Many Broadleaf trees  have white flowers. Use this option to identify these trees. Usually the flowers are only present for a few weeks  and some flower in spring before the leaves. Look at the size and shape of the flower and also whether it is single or in long spikes or tails or compact clusters. Some Flowering Cherries have white or pink flowers. 

Many flowers in a narrow cluster which may be upright (Horse Chestnut and Cherry Laurel)  or hang down in a tail (False Acacia, Bird Cherry,  Manchurian Cherry).