Thursday, October 31, 2013

Angled Onions leaving a sour taste

Angled Onion (Allium triquetrum) has been increasing in recent years along local roadsides, stream banks and bush land areas.  Thriving in damp areas and tolerating windy conditions, Angled Onion, (if left unchecked) has the potential to become even more common in South Gippsland.

For those not familiar with the plant, Angled Onion is a bulbous perennial herb growing 30- 50cm tall. It has bright green, limp, fleshy, pointed leaves with a strong onion smell when crushed and small, white, bell-shaped flowers, clustered at end of long, triangular stems from August to November. Each petal has a middle green line. The fruit is a round green capsule, 4- 6mm diameter, with black, oblong seeds presenting from September to December. 

Without adequate control, Angled Onion is capable of smothering and displacing native grasses and groundcovers by preventing seed germinating and subsequent regeneration. In addition, given that Angled Onion is seasonal and dormant leaving bare ground in summer, it increases the likelihood of soil erosion.  In agricultural situations, Angled Onion imparts a strong onion flavor and an unpleasant odor to dairy products and meat, making them unfit for sale. The weeds seeds are dispersed by water and ants. Seeds and bulbs are also spread by contaminated soil and garden refuse.

In terms of control, plants can be dug out ensuring that all bulbs, corms and rhizomes are removed. Remove small and scattered plants first and then target outer edges of larger infestations. Dispose of removed material by either burning in a very hot fire or seal in strong bags and take to the tip.

For larger infestations, treat using herbicide at the bulb exhaustion stage late winter to early spring as treatments outside this period do not provide the same degree of control. Brush Off and Pulse penetrant is effective (off label use).

If unable to spray, at the very least remove flower heads prior to seed set, using either a lawn mower or brush cutter. It may take several years to exhaust the bulb food supply. Continue cutting new growth and maintaining dense mulch.

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