1. Deciduous shrub bearing roundheaded flower clusters opening green and aging to pink or blue
   - hortensia

Type of: hydrangea

Part of: genus Hydrangea

• genus Oestrus
• genus Okapia
• genus Olea
• genus Oleandra
• genus Olearia
• genus Olfersia
• genus Oligoplites
• genus Oligoporus
• genus Ommastrephes
• genus Omphalotus
• genus Oncidium
• genus Oncorhynchus
• genus Ondatra
• genus Oniscus
• genus Onobrychis
• genus Onoclea
• genus Ononis
• genus Onopordon
• genus Onopordum
• genus Onosmodium
• genus Onychium
• genus Onychogalea
• genus Onychomys
• genus Opheodrys
• genus Ophiodon