Black Wattle Tree (Acacia mearnsii) yellow flowers hum with sound of bees.
Black Wattle trees flower into a mass of yellow this is replaced with seed pods that fall to the ground. On the ground the black wattle seeds from previous years (up to 50 years) forms a thick mulch awaiting a fire when they will germinate en masse. Then the bare ground will transform into a grass like carpet of black wattle seedlings. The Black Wattle seedlings grow rapidly upward competing for light and resulting in long straight wattle sticks (Wattle Screens & Wattle Panels ). These grow into Wattle Trees and the Wattle Wood is now useful as poles, posts and firewood .
Black Wattle was introduced into South Africa as a source of Tannin, fuelwood (firewood & charcoal) and cheap building materials. It is still used for these today.
Although Black Wattle is an Alien Invasive Species, Acacia Mearnsii or Black Wattle is also an extremely useful tree.
This is evident by the the following two interesting articles on Black Wattle, firstly Australian take on Black Wattle, Black Wattle Farm Forrestry & then the ever reliant Wikipedia article on Black Wattle, WikiPedia Black Wattle
). These grow into Wattle Trees and the Wattle Wood is now useful as poles, posts and firewood 
.