Weed With Black Seeds

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Weed control, management, ecology, and minutia Broadleaf and blackseed plantain Plantago major L. and P. rugelii Bahiagrass (Paspalum notatum), also known as highwaygrass, is an aggressive, warm-season perennial grass. Bahiagrass has a mat-forming habit with a light…

Weed With Black Seeds

This is a follow up article to a blog that my colleague, Guy Kyser wrote back in 2011 titled “Purple alert: Common Pokeweed”. Since that time, I probably get a dozen or so calls this time of year asking, “what is that huge weed growing in my yard with dark black berries and big green leaves.” Pokeweed!

I personally find this plant quite interesting. As a native to portions of the United States, it turns out this plant has a diverse history and in recent years it is being studied in cutting edge medical research and energy technology. Have I perked your interest? If so read on.

American pokeweed (Phytolacca americana) is a robust, non-woody shrub that is weedy throughout much of California. Native to the eastern United States from Maine to Wisconsin, south to Texas, Mexico and Florida, pokeweed now occurs throughout much of North America. It is sometimes cultivated as an ornamental or garden vegetable, however more often it’s considered an undesirable weed. Pokeweed is found in riparian areas, oak woodlands, forest edges, fence rows, forest openings, pastures, under power lines, disturbed areas, vineyards, orchards, cultivated fields, parks, and ornamental landscapes.

Also called poke salad, poke sallet, pokeberry, inkberry, American nightshade, American spinach, scoke, and pigeonberry, the plant’s uses are as diverse as its names. Pokeweed has an extensive history for being used as a food, medicine, herb, dye for clothing, ink for writing, colorant for wines, and much more. Although used for food, extreme caution should be used, as the entire plant is poisonous causing a variety of symptoms, including death in rare cases.

IDENTIFICATION

Pokeweed is an erect herbaceous perennial shrub, 4 to 10 feet tall and 3 to 5 feet wide, with large leaves and showy purple-black berries. It has a smooth, stout, purplish stem that branches extensively and can reach up to 2 inches in diameter. The bright green, elliptic leaves are smooth, tapered, and alternate on the stem. Leaves can be large, reaching up to a foot in length and 4 to 7 inches wide and have a strong unpleasant scent when crushed. The purple berries hanging from the bright green leaves and red stems in late summer are the most distinguishing characteristic of pokeweed.

BIOLOGY

Reproduction is by seed and a single plant can produce 1,500 to 7,000 seeds annually. The seeds are large, lens-shaped, glossy, and black. Seeds can remain viable in the soil for up to 50 years. Pokeweed berries serve as an important food source for many species of birds, including Robins, Cedar-waxwings, Warblers, pigeons, and many others. New populations of pokeweed are spread primarily by birds. Seeds germinate in mid spring through early summer when soils are warm and moist. Germination is followed by rapid growth.

Pokeweed flowers in mid-summer. Flowers are borne in white-pinkish clusters that hang from the branches. Flowers consist of 5 white sepals, no petals, and are erect when in bloom and begin to droop as fruits develop. Flowers are self-fertile resulting in high fruit set. Immature berries are dull green, turning glossy purple-black at maturity in late Summer.

Pokeweed’s above-ground growth dies back after the first Fall frost, leaving large skeletons that breakdown over the winter. In the Spring, plants resprout from a large fleshy taproot.

IMPACT

Pokeweed is an occasional weed throughout much of the United States and is increasing in abundance in some areas. Once seen as a wildland weed, pokeweed is now becoming more common as an urban and landscape weed. All plant parts, especially the roots, contain numerous saponins and oxalates and can be fatally toxic to humans and livestock when ingested raw or with improper preparations. Severe digestive tract irritations are the primary symptom.

HISTORICAL SIGNIFICANCE

American pokeweed has a long history in the United States. A wide variety of chemicals have been isolated from pokeweed that have medicinal properties and Native Americans have used the plant in herbal remedies for centuries. During the Civil War, soldiers wrote letters using the ink from American pokeweed berries, and the pigment is still used occasionally to dye fabrics. Pokeweed has also been a favorite staple of country cuisine since colonial times, when tender young shoots were boiled and eaten as “poke salad”. Resembling canned spinach, “Poke salad” or “Poke sallet” was once available commercially and still inspires “Poke” festivals across portions of the east coast and the Deep South. American singer-songwriter and guitarist, Tony Joe White is best known for his 1969 hit song “Polk Salad Annie”, that was performed by Elvis Presley and Tom Jones. The shoots proved so popular to the first European explorers to the New World, it is documented that early Europeans took the sprouts back to Europe where they were equally enjoyed.

While Pokeweed has been used in folk medicine to treat numerous health problems and is still used in many herbal remedies today, medical research has not shown whether pokeweed is indeed effective in treating many of these ailments. Recently a protein in the plant “pokeweed antiviral protein” shows promise in being used in treating cancer, herpes, human immunodeficiency virus (HIV), and for conferring broad spectrum disease resistance in agricultural crops.

Researches have also been examining pokeweed for other uses. The dark red dye made from pokeweed is currently being tested to coat fiber based photovoltaic solar cells. The dye acts as an absorber, helping the cells tiny fibers trap more sunlight to convert into power. This fiber cell technology can produce as much as twice the power that current flat-cell technology can produce, and the dye made from pokeweed is much less expensive than a polymer dye.

What’s in a name. The scientific name Phytolacca americana comes from the Greek word phyton meaning plant and lacca meaning crimson lake in reference to the deep reddish-purple fruits. The second term, americana is in obvious reference to this plant being native to America. The common name poke is derived from puccoon, pocan or poughkone (from an Algonquin Indian name for this plant). Berries were once used to make ink, hence the sometimes-used common name of inkberry. An additional common name is poke sallet, local term meaning salad.

MANAGEMENT

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Prevention

Pokeweed is spread by seed and new occurrences are often were birds frequent. Monitoring for new seedlings in areas below tree canopies, along fence rows, and below other perches, often provides the best strategy for surveillance and early detection.

Mechanical

Hand pulling is effective on small plants. Once plants are established and develop an extensive root system, hand removal is difficult. Digging out established plants with a shovel is effective, but often difficult in summer when soils are dry. Cutting well below the root crown prevents regrowth. Cultivation can also be effective on new seedlings in raised beds or other areas where tilling can be used.

Cultural Control

Grazing is not considered an effective control option and animals should not be encouraged or allowed to consume large quantities of pokeweed. Seeds and foliage contain numerous saponins and oxalates and can be fatally toxic to livestock when ingested.

Biological Control

There are no biological control agents currently available for the management of pokeweed.

Chemical Control

Foliar Sprays. The effectiveness of herbicides applied to the foliage depends on three factors—timing, achieving good coverage, and concentration.

Timing. Foliar application of herbicides to pokeweed is most effective after leaves are fully developed and when the plant is actively growing. This period normally is from April into July or August, when soil moisture remains adequate.

Don’t apply herbicides before plants begin their spring growth or in late fall when plants are stressed.

Although not typically a problem, dust can cover plants growing near roadsides. Herbicides, particularly glyphosate, can readily attach to dust or soil particles, thus reducing their effectiveness.

Coverage. You can apply herbicides as a foliar spray using one of two methods. The first is spray-to-wet, where all leaves and stems should glisten following an application. Coverage, however, should not be to the point of runoff.

The other method is a low-volume foliar application called drizzle. This technique uses a higher concentration of herbicide, but you spray it at a lower volume. This method is advantageous in dense shrubbery or where access is limited. To achieve proper coverage, spray the herbicide uniformly over the entire canopy in a “drizzle” pattern, using a spray gun.

Concentration. For spray-to-wet applications, products containing at least 41% glyphosate as the active ingredient can provide good to excellent control of pokeweed when applied at 3.75 ounces of product per gallon of water (3% of the total solution). Some products available for use in the home landscape with this concentration of active ingredient are Roundup Pro Concentrate®, FarmWorks Grass & Weed Killer 41% Glyphosate Concentrate, RM43 Total Vegetation Control, Compare-N-Save Grass & Weed Killer Concentrate, and Remuda® Full Strength. Glyphosate products that have a lower concentration of active ingredient, such as Roundup Weed & Grass Concentrate (18% active ingredient), will require about 6 ounces of product per gallon of water (4.7% of the total solution) for effective control.

Triclopyr is available in either amine or ester formulations, with triclopyr ester being more effective on pokeweed. Products containing a minimum of 61% active ingredient of the ester formulation can provide good to excellent control when applied at 1 to 1.25 ounces of product per gallon of water (0.75% to 1.5% of the total solution). One such product with this concentration is Brushtox Brush Killer with Triclopyr. Other ester formulations with less concentrate are also available including Crossbow. Mixing triclopyr ester with commercially available seed oils can offer better penetration. One available product is Southern Ag Methylated Seed Oil. Mix this at 1.25 ounces of product per gallon of herbicide solution (1% of the total solution). Triclopyr is also available in the amine formulation. Products available include Bayer Bio Advanced Brush Killer Plus, Ortho Brush-B-Gon Poison Ivy and Poison Oak & Brush Killer, and Monterey Brush & Vine Control.

The drizzle application method is good in situations of dense planting, or when it is difficult to cover an entire area due to topography. Glyphosate formulated into a product with 41% active ingredient can provide good to excellent control of pokeweed when applied at 13 ounces of product per gallon of water (10% of the total solution).

You also can apply triclopyr ester using a drizzle application. Products containing 61% active ingredient should be applied using 6.5 ounces of product (5% of the total solution) and 25 ounces of seed oil (20% of the total solution) per gallon of water.

Remember that although the drizzle technique uses a higher concentration of herbicide, you are applying it at a lower volume. One gallon of mixed herbicide solution should adequately treat one-half acre of densely populated pokeweed.

The best time to apply either herbicide is during active plant growth. Seedlings can be treated in early spring through summer. Mature plants should be treated in late summer during flowering as this will draw the herbicide into the root system. Glyphosate is a non-selective herbicide that has no soil activity and triclopyr is a broadleaf selective herbicide with very limited soil activity. When air temperatures are higher than 80°F, it is better to use glyphosate or the amine formulation of triclopyr, since the ester form is subject to vaporization.

All photos from J.M. DiTomaso and E.A. Healy, Weeds of California and Other Western States, 2007.

No endorsement of named products is intended, nor is criticism implied of similar products that are not mentioned.

Blackseed and broadleaf plantain

Family: Plantaginaceae (Plantain family)
Life cycle: Perennial, reproducing by seed
Native status: Broadleaf plantain is introduced to N. America, whereas blackseed plantain is native
Habitat: Turf, landscapes, waste areas

General description: Basal rosette of smooth, elliptic to oval leaves, up to 7 in long and 4 in wide. Leaves have prominent veins and usually inconspicuous hairs. As leaves mature the margins tend to get wavy. Flowers are inconspicuous, produced on a leafless stalk up to 10 in long. Flowers arranged in a spike that covers at least ¾ of the stalk. Has a fibrous root system.

Key ID traits: Rosette of oval leaves with prominent veins.

Similar species: Blackseed plantain can be difficult to differentiate from broadleaf plantain. Blackseed plantain usually has a red tinge at the base of leaf petioles and lacks hairs on leaf blades. Blackseed plantain has dull, black seeds whereas those of broadleaf are shiny and light to dark brown.

Miscellaneous: The plantains once were much more problematic as lawn weeds. They are much more susceptible to the growth regulator herbicides that are commonly used on lawns than many other perennial weeds. One reason for their greater sensitivity to herbicides than dandelion is the plantains have a fibrous root system rather than a taproot found on dandelions. The taproot stores more energy reserves than a fibrous root system, increasing the ability to come back from herbicide treatments.

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Oval leaves with long, flat petioles characteristic of plantain. The red base of petiole suggests this is blackseed plantain.

Seedheads of broadleaf (left) and buckhorn (right) plantain

Successful weeds adapt to stresses in the environment. This plantain is able to survive a mowing height of 0.5″ or less in a creeping bentgrass golf fairway.

Bahiagrass

Bahiagrass (Paspalum notatum), also known as highwaygrass, is an aggressive, warm-season perennial grass. Bahiagrass has a mat-forming habit with a light green color, coarse texture, and open canopy. It is native to South America and was introduced into the U.S. in Florida as a forage grass around 1913.

Bahiagrass is easily identified by its distinctive “Y-shaped” seed head. It tolerates a wide range of soil conditions and spreads by seeds and rhizomes (a horizontal, modified stem found at or just below ground level). Bahiagrass growth is favored by drought, so it is an indicator plant for droughty soil conditions. The aggressive nature and drought tolerance of bahiagrass make it ideal for erosion control along roadsides and highway rights of way. However, its aggressive nature also makes it difficult to control as a weed in the landscape.

Bahiagrass habit with seed heads.
Ted Bodner, Southern Weed Science Society, Bugwood.org

Bahiagrass has distinctive “Y-shaped” seed heads.
Bert McCarty,©Clemson University

Before starting a weed control program, homeowners should realize that the complete eradication of bahiagrass (or any weed) from the landscape is not practical. A more practical approach is to control (not eradicate) the weed by limiting the infestation to a tolerable level.

Control in Lawns

Maintaining the health and density of your lawn is the best method for preventing a weed problem. Proper mowing height, irrigation, and fertilization of turfgrass will be the best defense against weeds. For more information on these topics, see the following fact sheets: HGIC 1201, Fertilizing Lawns; HGIC 1205, Mowing Lawns; and HGIC 1207, Watering Lawns.

If bahiagrass becomes a problem in a turf area, it can be dug up, or an herbicide may be used. If an herbicide treatment is chosen, treatments should be timed appropriately for optimum effectiveness.

Since bahiagrass is a perennial weed that also reproduces by rhizomes, post-emergent herbicides will also be necessary for improved control. Post-emergent herbicide applications should start in May when bahiagrass is small and starting to actively grow. See table for safe herbicides according to turf species.

Turf Tolerance to Post-emergence Herbicides for Bahiagrass Control.

Herbicide Bermudagrass Centipedegrass St. Augustinegrass Tall Fescue Zoysiagrass
sethoxydim NR S NR NR NR
imazaquin S-I I I NR S
metsulfuron S S S-I NR S
atrazine D S S NR NR
S= Safe at labeled rates.
I= Intermediate safety, use at reduced rates. Temporary yellowing of the turfgrass may occur.
NR= Not Registered for use on and/or damages this turfgrass.
D= Dormant. However, with the mild winters of recent years, bermudagrass lawns may not become completely dormant.

Once bahiagrass weeds have been eliminated in areas of the turf, bare spots will be left behind. To prevent the invasion of new weeds in these bare spots, it is best to fill them with plugs or sprigs of the desired turfgrass.

Glyphosate: Non-selective herbicides, such as glyphosate, can be used for spot treatments; however, desirable grasses can be severely injured or killed with contact. Multiple applications of glyphosate will be required to control bahiagrass. Examples of glyphosate products in homeowner sizes are:

  • Roundup Original
  • Martin’s Eraser Systemic Weed & Grass Killer
  • Tiger Brand Quick Kill Grass & Weed Killer
  • Ultra Kill Weed & Grass Killer Concentrate
  • Ace Concentrate Weed & Grass Killer
  • Bonide Kleen-up Grass & Weed Killer
  • Gordon’s Groundwork Concentrate 50% Super Weed & Grass Killer
  • Monterey Remuda Full Strength 41% Glyphosate
  • Hi-Yield Super Concentrate Killzall Weed & Grass Killer
  • Southern States Grass & Weed Killer Concentrate
  • Zep Enforcer Weed Defeat III
  • Eliminator Weed & Grass Killer Super Concentrate

If it is not practical to prevent glyphosate from getting on desired grasses, then a selective herbicide should be used. The following information is a guideline for choosing a selective herbicide according to turfgrass type.

Atrazine: Atrazine is a post-emergence herbicide for bahiagrass control that also has pre-emergence activity to give fair control of bahiagrass seed. It will also give post-emergence control of many broadleaf weeds. However, it is only safe to use on centipedegrass and St. Augustinegrass lawns. For maximum effectiveness, apply atrazine when air temperatures reach 65-70 °F for four consecutive days. Examples of atrazine products in homeowner sizes are:

  • Hi-Yield Atrazine Weed Killer Concentrate
  • Southern Ag Atrazine St Augustine Weed Killer Concentrate

Sethoxydim: For centipedegrass lawns, the use of sethoxydim (BASF Segment II Herbicide) will suppress bahiagrass. Sethoxydim should be applied no sooner than 3 weeks after centipedegrass spring green-up. Wait until lawns are fully greened. For a more effective bahiagrass treatment, do not mow 7 days before or after treating with sethoxydim. Reapply sethoxydim 3 weeks after initial application to suppress bahiagrass growth and seed head development. Do not make more than two applications per growing season.

Imazaquin: Image Kills Nutsedge is a homeowner-packaged, post-emergence herbicide product that will aid in the control of and reduce competition from bahiagrass. It may be applied to established bermudagrass, Zoysiagrass, centipedegrass, and St. Augustinegrass but do not apply to tall fescue. Do not apply imazaquin to St. Augustinegrass for other weed control during the winter. Do not apply imazaquin just prior to or during spring transition (green-up of the lawn). Do not use imazaquin in vegetable gardens, and do not use the grass clippings from treated lawns as mulch in landscape beds or around vegetables, fruit trees, or small fruit plants. A repeat application may be made for difficult to control weeds after 6 weeks.

Metsulfuron: Quali-Pro MSM Turf Herbicide, Quali-Pro Fahrenheit, and Blindside Herbicide are professional use herbicide products that will control bahiagrass, as well as many broadleaf weeds.

Metsulfuron can be used on bermudagrass, St. Augustinegrass, centipedegrass, and zoysiagrass. The Quali-Pro Fahrenheit also contains dicamba for broadleaf weed control. Blindside Herbicide also contains sulfentrazone for nutsedge control.

A non-ionic surfactant (such as Southern Ag Surfactant for Herbicides, Hi-Yield Spreader Sticker, or Bonide Turbo Spreader Sticker) is required at 2 teaspoons per gallon of spray mix for best control with the metsulfuron products above. Read the metsulfuron product label for more information. Some discoloration of turfgrass may occur after the application of metsulfuron, and increased yellowing and stunting of turfgrass may occur with the addition of the surfactant. A repeat application may be required in 4 to 6 weeks for best control of bahiagrass. Follow label directions for a reduced rate on centipedegrass.

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Do not over-seed or re-sod for 8 weeks, or plant woody ornamentals in treated areas for one year after applying metsulfuron. Do not apply metsulfuron herbicides within two times the width of the drip line of desirable hardwood trees. Do not allow spray drift to contact desirable shrubs, and high temperatures at application may increase herbicide drift. Make metsulfuron applications when temperatures are below 85 °F. Allow one week between application of metsulfuron and other lawn pesticide products. Read the product label for other precautions for each turfgrass species.

Control in Vegetable Gardens

It is best to attempt to treat weeds before tilling the soil for a vegetable garden. Tilling can break up and spread weed seed and perennial grass rhizomes throughout the garden plot. Some methods used to remove weeds in the vegetable garden include hand pulling, mulch, and post-emergent herbicides.

Cultural Control: Hand pulling bahiagrass may be a practical choice for small garden plots. If hand pulling, be sure to work when the soil is moist so that the bahiagrass roots can easily be removed from the soil.

Organic mulch (such as pine needles, ground leaves, compost, old hay, or grass clippings) can be used in the garden to help suppress bahiagrass development. Before laying the mulch, apply a layer of 6 to 8 wet newspaper sheets to act as a weed barrier. The newspaper layer will prevent weed development by blocking light to the weeds underneath and prevent their growth. Best of all, the newspaper should decompose before next spring. To prevent low oxygen levels in the root zone, keep organic mulch levels at a maximum of 3-inches deep. For more information on mulching the vegetable garden, see HGIC 1253, Controlling Weeds by Cultivating & Mulching.

Glyphosate: A post-emergent herbicide can be used to treat the garden plot before planting. Glyphosate can be applied to the garden plot 3 or more days prior to planting. Glyphosate is most effective when weeds are actively growing, so do not apply during extreme heat, cold, or drought conditions. Multiple applications of a 1.5 to 2.0% glyphosate solution may be necessary to control perennial weeds like bahiagrass. See product label for mixing directions. For examples of glyphosate products in homeowner sizes, please see the “Control in Lawns” section.

Sethoxydim: Some products containing sethoxydim may be applied within the vegetable garden after planting. These will control most grass weeds, in addition to bahiagrass. However, do not apply near sweet corn. Examples of products labeled for use within vegetable gardens are:

  • Hi-Yield High Yield Postemergence Grass Herbicide
  • Bonide Grass Beater Over-the-Top Grass Killer II Concentrate
  • Ferti-lome Over-the-Top II Grass Killer Concentrate
  • Monterey Grass Getter
  • Poast Herbicide

Control in Landscape Beds

In landscape beds, bahiagrass can be hand dug or controlled with an herbicide. As mentioned previously, it is best to prevent the invasion of bahiagrass by maintaining ideal growing conditions and using a 3-inch mulch layer to block weed development. Bahiagrass is a perennial weed that can emerge from both seeds and rhizomes. Once bahiagrass has made its way into the landscape bed, an herbicide may be necessary if hand pulling is not practical.

Glyphosate: A non-selective herbicide, such as glyphosate, can be used for spot treatments around ornamental plants but should be used with caution. Do not allow glyphosate spray mist to contact ornamental foliage or stems, as severe injury will occur. A cardboard shield may be used to prevent glyphosate spray from drifting to nearby ornamentals. For examples of glyphosate products in homeowner sizes, please see the list above in the “Control in Lawns” section.

Sethoxydim: Sethoxydim is a selective herbicide that can be applied safely in landscape beds containing most landscape plants but check the product label for a listing of tolerant plant materials. Sethoxydim will only control grass weeds; however, do not allow sethoxydim to contact ornamental grasses. A 2.5% solution should be applied before bahiagrass reaches 4 inches tall. Read label directions for mixing. Examples of products containing sethoxydim in homeowner sizes are:

  • Hi-Yield Grass Killer Postemergence Grass Herbicide
  • Bonide Grass Beater Over-the-Top Grass Killer II Concentrate
  • Ferti-lome Over-the-Top II Grass Killer Concentrate
  • BASF Segment II Herbicide
  • Monterey Grass Getter

Glyphosate and sethoxydim are both more effective when weeds are actively growing and will not work well for weed control under drought conditions. As with all pesticides, read and follow all label instructions and precautions.

CAUTION: Atrazine and imazaquin can travel through soil and enter groundwater; please read the label for all environmental precautions. Users are advised not to apply atrazine or imazaquin to sand or loamy sand soils where the water table (groundwater) is close to the surface and where these soils are very permeable, i.e., well-drained.

Pesticides are updated annually. Last updates were done on 7/22 by Barbara Smith.

Originally published 10/08

If this document didn’t answer your questions, please contact HGIC at [email protected] or 1-888-656-9988.

Original Author(s)

Millie Davenport, Director of Home and Garden Information Center, Horticulture Program Team, Clemson University

Revisions by:

Joey Williamson, PhD, HGIC Horticulture Extension Agent, Clemson University

This information is supplied with the understanding that no discrimination is intended and no endorsement of brand names or registered trademarks by the Clemson University Cooperative Extension Service is implied, nor is any discrimination intended by the exclusion of products or manufacturers not named. All recommendations are for South Carolina conditions and may not apply to other areas. Use pesticides only according to the directions on the label. All recommendations for pesticide use are for South Carolina only and were legal at the time of publication, but the status of registration and use patterns are subject to change by action of state and federal regulatory agencies. Follow all directions, precautions and restrictions that are listed.

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