Ash trees are starting to bloom now as well. I have noticed that African Sumac has been flowering and is still flowering now. If you have been sneezing over the past couple of weeks, this could be the problem. Ash trees are starting to bloom now as well. Flowers of African Sumac I know you could say fruit trees, flowering plum, ornamental pear are flowering too but usually plants with brightly colored flowers do not contribute much to allergy problems. Flowers of ash. Coming up very soon are mulberries, pine and canary island date palms for allergy sufferers.