It takes considerably more time than 49 days to produce an onion. First the leafs (green tops) grow and multiply. Then they stop multiplying and start getting thicker....that's when the bulb start getting larger. It take about 5 months for the whole process to make the big onions you see in the markets.

Around the 5 month timeframe, you'll start to notice the green tops fall over. Wait about 2 weeks after that and harvest.