re Stumped! • If you need help: – Pictures • Overall view (growth habit) • Specific characteristics – – – –

Ligule (grasses) Hair characteristics Leaf shape Root system » Tubers, rhizomes, stolons – Stem shape – Seeds or flowers if available – Other characteristics we looked at earlier

So You’re Stumped! • If you need help: – Additional information • What type of area – – – –

Dry or wet Sandy or muck Cropped area, natural area, disturbed area History of area (previous crops, etc)

• Actual location – County, nearby town/city/landmark

Take Home • Weed ID can be challenging – Many resources available • Web is very helpful

– When you need help: • Provide as much information as possible – Quality plant sample – Identify important/unique characteristics – Site information (wet vs. dry, etc.)