Several years ago I had a truckload of topsoil delivered for a new flower bed in my front yard. Before I knew it, my plantings were surrounded by some unexpected company-white, yellow, pink and burgundy snapdragons. The interlopers soon filled out the bed, adding colour and fresh flowers for cut bouquets all summer long. They continued to reseed themselves for several years. The common snapdragon (Antirrhinum majus) performs like a short-lived perennial, and it's not unusual for this versatile plant to self-sow in the garden.
Native originally to North Africa, Spain and along the Mediterranean coast to Italy, the common snapdragon has become naturalized in temperate regions throughout the U.S. and southeast Canada. Like foxgloves, snapdragons belong to the Scrophulariaceae family and are available in many newly developed forms.
Snapdragons have upright stems and velvet-textured, tubular flowers; between 10 and 15 blooms appear on each flower spike, opening from the bottom up. They come in a rainbow of colours (almost every shade except for true blue), and some varieties are bicoloured.
Although snapdragons have been cultivated since the 1700s, they've only been hybridized since the 1950s. There are hundreds of cultivars, usually listed in one of five groups: tall (60 to 90 centimetres); intermediate (30 to 60 centimetres); short (20 to 30 centimetres); dwarf (10 to 20 centimetres); and trailing. Some modern varieties have open-faced, azalea-like, double flowers and even variations in leaf colouring. A fairly recent introduction, the butterfly cultivars have open-faced flowers with either single or double petals.
Propagate snapdragons by seeds or cuttings: seeds germinate in 10 to 14 days at 21°C and cuttings root readily.
Snapdragons are usually grown as annuals, and most cultivars come true from seed. Sow seeds outdoors in spring after danger of frost has passed. Alternatively, start them indoors six to eight weeks before the expected last frost, gradually acclimatizing young plants to outdoor conditions for a week or so before planting out.
Seeds need light to germinate, so just sprinkle them on the soil surface; then press them down into the soil so they won't get swept away by wind or rain. Pre-chilled seeds germinate best; freeze for 48 hours before sowing. If you're starting seeds in containers, water from below so you don't wash them away.
Early in the season use twiggy branches to support tall varieties that need to be staked. Snapdragons do best in full sun, in well-drained soil rich in organic matter, but can tolerate partial shade.
Spacing depends on the cultivar, but in general tall flowers should be planted 30 centimetres apart and shorter varieties 15 to 25 centimetres apart.
Water often for the first few weeks after transplanting (daily in sandy soils). Once established, water when the top few centimetres of soil feel dry to the touch or when it hasn't rained for at least five days. But don't overwater: you could stunt or even kill them.
Snapdragons perform best in cool weather, and most cultivars can tolerate frost and an occasional light freeze. Cover with mulch if a hard freeze is expected. With proper care, your snapdragons should bloom from late spring into early fall.
The secrets to encouraging branching and keeping snapdragons blooming through summer and fall are pinching them back when they're about six centimetres tall, cutting the flowers often and removing old flowers after they've bloomed.
When seedlings develop two or three sets of leaves, pinch back their tops. Dwarf forms don't need pinching.