Give your garden some color this spring!
Annuals quickly provide more color in the landscape for longer periods of time than any other garden plants. They are versatile, sturdy, and inexpensive.
Growth Rate
True annuals sprout from seed, flower, set seed, and die within one season. Many flowers that are not hardy such as begonias, impatiens, and geraniums are also grown as annuals.
In South Carolina many can be planted as seed in summer or fall to bloom the following spring or summer. A practical definition of annuals could be plants that must be replaced every year in the garden.
Annuals are commonly grouped as hardy, half-hardy, or tender. Hardy annuals — such as pansies and ornamental kale — are grown for color in cool and cold seasons. They are usually planted in the fall. Most decline or die with the onset of summer heat.
Half-hardy annuals - such as allysum and dianthus - can tolerate light frost and are usually planted in early spring for spring and early summer color. They usually decline in summer heat but may bloom again in the fall.
Tender annuals - such as vinca, zinnia, and impatiens - cannot tolerate freezing temperatures. They should be planted in the spring after all danger of frost is past.
Karen Russ, ©2007 HGIC, Clemson Extension
An annual flower bed with zinnias, salvia, and petunias
Landscape Use
Most annuals need full sun for at least 4 to 6 hours a day to flower well. Choose shade-tolerant species such as impatiens, coleus, or begonias for locations that receive less sun.
Avoid planting in areas where water stands after a heavy rain. Also avoid areas near large trees and shrubs that may have many thirsty feeder roots.
Planting
Wait to plant tender annuals until the danger of frost has passed. Many annuals, even if not injured by low temperatures, will not grow well until the soil warms.
Plant annuals with the top of the roots just under the surface of the soil. Be sure to remove paper, fiber, and plastic pots before planting.
Pinch off any buds and flowers when planting to promote better branching and a stronger plant.
Calliopsis (Coreopsis tinctoria ‘Highland Blast’).
Joey Williamson, ©2015 HGIC, Clemson Extension
Watering
Once transplanting is complete, water the plants thoroughly. Pay especially close attention to watering the first few weeks while plants develop their root systems. Adequate moisture is essential for the growth of flowering annuals. Most annuals need at least 1 to 1½ inches of water per week from rain or irrigation. More may be needed during very hot weather.
To promote deep root growth, water thoroughly and deeply. Allow the soil surface to dry before watering again. Soaker hoses and drip irrigation are ideal watering methods since they save water and avoid wetting leaves and flowers.
Maintenance
As flowers fade, remove them before seeds are formed to keep plants looking attractive and encourage continuing flowering. Heavy pruning can invigorate some species.
For instance, petunias can be cut back in midsummer to within a few inches of the ground, fertilized and heavily watered, and they will be full and attractive again in just a few weeks.
Adapted from HGIC Factsheet 1152 and reprinted courtesy of Clemson Cooperative Extension Home & Garden Information Center, https://hgic.clemson.edu.