Vespers (page 44): "I remember small things, flowers / growing under the hawthorn tree, bells / of the wild scilla"
Other names: Crataegus
Family: Rosaceae
Type: Deciduous (or rarely semi-evergreen) tree
Blooming period: Spring to Summer
Sun requirement: Full sun is best.
Soil requirement: Any but very wet.
Notes: The tree blooms widely, often with white flowers -- and also often shows fall colors later in the year.
Sources: [1]