Possible Clues:

• That blooming tree starts with a century at the double
• After a century or two it turns up A-one as it grows up
• Garden plant also known as wattle
• Bush, perhaps, angry initially about secret service
• Australian wattle
• Shrub of warm climates
• It grows for a century after a century to start with
• State after repeated account, it's a plant
• Tannin source
• First class accountants head over heels about the plant