bur·geon also bour·geon 
(bûrjən)
(bûrjən)intr.v. bur·geoned, bur·geon·ing, bur·geons also bour·geoned or bour·geon·ing or bour·geons
1.
a. To put forth new buds, leaves, or greenery; sprout.
b. To begin to grow or blossom.
2. To grow or develop rapidly; expand or proliferate.
[Middle English burgeonen, from Old French borjoner, from burjon, a bud, from Vulgar Latin *burriō, burriōn-, from Late Latin burra, a shaggy garment.]