AskIFAS Powered by EDIS

Thistle Control in Pastures

Brent Sellers, Pratap Devkota, and Jason Ferrell

If left uncontrolled, thick thistle stands can reduce grazing, result in less forage production, and ultimately lower calf weaning weight. A single thistle plant can produce at least 4,000 seeds, which increases the chance for higher thistle populations in the pasture the following year. Consequently, management practices need to be implemented prior to flower formation for effective thistle control. Even if thistles have not infested your pasture in the past, it is best to scout your pastures in late fall through mid-spring to ensure that thistles do not get out of control. New infestations are easier to manage than large-scale populations.

Although there are at least nine different species of thistle in Florida, most are closely related and control recommendations will not differ. While scouting, you may encounter tall thistle, Le Conte's thistle, swamp thistle, Nuttall's thistle, purple or yellow thistle, bull thistle, Virginia thistle, and possibly others. See the identification key (Table 1) if you are interested in identifying a particular species.

Biology and Control

All thistles mentioned above are biennials, with the exception of Le Conte's thistle, which is a perennial. Biennial plants are those that grow from seed in one year and produce seeds the second year. There are three distinct life stages that pertain to management of thistle. During the first year, the plant will grow as a rosette (a taproot with a cluster of leaves on or near the soil surface) (Figure 1). During the second year, a stalk enlongates (in a process often referred to as bolting) from the rosette (Figure 2). The plant then flowers, produces seed, and dies. In Florida, the rosette growth stage occurs primarily during the winter months. Bolting occurs from late January through July, and flowering occurs from April through August. The variation of growth among individual thistle plants can make control a daunting task.

Figure 1. Example of a thistle rosette.
Figure 1.  Example of a thistle rosette.
Credit: B. Sellers, UF/IFAS


Figure 2. Example of thistles at the bolting growth stage prior to flowering.
Figure 2.  Example of thistles at the bolting growth stage prior to flowering.
Credit: J. Ferrell, UF/IFAS


Mechanical Control

Preventing seed production is of utmost importance when attempting to manage thistle populations. Little can be done to effectively manage these plants if they are allowed to flower and produce seed before control occurs. Small rosettes can be removed by hand by cutting the plant below the soil surface to prevent regrowth. This is not a very practical approach; it is time-consuming and only effective on very small infestations. Mowing thistles can be an effective strategy, but timing is critical. Clipping thistles later in the spring (April to June) is quite effective when the flower stalk is typically hollow (late bolting stage). The plant is not likely to regrow or produce seed if mowed at this time. However, mowing when plants are in the rosette stage (prior to flower stalk formation—bolting) is not effective, and plants will regrow. Therefore, mow only after rosettes have bolted, but before flowers have formed. Timing a mowing treatment can be difficult because all thistles do not bloom at the same time. In addition, rising fuel costs may make mowing an uneconomic thistle control method, especially when multiple mowing treatments are required for effective control.

Chemical Control

Herbicides are often the most flexible and affordable option for thistle control in pastures. However, like mowing, timing is an important factor for many herbicides. Several commonly used pasture herbicides are highly effective on thistles if applied early in the growing season (Table 2). Thistles in the rosette stage are highly sensitive to herbicides and are easily controlled. However, delaying the application until after bolting can have a dramatic impact on effectiveness, particularly with 2,4-D. When applied at flowering, most herbicides provide less than 90% control, except for GrazonNext HL. In this case, using an herbicide may not be warranted, since it can provide short-term control but will not be effective in long-term management. GrazonNext HL will control flowering thistle, but if seeds are already produced and the plant is beginning to die, mowing may be the best (temporary) option. DuraCor, a herbicide that was recently introduced into the pasture market, will provide similar control as obtained with GrazonNext HL.

The importance of application timing cannot be overstated. Thistles are normally not visually evident as a problem until flowers are produced. However, the plants are present in the rosette form long before flowers emerge, and early scouting should facilitate early detection and optimum control. Quickly scouting the pastures in late winter (January to March) will reveal the presence of thistles (rosette stage) and allow for an inexpensive herbicide application. If you wait until thistles flower, mowing and/or herbicide options are limited, less effective, and more expensive. Take the time to scout early, because it is the key to better and more economical thistle control.


Wunderlin, R. P., and B. F. Hansen. 2003. Guide to the Vascular Plants of Florida. 2nd Ed. Gainesville: University Press of Florida.

Table 1. 

Identification key (adapted from Guide to the Vascular Plants of Florida).

1. Brown stemmed plants, with stems densely covered with long, soft hairs (mainly found in north Florida)

Blessed thistle (Cnicus benedictus)

1. Green stemmed plants

2. Stems winged with spiny leaf bases that extend downward

3. Stems and leaves covered with dense hairs giving the plant a felt-like appearance (rare)

Scotch thistle (Onopordum acanthium)

3. Stems and leaves coarse with sharp, long spines. Sometimes with sparse hairs on upper and lower leaves

Bull thistle (Cirsium vulgare)

2. Stems with or without wings, with leaf bases that extend downward

4. A secondary set of spiny bracts is present under the flower head (found throughout Florida)

Horrid thistle (Cirsium horridulum)

4. A secondary set of spiny bracts is not present under the flower head

5. Primary bract on flower head lacking an apical spine or with a vestigial spicule about 0.5 mm long (rare)

Swamp thistle (Cirsium muticum)

5. Middle and outer primary bracts tipped with an evident spine approximately 1 mm long

6. Lower leaf surface densely hairy

7. Series of bracts (involucre) 1.5–2.5 cm high, with individual bracts secreting a sticky substance on the central ridge (rare)

Virginia thistle (Cirsium virginianum)

7. Series of bracts (involucre) 2–4 cm high, with individual bracts not secreting a sticky substance (rare)

Tall thistle (Cirsium altissimum)

6. Lower leaf surface with sparse hairs or lacking hairs

8. Plant usually with much branching when flowering (found throughout)

Nuttall's thistle (Cirsium nuttallii)

8. Plant unbranched or with only a few branches when flowering (found occasionally)

Le Conte's thistle (Cirsium lecontei)

Table 2. 

Control of thistle at three growth stages with common pasture herbicides.



Thistle Growth Stage





――――% control――――


2 qt/A





0.3 oz/A





2 pt/A




Remedy Ultra

2 pt/A




Pasturegard HL

1.5 pt/A




GrazonNext HL

1.0 pt/A




a Approximate herbicide costs.

b The rosette stage is when the thistle forms a low-growing ring of leaves.

c The bolting stage is when the thistle forms a stalk and prepares to flower.

For use in bermudagrass, stargrass, or limpograss only; do not use in bahiagrass.

Publication #SS-AGR-95

Release Date:December 14, 2022

Related Experts

Ferrell, Jason A.


University of Florida

Sellers, Brent A.


University of Florida

Devkota, Pratap

University of Florida

Related Units


About this Publication

This document is SS-AGR-95, one of a series of the Agronomy Department, UF/IFAS Extension. Original publication date May 2006. Revised November 2019 and December 2022. Visit the EDIS website at for the currently supported version of this publication.

About the Authors

Brent Sellers, assistant professor, Agronomy Department, UF/IFAS Range Cattle Research and Education Center; Pratap Devkota, assistant professor, Agronomy Department, UF/IFAS West Florida REC; and Jason Ferrell, associate professor, Agronomy Department; UF/IFAS Extension, Gainesville, FL 32611.


  • Brent Sellers