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Dogfennel

Dogfennel (Eupatorium capillifolium) is a tall annual or short-lived perennial plant native to North America. Typically, this plant has densely hairy stems coming from a woody crown. Leaves are deeply dissected, giving it a hairy or feathery appearance. When crushed, the leaves give off a distinct, pungent smell. Flowers are a greenish-white and appear in midsummer until the first frost. In later months, the lower leaves may fall off, giving the plant a more shrub-like appearance with red-brown stems showing. Dogfennel can reach heights of over 6 feet.

This plant grows throughout South Carolina and is a common weed in pastures, abandoned fields, roadsides, and waste areas. Dogfennel prefers sites that receive full sun but can be found in areas of partial shade. Given time, dogfennel can establish small colonies of plants, as it is capable of sprouting multiple plants from the main rootstock. Dogfennel is also a prolific seeder, meaning that plants produce a large quantity of seeds each year, which germinate in the following years.

Dogfennel (Eupatorium capillifolium) normally stands above most other weeds, reaching over 6 feet in height.

Dogfennel (Eupatorium capillifolium) normally stands above most other weeds, reaching over 6 feet in height.
Adam Gore ©2019, Clemson Extension

Dogfennel (Eupatorium capillifolium) has heavily dissected leaves, which gives it a feathery look, along with greenish-white flowers.

Dogfennel (Eupatorium capillifolium) has heavily dissected leaves, which gives it a feathery look, along with greenish-white flowers.
Adam Gore ©2019, Clemson Extension

Dogfennel (Eupatorium capillifolium) can form thick colonies due to its ability to sprout from the existing rootstock.

Dogfennel (Eupatorium capillifolium) can form thick colonies due to its ability to sprout from the existing rootstock. Adam Gore ©2019, Clemson Extension

Dogfennel (Eupatorium capillifolium) seedlings can be easily pulled by hand due to little root development.

Dogfennel (Eupatorium capillifolium) seedlings can be easily pulled by hand due to little root development.
Adam Gore ©2019, Clemson Extension

Cultural Control

Dogfennel can be controlled in home lawn areas with a regular mowing schedule. Maintaining thick stands of grass with proper fertility and irrigation reduces the competitiveness of this plant. Young plants possess stems that are easily broken but become more difficult and woody as the plant matures. Due to its fibrous root system, removal of individual plants can prove difficult, and care must be taken to ensure that all roots are removed to prevent re-sprouting. Hand-removal of seedlings, before the development of an extensive root system, is effective.

In landscape beds, the use of mulch can inhibit the germination of dogfennel. Maintaining a mulch depth of 2 to 3 inches can aid in suppressing weed growth, as well as serve as a general benefit to desirable landscape plants. See HGIC 1253, Controlling Weeds by Cultivating and Mulching for more information on mulching.

Chemical Control

Before using any herbicide, be sure to read and follow all label directions. The label will specify any protective clothing, such as waterproof gloves and boots, which should be worn during handling and application.

Dogfennel is susceptible to a wide variety of herbicides but should be sprayed prior to reaching 20 inches in height. Herbicide applications made prior to reaching this height will provide better control. Applications should not be made during periods of prolonged dry weather, as drought causes the plants to “harden off” in an effort to conserve water.

Several 3-way herbicides containing 2,4-D, mecoprop (MCPP), and dicamba are available to homeowners for post-emergent control of dogfennel. Some products may also contain carfentrazone or sulfentrazone. Applications can be made at any time throughout the life cycle, but for best control, applications should be made at the seedling or immature stage to prevent seed development. These products can be used to spot treat dogfennel in lawns consisting of tall fescue, bermudagrass, and zoysiagrass. Areas containing centipedegrass or St. Augustinegrass may need reduced rates, which will be stated on the product label.

Products containing iodosulfuron, dicamba, and thiencarbazone are also effective and labeled for use on bermudagrass, centipedegrass, St. Augustinegrass, and zoysiagrass. In landscape beds, herbicides containing glyphosate are effective and will have less soil activity to injure nearby landscape plantings. Spring applications of a pre-emergent herbicide containing isoxaben can also reduce dogfennel pressure in lawns and landscape beds.

Injury to grasses may occur if post-emergent products are applied during spring green-up, the time of transition between dormancy and active growth, or if applied during any excessively hot (>85F) and dry times during the summer. Caution should be exercised when spraying close to desirable landscape plants to prevent off-target application and damage. See HGIC 2349, Herbicide Damage of Landscape Plants for more information on avoiding damage to desirable plants.

Table 1. Examples of Postemergent Herbicides for Control of  Dogfennel in Home Lawns.

Product Brands Active Ingredient % Active Ingredient Labeled for Use on Listed Turfgrass Species
Bayer BioAdvanced Southern Weed Killer for Lawns Conc.; & RTS1 2,4-D
Mecoprop
Dicamba
7.59
1.83
0.84
Bermudagrass
Centipedegrass
St. Augustinegrass
Tall Fescue
Zoysiagrass
Use lower label rate for:
Centipedegrass
St. Augustinegrass
Bayer BioAdvanced Southern Weed Killer for Lawns RTU2 2,4-D
Mecoprop
Dicamba
0.311
0.075
0.034
Fert-lome Weed Free Zone Conc.; & RTS1 2,4-D
Mecoprop
Dicamba
Carfentrazone
10.49
2.66
0.67
0.54
Gordon’s Trimec Ready to Spray Lawn Weed Killer RTS
2,4-D
Mecoprop
Dicamba
5.56
1.34
0.62
Ortho Weed-B-Gon Weed Killer for Lawns Conc.; & RTS1 2,4-D
Mecoprop
Dicamba
8.658
2.127
0.371
Spectracide Weed Stop for Lawns Concentrate; & RTS1 2,4-D
Mecoprop
Dicamba
7.59
1.83
0.84
Spectracide Weed Stop for Lawns RTU2 2,4-D
Mecoprop
Dicamba
0.593
0.144
0.066
Bonide Weed Beater Plus RTS1 2,4-D
Quinclorac
Dicamba
6.42
2.13
0.60
Bermudagrass4
Ryegrass
Tall Fescue
Zoysiagrass
Bonide Weed Beater Plus RTU2, 3 2,4-D
Quinclorac
Dicamba
0.313
0.104
0.029
Ortho Weed-B-Gon Plus Crabgrass Control Conc.; & RTS1 2,4-D
Quinclorac
Dicamba
6.42
2.13
0.60
Celsius WG Iodosulfuron
Dicamba
Thiencarbazone
8.70
1.90
57.40
Bermudagrass
Centipedegrass
St. Augustinegrass
Zoyisagrass
1RTS= Ready to spray; hose-end spray bottle
2RTU= Ready to use; pre-mixed spray bottle
3Labeled for spot treatments
4Products containing quinclorac may temporarily yellow bermudagrass lawns

Sources:

  1. David, Michael. October 2017. “Dogfennel Control in Pastures.” University of Florida Institue of Food and Agricultural Sciences Blog.
    http://blogs.ifas.ufl.edu/bakerco/2017/10/18/dogfennel-control-pastures/
  2. Eupatorium capillifolium”. North Carolina Extension Gardener Plant Toolbox. NC State Extension. https://plants.ces.ncsu.edu/plants/eupatorium-capillifolium/
  3. McCarty, L.B., J.W. Everest, D.W. Hall, T.R. Murphy, and F. Yelverton. 2008. Color Atlas of Turfgrass Weeds. 2nd Edition. John Wiley & Sons: Hoboken, New Jersey.

If this document didn’t answer your questions, please contact HGIC at hgic@clemson.edu or 1-888-656-9988.

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