Possible Clues:

• Thorny shrub with yellow or white-flowers
• Garden shrub, also known as wattle
• That's a double century and a single A for a tree
• Wattle is such a plant
• Savanna shrub
• Small flowering tree
• Top-rate accountants set up plant
• Bill doubled turnover for excellent ornamental tree
• One C one C one A, all growing
• It grows back in a first-class way with a couple of accountants