Weed alert: yellow burr weed

PRODUCTION ADVICE - NOVEMBER 2020 - PESTS & WEEDS

By Natasha Lappin
Regional Weeds Corrdinator
P: 02 6051 2231 | M: 0429 827 471 | E: natasha.lappin@lls.nsw.gov.au

Have you seen this plant?

It's yellow burr weed (Amsinckia calycina), and there have some reports of it showing up in the Murray region recently. It has most likely come in within hay brought in from outside the region. Its seed is easily transported in hay and fodder.

The seeds and foliage (often called fiddleneck or common fiddleneck) are poisonous to livestock, particularly cattle, because they contain alkaloids and high concentrations of nitrates. The plant's sharp hairs can also cause skin irritation in humans.

Yellow burr weed prefers areas with an average rainfall of more than 275 mm, but has been showing up in areas where it has previously not been found. It grows in a range of soil types, including black clays, red loams and sandy soils.

What does it look like?

Yellow burr weed is an erect annual herb that grows to 70cm. Stems grow erect and are green, branched or unbranched and covered with fine, stiff hairs or bristles. Adult leaves are lance-shaped and grow to 20cm long. Leaves are alternate and also covered with bristles. Rosette leaves have a short stalk, while the upper leaves are stem-clasping with no stalk.

Flowers are bright yellow to slightly orange and positioned on one side of the stem. They are 5-10mm long and surrounded by green hairy segments.