Vaseygrass (Paspalum urvillei; also seen as two words, or as vasey’s grass) is a warm-season perennial grass weed commonly found in pastures and hayfields in the southern half of Georgia. Recently, vaseygrass has begun to spread north in Georgia and can now be found sporadically throughout the Piedmont region of the state.
Vaseygrass thrives in wet, moist soil and is commonly found along waterways, ditches, disturbed sites, or in pastures and hayfields prone to flooding. However, vaseygrass is very adaptable and can easily spread to upland and dry environments, encroaching on unimproved pastures and in open canopies of weakened forage stands.
Vaseygrass is often mistaken for johnsongrass (Sorghum halepense) or dallisgrass (Paspalum dilatatum). Proper identification is key to ensuring appropriate herbicide recommendations. Although vaseygrass does not pose the same risks—of prussic acid poisoning from johnsongrass, or staggers from dallisgrass—the plant’s forage quality is not sufficient to meet the nutritional demands of most grazing animals.
Vaseygrass Identification
Growth Habit and Roots
Figure 1. Mature Vaseygrass Plants. Mature plants are easily identified by their bunch-type growth habit and distinct seedhead. ?
Vaseygrass has a bunch-type growth habit with a fibrous root system (Figure 1). Even when the plant is immature, the plant still grows in small bunches that quickly outpace the desirable pasture grasses around it (Figure 2). Unlike johnsongrass, vaseygrass does not have significant rhizomes. Rhizomes are belowground plant parts that allow for lateral plant growth and are common in many perennial grasses like johnsongrass, dallisgrass, or bermudagrass (Cynodon spp.).
?Figure 2. Immature Vaseygrass Plants Quickly Outpace Other Forage Grasses. This is especially true immediately after a grazing or harvest event (A), and vaseygrass will outcompete desirable forages throughout the growing period (B).
Seedhead and Seeds
Vaseygrass has alternating spikelets on the seedhead with multiple spreading branches (Figure 3A). Vaseygrass will produce seeds down the entire seedhead branch, and you may find silky hair around the seed. Vaseygrass seeds are small, oval, relatively flat, and light green in color.
By contrast, johnsongrass has a tall, open panicle with numerous whorled branches (Figure 3B). Johnsongrass seeds tend to be larger with a red or brown color as maturity increases. Dallisgrass (Figure 3C) has three to six slender alternating spikes along the main stem of the seedhead. The seeds of dallisgrass are visually similar to those of vaseygrass.
.jpeg)
Figure 3. Vaseygrass Seedheads (A) Compared to Other Grasses. Vaseygrass seedheads have alternating spikelets with light green seeds on the entire branch. Johnsongrass (B) has an open panicle seedhead with red or brown seeds on the ends of the branches. Dallisgrass (C) seedheads will have three to six slender, alternating spikes along the main stem, with green seeds.
Stems and Ligules
Figure 4. Vaseygrass Stems Compared to Other Grasses. Vaseygrass (left) has small stems with fine hairs at the ligules (location where the leaf meets the stem). Johnsongrass (middle) has a larger, smooth stem. Dallisgrass (right) is usually the smallest of the three and has smooth stems.
Vaseygrass will have hairy ligules and may have hairs at the base of the stem (Figures 4 and 5A). The ligule refers to the place where the leaf and stem meet. Johnsongrass has smooth stems and membranous (thin, translucent) ligules (Figures 4 and 5B). Dallisgrass is similar to johnsongrass with smooth stems and membranous ligules, but the stem size is typically finer (thinner) than both vaseygrass and johnsongrass (Figures 4 and 5C).
Figure 5. Vaseygrass Ligules Compared to Other Grasses. Vaseygrass (A) has hairy ligules (location where the leaf meets the stem). Johnsongrass (B) and dallisgrass (C) both have membranous ligules, but dallisgrass may have sparse hairs.
Leaves
Vaseygrass and dallisgrass leaves are narrower than johnsongrass leaves (Figure 6). Vaseygrass and dallisgrass have prominent, indented midribs, whereas johnsongrass has a large white midrib. The leaf margins of vaseygrass are more crinkled or wavy than the roughness seen on dallisgrass margins. Johnsongrass has smooth leaves that often look glossier than vaseygrass or dallisgrass.
Figure 6. Vaseygrass Leaves Compared to Other Grasses. Vaseygrass (left) has narrow leaves with wavy leaf margins or edges. Johnsongrass (middle) has wider leaves with a large white midrib. Dallisgrass (right) also has narrow leaves with rough margins that are less wavy than vaseygrass.
Integrated Weed Management of Vaseygrass
Like other perennial weed species, vaseygrass requires an integrated weed management approach for long-term control. Reduce seed spread through regular mowing of vaseygrass, especially before seed maturity; this depletes the root carbohydrate reserves and limits the spread of the weed.
Herbicides
Herbicides also will be required for long-term control. Fall herbicide applications are often more effective than spring treatments for long-term control of vaseygrass. These applications should occur in late August or September when vaseygrass begins allocating carbohydrates from leaves to roots. During this period, the herbicide will be more effectively moved to belowground plant parts, and control should be improved. Dry weather will limit the effectiveness of the fall herbicide applications. Spring treatments can provide temporary control, but regrowth from roots is very common.
Preemergence herbicides are not currently labelled for control of vaseygrass, but research is ongoing. These products will control annual grass weeds, which also removes competition from the vaseygrass, causing the weed to spread. Unfortunately, postemergent herbicide options are limited for the control of vaseygrass.
Glyphosate
There are no selective control options in bahiagrass (Paspalum notatum) or tall fescue (Lolium arundinaceum) forages, so spot treatment is required. Glyphosate is a nonselective herbicide and cannot be applied to desirable grasses without severe injury. Glyphosate will translocate, or move within, any plant that encounters the herbicide. Use caution to avoid injury to nontarget forage species.
Applications of glyphosate using a wick-bar or roller weed-wiper are possible. University of Florida researchers recommend mowing the field and following 30 days later with the weed wiper (Sellers, 2019). For best results, use a 10% volume for volume (v/v) glyphosate solution (12.8 fl oz per gallon) and wipe the mixture in two directions. Spot treatments should be made with a labelled rate of glyphosate. There are many different formulations of glyphosate, and actual rates will depend on the product used. Please refer to the herbicide label for mixing instructions.
Pastora
Vaseygrass responds to applications of Pastora (metsulfuron and nicosulfuron) or Impose (imazapic). These products are only labelled for use in bermudagrass. Both products are only rated as providing fair control and may only provide suppression of the vaseygrass by reducing the population or plant vigor.
Pastora should be applied in a broadcast application with a boom sprayer at 1.25 to 1.5 oz per acre. Spot treatments of Pastora can be made by mixing 2.5 oz of chemical with 25 gallons of water. This solution should be used to treat no less than 1 acre.
Applications should be made when the vaseygrass is 6 to 8 in. tall. This usually occurs approximately 7 to 14 days after a grazing or harvest event, depending on rainfall amount. The maximum application rate of Pastora is 2.5 oz per acre per year.
Impose
Impose should be applied in a broadcast application with a boom sprayer at 6 to 8 fl oz per acre. Spot treatments of Impose can be made by mixing a 1% solution (0.2 fl oz) of chemical and 1% methylated seed oil (MSO; 0.2 fl oz) per gallon of water. All applications should be made when the vaseygrass is 4 to 8 in. tall. This usually occurs approximately 7 days after a grazing or harvest event, depending on rainfall amount. The maximum application rate of Impose is 12 oz per acre per year.
Bermudagrass Injury
Bermudagrass injury or stunting is expected with both Pastora and Impose. Pastora will delay the next harvest by 7 days, and Impose will delay it by 21 days. This delay caused by the Impose application will generally lead to at least one lost harvest in the season of application. Do not apply either herbicide during the transition period, from dormancy until 100% green-up. Follow all label instructions to avoid additional injury to the bermudagrass stand.
Multiple herbicide applications will be required to improve control of vaseygrass. Do not exceed the maximum annual rate of the herbicides per application or year.
Improved Cultural Practices
Improved cultural management of the pasture or hayfield can also improve suppression of vaseygrass and other weed species. Improved management practices to consider are:
- Correct nutrient deficiencies in the soil following the recommendations from a soil sample test.
- Correct soil pH following soil-test recommendations.
- Increase grazing or harvest height to 3 in. for bermudagrass, 3 in. for bahiagrass, and 4 in. for tall fescue.
- Minimize soil disturbance by discontinuing vertical tillage or aeration.
- Improve soil drainage by clearing drainage ditches or installing drainage systems.
Each of these management practices will help promote the growth and persistence of the desirable forage species. This should result in improved ground coverage, which increases competition for weeds that may try to encroach into your pasture or hayfield. Open gaps in the forage canopy enable invasion of undesirable weed species.
Conclusion
Vaseygrass is an increasingly problematic weed for forage producers across Georgia. This weed is persistent and will quickly invade open ground in pastures or hayfields. Control options are limited, but Georgia producers have several options available when practicing integrated weed management on their farm.
References
Sellers, B. (2019). Controlling broomsedge and vaseygrass in pastures using a weed-wiper. UF-IFAS Extension.
Status and Revision History
In Review on May 14, 2025
Published on May 16, 2025
