Season-by-Season Guide to Annual Flowers

Season-by-Season Guide to Annual Flowers

Instant impact! That’s what you get when you plant annual flowers in beds, borders, and containers. Here's a seasonal guide to care and use. By Doug Jimerson
By Doug Jimerson

Instant impact! That’s what you get when you plant annual flowers in beds, borders, and containers. These beauties are a snap to grow and come in an almost unlimited selection of colors, shapes, and sizes. Here’s a quick seasonal guide. 

In the north, as soon as temperatures remain safely above freezing, start planting cool-weather annuals such as osteospermum, dusty miller, sweet alyssum, pansy, and snapdragon. All of these beauties thrive in containers or planted directly in the garden border.

It’s also time to start seeds indoors of heat-loving flowers such as zinnia, marigold, and salvia. These plants can go outdoors after all frost danger has passed.

In southern areas (such as Florida and parts of Texas), spring is a great time to fertilize annual flowers you planted in the fall and winter. And, it’s also time to start thinking about replacing your cool-weather flowers with varieties that can take the summer heat.

Once the weather heats up, some cool-weather annuals such as pansy and osteospermum will start to look tired and cease blooming. Replace them with heat- loving species such as verbena, calibrachoa, and begonia. To promote a continuous supply of blooms, do your best to remove the flowers as they fade (deadheading). This will also help keep your garden looking neat and tidy.

Small flowered annuals, such as sweet alyssum, calibrachoa, and petunia, often benefit from a midsummer haircut. Shear these plants back by a third if they start looking leggy. Tall annuals such as cleome or standard-sized zinnias may require staking to keep them from flopping over. Fertilize annuals to keep them in top form all summer long. Spreading a 2- to 3-inch-deep layer of mulch over the soil will also help keep gardening easy by allowing the soil to hold moisture longer and prevent weeds from growing. 

In warmer regions of the country, focus on annual varieties that can tolerate heat and humidity. Some good picks include: salvia, marigold, vinca, verbena, and begonia. And don’t forget to mix in some tropical plants such as mandevilla, caladium, croton, and tropical hibiscus.

In the early fall, boost the color in your garden by adding a selection of bright, cool-weather annuals such as flowering kale and cabbage, dusty miller, and sweet alyssum. As the season progresses, remove any annuals that may have been blackened by frost and toss them on your compost pile. Be sure to haul away all the dead foliage in order to prevent insect pests and diseases from overwintering in your garden.

In warmer regions, remove and replace any tired looking summer flowers with a fresh crop of cool-weather bloomers. Depending on where you live, these cool weather annuals may keep your garden colorful all winter along. Most cool season annuals can tolerate an occasional light frost.

Because annual flowers can’t tolerate freezing temperatures most gardeners can’t enjoy them outdoors through the winter. However, winter is the perfect time to plan next year’s garden. Working with annuals is a lot of fun because you can plug them into your garden easily and enjoy instant results. Plus, you’ll find annuals that grow in either sun or shade. For shady spots try begonia, coleus, wishbone flower, impatiens, and pansy.

In milder climates, fertilize cool-weather annuals to keep them in top form. Use a dilute solution of liquid fertilizer every few weeks or apply a dry, granular slow release plant food. You can also add additional plants throughout the winter to increase the flower show. Always cover plants with a sheet or blanket if an unexpected freeze is predicted.

5 Surprising Facts About Annuals

1. Some plants considered annuals in one part of the country are actually perennials in other regions. Lantana, for example, is grown as an annual in the north, but forms a perennial shrub in the Deep South.

2. A few annuals such as petunia and geranium thrive in different seasons depending on where you live. These easy-care beauties actually prefer summer temperatures in the North and winter temperatures in the Deep South.

3. Coleus and SunPatiens are two easy-to-grow annuals that thrive in either sun or shade. Few plants are as versatile or as colorful as these plants.

4. Heights within a particular plant family vary greatly. Zinnias, for example, can grow as low as 6 inches and as tall as 3 feet. Always check the plant label before you buy because young plants often look alike.

5. You can grow your own colorful privacy screen by planting annual vines on a trellis or arbor. Quick-climbing annual flowers include morning glory, black-eyed Susan vine, cardinal climber, hyacinth bean vine, and cypress vine.