Tips on Keeping Snapdragons Blooming

Written by alicia rudnicki
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Tips on Keeping Snapdragons Blooming
Snapdragons blossom more in cooler temperatures. (Brand X Pictures/Brand X Pictures/Getty Images)

Getting snapdragons (Antirrhinum) to keep blooming involves removing spent blossoms, pruning and enriching the soil. Other tips for maximum bloom, include keeping soil moist and providing preferential locations where snapdragons will receive plenty of sunshine, but not the most extreme heat of day. Local climate also has a major impact on the bloom cycle and whether snapdragons act like annuals or perennials.

Annuals Versus Perennials

To understand the bloom seasons of snapdragons -- which are categorised as annuals in most parts of North America-- it is necessary to consider the main difference between annuals and perennials. Annuals are plants that die in winter and are replanted for the next growing season. Perennials remain alive from one growing season to the next. Snapdragons that are protected from the cold may winter over in northern states. However, the majority that "come back" do so by self-seeding.

The Missouri Botanical Garden classifies the main species of snapdragon (A. majus) as a "tender perennial" in U.S. Department of Agriculture (USDA) cold hardiness zones 7 to 10 where winters are warm enough to keep the plants alive all year. But that doesn't mean year-round blooms.

Length and Timing of Bloom

Snapdragons prefer a temperature range of 4.44 to 26.7 degrees Celsius. In areas where summer heat is mild, snapdragons bloom from spring through fall if watered, fed and deadheaded properly. In areas with extreme summer heat, such as Mississippi, they grow during summer, but usually only bloom from autumn to spring.

In areas with excessively hot summers, planting snapdragons in parts of the yard with east exposures may prolong bloom time by providing afternoon shade to cool the plants. Similarly, in cooler climates, snapdragons snuggled up against the house may bloom longer into autumn. In the Deep South, it is best to plant snapdragons in the autumn. In the North, spring planting lengthens bloom time.

Tips on Keeping Snapdragons Blooming
Cutting snapdragons for bouquets is a practical pruning idea. (Dynamic Graphics/Polka Dot/Getty Images)

Sun, Soil and Moisture

Proper growing conditions increase the bloom time for any flowering plant. Snapdragons should be planted where they will get at least four hours of direct sunlight daily. Mix fertiliser and lots of organic matter into the soil to depth of about 9 inches before planting. Similar to most garden plants, snapdragons like a soil pH that is slightly acidic (6 to 6.5). They need at least an inch of water per week, but soggy soil will stunt or kill them.

Deadheading and Pruning

Removing (deadheading) fading blossoms before they begin to set seed is an important tip for prolonging the blossoming of snapdragons. However, the Missouri Botanical Garden says that if flowering decreases dramatically after the first round of blossoms, it may be necessary to prune several inches off the top of the plants and add extra fertiliser. To increase the number of blossoms, pinch off some of the plant tips to encourage bushiness.

Heat-Hardy Look Alike

The heat-tolerant plant Angelonia augustifolia, which is commonly called summer snapdragon, is a perennial in USDA zones 9 to 11 and blooms from June to October. It is not a member of the true snapdragon clan, but is a genus along with Antirrhinum in the figwort family (Scrophulariaceae). Angelonia blossoms look similar to the open-faced antirrhinums that don't have "jaws."

Tips on Keeping Snapdragons Blooming
Angelonias love heat. (Medioimages/Photodisc/Photodisc/Getty Images)

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