Select the largest size bulb within the variety of flower you are looking to purchase. The size of bulbs can vary between different varieties of flowers.
Be aware of the differences between the metric and U.S. (standard) systems of measurements. Many bulbs are imported from Holland and are sized by centimeters. As a point of reference, 2 ½ centimeters is equal to an inch.
Check bulbs for bruising, mold, or mildew. Reject any bulb with green tips because this is a sign the bulb has begun to grow, making it less viable.