Zone 3 on the USDA hardiness scale refers to regions where winters are harsh, bringing low temperatures between -30 and -40 degrees Fahrenheit. In the United States, few areas are designated as zone 3: states with substantial zone 3 coverage include Montana, North Dakota, Minnesota and Wisconsin. Annual flowers are not designed to endure the winter, but lots of species will thrive in zone 3 during the summer.
Morning glory is a general botanical term used to refer to more than 1,000 flowering vine species within the Convolvulaceae family. Morning glory is low-maintenance, but does require full sunlight and light watering, and some vines may need a little support in order to grow and spread properly. Its trumpet-shaped blossoms open in the early morning sunlight, lending the flower category its name. Blossoms come in blue, purple, red, white and yellow, and a single vine can grow more than 10 feet in a season. Morning glory typically dies upon first frost.
Begonia is a common flower genus with more than 1,500 distinct species. They make popular garden additions because their flowers tend to be big and bright, in showy hues of red, yellow, pink and white; leaves are usually asymmetrical and marked with intricate fractal lines. Native to tropical climates, begonias can be grown year-round, but they can still thrive as annuals during the warm weather season of zone 3. In cooler temperate climates, they require partial shade and well-drained soil.
Daisies are among the most common flowers in temperate regions, and the plant family includes nearly 25,000 distinct documented species. While many of these species are annuals and a variety will grow during zone 3's growing season, the extreme durability of the Arctotis genus, more commonly known as the African daisy, is well-suited to the zone's short summers. Well-defined blooms with sharp petals grow in red, orange, yellow, pink and white. African daisies do well in full sun and can thrive even under drought conditions.
The petunia genus is a popular choice among ornamental flowers because petunias grow quickly, require little maintenance and tend to grow thick clusters of attractive, brightly colored blooms. Common flower colors include blue, purple, red, white and yellow, though many varieties feature multi-colored blooms and some produce blooms of different colors within a single plant. Most varieties grow best in raised planters or hanging baskets, but some petunias are designed specifically to act as groundcover. Petunias like full sunlight and well-draining soil, but require only light watering and can do well in the absence of fertilizer.