Here is a list of summer flowers and their short descriptions:

Anemone - Daisy-like round petals and ferny leaves that frame the flower. Comes in vibrant colors of red, purple, and pink with black hearts ringed in white.
Bird of Paradise - “Crane flower.” Leathery leaves that form a crane-shape and are held upright by stiff stalks. Bloom is a combination of blue and orange petals that grow out of the top of the leaves.
Calla Lily - Arrowhead-shaped leaves with funnel-shaped flower heads in reds, whites, yellows, and pinks.
Dahlia - Various types of petals including spiky, wispy, round, thin, and more. Available in a wide variety of colors, most notably reds, oranges, yellows, pinks, and whites.
Day Lily - Large flowers with 3 petals, 3 sepals, and band-shaped leaves. Many colors available.
Forsythia - Shrub; bright yellow, little 4 petaled flowers with opposing spear-shaped leaves.
Freesia - Little to no foliage and 5-10 trumpet-shaped flowers with sword-shaped leaves. Comes in white, yellow, orange, red, pink, mauve, lavender, purple, and some bi-colors.
Gerbera Daisy - 2 edged ray florets in red, yellow, orange, white, or pink shades. Also hybrid into a wide variety of other colors.
Gloriosa - Red/orange and yellow, long, reflexed petals with spiral-shaped leaves.
Iris - Made up of 6 lobe-shaped flowers; 3 pointing downward, and 3 upright. Comes in vibrant purple, blue, white, or lavender.
Magnolia - Wide petals that are pink and fade to pink with large, glossy leaves.
Peony - Deeply lobed leaves with large, cup-shaped drooping flowers in red, pink, white, and yellow.
Poppy - Cup or bowl-shaped petals (4-6) with one flower per stem. Comes in white, pink, yellow, orange, red, and blue with dark centers.
Rose - Long, alternating leaves and thorned stems. Most roses have 5 petals with 2 lobes per petal. 5 sepals grow beneath the petals. Large variety of colors and types available.
Sunflower - Large flower head made up of disc and ray florets arranged spirally. Have rough, hairy stems and rough, broad leaves. Common colors are bright yellow, maroon, and orange.

Other popular summer flowers include all tropical flowers as well as orchids.