Category: Learn

Biology: Field paspalum (Paspalum laeve Michx.) is a warm-season perennial weed with short rhizomes similar to dallisgrass (Paspalum dilatatum Poir.). Much of the below Weed of the Month entry comes from research conducted in Indiana on how to control Field Paspalum. That research was published in 2012. Reicher, Z.J., A.J. Patton, and D.V. Weisenberger. 2012. Suppression of field paspalum in Kentucky bluegrass with mesotrione. [Online]. Appl. Turfgrass Sci. doi:10.1094/ATS-2012-0626-01-RS.

Identification: Field paspalum is a wide-bladed (3-10 mm wide), warm-season perennial turfgrass that becomes easily visible in mid-summer. It can have either dark green or yellow green foliage. It is found in cool-season and warm-season turf. It has a short rhizomes near the soil surface but spreads primarily by seed. Although these species have short rhizomes, they effectively are a bunch-type plant and form scattered clumps of grass in the landscape.

Field paspalum and dallisgrass can be distinguished from one another by a few characteristics although they are more similar than different. The range of adaptation is different with field paspalum distributed into farther north than dallisgrass. Field paspalum can be found in Kansas, Missouri, Illinois, Indiana, Ohio, Pennsylvania, and Maryland whereas dallisgrass is less commonly distributed in those areas (Fig. 1). Leaf sheath, leaf blades, and rhizomes of the two species are similar (Fig. 2). Both species have terminal panicles with racemosely arranged branches of similar number and length (Fig. 3). Dallisgrass can be distinguished from field paspalum by the spikelets in pairs appearing to be in four rows on dallisgrass compared to two in field paspalum (Fig. 3). Additionally, dallisgrass has long, silky hairs on the spikelets while field paspalum is glabrous (Fig. 3). Dallisgrass also has a 5- or 7-veined glume while field paspalum has a 3-nerved upper glume with veins at the margins (Fig. 3).

Cultural control: Reduce soil compaction and promote practices that increase turf density. The most effective way to control these weeds is to dig up the clumps in the turf with a shovel.

Biological control: None known.

Chemical control: Another option is spot treatment with the nonselective herbicide glyphosate (Roundup and others). At least two glyphosate applications are needed. Apply when the plant first greens up in the spring (late April or May), and again when regrowth appears. Multiple follow-up applications may be required. You can also spray dallisgrass and field paspalum in October before they turn off color and enter winter dormancy. Use a 1-2% spray solution (1.3-2.6 fl oz of glyphosate/gal of water).
Obviously, glyphosate is going to kill some of the desirable grass and could leave big, brown spots in the turf so spot apply the herbicide only to the weed and not to the turf, if possible. You can even use a paintbrush, sponge, or foam applicator to apply the glyphosate only to the weed to help reduce the risk of injuring the desirable turf.
In Kentucky bluegrass, fine fescue, tall fescue, or perennial ryegrass lawns, three applications of mesotrione (Tenacity) at 5 oz/A spaced with a two-week application interval should reduce dallisgrass and field paspalum by 75 percent or more. Start making these applications in June. In tall fescue, two applications of fluazifop (Fusilade II) at 5-6 oz/A at three- to four-week intervals starting in late-April and September will suppress field paspalum and dallisgrass. Adding triclopyr (Turflon Ester Ultra or Triclopyr 4) at 1 qt/A to fluazifop will improve turfgrass safety. Do not use on seedling tall fescue less than four weeks old.
Tribute TOTAL (thiencarbazone + foramsulfuron + halosulfuron) at 3.2 oz/A also is effective at controlling dallisgrass in bermudagrass and zoysiagrass turf when making multiple applications in later summer and early fall before winter dormancy, and a subsequent follow-up application in spring.
In zoysiagrass, two applications of fluazifop (Fusilade II) at 3-4 oz/A at three- to four-week intervals during the summer will suppress field paspalum and dallisgrass. Adding triclopyr (Turflon Ester Ultra or Triclopyr 4) at 1 qt/A to fluazifop will improve turfgrass safety.

Biology: Fountain grass ((Pennisetum spp.) is an ornamental grass common to the landscapes of homes, commercial sites, and golf courses. However, following years of planting in these landscapes, we now realize that this species produces many viable seeds that drop onto the adjacent turf and then become tough-to-control perennial grassy weeds. Although most of the ornamental grasses cannot withstand short mowing, fountain grass does.

Identification: Typically, this grass can be identified by its visible shredded leaf blades in mid- and late summer, which leaves a whitish, wispy looking clump when mown.

Even when mown, fountain grass will produce a seedhead occasionally in summer.

Cultural control: Don’t plant fountain grass in landscape beds unless you want it in the adjacent turf.

Biological control: None known.

Chemical control: This weed can be controlled by applying herbicides that contain quinclorac (Drive, Drive XLR8, Eject 75DF, Momentum Q, Onetime, Q4 Plus, Quincept, Quinclorac 75DF, QuinPro, Solitare, SquareOne). Two applications are needed for control. Glyphosate (Roundup and others) will also work as a nonselective spot-treatment option.

Biology: Goosegrass (Eleusine indica) is an late-germinating summer annual grass that is often found in compacted areas or areas disturbed in the summer. These areas include compacted areas next to sidewalks or cart paths, golf course tees, and areas were soil is disturbed during the summer. Germination typically starts about two to three weeks after crabgrass germinates in early May in most Midwestern States although goosegrass is less common in northern areas of the Midwest like Michigan, Minnesota and Wisconsin.

Identification: Goosegrass is a prostrate growing summer annual grass which forms a mat-like rosette. Its flattened leaf sheaths are typically a white to silver color, especially at the base of the leaf sheath. Because of this coloration and its similarity to crabgrass some call it silver crabgrass.

Seedlings develop several leaves (sometimes six or more) before tillering.

As the plants mature they tiller and become very tough and more prostrate in growth (especially in mown turf). Goosegrass produces seedheads from July to September in Indiana. The seedheads are similar in appearance to crabgrass but the seeds are slightly larger than crabgrass seeds and the spikes on the seedhead are often described as being “zipper-like” in appearance.

Biology: Ground ivy (Glechoma hederacea), also known as creeping Charlie, is a very difficult to control perennial broadleaf weed. It can often be seen growing in the shade and invading turfgrass and other mowed areas throughout the United States. Ground ivy thrives in moist, rich soils located in shaded areas, but will grow in full sun as well. These traits combined with the ability to produce aggressive rooting stolons, tolerate low mowing heights, and shade/crowd-out surrounding plants, help to make ground ivy one of the most difficult-to-control turf weeds in lawns.

Identification: Ground ivy is a perennial broadleaf weed that invades turf through aggressive stolons that ‘creep’ below the turfgrass canopy. It forms very dense, mat-like patches that effectively crowd-out the surrounding turf. Like other members of the mint family, ground ivy has distinctive square stems with two leaves branching from each origin point (node) and emits a disagreeable odor when crushed, damaged, or mown. Leaves are round to kidney-shaped with prominent veins and broad rounded edges. These leaves are held above the canopy by long petioles (leaf stems) which can effectively shade and weaken the surrounding turf. Spreading stolons root aggressively at the node, further making ground ivy difficult to control. It produces flowers from April to June that are tubular in shape, purplish blue with red speckles, lobed petals, and are arranged in groups of three to seven. Ground ivy can often be mistaken for other broadleaf weeds such as common mallow or henbit. However, common mallow has rounded stems and sharply toothed leaf edges while henbit stems do not ‘creep’ along the ground nor root at the nodes.

Cultural control: Because of its aggressive growth and establishment, there are very few cultural practices that have been observed to effectively control ground ivy. Management practices such as improving surface drainage, watering deeply and infrequently, and cultivating (aeration) compacted soils may hinder the development of ground ivy in favor of a more dense, aggressive turf. Nitrogen fertilization will also provide some reduction of ground ivy cover in turf.

Biological control: None known for specific use in ground ivy. Our preliminary research suggests that iron HEDTA (FeHEDTA) may be used to manage ground ivy with multiple applications.

Chemical control: Because of its aggressive nature and the survivability of stolons, there are no preemergence herbicide options for the control of ground ivy in turf although Gallery (isoxaben) can help reduce the ability of stolons from rooting which will slow the spread of this weed. As a result, management must focus on postemergence herbicides. Repeat applications of two- or three-way mixtures of 2,4-D, dicamba, MCPP, of MCPA may offer fair levels of control. Turflon Ester (triclopyr) typically provides better control. Additionally, products that contain triclopyr or fluroxypyr as one of the ingredients in a two- or a three-combination herbicide will work well. In warm-season turf, Manor (metsulfuron) can control ground ivy when applied in combination with a non-ionic surfactant (0.25%). Most of these herbicides require supplemental applications for adequate control.

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.

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.

Biology: Large crabgrass ( Digitaria sanguinalis ), smooth crabgrass (Digitaria ischaemum), and to a lesser extent southern crabgrass (Digitaria ciliaris) are all species found in the Midwest that are collectively referred to as crabgrass. Large crabgrass is probably the most common of these in Indiana lawns. Combined, these crabgrass species are often considered to be the most problematic weed in lawns. Large crabgrass is summer annual grass that typically germinates in April in the Midwest (late March in southern areas and late April in northern areas). A germination tracker at www.gddtracker.net can be used to track the germination of crabgrass.

Identification: Large crabgrass is one of the first summer annual grasses to germinate in Indiana. Look for it first in bare soil areas like a garden or very thin turf areas and in areas with south facing slopes. First germination has occurred between March 22 and April 20 in the Lafayette area the past several years. Initial seedlings have an almost oval shaped, cotyledon.

Nimblewill will have a membranous ligule and sparse hairs and bermduagrass has a hairy ligule and is usually very hairy.

Biology: Pineapple weed (Matricaria matricariodies), behaves as either a summer or winter annual and it is commonly found throughout the United States. It is a weed of both high- and low-maintenance turfgrass lawns, landscapes, and nursery crops. Its ability to tolerate low mowing heights and highly compacted soils allow pineapple weed to compete with in weak turf.

Identification: Pineapple weed can behave as either a summer or winter annual broadleaf in both high- or low-maintenance turf throughout the Midwestern United States. It has a very low-growing, bushy, and branching growth habit and it reproduces by seed, which have the ability to emerge year-round if environmental conditions are favorable. Typically, the seedlings germinate in late summer to early fall and again from early spring to early summer. Young plants form a small, but dense rosette of fragrant, hairless, shiny bright green leaves that are also thick and succulent. Rosettes form from a very shallow taproot with a secondary fibrous root system. As the plant matures, the smooth, hairless stems continue to elongate in either an erect or a low-branching/spreading growth habit. The leaves are also hairless, fleshy and are pinnately divided with deep, finger-like lobes and short linear segments. All pineapple weed foliage (stems and leaves) have a very sweet odor similar to that of pineapple when damaged or crushed; thus, giving the plant its common name. From May through September, the plant produces flowers that are yellow, egg-shaped, and are composed of densely-packed, tiny, yellowish-green flowers. Flowers also emit a very sweet, pineapple like odor when crushed. Pineapple foliage can sometimes be confused with that of wild chamomile; however, the foliage of plants in the chamomile family can range from highly bitter to absent, not sweet and pineapple-like.

Cultural control: None known specifically for pineapple weed. Though it tolerates low mowing heights and compacted soils, a combination of frequent mowing, adequate fertilization, and irrigation to keep turf dense will help the desired turf compete and gradually eradicate pineapple weed. Reducing traffic will also help increase turf density and reduce pineapple weed invasion. Additionally, hand pulling small populations may help to physically remove pineapple weed due to its shallow tap root.

Biological control: None known specifically for pineapple weed.

Chemical control: Since it reproduces from seed, it is possible to manage pineapple weed through the use of preemergence herbicides. However, control with preemergence herbicides may be difficult since the seeds have the ability to germinate year-round under favorable environmental conditions. Postemergence applications of two- or three-way mixtures of 2,4-D, dicamba, MCPP, or MCPA will likely provide adequate control in established turf. Though dicamba does the majority of the work in controlling pineapple weed, the addition of MCPP often helps to increase the effectiveness of the overall application. These products are available in multiple formulations at local retailers.