Possible Clues:

• Member of the mimosa family
• Plant such as a wattle
• First-rate accountant about to turn round plant
• I will join accountants up a gum tree
• Tree of the mimosa family...mmm, mimosas
• Wattle genus
• Plant doubly if little account comes up very well
• Thorny flowering shrub
• Twice Bill and I get together in a gum tree
• Umbrella-shaped savanna tree