Nuttallia (Mentzelia) nuda - White Evening star - Stickleaf Family (Loasaceae) - Summer and Late - Colorado Wildflower - Flowers of Nuttallia nuda have ten non-overlapping petals and numerous long stamens. Flowers open in late afternoon. Nuttallia nuda is a common plant on dry, sandy plains sites. Compare to Nuttallia decapetala.
Oxybaphus (Mirabilis) hirsutus - Umbrellawort - Four-O'Clock Family (Nyctaginaceae) - Colorado Wildflower - The stems, leaves and calyx of Hairy Four-o'clock are pubescent. Stem leaves are sessile (attached directly, lacking a petiole).