Tulip Fields, Keukenhof, The Netherlands

Classification
In horticulture, tulips are divided up into fifteen groups (Divisions) mostly based on flower morphology and plant size.
• Div. 1: Single early - with cup-shaped single flowers, no larger than 8 cm across (3 inches). They bloom early to mid season. Growing 15 to 45 cm tall.
• Div. 2: Double early - with fully double flowers, bowl shaped to 8 cm across. Plants typically grow from 30–40 cm tall.