Weed of the Month for April 2013 is Purple Deadnettle

Purple Deadnettle 

Biology: Purple deadnettle (Lamium purpureum) is a common winter annual broadleaf weed found throughout the US. It is closely related to another winter annual broadleaf, henbit (Lamium amplexicaule). Both have vibrant purple flowers that can been seen now in lawns, landscapes, and fields.

Identification: Purple deadnettle is a winter annual meaning that it germinates in the fall, survives the winter as a plant, then flowers, develops seeds, and then dies when temperatures rise in late spring and early summer. Purple deadnettle blooms are mainly visible in April although you can find it blooming earlier and later depending on the area it is growing and the temperatures. Purple deadnettle is a member of the mint family and has a characteristic square stem. Purple deadnettle flowers are light purple in color and are small and tubular in shape.  

Purple deadnettle leaves are triangular in shape with shallow lobes. Typically, the upper leaves are more purple-red in color than the lower leaves.  

Cultural control: Purple deadnettle mainly occurs in turf and soils that are disturbed during the fall when it germinates. Proper mowing (higher mowing heights), proper fertilization (some rather than none to improve turf density), irrigation to prevent summer dormancy during drought, and aerification of compacted areas to improve turf health are all cultural practices that can be used to reduce purple deadnettle. If you only have a few purple deadnettle plants, you can usually pull them by hand.

Biological control: Some organic herbicides are available. Among the postemergence organic herbicides, the most common are pelargonic acid (Scythe) and acetic acid (5 percent or greater solutions). Other products that contain medium-length fatty acids and clove oil (eugenol) show some promise; however, these organic postemergence herbicides are nonselective and can injure actively growing desirable plants in the lawn and landscape, so their use should be limited to directed spot treatments. The bottom line is that most organic postemergence herbicides have limited use in turf and are better suited to weed control in parking lots, fence rows, and other bare ground applications. Many new organic products contain the active ingredient iron HEDTA (FeHEDTA). Multiple applications of this product are required for control. FeHEDTA containing products injure turf less (can actually make turf darker green), but their efficacy for weed control is yet to be well documented.

Chemical control: Purple deadnettle can be controlled using preemergence or postemergence products, but I will mainly discuss postemergence control as preemergence control is more limited to bermudagrass and zoysiagrass lawns.

The more common approach to controlling purple deadnettle in cool-season turf is to use postemergence herbicides after it has already emerged. Most postemergence herbicides including those containing 2,4-D, dicamba, fluroxypyr, and others will control purple deadnettle. As plants get bigger, herbicides will be less effective at controlling this weed. Additionally, since it is a winter annual, it will naturally die in the summer so late spring herbicide applications aren’t necessarily warranted. You can tell that purple deadnettle is beginning to die from summer heat stress when the leaves start to turn yellow in color.

For more information on weed control, search this blog (search box in upper left corner of page) and archived turf tip postings and check out our Turfgrass Weed Control for Professionals Publication.

Aaron Patton, Turfgrass Extension Specialist

Weed of the month for April 2014 is Mouse-ear Chickweed

Mouse-ear Chickweed  

Biology: Mouse-ear chickweed (Cerastium vulgatum) is a broadleaf weed that normally acts as a perennial; however, it has the ability to act as a winter annual depending climate conditions. Mouse-ear chickweed germinates by seed from late summer to fall or early spring. As long as cool climate conditions and moist soil persist, germination can also continue into the summer. Similar to common chickweed, its prostrate growth habit and capabilities to withstand low mowing practices make mouse-ear chickweed a prominent weed in turfgrass and other mowed areas throughout the United States.

Identification: Mouse-ear chickweed is a perennial broadleaf weed that invades turf through the spreading of prostrate stems which form dense, mat-like patches. In unmowed areas, plants can form a more upright mound which then give rise to spreading and invasive stems. Mouse-ear chickweed stems are sticky/hairy and are capable of producing roots when nodes (origin points for leaves) come into contact with soil. Leaves are located opposite of each other on the stem and are dark green in color, oval to oblong shaped, and distinctly hairy on the entire upper surface and along the veins on the lower surface. Leaves also lack petioles (stems) and tend to overlap like a cup around the main stem at the base of the leaf. From May to October, mouse-ear chickweed produces small white flowers with five petals that are deeply clefted to the point where it looks like there are ten petals. Each flower has hairy sepals (green leaf-like structures that enclose and protect unopened flowers) that are almost as long as the petals. Mouse-ear chickweed can sometimes be mistaken for common chickweed; however, common chickweed does not have hairy leaves and its nodes cannot form roots when they touch soil.  

Oblong leaves with dense hairs on upper surface

Oblong leaves with dense hairs on upper surface

Daisy-like petals with 5 petals. Deep clefts in the center of each petal give the appearance of 10 total petals.

Dense, mat-like growth at low mowing heights

Large patch of mouse-ear chickweed in cool-season turf

Cultural control: Mouse-ear chickweed can form dense, mat-like patches which help to crowd out desirable turfgrass. Cultural management practices to develop a dense, aggressive turf may help to hinder the invasive qualities of mouse-ear chickweed. Since it has a weak and shallow root system, the weed could be managed by hand pulling when populations are small enough and the expanding stems haven’t already rooted.

Biological control: None known for specific use in mouse-ear chickweed. There are some organic postemergence herbicides available for turf weed control such as pelorgonic acid (Scythe), acetic acid (5% or greater solutions), and medium-length fatty acids (Eugenol); however, these products do not differentiate between the target weed and the desired turf (non-selective). As a result, these products are often used as spot treatments for weed control in parking lots, along fence rows, and in other bare-ground areas.

Other organic products that contain iron HEDTA (FeHEDTA), may be used to manage mouse-ear chickweed; however, their ability to control this weed has not been effectively researched.

Chemical control: Control options for mouse-ear chickweed include both pre- and postemergence management strategies similar to those of common chickweed. However, since mouseear chickweed may behave as a perennial, a postemergence weed management strategy may be more effective.

Postemergence control can be achieved with repeat applications of two or three-way mixtures of 2,4-D, dicamba, MCPP, or MCPA. A repeat application may be required.

For more information on weed control, search this blog and check out our Turfgrass Weed Control for Professionals Publication.

For archives of past weed of the month postings, visit our Weed of the Month Archive.

Aaron Patton, Turfgrass Extension Specialist

Leslie Beck, Postdoctoral Research Associate

Weed of the month for March 2014 is Common Chickweed

Common Chickweed  

Biology: Common chickweed (Stellaria media) is a winter annual broadleaf weed. It forms dense, prostrate patches in turfgrass throughout North America, though it can grow much taller when it’s not mowed. Common chickweed germinates from seed in late summer or early fall. However, germination timings can vary throughout the year if conditions are shady, and moist enough. Its prostrate growth habit and capabilities to withstand low mowing practices make common chickweed a widely distributed turfgrass weed in all regions of the United States.

Identification: Common chickweed is predominantly a winter annual broadleaf weed that can be identified by its prostrate growth habit and leaf shape. Common chickweed leaves are located opposite each other on stems that may be hairy on older portions and smooth on newer growth. Additionally, leaves are light green, smooth, and oval- to egg-shaped that come to a point at the apex. Leaves located on the upper portions of the stems have no petioles (leaf stems) while leaves located lower on the stems have long, sparsely-hairy petioles. Common chickweed produces small clusters of white flowers with five daisy-like petals in early spring. Flower petals have a deep centered lobe that makes it appear as though there are ten petals. Common chickweed can often be mistaken for mouse-ear chickweed; however, mouse-ear chickweed leaves are more oblong in shape and are densely covered in soft hairs. 

Light green leaves with tiny point at the apex

Leaves may often look more succulent than herbaceous

Daisy-like flowers with 5 petals. Petals have deep lobes so it appears there are 10 petals

Prostrate growth habit via laterally spreading branches

Dense, mat-like growth

Presence may indicate moist, poorly drained, or compacted soils

Cultural control: Proper turf maintenance such as adequate mowing height, fertilization, and irrigation will help to develop a dense, aggressive turf capable of out-competing invading weeds. Common chickweed is also an indicator weed, meaning its presence might indicate underlying management issues that are allowing the weed to dominate spaces meant for turf. For example, it thrives in compacted soils that are consistently moist or poorly drained. Its presence might indicate that the soil should be cultivated (aeration) and irrigation practices should be adjusted to reduce excess moisture in the soil. Common chickweed also thrives in shady conditions; thus, efforts to reduce shade if possible, such as pruning tree branches, may also help turf out compete common chickweed. Hand-pulling common chickweed when populations are small may also be an effective cultural weed management tool.

Biological control: None known for specific use in common chickweed. There are some organic postemergence herbicides available for turf weed control such as pelorgonic acid (Scythe), acetic acid (5% or greater solutions), and medium-length fatty acids (Eugenol); however, these products do not differentiate between the target weed and the desired turf (non-selective). As a result, these products are often used as spot treatments for weed control in parking lots, along fence rows, and in other bare-ground areas.

Other organic products that contain iron HEDTA (FeHEDTA), may be used to manage common chickweed; however, their ability to control common chickweed has not been effectively researched.

Chemical control: Control options for common chickweed include both pre- and postemergence management strategies. Preemergence herbicides such as Gallery 75 (isoxaben), Pendulum (pendimethalin), Barricade (prodiamine), and Dimension (dithiopyr) are available for use in home lawns; however, it is important that they are applied prior to common chickweed germination in autumn.

Postemergence control can be achieved with repeat applications of two or three-way mixtures of 2,4-D, dicamba, MCPP, or MCPA in cool-season turf.  In warm-season grasses, Manor (metsulfuron), Katana (flazasulfuron), or Celsius (thiencarbazone + iodosuluforn + dicamba) can control common chickweed when applied in combination with a non-ionic surfactant (0.25% v/v).

Most of these herbicides require supplemental applications for adequate control especially in spring when common chickweed plants are larger.

For more information on weed control, search this blog and check out our Turfgrass Weed Control for Professionals Publication.

For archives of past weed of the month postings, visit our Weed of the Month Archive.

Aaron Patton, Turfgrass Extension Specialist

Leslie Beck, Postdoctoral Research Associate

Weed of the month for February 2014 is Wild Garlic

Wild Garlic  

Biology: Wild Garlic (Allium vineale) is a monocotyledonous cool-season perennial that can be found throughout most of the eastern and southern United States. Despite having linear leaves and parallel veins, wild garlic is neither a grass nor a sedge; it is a member of the lily family. Wild garlic is more noticeable in the winter months when the turf is not actively growing or being mown. Plants reproduce from seeds and aerial bulbets from early spring and throughout the summer months. Its ability to tolerate a wide range of soil types, and to survive mowing height typical of lawns make wild garlic a difficult-to-control weed in cool-season turf.

Identification: Wild garlic is a bulbous perennial with grass-like leaves that emerges in turf in the early spring. Leaves are slender, rounded, and hollow. Wild garlic is often mistaken for wild onion; however, wild onion leaves are more flattened and are not hollow. Wild garlic leaves have a distinct garlic-like odor when crushed or mown. Leaves emerge from an underground white bulb with a papery outer coating, which also gives rise to multiple bulbets that are flattened on one side and also covered by a papery-like membrane. Greenish-white ‘flowers’ can be observed atop short flowering stems in late spring through early summer. In the place of flowers, small globe-shaped aerial bulbets are produced that are greenish-white and have long tail-like green leaves. Wild garlic plants may die back in the summer, but leafless stalks bearing viable seed capsules may remain.

Wild garlic's grass-like growth in dormant turf

Hollow stems

Aerial bulbet

Wild garlic clumps in dormant turf

At times, wild garlic leaves can appear curved or curled

Cultural control: Proper turf maintenance such as adequate mowing height, fertilization, and irrigation to develop a dense, aggressive turf leading into the winter months may help to manage wild garlic. Hand-pulling wild garlic is generally not an effective method of weed control since hollow stems are easily broken leaving the bulb below the soil to generate new leaves and new bulbets. As a result, bulbs need to be dug-up in order to achieve an adequate level of control.

Biological control: None known for specific use in wild garlic.

Chemical control: In cool-season turf, wild garlic is difficult to control. There are no preemergence herbicide options for wild garlic in cool-season turf; however, there are a few postemergence herbicide options. Applications of 2,4-D alone or in multiple combinations with MCPP and dicamba (Trimec, Triplet, etc.) may achieve fair levels of control. The ester formulations of 2,4-D are more effective against wild garlic than the amine formulations (consult the Purdue Turfgrass Weed Control for Professionals extension publication (link below) for more information regarding the differences between amine and ester 2,4-D formulations). Additionally, mowing the weeded area prior to application may improve herbicide uptake and overall control of wild garlic in cool-season turf.

For more information on weed control, search this blog and check out our Turfgrass Weed Control for Professionals Publication.

For archives of past weed of the month postings, visit our Weed of the Month Archive.

Aaron Patton, Turfgrass Extension Specialist

Leslie Beck, Postdoctoral Research Associate

Weed of the month for January 2014 is Annual Bluegrass

Annual Bluegrass 

Biology: Annual bluegrass, commonly referred to by its scientific name Poa annua (sometimes pronounced Po anna on TV), is a winter annual grass that is a difficult-to-control weed in turf. Seeds germinate in late summer, early autumn, and spring. Annual bluegrass is found throughout the United States, particularly in highly compacted, excessively wet soils. Despite having a bunch-type/clumping growth habit (some biotypes have short stolons), it can withstand extremely close mowing heights; thus, allowing the weed to successfully establish in home lawns and other high maintenance turf, such as golf courses or sports fields.

Identification: Annual bluegrass is an upright, clump-forming grassy weed that expands through the development of aggressive tillers. It is generally identifiable by its light green leaf blades that are smooth on both surfaces, have two distinct, clear lines on each side of the midrib, and a boat-shaped leaf tip. Annual bluegrass also has a slightly pointed, membranous ligule. One of the factors that makes annual bluegrass so difficult to control is its ability to produce a large amount of seedheads, even at putting green mowing heights. These seedheads can be observed as a greenish to white, open, pyramid-shaped panicle. A single annual bluegrass plant is capable of producing up to 360 viable seed that have the ability to lie dormant in the soil for many years before finally germinating.

Annual bluegrass is a prolific seed producer

Annual bluegrass membranous ligule

Boat-shaped leaf tip

Annual bluegrass seedhead

Prolific seedhead production

Bunch-type growth habit

Light-green annual bluegrass color in a cool-season lawn. Notice it is growing in a trafficked, compacted area.

Light green color and prolific seedhead production at low mowing heights

Annual bluegrass invading a creeping bentgrass putting green.

Annual bluegrass produces seedheads even at putting green heights

Light green color and prolific seedhead production in a golf course putting green

Cultural control: The use of cultural practices to increase the competitive growth and development of the desired turf over annual bluegrass is one of the limited options for cultural control. However, annual bluegrass’ ability to tolerate extremely low mowing heights and prolific production of viable seed severely limits a professional turf manager’s ability to control the weed using cultural methods.

Biological control: No consistently effective biological control for annual bluegrass although previous research has examined some options.

Chemical control: There are options for controlling bluegrass through the use of herbicides; however, those options are generally specific to the species of the desired turf and the use of the area which is being treated (i.e. home lawns, golf course, sports turf, etc.). One could literally write a book on how to control this species.

To keep annual bluegrass out of your home lawn.

1. Do not over-water yours lawns as annual bluegrass likes moist areas.
2. Do not compact your soil through traffic where possible and aerify your lawn to reduce soil compaction as annual bluegrass grows well in thin, compacted areas.
3. Maintain dense turf through fertilization, overseeding, and weed control (crabgrass and broadleaf weeds).
4. Mow your lawn at higher heights of cut (>2.5 inches) as annual bluegrass is less competitive at a higher cutting height.

Homeowners should also read, ID and Control of Annual Bluegrass and Rough Bluegrass in Lawns (AY-41-W) 

For professionals, more information on annual bluegrass control is available in Turfgrass Weed Control for Professionals Publication.

For archives of past weed of the month postings, visit our Weed of the Month Archive.

Aaron Patton, Turfgrass Extension Specialist

Leslie Beck, Postdoctoral Research Associate

Weed of the month for December 2013 is Henbit

Henbit  

Biology: Henbit (Lamium amplexicaule) is a common winter annual broadleaf weed found throughout the United States. It can often be mistaken for another closely related winter annual broadleaf, purple deadnettle. Both can be observed by their showy pink to purple flowers which are primarily produced in April, but can appear from March to November in Indiana.

Identification: Henbit is a winter annual, meaning that it germinates in the fall, survives the winter as a vegetative plant which eventually flowers, develops seed, and dies as temperatures increase in late spring to early summer. As a member of the mint family, henbit has a characteristic four-sided (square) stem which can be sparsely hairy and greenish to purplish in color. All henbit leaves are hairy. Upper leaves are deeply lobed and encircle the main stem at the base (no leaf stem). In contrast, purple deadnettle leaves are more triangular, less deeply lobed, and are more reddish in color than henbit. Henbit flowers are small, pinkish-purple with darker coloring on the lower petal, arranged in whorls, and are tubular in shape.

Early growth stage. Leaves are lobed and round-shaped.

Square-shaped stem

Tubular-shaped flowers

Two-lipped opening at the top of mature flowers

Upper leaves have no leaf stems (petioles)

Leaves toward the base of the plant have long stems (petioles)

Prostrate growth habit in dormant turf

Prostrate growth habit in a landscape

Bermudagrass lawn heavily populated with henbit

Cultural control: Cultural practices that promote a dense, vigorous turf are the best way to reduce the encroachment of annual broadleaf weeds. For example, proper mowing (increased mowing heights), proper fertilization to improve turf density, irrigation to prevent drought stress, and aerification of compacted soils to improve root health are all cultural practices that can be used to manage henbit in turf. However, in situations where you only have a few plants, you can usually just pull henbit by hand.

Biological control: There are some organic postemergence herbicides available to control henbit. For example, pelargonic acid (Scythe) and acetic acid (5% or greater solutions) may be used to manage weeds. Other products such as Eugenol, which contain medium-length fatty acids and clove oil, have shown also some promise as an effective weed control tool. However, these organic herbicides do not differentiate between the target weed and the desired turf (non-selective) and should only be applied as spot treatments in direct contact with the weed only. As a result, most of these organic herbicides have limited use in turf and are better suited for weed control in parking lots, along fence rows, and in other bare-ground areas.

Many new organic products contain iron HEDTA (FeHEDTA) as the active ingredient. Multiple applications of these products are required for adequate weed control and turf injury is generally decreased (can actually make the turf darker); however, their ability to control weeds is not well-documented.

Chemical control: Henbit can be controlled by using both preemergence and postemergence herbicides. However, preemergence control is mostly utilized in bermudagrass and zoysiagrass lawns so chemical control discussions will focus predominantly on postemergence herbicides. Most postemergence herbicides that contain 2,4-D, dicamba, floroxypyr, triclopyr, and others will control henbit. The ideal time to make herbicide applications is when the plant is small in autumn. As the plant gets bigger, herbicides will become less effective at controlling henbit. Additionally, winter annuals will naturally die in the summer; therefore, late spring herbicide applications are generally not needed. When henbit leaves start to turn yellow in color, they are beginning to die naturally from heat stress and herbicide applications are no longer necessary.

For more information on weed control, search this blog and check out our Turfgrass Weed Control for Professionals Publication.

For archives of past weed of the month postings, visit our Weed of the Month Archive.

Aaron Patton, Turfgrass Extension Specialist

Leslie Beck, Postdoctoral Research Associate

Weed of the month for November 2013 is Black Medic

Black Medic  

Biology: Black Medic (Medicago lupulina) is a summer annual (or less commonly a winter annual) broadleaf weed that can be found throughout the United States. Seeds germinate in the spring and are capable of establishing in drought-prone or disturbed soils. Black medic is a legume, meaning that it has the capabilities to fix its own nitrogen; thus, allowing it to out compete turf in nutrient-poor soils as well. These factors, in combination with its ability to tolerate low mowing heights, make black medic a common weed in lawns and other high-maintenance turf throughout Indiana.

Identification: Black medic has low-growing, prostrate, somewhat square stems that extend underneath the turf canopy to lengths up to 2 feet long. Despite the production of these invasive stems, it germinates from seed in early autumn or spring. Black medic stems do not have the ability to root as they establish; however, the plant is well-anchored by a deep, central taproot. The leaves are trifoliate (3 leaves), dull green on the top, pale green below, wedge-shaped, as long as they are broad, toothed near the tip, and display a projecting tip or spur at the apex. Black medic can often be mistaken for oxalis (yellow and creeping woodsorrel) and white clover which also have very similar trifoliate leaf arrangements. However, the leaf stem (petiole) of the center leaf in black medic is slightly longer than the two lateral leaves, thus distinguishing it from oxalis and white clover. Black medic produces a very tight, compressed cluster of small yellow flowers in the spring and until the fall. Once the flowers mature, they form a very tightly coiled black seedpod, hence the name ‘black medic’.

Oblong leaves are as wide as they are long. With a notch (spur) at the leaf tip.

Trifoliate (3-leaves), wedge shaped leaves

Center leaf has a longer petiole (leaf stem) than the two lateral leaves

Small cluster of yellow flowers

Immature seedpod

Cluster of blackened mature seedpods

Spreads by low-growing prostrate stems

Black medic can tolerate low mowing heights

Black medic invading cool-season turf

Presence of black medic could indicate dry soils or low fertility

Cultural control: The use of cultural practices to increase turf competition may help to manage invading weeds like black medic. Black medic is not shade tolerant, therefore the development of a thick, dense turfgrass canopy may improve competition. Additionally, black medic is a legume capable of fixing its own nitrogen; as a result, adequate nitrogen fertilization techniques will help to manage the weed and further develop a more competitive turf. The presence of black medic in the field may also indicate a particularly dry soil in need of irrigation. Black medic can also be easily pulled by hand if populations are small enough, though it is important to remove as much of the taproot as possible. Hand-weeding should be done when the plant is in the early growing stages, especially before it produces viable seed.

Biological control: None known for specific use in black medic. There are some organic postemergence herbicides available for turf weed control such as pelorgonic acid (Scythe), acetic acid (5% or greater solutions), and medium-length fatty acids (Eugenol); however, these products do not differentiate between the target weed and the desired turf (non-selective). As a result, these products are often used as spot treatments for weed control in parking lots, along fence rows, and in other bare-ground areas. Other organic products that contain essential micronutrients such as iron HEDTA (FeHEDTA), may be used to manage black medic; however, their ability to control black medic has not been adequately researched.

Chemical control: Chemical management of black medic is generally focused on a postemergence strategy over a preemergence strategy. The best postemergence management strategy is to apply two- or three-way mixtures of 2,4-D, dicamba, MCPP, or MCPA. Other options for selective control may include products such as Turflon Ester (triclopyr) or Drive (quinclorac) which may require multiple applications for adequate control.

For more information on weed control, search this blog and check out our Turfgrass Weed Control for Professionals Publication.

For archives of past weed of the month postings, visit our Weed of the Month Archive.

Aaron Patton, Turfgrass Extension Specialist

Leslie Beck, Postdoctoral Research Associate