Biennial and Perennial Weed Control is Best in the Fall

Dwight Lingenfelter, Extension Associate, Weed Science, Penn State University
William S. Curran,Ph.D., Emeritus Professor of Weed Science, Penn State University

Fall is an excellent time to manage biennial and perennial weeds. In particular, biennials such as common burdock, wild carrot, and bull, musk, and plumeless thistles are much easier to kill while they are in the rosette stage of growth, prior to surviving a winter. Once biennials start growth in the spring they rapidly develop with the goal of reproducing and it becomes more difficult to control them.

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Biennial and Perennial Weed Control is Best in the Fall

– Dwight Lingenfelter, Extension Associate, Weed Science, Penn State and William S. Curran,Ph.D., Emeritus Professor of Weed Science, Penn State

Fall is an excellent time to manage biennial and perennial weeds. In particular, biennials such as common burdock, wild carrot, and bull, musk, and plumeless thistles are much easier to kill while they are in the rosette stage of growth, prior to surviving a winter. Once biennials start growth in the spring they rapidly develop with the goal of reproducing and it becomes more difficult to control them.

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Ohio Noxious Weed Identification – Week 21 Palmer Amaranth

Palmer Amaranth

FamilyPigweed, Amaranthaceae.

Habitat: Crop fields, pastures, and roadsides.

Life cycle: Summer annual.

Growth habit: Erect up to 6 ft. high.

Leaves: Prominent white veins on the undersurface unlike redroot pigweed, not pubescent, alternate, without hairs (glabrous), and lance or egg-shaped.  Leaves are 2 to 8 inches long and 1/2 to 2 1/2 inches wide with prominent white veins on the undersurface.  Leaves occur on relatively long petioles.

Flower: Small, green, inconspicuous flowers are produced in dense, compact, terminal panicles that are from 1/2 to 1 1/2 feet long. Smaller lateral flowers also occur between the stem and the leaf petioles (leaf axils).  Male and female flowers occur on separate plants. Each terminal panicle contains many densely packed branched spikes that have bracts that are 3 to 6 mm long; can produce 500 thousand to 1 million seeds per plant.

Roots: Taproot that is often, but not always, reddish in color

Stem: One central stem occurs from which several lateral branches arise.

Similar Plants: Loosely resembles many other pigweed species. Palmer’s petioles are as long or longer than the actual leaf. This plant is hairless and has elongated seed heads. Leaves are typically more diamond shaped than other pigweed species, and occasionally has one hair at the tip of the leaf.

The Problem is……..Palmer amaranth is one of the most difficult weeds to control in agricultural crops.  It developed a major glyphosate resistance problem in the southern US from 2006-2010, and has been spreading in the midwestern US since, causing crop loss and increases in weed management costs. Characteristics that make it a successful annual weed include: rapid growth rate; wide window of emergence (early May through late summer); prolific seed production (upwards of 500,000 seeds/plant); tendency to develop herbicide resistance; and tolerance to many post-emergence herbicides when more than 3 inches tall.

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Ohio Noxious Weed Identification – Week 20 Marestail

Marestail

FamilyComposite, Asteraceae.

Habitat: Thin turf, agronomic crops, pastures, orchards, fallow fields, waste areas, and roadsides.

Life cycle: Summer or winter annual.

Growth habit: Seedlings develop a basal rosette and mature plants erect are reaching 6 1/2 ft in height.

Leaves: The mature plant has leaves that are entirely without petioles (sessile). Leaves are 4 inches long, 10 mm wide, alternate, linear, entire or more often toothed, crowded along the stem, and hairy. Leaves become progressively smaller up the stem.

Stem: Erect, solid, hairy, reaching 6 1/2 ft in height.

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Ohio Noxious Weed Identification – Week 18 Wild Mustard

Wild Mustard

FamilyMustard, Brassicaceae.

Habitat: Wasteland, roadsides, grain and other fields crops, primarily in northern Ohio.

Life cycle: Annual annual or summer annual.

Growth Habit: 1-2 feet high, branched and erect.

Leaves: Alternate, 2-7 inches long. Lower leaves have petioles and are irregularly lobed and toothed with bristly hairs; upper leaves are smaller and may not be lobed; petioles lacking or short.

Stem: Branched near top, bristly.

Flower: June – October. 1/2 inch, bright yellow, four-petal flowers borne in small terminal clusters.

Fruit: Slender, slightly curved, smooth seedpod about 1 inch long; borne on upper branches.

Similar plantsThe yellow rocket looks similar but has rounded lower leaves that are more heart shaped.

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Palmer Amaranth

Palmer Amaranth 

Palmer Amaranth has been found in Knox County.

Watch this video for more information.

Palmer Amaranth is on the Ohio Noxious weed list.

Check back for more videos discussing identification and control of this devastating weed!

A big thanks to our co-workers in Delaware County for making this video available!

Checkout other videos on our YouTube Channel.

Ohio Noxious Weed Identification – Week 17 Wild Carrot

Wild Carrot

Family: Parsley, Apiaceae.

HabitatDry fields, wastelands, pastures, and no-till field crops.

Life cycleBiennial, forming a rosette the first year and producing flowers and seed in the second.

First Year Growth Habit: A basal rosette.

Second Year Growth Habit1-3 feet tall, branched and erect.

Leaves: Alternate, pinnately compound, finely divided and hairy.

Flowering StemTall, hairy, stout, and branched.

Flower: June – October (second year). Small, lacy white 5-petaled flowers in flat-topped, umbrella shaped clusters with one dark reddish-brown flower in the center. Flower closes up and turns brown as it matures.

Root: Fleshy taproot.

Similar plants: Leaves have the appearance and odor of a garden carrot. Wild carrots taproot is not as large as the garden carrot. The plant also resembles poison hemlock (Conium maculatum). However, wild carrot has a hairy stem while poison hemlock has a smooth stem with purple blotches. The dark floret in the center of the inflorescence in second year and a distinctive carrot smell in the first year will also help distinguish this common weed.

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Does Crabgrass Really Hate You?

Originally posted on the Sheep Newsletter, By: Christine Gelley, OSU Extension Educator, Noble County

You may have heard the rumor that crabgrass (Digitaria sanguinalis) hates you. Those who profit from the sale of lawn care products may like you to believe that, but despite the claims, it really isn’t true. Each year crabgrass works toward accomplishing the goal of all living things, to reproduce, and if it had a life motto, it might be something like “Life is short, so live it!” Any plant out of place can be considered a weed and in the eye of many, crabgrass fits this description. However in a forage system, crabgrass can be the right plant, in the right place, at the right time.

Forage type crabgrass – ‘Quick-N-Big’

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Ohio Noxious Weed Identification – Week 16 Poison Hemlock

Poison Hemlock

Family: Parsley, Apiaceae.

Habitat: Wet sites, gardens, roadsides, wastelands, pastures, and meadows.

Life cycleBiennial, forming a rosette the first year and producing flowers and seed in the second.

First Year Growth HabitBasal rosette of finely divided leaves with a pungent odor.

Second-Year Growth Habit: 2-7 feet tall, branched plant with flowers.

LeavesAlternate, pinnately compound, finely divided, toothed, and glossy green.

Stems: Branched, waxy with purple blotches; hollow between nodes and grooved.

FlowerJune – August (second year). Clusters of small white flowers with 5 petals in a loose, umbrella-like cluster, 2-7” across.

Root: Fleshy taproot.

Similar plants: During the first year, poison hemlock resembles wild carrot, but has a strong, pungent odor. Further, young leaves of wild carrot are more finely divided and its stem is hairy. At maturity, poison hemlock can be difficult to distinguish from water parsnip and water hemlock. Look for purple blotches on the stem to identify poison hemlock. Water hemlock (Cicuta maculata), which is also highly poisonous, has a magenta-streaked stem and lanceolate leaflets with sharply-toothed edges. Water parsnip (Sium suave) is not poisonous and has toothed lanceolate leaflets.

The problem is….This plant is highly poisonous to both humans and animals. Poison hemlock is a large and impressive plant which has been planted as an ornamental in some areas. It grows quickly in fertile soils.

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Ohio Noxious Weed Identification – Week 15 Johnsongrass

Johnsongrass

FamilyGrass, Poaceae.

Habitat: Rich soils, cultivated fields throughout Ohio.

Life cycle: Perennial, spreading by rhizomes and seed.

Growth Habit: 3-6 feet or more.

Leaves: 0.5 -1 inch wide, smooth blades with a prominent white midvein.

Flower: July – October. Can be up to 1 foot or more in length; panicles are loosely branched, purplish, and hairy. spikelets occur in pairs or threes.

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