Each year the National Garden Bureau (ngb.org/year-of) names plants of the year, with the annual flower (lives only one year) for 2019 being snapdragon. This upright flower is easy to grow, has multiple garden uses, and comes in a multitude of colors.
Although snapdragons are winter-hardy in warmer climates (USDA zones 7 to 10, such as the mid-Atlantic states and south), the fact that they need cooler temperatures to bloom well makes them a good choice for northern summer gardens. If day temperatures remain in the 80’s, flowering will slow down, and plants may even die if it gets too hot. They may go semi-dormant during the heat of mid-summer, reblooming when cooler temperatures return.
Since snapdragons generally withstand some cold, they’re good candidates to plant in early spring. Since plants you buy may not have been “hardened” off to the cold from their cozy greenhouse homes, it’s a good idea to expose them to outdoor temperatures for a week or two prior to planting. While hardened plants can withstand a light frost, and plants can survive temperatures in the 20’s (blooms may not), those you buy should be brought indoors or protected (with frost covers) from freezing.
The scientific genus name (Antirrhinum) comes from the Greek words “anti” meaning “like”, and “rhin” meaning nose or snout, referring to the flower shape. The dragon-shaped flowers are favorites with children, pinching the sides to make the flowers “snap” open like a mouth. Flowers come in most colors, except for blue. Bicolors are popular and attractive, the “throat” of the flower usually being white and the “lip” being another color such as red.
Flowers are produced along the tops of upright stalks, the heights varying with cultivar (cultivated variety). While the dwarf selections are good in pots or massed, the larger ones are good in backs of beds and borders, or used as cut flowers. The dwarf ones are the type usually found in garden stores, while the taller ones you may need to start yourself from seeds (indoors, 6 to 10 weeks prior to planting outside).
Most snapdragons have a pleasant fragrance, noticed especially on calm days, along walks, and when they’re planted in a mass. They attract pollinators that can handle the relatively (for them) large flowers, including hummingbirds, bumble bees, and other large bees. Yet they tend not to attract rabbits and deer. They are on edible flower lists as they can be eaten by humans, but are more decorative than tasty (being bland to bitter, depending on selection).
When planting, space plants 6 to 8 inches apart. If you’d like more bushy plants, especially of taller selections, you can pinch tops off plants when they’re 4 to 6 inches tall. You’ll get more, but delayed, blooms this way. These can be spaced 8 to 12 inches apart. Prepare soil, and fertilize, as you would for other annual flowers.
When watering, water deeply so the fibrous roots will go deeper in the soil. This will help prevent them from toppling. The taller selections, however, still may need staking or support (as with netting or strings between posts). Keeping spent flowers removed (“deadheading”) after bloom will help keep them reblooming and, if the season is wet, will help prevent gray mold or botrytis disease forming on old flowers.
Trailing snapdragons include the Candy Showers series and Cascadia mix (a mix of colors). Instead of growing upright, these are low and trailing, which makes them great for raised beds, planters, and hanging baskets.
Dwarf series (a variety of colors) grow 8- to 12-inches tall, and include Floral Showers (often includes bicolors), Twinny mix (double flowers) or single colors, Frosted Flames mix
(green leaves with variegated cream edges), and Palette mix (an improved Royal Carpet with earlier and longer bloom period).
Medium series grow 12- to 24-inches tall, and include the unique Tutti Frutti (solid color flowers speckled with contrasting colors), Cinderella mix (multiple side shoots after the first bloom produce subsequent blooms), Liberty mix, Sonnet Crimson (dark red), Night and Day (dark red and white, a descendant of Black Prince), and Lucky Lips (white with purple-red).
Tall series grow 24- to 36-inches tall, and include the white Royal Bride, Madame Butterfly mix (ruffled, azalea-type double flowers in various colors) or single colors, Costa mix (a cut flower type that flowers early), Supreme mix, and Chantilly mix (open “butterfly” type flowers) or single colors. Chantilly flowers are in designer colors—more subdued than usual snapdragons—and last longer than many, in both the garden and cut in vases. They make good cut flowers during the cooler early or late seasons.
Potomac mix, or single colors, are better adapted than most to high light and warm summer temperatures, and are mainly grown for cut flowers. Another good tall snapdragon for summer is the Rocket mix (bright colors with a cinnamon fragrance).
If growing taller snapdragons for cut flowers, the best time to cut them is in the morning, putting the flower stalks directly into a container of water. Flower stems last longest (7 to 10 days) if they’re cut when only the bottom 3 to 5 flowers are open. Make sure to keep them upright, otherwise horizontal stems (even for an hour or two) will begin to curve upright (“geotropism”— a response to gravity).
Dr. Leonard Perry, Horticulture Professor Emeritus
University of Vermont