Possible Clues:

• One C one C one A, all growing
• Locust tree, e.g.
• Twice with a hundred and one A grows up
• Spies appear after hiding odd bits of larch and oak tree
• Tree source of gum
• Two of a century with one of an A in the form of a tree
• A cold continent reportedly providing growth
• It takes a double century to start to get growing
• Subtropical shrub or tree
• Bills for one with a tree