Most gardens in the northern hemisphere hit their stride with nonstop blooms in June. Late spring flower beds are bursting with color. Any chance of frost is long gone and the heat of summer hasn't hit yet. When exactly in June a certain flower will bloom depends on the hardiness zone and weather conditions.
Bulbs
June blooming bulbs are usually planted in early fall before the ground freezes. Daylilies are found growing wild in the East and Midwest along side roads. The blooms only last a day but one plant may have 20 or 30 blooms at the same time. Wild daylilies are found mostly in orange and yellows. Hybrid lilies bloom in purples, pinks, and cream, as well as yellow and oranges. Oriental lilies are typically very fragrant growing to four feet high. Several flowers bloom on the same stem. The flowers last for several days and make good cut flowers. Irises--bearded, Dutch and Japanese--all bloom in June. Bearded Irises are fragrant and the largest flower of the three. Dutch and Japanese irises are primarily blue, purple, yellow and white.
Annuals
Of course annuals bloom from early spring right after the first frost to late fall. Many of them thrive in June before the summer heat. Cosmos are five petaled daisy-like flowers on bushes four to five feet high. Colors include deep pink, pink, white, and yellows. Zinnias are known as the can't-fail-flower for many gardeners. Sizes range from Thumbelina about six inches high with quarter-size blooms to bushes three feet high bushes with blossoms three inches wide. Zinnias come in lots of colors with the exception being blue. Some varieties have petals edged with a contrasting color. Marigold is another flower that is easy to grow and blossoms profusely in June. It has a musky scent that some people don't like.
Perennials
Perennials are plants that grow through the season, die back, and then return the next growing season. Their blooming season is short, usually only a few weeks, compared to annuals that bloom an entire season from start to finish. Foxglove, delphinium, dianthus, cornflowers are all perennials that bloom in June.
Roses are often considered in a class by themselves even though they are perennials. They are the exception to the rule that perennials only bloom for a few weeks. Most roses have a flush of bloom in late spring, bloom throughout the summer and then have a second flush of bloom when the weather cools off again in early fall.