Weed of the month – Dec 2017


(Brassica napus)

   (Photos: C. Schultz; Left to right: large clump of canola plants; flowers with unopened buds; flowers and developing seed pods)

We all know canola because of the edible oil derived from its seeds, making a really good cropping plant. When mature seeds blow into coastal heath, however, this useful plant becomes a weed very quickly! An Agriculture Victoria website[1] advises that “Once established, canola is effective at crowding out weeds.” Given it can crowd out weeds in a cropping situation, it is no wonder it crowds out natives in remnant vegetation. We’ve seen this at Cape Jervis, where canola established itself in one season after weed clearing. You will spot the bright yellow flowers, which can appear even on very young plants. And you will smell them! The brassica family includes broccoli, cabbage, cauliflower and turnip… all strong smelling. The plant grows to about 1.5m tall, with an open habit of a central stem and many side branches. It has a central tap root, which with the right amount of moisture can grow 2cm a day! Remove the seed pods well before they ripen; if you just pull out the plant the seeds might after-ripen. 

[1] http://agriculture.vic.gov.au/agriculture/grains-and-other-crops/crop-production/growing-canola; sighted 10-11-17