Weed control in ornamental grasses

Weed control 

in ornamental grasses 

Ornamental grasses can tolerate some common herbicides. 

John Tallarico, M.S., and Tom Voigt, Ph.D. 

Ornamental grasses are considered lowmaintenance 

because they usually require little 

more than an annual pruning and 

occasional — the frequency depends on the 

grass — division to prevent overgrowth or 

encourage new growth (4). As use of ornamental 

grasses continues to rise, proper management 

practices need to be explored so that 

the plants will always look their best. Perhaps 

the greatest challenge in maintaining ornamental 

grasses is effective weed control. 

Traditional weed control 

A number of traditional methods exist for 

controlling weeds in ornamental plantings. 

One is to start with a clean planting bed by 

allowing the bed to go fallow and then rotary 

tilling it several times. Treating the planting 

bed with a nonselective systemic herbicide 

such as glyphosate can help control undesirable 

plant growth before planting. 

After planting, covering the bed with a 2to 

3-inch (5- to 7.6-centimeter) layer of a 

fine-textured organic mulch such as shredded 

bark or well-rotted compost inhibits weed 

invasion and water evaporation from the soil 

and moderates soil temperatures. 

KEY points 

More Info: www.gcsaa.org 

Although ornamental grasses are 

attractive low-maintenance plants, 

weed control can be a problem. 

Starting with a clean planting bed 

and using mulch or weed mats are 

traditional ways of limiting weeds 

in ornamental grasses. 

Our studies showed that several 

ornamental grasses were highly 

tolerant of five common herbicides. 

In the future, these herbicides may 

be labeled for weed control in 

ornamental grasses. 

RESEARCH 

Figure 1. In all three studies, only the 1× + 1× application rate of Lontrel (clopyralid) caused damage to maiden grass 

(Miscanthus sinensis Gracillimus). Moudry fountain grass (Pennisetum alopecuroides Moudry) did not exhibit 

damage from applications of Lontrel. 

In some cases, breathable weed mats can 

be placed on the soil beneath the mulch to 

reduce weed encroachment. These mats, 

however, can restrict the growth of rhizomatous 

ornamental grasses. 

Using proper spacing can create a living 

mulch of ornamentals by covering the entire 

planting bed, decreasing open area and light 

and thereby limiting weed growth. Finally, 

once weeds begin to invade a bed, mechanical 

removal (hand pulling, hoeing or cutting) 

and/or herbicides are control options. 

Herbicides for weed control 

Herbicides applied to ornamental grasses 

must control weeds without damaging desirable 

plants. Unfortunately, only a few pertinent 

studies about herbicide use in ornamental 

grasses have been published (3,5,6,7), and only 

a modest number of herbicides are labeled for 

use on ornamental grasses (Table 1). 

In 2000, we began experiments to evalu- 

ate the damage caused to ornamental grasses 

by several pre- and post-emergence herbicides. 

Study 1 

In the first study, we applied Lontrel 

(clopyralid) to container-grown grasses. 

Lontrel, a post-emergence herbicide, is used 

to control many annual and perennial 

broadleaf weeds (1). The 35 ornamental 

grasses arrived as 2.25-inch (5.7-centimeter) 

square plugs in April and were potted in 1gallon 

(3.7-liter) nursery pots containing a 

mix of 75% high-porosity artificial potting 

mix and 25% silty clay loam in May and June 

2000 (Table 2). The pots were placed on an 

outdoor gravel pad at the University of 

Illinois Landscape Horticulture Research 

Center in Urbana and watered as necessary as 

a randomized complete-block experimental 

design with four replications. The first experiment 

began on June 12 and was repeated, 

beginning on July 10. 

February 2004 

GCM 143 

Photos courtesy of Tom Voigt

RESEARCH 

Each plot had three treatments: an 

untreated control, Lontrel applied at a rate of 

1 1 ⁄3 pints product/acre (1.5 liters/hectare) (1× 

the label rate), and Lontrel applied at a rate 

of 2 2 ⁄3 pints product/acre (3.1 liters/hectare) 

(2× the label rate). The herbicide was 

applied twice at 30-day intervals in each 

experiment. Therefore, by the conclusion of 

each experiment, each herbicide-treated grass 

had received the equivalent of either two or 

four times the label rate of Lontrel (Figure 1). 

In each experiment, ornamental grass 

damage was rated five times at two-week 

intervals, using a subjective scale of 0-10, 

where 0 = no herbicide damage and 10 = grass 

death. A rating of 0-3 was considered commercially 

acceptable. 

HERBICIDES 

Grass Herbicides 

Arundo spp. (giant reed) 

Cortaderia spp. (Pampas grass) 

Deschampsia caespitosa 

(tufted hair grass) 

Festuca ovina glauca 

(blue fescue) 

Hakenochloa macroaureola 

(golden hakone grass) 

Miscanthus sinensis 

Ornamental grasses 

Pennisetum spp. (fountain grass) 

Phalaris arundinacea picta 

(ribbon grass) 

Saccharum ravennae (ravenna grass) 

*Treflan 5G label (United Horticultural Supply). 

Table 1. Herbicides labeled for ornamental grass application (2). 

144 GCM February 2004 

Study 2 

In the 2001 study, Gallery (isoxaben) and 

Snapshot TG (isoxaben + trifluralin) were 

applied in two experiments to field-grown ornamental 

grasses to determine potential plant 

injury. Gallery is a pre-emergence herbicide that 

controls many annual broadleaf weeds. A preemergent 

with the characteristics of Gallery, 

Snapshot TG also controls annual grasses and 

small-seeded broadleaf weeds because it contains 

trifluralin as well as isoxaben (1). 

Fifteen ornamental grasses (Table 3) were 

field-planted May 18-22, 2001, using 2.25inch 

(5.7-centimeter) square plugs in silty clay 

loam soil at the University of Illinois Landscape 

Horticulture Research Center. The study plots 

were unfertilized and received irrigation to 

pendimethalin 

dithiopyr, pronamide, prodiamine, fluazifop-pbutyl, 

isoxaben, isoxaben + trifluralin, 

metolachlor, oryzalin, pendimethalin, sethoxydim, 

trifluralin* 

dithiopyr, isoxaben, isoxaben + trifluralin, 

pendimethalin, trifluralin* 


oryzalin, pendimethalin, sethoxydim, trifluralin* 

isoxaben, isoxaben + trifluralin, trifluralin* 

isoxaben, isoxaben + trifluralin, pendimethalin, 

prodiamine, pronamide, trifluralin* 

clethodim, dithiopyr, fenoxaprop-p-ethyl, fluazifop-p-butyl, 

imazaquin, isoxaben, isoxaben + 

trifluralin, metolachlor, pendimethalin, prodiamine, 

pronamide, oxadiazon, oryzalin, sethoxydim 

dithiopyr, fenoxaprop-p-ethyl, isoxaben, isoxaben 

+ trifluralin, fluazifop-p-butyl, oryzalin, 

pendimethalin, prodiamine, pronamide, sethoxydim, 

trifliuralin* 


pendimethalin, trifluralin* 

isoxaben, isoxaben + trifluralin, oryzalin 

ensure grass survival and to incorporate herbicide 

treatments into soil. A split-plot design was 

used; there were four replications. Treatment 

plots were hand-weeded weekly to prevent limitation 

of grass growth by weeds. 

Each plot contained five individual plants 

of the same species. The five treatments were: 

an untreated control; Gallery at 1.3 pounds 

product/acre (1.4 kilograms/hectare); Gallery 

at 2.6 pounds product/acre (2.9 kilograms/hectare); 

Snapshot TG at 200 pounds 

product/acre (224.1 kilograms/hectare); and 

Snapshot TG at 400 pounds product/acre 

(448.3 kilograms/hectare). These rates correspond 

to 1× and 2× label rates of Gallery and 

Snapshot (Figure 2). 

Gallery was applied over the top of the 

plants using a CO2 backpack sprayer. 

Snapshot TG, a granular product, was 

applied over the top of the plants with a turf 

drop spreader. The herbicides were applied on 

June 8 and July 6 in experiment 1 and July 6 

and Aug. 4 in experiment 2. Therefore, by the 

conclusion of each experiment, each herbicide-treated 

grass had received the equivalent 

of either two or four times the label rates of 

Gallery or Snapshot TG. An area 3 feet by 3 

feet (0.9 meter by 0.9 meter) around each 

plant was treated. 

In both experiments, subjective visual ratings 

were used to evaluate the tolerance of 

newly transplanted grasses subsequent to herbicide 

applications of Gallery and Snapshot. 

Herbicide-caused plant injury was visually evaluated 

five times at two-week intervals in each 

experiment, using a scale of 0-10, where 0 = no 

damage and 10 = plant death; a rating of 0-3 

was considered commercially acceptable. 

Extreme cases of reduced plant size and shoot 

deformations, or combinations thereof, led to 

ratings that were not commercially acceptable. 

After the final plant evaluation, the 

grasses were removed and shaken to remove 

loose soil. The root systems were immediately 

rated using the same visual rating scale. 

Considerations affecting root ratings were 

reductions in the overall size of the root system 

(development of lateral and secondary 

roots) and swelling of roots. 

Study 3 

In this 2001-2002 study, ornamental 

grasses were treated with Ronstar G (oxadiazon) 

or Preen (trifluralin). Both of these are 

pre-emergence herbicides that control many 

annual grasses and broadleaf weeds (1). On 

May 23 and 24, 2001, eight ornamental

grasses were field-planted using 2.25-inch 

(5.7-centimeter) square plugs and treated 

with Ronstar G (oxadiazon) and Preen (trifluralin) 

(Table 4, Figure 3). The plants were 

watered as needed to ensure survival and 

incorporate herbicides. 

Separate sets of grasses were planted in 2001 

for each year of the study. The 2001 evaluation 

was conducted on newly planted grasses. The 

2002 results are from plants that had been 

growing on the site for one season. The only 

exception is purple fountain grass plants, 

which were replanted in 2002 because they are 

unable to survive the winter in central Illinois. 

The grasses were planted using a randomized 

complete block design with three 

replications. The plants were spaced 4 feet 

(1.2 meters) apart within rows and 8 feet (2.4 

meters) apart between rows. Each plot had 

three plants: an untreated control; a plant 

treated with Ronstar (150 pounds product/acre 

[168.1 kilograms/hectare]); and a 

plant treated with Preen (272 pounds product/acre 

[304.8 kilograms/hectare]). 

Both herbicides were applied on June 14, 

2001, and June 24, 2002, by treating a 2foot-by-2-foot 

(0.6-meter-by-0.6-meter) area 

around each plant in 2001, and a 3-foot-by- 

3-foot (0.9-meter-by-0.9-meter) area around 

each plant in 2002 when plants were older 

and larger. Phytotoxicity was evaluated using 

a scale of 0-10, where 0 = no damage and 10 

= plant death; a rating of 0-3 was deemed 

commercially acceptable. 

Results 

This work was conducted to evaluate 

product-plant interactions, and the results of 

these experiments are not intended as use recommendations. 

Be sure to read, understand 

and follow pesticide label instructions for the 

safest, most effective pest control. 

Study 1 

At each evaluation, the grass species 

showed significant differences in foliage ratings 

(data not shown), but the foliar conditions 

could not be attributed to herbicide 

applications. The differences among grass 

species were more likely due to the natural 

differences among the 35 species, their 

interaction with the environment or the quality 

of the original transplants. 

The herbicides did not have significant 

effects on grasses at any evaluation (data not 

shown). At one foliar evaluation in experiment 

1 (July 10, 2000), treated grasses had 

FOLIAR QUALITY 

RESEARCH 

Grass 2× rate* 4× rate † 

Control 

Arrhenatherum elatius ssp. bulbosum Variegatum 

(striped tuber oat grass) 2.9 3.1 2.7 

Bouteloua curtipendula Trailway (trailway side-oats grama) 2.6 3.3 2.9 

B. gracilis (blue grama) 2.8 3.1 3.1 

Briza media (common quaking grass) 2.6 3.0 3.0 

Calamagrostis brachytricha (Korean feather reed grass) 3.3 3.2 3.2 

C.× acutiflora Karl Foerster (Karl Foerster feather reed grass) 3.6 3.4 3.7 

Chasmanthium latifolium (northern sea oats) 3.6 3.5 3.7 

Cortaderia selloana (pampas grass) 2.0 2.0 2.0 

C. a selloana Rosea (rosea pampas grass) 1.9 2.2 2.0 

Deschampsia caespitosa (tufted hair grass) 2.9 3.1 3.2 

Hystrix patula (bottle-brush grass) 5.5 5.3 5.2 

Imperata cylindrica Red Baron (Japanese blood grass) 2.5 2.1 2.5 

Leymus arenarius (blue lyme grass) 2.6 2.7 2.8 

Miscanthus Purpurascens (autumn red flame grass) 2.7 2.6 2.6 

M. sinensis Adagio (adagio miscanthus) 2.8 2.9 2.8 

M. s. Gracillimus (maiden grass) 3.6 3.1 3.1 

M. s. Sarabande (sarabande miscanthus) 2.4 2.6 2.4 

M. s. Variegatus (variegated miscanthus) 3.2 4.0 3.7 

M. s. Zebrinus (zebra grass) 3.7 3.9 3.4 

Nasella tenuissima Ponytails (ponytails Mexican feather grass) 3.5 3.5 3.2 

Panicum virgatum Trailblazer (trailblazer switch grass) 3.7 3.2 3.2 

Pennisetum alopecuroides (fountain grass) 3.4 3.3 3.3 

P. a. Caudatum (white flowering fountain grass) 2.9 2.5 2.6 

P. a. Hameln (Hameln fountain grass) 2.1 2.1 2.0 

P. a. Moudry (Moudry fountain grass) 3.1 3.2 3.1 

P. setaceum Rubrum (purple fountain grass) 3.2 3.4 3.3 

P. villosum (feathertop) 4.1 3.8 4.0 

Phalaris arundinacea Feesey (strawberries and cream ribbon grass) 3.7 3.4 3.6 

P. a. Picta (gardener’s garters) 3.0 2.8 2.8 

P. a. Woods Dwarf (dwarf’s garters ribbon grass) 3.1 2.9 3.0 

Rhynchelytrium nerviglume Pink Crystals (pink crystals ruby grass) 2.9 2.8 2.6 

Saccharum ravennae (ravenna grass) 3.8 3.7 3.8 

Schizachyrium scoparium Blaze (blaze little bluestem) 2.7 2.6 2.5 

Sesleria autumnalis (autumn moor grass) 3.1 3.3 3.0 

S. caerulea (blue moor grass) 2.3 2.3 2.2 

Note. Treatment means of five evaluations of four replications over two experiments (a total of 40 ratings) in 

2000 at the University of Illinois Landscape Horticulture Research Center in Urbana. Grasses were rated on a 

scale of 0-10; 0 = no damage, 10 = death. Plants exhibiting a mean rating of 3 or less were deemed commercially 

acceptable. 

*Two applications of 1 1 ⁄3 pints product/acre (1.5 liters/hectare) (1×+ the label rate); one application on June 

12 and one on July 10. 

† 

Two applications of 2 2 ⁄3 pints product/acre (3.1 liters/hectare) (2× the label rate); one application on July 11 

and one on Aug. 9. 

Table 2. Foliar quality means following application of Lontrel (clopyralid) to 35 container-grown grasses. 

February 2004 

GCM 145

RESEARCH 

QUALITY RATINGS 

2× 4× 

2× 4× isoxaben + isoxaben + 

Grass isoxaben † 

Note. Treatment means are of five evaluations of four replications over two experiments (a total of 40 ratings) 

in 2001 at the University of Illinois Landscape Horticulture Research Center in Urbana. The grasses were rated 

on a scale of 0-10; 0 = no damage, 10 = death. Plants exhibiting mean rating of 3 or less were deemed commercially 

acceptable. 

*Root ratings were made at the conclusion of each experiment in 2001 and are of one evaluation of four repli- 

cations over two experiments (a total of 10 ratings). 

† 

Two applications of Gallery at 1.3 pounds product/acre (1.4 kilograms/hectare) (1× label rate). 

‡ 

Two applications of Gallery at 2.6 pounds product/acre (2.9 kilograms/hectare) (2× label rate). 

§ 

Two applications of Snapshot TG at 200 pounds product/acre (224.1 kilograms/hectare) (1× label rate). 

// 

Two applications of Snapshot TG at 400 pounds product/acre (448.3 kilograms/hectare) (2× label rate). 

Table 3. Field-grown ornamental grasses in isoxaben and isoxaben + trifluralin herbicide trial. 

146 GCM February 2004 

isoxaben ‡ 

trifluralin § 

trifluralin // 

Control 

Calamagrostis brachytricha 

(Korean feather reed grass) 2.8 2.5 2.4 2.7 2.4 

Root rating* 3.0 2.0 1.8 3.3 1.5 

Calamagrostis × acutiflora 

Karl Foerster (Karl Foerster 

feather reed grass) 1.7 1.6 1.9 1.7 1.4 

Root rating 1.3 1.1 1.8 1.8 1.0 

Chasmanthium latifolium 

(northern sea oats) 1.7 2.7 1.6 3.0 1.9 


Miscanthus Purpurascens 

(flame grass) 2.2 3.8 4.3 3.5 2.2 


M. sinensis Arabesque 

(arabesque miscanthus) 2.1 2.7 2.1 1.6 1.8 


M. s. Gracillimus (maiden grass) 1.7 2.0 2.1 1.8 1.3 


M. s. Malepartus 

(malepartus miscanthus) 1.7 2.9 3.5 2.9 2.8 


M. s. Morning Light 

(morning light miscanthus) 2.2 2.3 2.4 2.9 1.7 


M. s. Sarabande 

(sarabande miscanthus) 1.4 2.4 2.3 2.2 2.2 


M. s. Variegatus 

(variegated miscanthus) 2.7 1.8 2.3 2.1 2.9 


M. s. Zebrinus (zebra grass) 1.3 1.5 1.7 2.3 1.7 


Pennisetum alopecuroides 

(fountain grass) 1.8 1.9 1.9 1.9 1.1 


P. a. Caudatum 

(white flowering fountain grass) 2.1 2.3 2.3 2.3 2.0 


P. setaceum Rubrum 

(purple fountain grass) 1.6 1.4 1.7 1.7 2.4 


Sorghastrum nutans Indian 

Steel (Indian steel Indian grass) 1.8 1.9 1.0 2.8 1.5 


significantly different ratings from untreated 

(control) grasses. In this case, the mean ratings 

for all herbicide treatments and 

untreated controls, however, were less than 3, 

the maximum commercially acceptable rating, 

so no herbicide treatments caused unacceptable 

foliage damage. 

When examining the data in Tables 2-4, 

it is important to compare the treated 

means with the control means, keeping in 

mind that a rating of 3 or less reflects commercially 

acceptable quality. In most 

instances, the means were similar to the control 

(within 0.1) or were less than 3. 

However, in several cases in study 1 (Table 2) 

(striped tuber oat grass, Japanese blood grass, 

maiden grass, zebra grass, ponytails Mexican 

feather grass, trailblazer switch grass), the rating 

for the control was noticeably lower than 

that for the herbicide-treated grasses. 

Although it appears that neither herbicide 

treatment in study 1 caused unacceptable 

foliage damage to most of the ornamental 

grasses, further work, particularly on the six 

grasses in question, should be conducted. 

Study 2 

At each evaluation, grass species showed 

significant differences in foliar ratings and root 

ratings (data not shown). These differences 

could, as in study 1, be attributed to the interaction 

of each species with the environment or 

to the original quality of the transplants. Foliar 

and root conditions should not be attributed 

to herbicide applications because only one 

foliar evaluation in each study (Aug. 3, 2001) 

showed significant effects of herbicides on 

grasses, and this effect could be attributed to 

excessively hot weather in the weeks before the 

evaluation (data not shown). In both experiments, 

the grasses did grow out of this, and 

subsequent ratings improved. 

In both experiments 1 and 2, quality ratings 

for the four herbicide treatments were 

not significantly different from one another, 

but they were significantly higher than the 

untreated controls (data not shown). 

However, the mean ratings for all herbicide 

treatments and the untreated controls were 

less than 3, so none of the plants suffered 

unacceptable levels of damage (Table 3). 

Overall, applications of Gallery and 

Snapshot herbicides at 2× and 4× label rates 

did not cause unacceptable foliar or root damage 

to the 15 grasses in this study, and we recommend 

that the ornamental grasses tested be 

added to the Isoxaben and Snapshot herbicide

labels at the 1× rates. 

Study 3 

In the two years of study 3, zebra grass 

displayed unacceptable phytotoxicity in three 

evaluations (July 7, Aug. 6 and Aug. 21, 

2002) (data not shown). Because herbicides 

had no significant effects on zebra grass on 

these dates, foliar quality could not be attributed 

to herbicide application. 

In the two years of this study, treatment 

significantly affected the quality of the grasses 

at only one evaluation (Aug. 12, 2001) (data 

not shown). At this evaluation, however, the 

quality resulting from the application of oxadiazon 

was not significantly different from the 

control, nor was it significantly different from 

the quality of the trifluralin-treated grasses. 

Thus, there were no evaluations in which the 

application of oxadiazon or trifluralin caused 

concern. In fact, the two-year mean ratings 

were all less than 3 (Table 4), and overall the 

application of oxadiazon and trifluralin did 

not result in commercially unacceptable phytotoxicity 

in the two years of study on the 

eight field-grown ornamental grasses. 

Conclusion 

The results of these studies show that ornamental 

grasses are, for the most part, a tough 

group of plants capable of tolerating a number 

of different herbicides, even when the herbicides 

are applied in excess of the label rate, as 

they were in studies 1 and 2. Following these 

and additional studies elsewhere, we anticipate 

the addition of several grasses to the herbicide 

labels. Additional tools should soon be available 

for battling weeds in landscape plants. 

Acknowledgments 

The authors thank J. Meyer, B.E. Branham and T.W. 

Fermanian of the University of Illinois and J.M. Breuninger 

of Dow AgroSciences for their assistance. We also gratefully 

acknowledge funding for this work from the state of 

Illinois through the Illinois Council on Food and Agricultural 

Research (C-FAR), Dow AgroSciences, Aventis Environmental 

Science and the Illinois Turfgrass Foundation. 

Literature cited 

1. Ahrens, W.H. (ed.). 1994. Herbicide handbook 

7th ed. Weed Science Society of America, 

Champaign, Ill. 

2. C&P Press. 2003. Turf and ornamental reference 

for plant protection products, 12th ed. C&P Press, 

New York. 

3. Cole, J.T., and J.C. Cole. 1999. Tolerance of five 

perennial ornamental grasses to five preemergent 

herbicides. SNA Research Conference 44. 

www.sna.org/research/99proceedings/Section0832 

.html. Verified Nov.17, 2003. 

4. Darke, R. 1999. The color encyclopedia of ornamental 

grasses: Sedges, rushes, restios, cat-tails, 

and selected bamboos.Timber Press, Portland, Ore. 

RESEARCH 

Figure 2. Moudry fountain grass (Pennisetum alopecuroides Moudry) (foreground) did not exhibit damage from applications 

of clopyralid, and Korean feather reed grass (Calamagrostis brachytricha) (background) was not damaged by 

clopyralid, isoxaben or isoxaben + trifluralin. 

5. Derr, J.F. 2002. Tolerance of ornamental grasses to 

preemergence herbicides. Journal of Environmental 

Horticulture 20(3):161-165. 

6. Hubbard, J., and T. Whitwell. 1991. Ornamental 

grass tolerance to postemergence grass herbicides. 

HortScience 26(12):1507-1509 

7. Neal, J.C., and A.F. Senesac. 1991. Preemergent 

herbicide safety in container-grown ornamental 

grasses. HortScience 26(2):157-158. 

FIELD HERBICIDE TRIALS 

John Tallarico (tallaric@students.uiuc.edu) recently 

completed an M.S. degree in horticulture at the 

University of Illinois, Urbana-Champaign and will enter 

the U.S. Army’s officer candidate school in spring 

2004. Tom Voigt, Ph.D., is an assistant professor in the 

department of natural resources and environmental 

sciences at the university. 

Ratings 

Grass Oxadiazon Trifluralin Control 

Calamagrostis × acutiflora Karl Foerster 

(Karl Foerster feather reed grass) 

M. sinensis Arabesque 

1.4 1.4 1.5 

(arabesque miscanthus) 1.2 1.1 1.5 

M. s. Gracillimus (maiden grass) 0.7 0.5 0.7 

M. s. Variegatus (variegated miscanthus) 0.9 2.1 1.3 

M. s. Zebrinus (zebra grass) 2.5 2.8 2.2 

Pennesetum alopecuroides (fountain grass) 1.3 1.6 1.3 

P. setaceum Rubrum (purple fountain grass) 

Sorghastrum nutans Indian Steel 

0.5 1.1 1.3 

(Indian steel Indian grass) 1.8 1.3 2.0 

Note. Treatment means of four evaluations of three replications over two experiments (a total of 24 ratings) 

in 2001 and 2002 at the University of Illinois Landscape Horticulture Research Center in Urbana. The grasses 

were rated on a scale of 0-10; 0 = no damage, 10 = death. Plants exhibiting mean rating of 3 or less were 

deemed commercially acceptable. 

Table 4. Field-grown ornamental grasses in oxadiazon and trifluralin herbicide trial. 

February 2004 

GCM 147

Weed control in ornamental grasses

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