If you keep an eye out while driving around Forster (or just about anywhere else) around autumn time, the bright yellow flowers of Cassia (winter senna) make it difficult to miss. These attractive flowers are the main reason Cassia was so popular as a garden plant in past decades. This photo was taken by the road side in Forster. Cassia was the second most common weed found on properties during the 2013 weed inspections in Forster, and is common on both private properties and in bushland reserves. Once established in a garden, it spreads easily.
Check out the Cassia identification and control video from the Pittwater Ecowarriors:
The photos below show detail of the cassia flowers and seed pods. Starting out looking like green beans, they turn brown as they ripen. Each pod contains hundreds of viable seeds.
Breynia oblongifolia (pictured below) is a native plant often confused with Cassia. The easiest way to tell them apart is the alternate leaf arrangement along the stems of Breynia. Cassia leaves grow directly opposite each other along their stems. Also look out for reddish stems on Breynia, as well as very small flowers and fruit.
To control Cassia first collect seedpods and dispose of them in red bins. Then either scrape a length of bark from the main stem and paint exposed surface with herbicide, or cut at base and paint with herbicide.
Smaller plants are easily pulled out by hand.