It's time to talk about our many species of blooming goldenrod (Solidago), but before we do that, here is a good look at ragweed vs. goldenrod. Both bloom at the same time but ragweed has green flowers while goldenrod has bright yellow flowers. Ragweed's flowers are full of lightweight pollen that is picked up by the wind, causing allergies. Goldenrod's flowers have pollen that is heavy and carried by insects. They often grow together on roadsides.