United States Department of Agriculture

Field Guide for Managing

Perennial Pepperweed

in the Southwest

Forest 

Service

Southwestern

Region TP-R3-16-23 Revised June 2017
Cover Photos

Top right: USDA Agricultural Research Service

Left: Mary Ellen (Mel) Harte, Bugwood.org

Bottom right: Steve Dewey, Utah State University, Bugwood.org

In accordance with Federal civil rights law and U.S. Department of Agriculture (USDA) civil rights 

regulations and policies, the USDA, its Agencies, offices, and employees, and institutions participating in or 

administering USDA programs are prohibited from discriminating based on race, color, national origin, 

religion, sex, gender identity (including gender expression), sexual orientation, disability, age, marital 

status, family/parental status, income derived from a public assistance program, political beliefs, or reprisal 

or retaliation for prior civil rights activity, in any program or activity conducted or funded by USDA (not all 

bases apply to all programs). Remedies and complaint filing deadlines vary by program or incident. 

Persons with disabilities who require alternative means of communication for program information (e.g., 

Braille, large print, audiotape, American Sign Language, etc.) should contact the responsible Agency or 

USDA’s TARGET Center at (202) 720-2600 (voice and TTY) or contact USDA through the Federal Relay 

Service at (800) 877-8339. Additionally, program information may be made available in languages other 

than English. 

To file a program discrimination complaint, complete the USDA Program Discrimination Complaint Form,

AD-3027, found online at http://www.ascr.usda.gov/complaint_filing_cust.html and at any USDA office or 

write a letter addressed to USDA and provide in the letter all of the information requested in the form. To 

request a copy of the complaint form, call (866) 632-9992. Submit your completed form or letter to USDA 

by: (1) mail: U.S. Department of Agriculture, Office of the Assistant Secretary for Civil Rights, 1400 

Independence Avenue, SW, Washington, D.C. 20250-9410; (2) fax: (202) 690-7442; or (3) email: 

program.intake@usda.gov. 

USDA is an equal opportunity provider, employer and lender.

Printed on recycled paper
1 

Perennial pepperweed (Lepidium latifolium L., formerly Cardaria latifolia L.)

Mustard family (Brassicaceae)

line

Perennial pepperweed is an invasive plant that has been

listed as a noxious weed in New Mexico. This field guide 

serves as the U.S. Forest Service’srecommendations for 

management of perennial pepperweed in forests, 

woodlands, and rangelands associated with its

Southwestern Region. The Southwestern Region covers 

Arizonaand New Mexico, which together have 11 national

forests. The Region also administers 4 national grasslands

located in northeastern New Mexico, western Oklahoma, 

and the Texas panhandle.

Description

Perennial pepperweed (synonyms: broadleaved

pepperweed, tall whitetop, peppercress, iron weed) is an

introduced perennial broadleaved plant native to Eurasia.

It is similar in appearance to hoary cress (Cardaria draba), 

which is also called whitetop. However, pepperweed is 

considerably taller than hoary cress, and its upper leaves do 

not clasp the stem. Perennial pepperweed shoots emerge

early in the spring forming a rosette that will persist for 

several weeks. By middle to late spring, plants produce an 

inflorescence of white flowers after bolting. Flowering 

shoots senesce after seed production, although new rosettes

can emerge in the fall in moistsoils.

Growth Characteristics

• Perennial herbaceous plant; average height is 3 to 5 

feet; may grow up to 8 feet.

• Rhizome-like creeping roots that smell like 

horseradish; dense, semi-woody crown.

• Foliage is glabrous and green to gray-green in color.

• Multi-stemmed; stems are upright, dull-gray-green 

and waxy; may have reddish spots.

• Rosettes have ovate to oblong leaves with entire to 

serrate margins on long petioles. Young leaves on 

the stems are sessile to lanceolate with smooth to

jagged edges. Mature leaves are alternating and 1 to 

2 inches wide, 4 to 12 inches long with a small stem 

connecting the leaf to the branch; older leaves lack

the small connecting stem and decrease in size

toward the top of the plant.

• White, 4-petalled flowers occur in dense, bunched 

panicles on each stem; May-July flowering.

• Fruits are small, round to oval-shaped, 2-chambered 

pods, each with two flattened seeds.

Ecology

Impacts/Threats

Perennial pepperweed develops dense, monotypic stands

that can reduce availability of quality forage for cattle and

horses, degrade wildlife habitat, and lower diversity of 

flora and fauna species. The weed acts as a salt pump, i.e., 

it draws salt ions from deep within the soil profile and

increases salinity near the surface, which can be 

disadvantageousfor plants intolerant to salt.

Site/Distribution

This weed invades disturbed areas and is common in 

riparian areas, flood plains, wetlands, pastures, and alfalfa 

fields; it is also widely found along roadsides and irrigation

ditches. Large infestations of perennial pepperweed occur

in the Rio Grande River watershed in central New Mexico, 

and new populations are emerging throughout the State.

Spread

Perennial pepperweed spreads either by seed or roots; 

however, seedlings are rarely seen in the field. Plants 

mostly originate from its creeping root system which may

expand at a rate of 10 feet per year. Root segments produce 

adventitious buds; pieces as small as 1 inch in length are 

capable of generating new shoots. Fragments might be

spread over long distances as a contaminant in transported 

soil, hay bales used for erosion control, and alfalfa hay

used for feed. Seed or root fragments easily adhere to

surfaces and undercarriages of vehicles and road

maintenance equipment.
2 

Invasive Features

With extensive carbohydrate reserves stored in its large 

root system, perennial pepperweed produces new shoots 

that emerge early and grow rapidly in the spring.Perennial

pepperweed tolerance to alkaline and saline soils allowsit

to thrive in a wide range of habitats. Invasions often occur 

in sensitive areas, thus possibly limiting control options.

Management

Early detection and proactive management should be used 

to control perennial pepperweed since well-established 

stands are difficult to control. Frequent monitoring is 

critical to locate new plants before they become 

established. When new infestations are discovered, plants 

should be removed immediately to prevent further

spread. The following actions should be considered when

planning an overall management approach:

• Healthy plant communities should be maintained to 

limit perennial pepperweed infestations. If

necessary, include revegetation methods to reduce 

the possibility of further invasion.

• Periodically check areas where the soil has been 

disturbed for presence of root fragments or sprouts 

of perennial pepperweed.

• Eradicate new populations of perennial pepperweed 

as early as possible.

• Combine mechanical, cultural, biological, and 

chemical methods for most effective perennial 

pepperweed control. 

Table 1. Management options*

Site Physical Control Cultural Control Biological Control Chemical Control

Roadsides, 

fence lines, or 

non-crop 

areas

Mow at flower bud stage;

apply herbicide to re-sprouts. 

Hand pull or grub

small patches.

Use seed, mulch, and fill 

materials certified to be weedfree. 

Clean machinery following 

activity in infested areas.

Train road crews and the public 

to identify and report 

infestations; map reported

populations. 

USDA-approved 

biocontrol agents are 

unavailable. 

Spray at flower bud stage.

For ground application, use

truck-mounted or tractorpulled spraying equipment. 

Wash under vehicle after

application to prevent spread.

Rangeland or 

pasture 

Disking alone can spread the 

weed; combine any

cultivation with herbicide 

control. 

Use of prescribed fire is not 

recommended except to

remove dead material.

Use seed and forage hay 

certified to be weed-free; use 

pellets for horses in 

backcountry areas.

Monitor areas where soil

was imported or hay was

used for erosion control.

Reseed with desirable 

competitive plants.

Use prescribed grazing 

with sheep or goats in the

spring followed by

herbicide at flower bud

stage. Closely manage 

grazing to prevent 

overuse. 

Spray at flower bud stage.

For extensive and dense 

infestations, use ground or 

aerial broadcast spraying. 

For sparse infestations,

use backpack or hand-held

sprayer. 

Wash under vehicle after 

application to prevent spread.

Riparian 

areas, 

wilderness, 

and other 

natural areas,

and/or small

infestations 

Hand pull or grub small 

patches; remove as much of 

the root as possible; bag and 

dispose of debris 

appropriately. 

Use seed and forage hay 

certified to be weed-free; use 

pellets for horses in 

backcountry areas.

After passing through infested 

areas, inspect and remove any 

seed or root fragments from

animals, clothing, and vehicles.

Same as above. Spray at flower bud stage.

Use backpack or hand-held 

sprayers or use wick method 

for individual plant treatment 

(IPT). 

Broadcast spraying by aerial

or ground methods may be 

used on thicker stands, if

allowed.

* Choice of a particular management option must be in compliance with existing regulations for the land resource. 
3 

• Detect, report, and map large infestations. Keep 

annual records of reported infestations.

Table 1 summarizes some management options for 

controlling perennial pepperweed under various situations. 

Further details on these management options are explained 

below. Choice of individual control method(s) for 

perennial pepperweed depends on the extent and density

of infestation, current land use, and site conditions

(accessibility, terrain, microclimate, other flora andfauna 

present, etc.). Other important considerations include

treatment effectiveness, overall cost, and the number of 

years needed to achieve control. More than one control

method may be needed for a particular site.

Physical Control

Although labor intensive, physical methods used 

consistently and repeatedly are effective at controlling

perennial pepperweed. In general, effectiveness of

physical methods is improved when combined with

herbicide control.

Manual Methods

Hand pulling or digging – Seedlings are easily controlled

by hand pulling, hoeing, or grubbing; but these techniques 

do not work well on established plants since shoots

quickly re-sprout from deep roots. Ideally, remove as 

much of the above and below ground plant parts as 

possible, and dispose of debris by bagging and depositing 

bags in a landfill, or by burning.

Mechanical Methods

When using machinery to manage perennial pepperweed, 

the equipment should be cleaned to prevent movement of 

seed or root fragments into un-infested areas.

Mowing – Without care, mowing can contribute to further 

spread and increased densities of perennial pepperweed. It 

is a helpful tool for removing accumulated dead stems and 

fits well in an integrated approach. While not effective in 

reducing perennial pepperweed stands, mowing can

enhance the effectiveness of herbicides. For best results, 

mow perennial pepperweed at the bolting or flower bud 

stage and allow shoots to re-sprout before applying

herbicide. Mowing causes the plant to produce larger

leaves that are perpendicular to the ground thereby

allowing better herbicide coverage.

Tillage – By itself, cultivation can spread viable root 

fragments and contribute to increased densities of

perennial pepperweed. Cultivation in combination with 

well-timed herbicide use and mowing can reduce 

population size in areas suitable for these practices. 

Research using this integrated approach has reported up to 

95 percent reduction in perennial pepperweed biomass. 

Perennial pepperweed infestations should be disked in the 

fall. When plants re-sprout and form flower buds in the 

spring, mowing should then be used. Allow plants to resprout and reach flower bud stage once again before 

applying herbicide. Anticipate that further spraying may be 

needed later.

Prescribed Fire

Burning actively growing perennial pepperweed is not

recommended as shoots rapidly regrow shortly after fire.

However, it can be helpful for removing old growth and is 

also acceptable as a means to dispose of plant debris.

Flooding

Where conditions are feasible, continual flooding can be 

an effective control method. As an example, a perennial 

pepperweed population that was inundated for 2

consecutive years was nearly eliminated at a California 

site. However, plants that escaped flooding (e.g., those 

growing on levees) required further management. 

Cultural Control

Early detection and plant removal are critical for 

preventing perennial pepperweed establishment. Land 

managers, the local public, and road crews should be 

educated on identifying nonnative noxious species so that

suspected infestations will be reported. Vehicles, humans,

and livestock should be discouraged from traveling

through infested areas. A program to check and remove 

seeds and root fragments from vehicles, equipment, and 

livestock should also be implemented to help stop 

dispersal. Seed and materials used for mulch, forage, or 

fill should be certified to be weed-free; pellets may be 

used for horses in backcountry areas. Reseeding with 

competitive desirable species should be considered for 

areas failing to recover naturally following suppression 

efforts.
4 

Biological Control

Grazing

Intensive livestock grazing early in the growing season can 

effectively suppress populations, but perennial pepperweed 

quickly recovers once animals are removed. Therefore,

grazing should be integrated with other tools. Goats,sheep,

and cattle will graze new foliage growth but will stop eating

perennial pepperweed when the early flowering stage is 

reached. Horses reportedly have been poisoned after eating

the weed in hay.

Classical Biological Control

No classical biocontrol agents (insects, pathogens, etc.) have 

been approved by USDA for perennial pepperweed control. 

Chemical Control

Herbicides can be an effective tool for managing perennial

pepperweed, especially when used as part of an integrated

strategy. Table 2 has a summary of common herbicide

choices. Herbicide choice depends on label restrictions, land 

use objectives, and cost. Aquatically approved herbicide 

formulations and surfactants must be used in or near water. 

Each herbicide product will have different requirements and 

restrictions according to the label. Read and understand 

prior to any application. Consult the registrant if you have 

questions or need further detail.

Herbicide Application

Herbicide applications should be timed to coincide with the 

period when carbohydrate root reserves are lowest. For

perennial pepperweed, this is during the early flowering or 

bud stage. If young plants or seedling are found, apply

herbicides as soon as possible to prevent them from

producing new lateral shots from the root.

Chemical “mowing” with herbicide has been used for 

perennial pepperweed in some inaccessible areas such as

riparian communities that do not allow mechanical methods. 

Chemical mowing retards growth of a plant while allowing 

it to provide erosion protection. Results have varied and 

while plant suppression is usually achieved, complete 

control with this method is rare. Apply herbicide such as 

imazapic when perennial pepperweed is in the flower bud

stage; then repeat chemical mowing in late summer to

plants that have re-sprouted. For sites where water is not

present year round, chlorsulfuron may be used as long as 

the herbicide has time to degrade within soil before water 

returns. Rates described in table 2 may be used to perform 

the chemical mowing.

Herbicides may be applied with wicks, backpack or handheld sprayers, ATV or UTV sprayers, or conventional boom 

sprayers that are pulled or attached to a tractor or truck. Any 

equipment used to spray herbicide should be calibrated. For

sparse populations, one person or a small team can spray or 

wick perennial pepperweed in an area using individual plant

treatment (IPT). Spray plants directly by wetting the foliage 

and stems without dripping using an adjustable spray nozzle

attached to a backpack or hand-held sprayer. Wick plantsin 

riparian areas with 100 percent solution of 2,4-D for several 

consecutive years to suppress perennial pepperweed while

allowing desirable plant species reestablish. Precautions 

should be taken if non-target plants(including woody 

species) need to be protected. This includessituations where 

spray drift, soil erosion, or water movement potentially

could occur.

Integrated Control Methods

Regardless of the management approach, perennial

pepperweed typically cannot be effectively controlled by 

using only one method. A combination of control methods, 

as outlined in this guide, should always be considered in a

long-term approach to perennial pepperweed control. For 

example, the combination of physical methods used in 

conjunction with chemical control can be quite effective. 

Management Strategies

Small or isolated infestations on otherwise healthy sites 

should be given high priority for treatment, followed by 

treatment of corridors such as waterways and irrigation

structures that have a high likelihood for spreading 

pepperweed. To enhance long-term control, consider an 

approach that encourages and maintains competitive 

desirable plants. A healthy, well maintained native plant

population can dramatically slow the introduction and

spread of perennial pepperweed.
5 

Table 2. Herbicide recommendations

Common

Chemical

Name

(active 

ingredient)

Product

Example1

Broadcast 

Treatment 

(rate per 

acre)

Spot 

Treatment 

(spray 

solution)2

Time of

Application Remarks

Chlorsulfuron Telar 1–2 ounces NA Flower bud 

stage.

Selective; safe for labeled grasses; use 0.25% 

v/v NIS3

; provides 1–2 years control. Not for 

use near water bodies. If area is mowed 

before herbicide is applied, lower rate is 

effective. 

Metsulfuron Escort 

Ally

[others 

available] 

0.75–1.0 ounce NA Flower bud 

stage or in fall.

Selective; safe for most perennial grasses; add 

0.25% v/v NIS3

. Not for use near irrigation

water. May apply in fall if part of plant is still

green. 

Glyphosate Rodeo 

Roundup 

[others 

available] 

Depends upon 

formulation: 

3 quarts Rodeo

1 gallon 

Roundup 

Rodeo: 

0.75–2% + NIS3

Roundup: 

2% 

Flower bud 

stage.

Nonselective; if infestation is dense, mow,

then apply glyphosate when regrowth reaches

flower bud stage.

Rodeo is labeled for use in or near aquatic 

areas. Good treatment if reseeding is planned. 

2,4-D ester 

or amine4

Several 

products and

manufacturers 

Depends upon 

formulation

(1–2 pounds 

per acre)

5% Same as above. Selective; apply annually for 2 years or more 

to control established stands. If infestation is 

dense, mow first and apply to regrowth at 

flower bud stage.

Triclopyr Garlon 3A

[others 

available] 

3 quarts 5% Flower bud 

stage in spring 

or in the fall to

rosettes.

Selective; safe for most perennial grasses; add 

0.25% v/v NIS3

; labeled for riparian areas and 

use near water bodies; chemically mow second 

application: 2 quarts/ac is effective.

Imazapyr Arsenal

Habitat

[others 

available] 

2–3 pints 3% Same as above. Nonselective; total vegetation control. 

Labeled for fence lines, rights-of-way, 

railways, and aquatic situations. Add 0.25% 

v/v NIS3 for post-emergent use.

In addition to spray drift, non-target plants 

may also be killed or injured by imazapyr 

through runoff, residue movement in soil, 

or root exudates from treated plants.

Imazapic Plateau 12 fluid ounces 5% Same as above. Selective but may retard growth ofsome

grasses. This herbicide is the preferred

alternative to imazapyr if protection of 

desirable plants is needed.

1 Trade names for products are provided for example purposes only, and other products with the same active ingredient(s) may be available. Individual 

product labels should be examined for specific information and appropriate use with perennial pepperweed.

2 Spray solution is the herbicide/water ratio in a spray mix that may be used for spot treatment with backpack or hand-held sprayers. The amount of product 

applied during an annual growing season must not exceed the maximum application rate per acre as specified by the product label – refer to the product 

label for the site type and application. 

3 NIS is an abbreviation for nonionic surfactant which is an additive commonly recommended by herbicide labels for post-emergent foliar application of

herbicide.

4 2,4-D is a restricted use pesticide in New Mexico only. A certified applicator’s license is required for purchase and use. 
6 

Because each treatment situation is different, any strategy 

adopted for managing perennial pepperweed must involve 

careful planning and a long-term commitment. Complete

eradication will likely require 3 to 10 years of repeated 

control methods. Since it is ordinarily useless to treat an 

area only one time without retreatment, sufficient 

resources must be allocated for the area where control is 

attempted. After initial treatment, it is especially important 

that resources are also available to respray or retreat the 

treated area as necessary. Components of a successful

control program for perennial pepperweed should include

monitoring of treated areas and taking measures to control

missed plants and newly emerged seedlings. Monitoring

should be conducted in early spring and late summer to

detect rosettes that form the leading edge of expanding

populations.

References and Further

Information

Boelk, D.A. 2005. Least Wanted: Perennial Pepperweed 

Fact Sheet. Plant Conservation Alliance. Available at

http://www.nps.gov/plants/alien/fact/lela1.htm 

(accessed July 2010) 

Davison, J.C., E. Smith, and L.M. Wilson. 2007. Livestock 

Grazing Guidelines for Controlling Noxious Weeds 

in the Western United States. A Western Region 

Sustainable Agriculture, Research and Education 

Project. EB-06-05. Pp. 36–37. Available at 

http://www.cnr.uidaho.edu/rx-grazing/Livestock_

Graizng_Guidelines%28Davison_et_al.%202007%2

9.pdf (accessed July 2010) 

Duncan, K, K. McDaniel, and M. Renz 2005. Chemical 

Weed and Brush Control for New Mexico

Rangelands. New Mexico State University College 

ofAgriculture and Cooperative Extension Service. 

Pp. 11.Available at http://aces.nmsu.edu/pubs/ 

_circulars/CR_597.pdf (accessed July 2010)

Encycloweedia Datasheets. California Department of Food

and Agriculture. Available at http://www.cdfa.ca. 

gov/phpps/ipc/weedinfo/lepidium.htm (accessed 

July 2010). 

Howald, A. 2000. Perennial Pepperweed (Lepidium

latifolium) In: C.C. Bossard et al. (eds.) Invasive 

Plants of California’s Wildlands. University of 

California Press.Berkley, CA. Available at

http://www.cal-ipc.org/ip/management/ipcw/

online.php (accessed July 2010)

Invasive Plant Atlas of the United States. Available at

http://www.invasive.org/weedus/index.html 

(accessed July 2010)

Jacobs, J. and J. Mangold. 2007. Ecology and 

Management of Perennial Pepperweed. 

USDA/NRCS Invasive Species Technical Note

Number MT-11.Available at ftp://ftp-fc.sc.egov. 

usda.gov/MT/www/technical/invasive/Invasive_

Species_Tech_Note_MT11.pdf (accessed July 2010)

Renz, M.J. 2001. Element Stewardship Abstract for 

Lepidium latifolium L. Available athttp://www.

invasive.org/weedcd/html/esas.htm (accessed July 

2010)

Renz, M.J., C.E. Bell, C. Wilen, and J. DiTomaso. 2002. 

Perennial Pepperweed: Foreign Invader in 

California’s Wildlands. University of California 

WEED Research and Information Center. Available 

at http://wric.ucdavis.edu/information/pepperweed.

html (accessed July 2010)

Renz, M.J. and R.G. Wilson. 2005. Perennial Pepperweed. 

NMSU Weed Factsheet. Available at http://weeds. 

nmsu.edu/pdfs/perennial_pepperweed_factsheet_ 

11-06-05.pdf (accessed July 2010)

USDA Forest Service. 2006. Weed of the Week: Perennial 

Pepperweed (Lepidium latifolium L.). Availableat

http://www.na.fs.fed.us/fhp/invasive_plants/weeds/

perennial_pepperweed.pdf (accessed July 2010)

USDA Plants Database. 2010. Available at http://plants.

usda.gov/index.html. (accessed July 2010)

Zouhar, K. 2004. Lepidium latifolium. In: Fire Effects

Information System. USDA, Forest Service, RMRS, 

Fire Sciences Lab (Producer). Available athttp://

www.fs.fed.us/database/feis/ (accessed July 2010)
7 

Suggested Web Sites

For information on invasive species: 

National Invasive Species Information Center

http://www.invasivespeciesinfo.gov/ 

Invasive.Org

https://www.invasive.org/species.cfm

For information about calibrating spray equipment: 

NMSU Cooperative Extension Service Guide

A-613 Sprayer Calibration. Available at

http://aces.nmsu.edu/pubs/_a/A-613.pdf 

Herbicide labels online:

http://www.cdms.net/
For more information or

other field guides, contact:

USDA Forest Service 

Southwestern Region

Forest Health

333 Broadway Blvd., SE 

Albuquerque, NM 87102

Or visit the Southwestern Region’s 

website for invasive species:

http://www.fs.usda.gov/goto/r3/invasivespecies

The use of trade or firm names in this publication is for reader 

information only and does not imply endorsement of any 

product or service by the U.S. Department of Agriculture. 

Recommendations made here for 

pesticide use are not obligatory, 

nor do they imply that discussed 

uses have been registered. All 

uses of pesticides must be 

registered by appropriate State 

and/or Federal agencies before 

they can be applied. 

CAUTION: Pesticides can be 

injurious to humans, domestic 

animals, desirable plants, and fish or other wildlife—if they 

are not handled or applied properly. Use all pesticides 

carefully and lawfully. Follow recommended practices for the 

disposal of surplus pesticides and pesticide containers.