The Language of Dreams
If the hawthorn appears in bloom, this represents happiness.
In Europe this tree has somewhat divergent meanings, being both chastity and fertility.
For the purpose of dream interpretation, this might mean maintaining your devotion to someone or something for a productive outcome.
Along with the oak and ash, this is a sacred fairy tree, and may represent a subconscious connection to Devic realms and messages.... The Language of Dreams
Dream Symbols and Analysis
Mystic Dream Book
The colour, White, helps considerably in this case.... Mystic Dream Book