Annuals are flowering plants that complete their entire life cycle in a single growing season. Emerging in the spring, annuals flower throughout the hot summer months, produce seed and then die when the temperatures drop below freezing in autumn. Due to their short but prolific life cycle, many annuals grow quickly after they are planted outdoors, but some annuals have a faster growth rate than others.
Marigolds, native to the warm regions of subtropical America, are popular annuals because they are simple to grow, have few pest or disease problems and flower abundantly throughout the summer growing season. Marigolds have a fast rate of growth and range in size from 6 inches to 3 feet in height. Depending upon the variety, marigolds can produce an assortment of flower colors including orange, yellow and gold, or a combination of all three, as well as red, burgundy and cream.
Use marigolds for borders, as edging or container plants or in mass garden plantings. Plant marigold seedlings or young transplants outdoors after the danger of frost has passed. Choose a planting location with well-drained soil that has been mixed with organic compost. Make sure the plants receive six to eight hours of direct sunlight every day and at least 1 inch of water each week through rain or irrigation.
Zinnias are easy-to-grow annual flowering plants native to North and South America. Zinnias are popular among gardeners because they grow quickly, come in a wide variety of colors, shapes and sizes and can tolerate many types of soil and growing conditions. Available with single, double and semi-double flower forms in every color but blue, zinnias add beauty to any location in the landscape.
Depending upon their maturity size, zinnias can be planted in garden areas, hanging baskets, large pots or window boxes. Sow zinnia seed or set young zinnia transplants outdoors after the last frost. Select a planting area with good drainage that receives at least six hours of direct sunlight each day. Water zinnias regularly and apply a water-soluble fertilizer at least twice during the warm summer growing season.
Cosmos, a fast growing annual native to South America and Mexico, is a favorite among many gardeners in semi-arid regions. Typically pest-free, cosmos will tolerate and often thrive in hot, dry climates with poor soil conditions. The two most commonly grown species of cosmos produce blooms in fiery shades of red, orange and yellow, as well as white and various shades of pink to deep burgundy.
Line driveways or garden paths with medium height cosmos varieties, and use larger varieties to create colorful garden backgrounds. Seed cosmos in spring after the danger of frost has passed. Since cosmos is well adapted to hot and dry conditions, water sparingly once new growth emerges. In summer when blooming declines and seed pods appear, trim spring-planted cosmos down to a height between 12 and 18 inches to encourage plants to rebloom.