Horse chestnut blossoms. Blossoms of the horse chestnut (Aesculus hippocastanum), a tree used in herbal medicine. The bark and parts of the fruit of this tree are believed to have astringent properties. They may also promote the constriction of blood vessels when taken internally. The seeds of the horse chestnut are also used as a natural remedy for colds; they may have a decongestant effect. These treatments are taken as a powder, ointment or tincture (spirit solution).