Snapdragon (Antirrhinum majus)

Common Snapdragon, Garden Snapdragon, Snapdragon

The garden snapdragon (Antirrhinum majus) is a flowering perennial that is commonly cultivated as an annual or biennial ornamental plant. When the throats of its flowers are squeezed together, its lips snap open like a dragon’s mouth; this is the origin of the common name. The garden snapdragon’s speedy cultivation and ease of pollination made it a good target for research, so it has now become a model organism for plant genetics studies.

I. Appearance and Characteristics 

Antirrhinum majus, the common snapdragon (often – especially in horticulture – simply “snapdragon”), is a species of flowering plant belonging to the genus Antirrhinum. The plant was placed in the family Plantaginaceae following a revision of its prior classical family, Scrophulariaceae.

The common name “snapdragon”, originates from the flowers’ reaction to having their throats squeezed, which causes the “mouth” of the flower to snap open like a dragon’s mouth. It is widely used as an ornamental plant in borders and as a cut flower. It is perennial but usually cultivated as an annual plant. The species has been in culture since the 15th century.

It is an herbaceous perennial plant, growing to 0.5–1 m tall, rarely up to 2 m. The leaves are spirally arranged, broadly lanceolate, 1–7 cm long and 2-2.5 cm broad. The upper glandular stalk is stalk-round, sometimes woody to the middle. The opposite leaves are simple, elliptic or ovate to broad-lanceolate, sometimes linear and usually bleak. Leaflets are missing.

The flowers are produced on a tall spike, each flower is 3.5-4.5 cm long, zygomorphic, with two ‘lips’ closing the corolla tube lobed divided into three parts and is purple red, almost 5 cm long. Wild plants have pink to purple flowers, often with yellow lips. Most 8 to 30 short stalked flowers are in an inflorescence together; the inflorescence axis is glandular hairy. The crown is 25 to 45 (rarely to 70) millimeters long and in different colors (red, pink, orange, yellow, white). The “maw” of the crown is closed by protuberance of the lower lip, one speaks here of “masked”, and everted baggy at the bottom. There is a circle with four stamens. The plants are pollinated by bumblebees, who are strong enough to gently and briefly open male flowers to enter and exit them without difficulty, collecting pollen in the process. A snapdragon’s calyx is up to 8 mm long, with sepals of equal length, oblong to broad.

The ovary is supreme. The fruit is an ovoid capsule 10–14 mm diameter shaped like a skull, containing numerous small seeds.

Antirrhinum majus can survive a certain amount of frost, as well as higher temperatures, but does best at 17–25 °C (63–77 °F). Nighttime temperatures around 15–17 °C (59–63 °F) encourage growth in both the apical meristem and stem. The species is able to grow well from seeds, flowering quickly in 3 to 4 months. It can also be grown from cuttings.

II. How to Grow and Care

Sunlight

Your snapdragons will bloom most profusely in full sun to partial shade. Once the temperature heats up, they may stop blooming altogether. Planting them in part shade and keeping them well-watered will help them make it through the summer and they will likely bloom again in fall.

Temperature and Humidity

Snapdragons are tender perennials that are hardy in USDA zones 7-11. But snapdragons prefer cooler temperatures and are at their best when nighttime temperatures are in the low 40s F and daytime temperatures in the low 70s F. For this reason, they are usually grown as annuals to provide garden color in the cooler months of spring and fall.

Once established in the bed and hardened off, snapdragons can withstand sub-freezing temperatures. If you make sure they stay well-watered during cold spells and add a layer of pine straw mulch, they can last for quite some time and will survive quite low temperatures until the chill has passed.

Seedlings grown indoors need to be hardened off for about 10 days to two weeks before planting in the garden.

Watering

Snapdragons need adequate watering. Keep seedlings moist for the first few weeks. Once established, snapdragon will need approximately 1 inch of water per week in times of no rainfall. Water near the crown of the plant and avoid overhead watering to keep your snapdragon healthy. Once established, let the top inch of soil dry fully before watering.

Soil

Snapdragons like a neutral soil pH between 6.2 and 7.0, rich in nutrients and well-draining. As short-lived plants, they are not heavy feeders, but adding organic matter will help keep them healthy and blooming.

Fertilizing

Wait until the garden snapdragon starts to flower before adding fertilizer. Then apply a balanced all-purpose fertilizer, using plenty of water to allow the fertilizer to reach the plant’s roots. Use slow-release fertilizer in low volumes and avoid leaves and flowers to prevent burn damage.

Planting Instructions

Pruning

When the plant is about four inches tall, pinch it back to encourage side shoots to form more blossoms. This pruning is optional. Pinching like this will delay the harvesting time if you intend to cut stems for cut flower production.

Propagation

Snapdragons propagate quickly from cuttings and root division. Here is how to propagate snapdragons from cuttings:

  • First, take cuttings from a healthy snapdragon in the summer—around six weeks before the first frost. Check your local area for expected frost dates. 
  • Choose a selection with foliage still attached. 
  • Dip the cutting into a rooting hormone to help it take root. 
  • Plant the cuttings in potting soil. Keep the soil moist and maintain healthy air circulation throughout the winter. 
  • Roots will establish throughout the winter. Transplant healthy snapdragons outside in the spring after the final frost passes.

How To Grow from Seed

For Upper and Middle South gardeners, start sowing seeds indoors under lights about eight weeks before the average last frost. The plants will bloom in the spring and early summer. For the Lower South, Coastal South, and Tropical South gardeners, sow the seeds at the end of September to plant snapdragons in the garden by the end of November. The winters are mild enough for the plants to grow and bloom in winter and spring.

  • Add moistened seed starting mix in clean seed starting trays (with drainage holes). Sprinkle snapdragon seed on top or sow evenly with a moistened toothpick. The seeds are very fine and need light to germinate. Press the seed onto the moistened mix for contact, but do not cover it with a different mixture.
  • Place under grow lights or fluorescent tubes, leaving lights on for 14 to 16 hours daily.
  • The lights have to be adjustable. They should be only a few inches away from the plant. 
  • It can take two weeks for seeds to germinate, so be patient.
  • Mist with water frequently so seeds do not dry out. They must not dry out when germination begins because germination will stop if allowed to dry, and the seeds cannot be “revived.”
  • As the seed germinates and grows, you may have to adjust the lights to remain only a few inches away from the plant. 
  • As the seedling grows, you can water or mist less often because the roots have formed and can obtain water from a lower depth in the mix. 
  • Thin the seedlings to reduce the number to create space for the rest. Cut the weakest seedlings with nail or manicure scissors at the base—This will make room for the strongest. Best to cut, do not pull seedlings out, as this will disrupt the rest of the seedlings. 
  • When true leaves have developed, a few weeks away from the average last frost, they can transplant into a garden or container. Snapdragons can tolerate a light frost, so it is okay to plant outside one or two weeks before the average last frost. 
  • Continue to water to establish the plants.

Overwintering

These short-lived perennials are usually grown as annuals. Even when they do overwinter, snapdragons never seem to bloom as robustly as they did in their first year. However, they should form seed pods in the first year; if you are lucky, they may even self-sow in the garden.

Pests and Diseases

Antirrhinum majus may suffer from some pests and diseases.

Common Pests

Insects are the primary pests that affect A. majus.

  • Aphids: They target and consume the terminal growth and underside of leaves. Aphids consume the liquids in the plant and may cause a darkened or spotted appearance on the leaves.
  • Frankliniella occidentalis: These insects affect even strong growing and healthy Antirrhinum; they are commonly seen in newly opened flowers. They will cause small lesions in the shoots and flower buds of A. majus as well as remove pollen from the anther. This case is difficult to treat, but may be kept manageable with the predatory mite Neoseiulus.

Common Diseases

Antirrhinum majus suffers mostly from fungal infections.

  • Anthracnose: A disease caused by fungi of the genus Colletotrichum. This disease targets the leaves and stem causing them a yellow with a brownish border to the infected spot. It is recommended to destroy infected plants and space existing ones farther apart.
  • Botrytis: Also known as Grey Mould, this infection occurs under the flower of A. majus. Botrytis causes wilting of the flower’s spikes and causes a light browning of the stem below the cluster of flowers. Botrytis causes quick and localized drying and browning in the flower, leaves, and shoots of A. majus. In warmer weather, Botrytis becomes more severe. Treatment of Botrytis involves cutting off the infected stock and clearing the surrounding area of A. majus from any of this debris.
  • Pythium: Wilting in the plant may be caused by a Pythium species fungal infection if the plant is receiving adequate water.
  • Rust: Another fungal disease that A. majus is susceptible to is rust. It can first be seen on the plant as light-green circles, on the stem or underside of its leaves, that eventually turn brown and form pustules. Rust may cause A. majus to bloom prematurely, sprout smaller flowers, and begin decomposition earlier.
  • Stem rot: A fungal infection, it can be seen as a cottony growth on the stem, low, near the soil. If infected, it is suggested the plant be destroyed.

III. How to Get Snapdragon to Bloom

Snapdragons are known for their colorful blooms. They start blooming in early spring, and keep blooming all season long. They are short-lived perennials that act like annuals, and don’t usually flower for more than one season.

The right amount of sunlight is the secret sauce to getting your snapdragons to bloom: from full sun to partial shade, adjusting the amount of sun your plants get is the answer. Deadheading the dying flowers will keep your plant blooming abundantly.

IV. Uses and Benefits 

Garden snapdragon is most commonly clustered in flowerbeds and gardens. Popular for its bright, attractive flowers with their distinct dragon-snout shape, this plant is a mainstay in most traditional flower gardens and is used in patio containers, borders, and flower boxes. It is often planted with lower-growing flowers like lobelia and pansies for a satisfying height contrast.

Snapdragon (Antirrhinum majus) Details

Common name Common Snapdragon, Garden Snapdragon, Snapdragon
Botanical name Antirrhinum majus
Plant type Annual
Hardiness zone 7a, 7b, 8a, 8b, 9a, 9b, 10a, 10b
Growth rate Medium
Height 0 ft. 6 in. - 3 ft. 0 in.
Width 0 ft. 6 in. - 3 ft. 0 in.
Sunlight Full sun (6 or more hours of direct sunlight a day)
Soil condition High Organic Matter
Flower color Gold/Yellow
Leaf color Green