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Fireweed

Fireweed 1

Fireweed 2

Fireweed 3

Fireweed plant

Fireweed seedling

Fireweed bracts

Fireweed bracts2

Fireweed control with sheep

Fireweed seed

Fireweed, 21 bracts

Fireweed seedling

Senecio pinnatifolius tablelands form

Senecio pinnatifolius, coastal

Senecio pinnatifolius 13 bracts

Senecio pinnatifolius seeds

Senec linearif1

Senec linearif2

     


BOTANICAL NAME:

Senecio madagascariensis


Family:

Asteraceae (daisy family)

Status:

Fireweed is declared noxious in the Southern Tablelands and South East Region in all except Queanbeyan and Illawarra LCAs, in class 4.

Description

Low branching annual herb with 13-petalled yellow daisy flowers held on slender stems in branched terminal open clusters and leaves which are bright green, thin textured and lobed, toothed or smooth-edged. The leaf shape is very variable, and often all three leaf types will occur on the one plant (see second seedling photo). The flowers are enclosed by a single row of green involucral bracts which have a darkened tip (see photo 6 above - the bracts are easiest to count just before the flower opens out to reveal the "petals", when the bract tips are all clustered at the top of the "bud", or after the seed has been shed when the bracts remain behind - see photo 10). Typically fireweed has about 21 bracts, which helps to distinguish this species from similar native daisies in the genus Senecio. When counting the bracts it is easiest to flatten the flower head between the fingers and count along one side only, then double the count.  The native should have 6 or 7 per side, fireweed, 10 or 11.

preferred habitat and impacts

Fireweed will grow in pasture, on road verges and in native grassland, woodland or forest, but it is most invasive in grazed pasture, where there is bare soil present for seedlings to become established on. Note in photo 3 above the difference in fireweed numbers between the grazed paddock and the densely grassed road verge.

It is toxic to stock, causing progressive liver damage. It is not readily grazed except by sheep and goats which tolerate the toxins better than other stock. Each plant can produce hundreds of seeds and density in pasture can become very high, greatly reducing carrying capacity.

Dispersal

Seed is very fine and wind-blown, and also moved around in soil and on vehicles. It is beginning to invade the tablelands from the south coast where it is well established in pockets and continually expanding its range, south from the Sydney and Illawarra areas and north from Bega Valley.

Most growth occurs after rain, at whatever time of year this occurs. Plants are frost tolerant and can grow through the winter, to flower and seed in spring, but rain at any time will trigger another flush of growth and seeding.

Look-alikes

There are many other weedy yellow daisies, such as dandelions, which mostly consist of a single basal rosette of leaves and a simple or branched flower stalk rather than having a branching habit from the base. Their flowers typically consist of multiple layers of "petals", not a single whorl of 13 "petals".  None are illustrated here. 

The native species Senecio pinnatifolius (formerly known as Senecio lautus) is extremely variable in leaf shape and growth habit.  One form of this species grows in grassy forest along the eastern edge of the Monaro, usually around the edges of swamps. Photo 9 above is this form. It has a weak trailing growth habit and more deeply toothed leaves. Another form of  Senecio pinnatifolius grows on coastal headlands and along the back of beaches (where fireweed has also become established in some instances, making detection difficult). It has fleshier leaves, sometimes deeply lobed with the lobes being very narrow. The flowers and seeds are very similar but the number of involucral bracts is only about 13. This is the best feature for distinguishing Senecio pinnatifolius from fireweed. The final two photos are the native "fireweed groundsel" (Senecio linearifolius). This is a robust species to over a metre in height, which grows as a cluster of stiff stems. "Petals" are shorter and fewer (8 or less) than in fireweed and leaves are much larger, with the veins conspicuous on the upper surface and the margins finely and regularly toothed and slightly rolled under. This difference in the leaves is apparent in the seedlings as well. This species is an opportunistic coloniser of bare ground and may give some cause for alarm by behaving in a weedy manner after disturbances such as clearing of forest, fire or drought. It is not listed as noxious, but it may reduce carrying capacity in pastures close to forest in the farming areas of the coast.

Control

Hand-pull fireweed as soon as the plants become visible by beginning to flower. Bag the whole plant for safe disposal or just the flowers and seed heads. It is safe to leave the plant with the flowers pulled off lying on the ground if grass length is sufficient that the plant will be held clear of the ground, or conditions are dry. If the ground is wet and the grass is very short it would be safer to bag and remove the whole plant, though this does create disposal difficulties. Check for seedlings in the vicinity of the more visible plants. Larger infestations can be spot sprayed or boom sprayed with a selective herbicide.

Slashing can reduce seed set, but is generally not recommended as a method of control as it only prolongs the life of the plants, which would otherwise die after producing seed.  Sheep have proven very effective at reducing seed production by grazing off leaves and flowers. Although the plant appears to be less toxic to sheep than to other livestock, continued consumption of large numbers of plants is likely to be damaging to their health eventually. Goats are also more resistant to the toxin than cattle and horses but do not appear to seek out the plants as actively as sheep. See photo 8 for an example of control by sheep (in the paddock on the left).

Maintaining vigorous pasture growth will reduce the number of seedlings which can become established, so avoid over-grazing. The native kangaroo grass appears much more resistant to infestation than exotic pasture such as kikuyu or ryegrass, and managing native pastures in vigorous growth may be a good long-term strategy for keeping this weed at bay. Because the plant is wind-dispersed, planting windbreaks across the direction of the prevailing wind and allowing grass growth beneath the trees may be effective at intercepting much of the incoming seed, giving a smaller area to search for seedlings, with the dense grass and strong competition for soil moisture provided by the trees providing a less hospitable seed bed for the weed.