Fireweed is a member of the Asteraceae plant family. It is a daisy-like plant with endearing yellow flowers. It comes in a herb form and originated from South Africa. Fireweed has a variable growth habit and leaf structure, growing from 10 to 50 cm high. In coastal districts the most common form of fireweed is a low, heavily branched, short-lived perennial plant. Although leaf shape and structure can vary, leaves are generally bright green, alternate, narrow with serrated, entire or lobed margins. The broader leaves are usually clasped around the stem and are 2-6 cm long, occasionally reaching 8-10 cm on vigorous and older plants.
Fireweed has a shallow, branched tap root with numerous fibrous roots, growing from 10 to 20 cm deep. Petal numbers are usually a constant 13. Plants flower mainly from April to September, with individual plants often having a wide range of flowering stages at any one time. Seeds are small (1-3 mm long), light and slender. They are cylindrical in shape, with a downy surface and attached to a pappus of fine, silky white feathery hairs. The plant produces large quantities of seed over long periods that are easily dispersed by the wind. Each flower produces between 100 and 150 seeds. Long distance dispersal also occurs by seeds on animals, in stock feed or in mud on vehicles. Its main disadvantage is that it can outgrow most useful pasture plants. Fireweed also readily invades pastures damaged by overgrazing and drought. Fireweed seems equally at home in low-elevation, arid pastures as in high-elevation, moist pastures.
For best results in control of fireweed, treat seedling plants prior to flowering. Both Grazon Extra Herbicide at 350 mL/100 L of water and Hotshot Herbicide at 500 mL/100 L of water are registered for foliar/spot application.
Hotshot is also registered for boom application at 1.5 L/ha and should be used in predominately grass based pastures.
Herbicides for Control of Fireweed
#Note: Preferred product option in bold. *Consult label for details of growth stage and use, especially where range of rates is given.