Dogfennel (Eupatorium capillifolium) is a tall annual or short-lived perennial plant native to North America. Typically, this plant has densely hairy stems that arise 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 greenish-white and appear from midsummer until the first frost. The lower leaves may fall off in later summer months, giving the plant a more shrub-like appearance by revealing red-brown stems. 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 can be controlled in home lawn areas with a regular mowing schedule. Maintain a thick stand of turfgrass with proper fertility and irrigation to reduce the competitiveness of the dogfennel. Young plants possess stems that are easily broken but become stronger and more 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 seeds. Maintaining a mulch depth of 2 to 3 inches can aid in suppressing weed growth, as well as conserve soil moisture for desirable landscape plants. See HGIC 1253, Controlling Weeds by Cultivating and Mulching, for more information on mulching.
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 mixing and application.
Dogfennel is susceptible to a wide variety of herbicides but should be sprayed before 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” 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. They can also be used in lawns containing centipedegrass or St. Augustinegrass but may need to be applied at reduced herbicide rates, which will be stated on the product labels. See Table 1 for examples of post-emergent herbicide brands for dogfennel control.
Products containing a mixture of 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 significantly less soil activity that could potentially injure nearby landscape plantings. Do not allow glyphosate spray to contact foliage, stems, or trunks of landscape plants.
Spring applications of a pre-emergent herbicide containing isoxaben can also reduce dogfennel seedling emergence in lawns and landscape beds. See Table 2 for pre-emergent herbicide brands for use in landscape beds.
Injury to turfgrasses may occur if post-emergent products are applied during spring green-up, the time of transition between turfgrass 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|
|Southern Ag Lawn Weed Killer with Trimec Concentrate||2,4-D||3.05||Bermudagrass
ZoysiagrassUse lower label rate for:
|Ferti-lome Weed-Out Lawn Weed Killer with Trimec Concentrate||2,4-D||5.88|
|Bayer BioAdvanced Southern Weed Killer for Lawns Conc.; & RTS1||2,4-D||7.59|
|Bayer BioAdvanced Southern Weed Killer for Lawns RTU2||2,4-D||0.311|
|Fert-lome Weed Free Zone Concentrate; & RTS1||2,4-D||10.49|
|Gordon’s Trimec Ready to Spray Lawn Weed Killer Concentrate; & RTS1||2,4-D||5.56|
|Ortho Weed-B-Gon Lawn Weed Killer Concentrate; & RTS1||2,4-D||8.658|
|Ortho WeedClear Weed Killer for Lawns Concentrate||2,4-D||8.658|
|Spectracide Weed Stop for Lawns Concentrate; & RTS1||2,4-D||7.59|
|Spectracide Weed Stop for Lawns RTU2||2,4-D||0.593|
|Bonide Weed Beater Plus RTS1||2,4-D||6.42||Bermudagrass4
|Bonide Weed Beater Plus RTU2, 3||2,4-D||0.313|
|Ortho Weed-B-Gon Lawn Weed Killer Plus Crabgrass Control Conc.; & RTS1||2,4-D||6.42|
|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.
Table 2. Examples of Pre-emergent Herbicides for Control of Dogfennel in Home Lawns & Landscape Beds.
|Product Brands||Active Ingredient||% Active Ingredient||Labeled for Use on Turfgrass or in Landscape Beds|
|Ferti-lome Broadleaf Weed Control with Gallery||Isoxaben||0.38||For lawns & landscape beds|
|Snapshot 2.5TG||Isoxaben||2.0||For landscape beds only|
|For use in lawns: Isoxaben can be used in all established turfgrass lawns in spring; however, tall fescue lawns cannot be over-seeded during spring if any pre-emergent herbicides are also applied then. Granular pre-emergent herbicides must be watered into the soil with ½ inch of irrigation water.
For landscape beds: Pre-emergent herbicides are for use around established landscape plants.
They may inhibit the rooting of newly installed plants, especially bedding plants and perennials. Do not incorporate herbicide into the soil. Check the product label for tolerant landscape species. Hose off any herbicide granules from landscape plants after application, and then water the herbicide into the soil.
- David, Michael. October 2017. “Dogfennel Control in Pastures.” University of Florida Institue of Food and Agricultural Sciences Blog.
- “Eupatorium capillifolium”. North Carolina Extension Gardener Plant Toolbox. NC State Extension. https://plants.ces.ncsu.edu/plants/eupatorium-capillifolium/
- 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.
Pesticides are updated annually. Last updates were done on 8/21 by Joey Williamson.
Originally published 02/20