Many annual flowers love the cool weather of spring and fall, flowering best when temperatures stay below 80F. They provide a cheerful beginning to the garden season in Spring, and a colorful ending in fall. Some annuals are even frost-tolerant and may flower through winter in mild regions. However, during the heat of summer you may want to replace these cool-loving annuals with heat-lovers, such as verbena, nicotiana and pentas. Here are some cool-loving annuals that will extend your flower gardening season.
Snapdragon. These stately annuals produce the healthiest plants and most colorful flower stalks under cool conditions. They can grow from 1 to 2 feet tall depending on the variety, producing flowers in a multitude of colors. While the more common upright varieties look great planted in beds and used as cut flowers, new trailing varieties also make great additions to a mixed container planting.
Petunia. There are many varieties of petunias available, so read plant labels carefully to choose the best type for your situation. For example, some are low-growing and spreading, while others are more upright. Depending on the variety, plant petunias at the edge of flower beds, in hanging baskets, or in containers mixed with taller cool-season annuals such as dianthus.
Dianthus. These 10- to 20-inch-tall plants are annuals, biennials or perennials, depending on the variety. Common names include carnations and pinks. These cool-season, sun-loving plants feature large flowers in jewel colors such as cherry, salmon, rose, lilac, and white. They look great in garden beds or containers. Keep plants well watered and fertilized.
Viola. These prolific annuals are the classic early spring and late fall annual flower. Both cheery "faced" varieties and solid-colored types will brighten up any garden. In spring gardens, they grow best in raised beds or containers because these allow the soil to dry out and warm up quickly. While they won't survive the heat of summer in most areas, in cool summer areas they can be cut back in early summer, then will grow and flower again in fall. Protect young plants from slugs and other cool and moisture-loving pests.
Garden Mum. This classic fall garden plant comes in a range of flower sizes and colors. Grow them right in garden beds or place in individual containers. In regions with moderate winters, mums can survive through the winter and be grown as perennials. Plant in full sun and keep them well-watered, fertilized and pinched back when young to produce the largest blooms.
Cool-Season annuals grow best when: