How to Grow Snapdragons

Pick the right height

Snapdragons range from 6-inch carpet types to 3-foot cutting varieties, and choosing the right group solves most later problems. Nebraska Extension sorts them this way:

• Dwarf (6 to 10 inches): Floral Showers, Floral Carpet, Magic Carpet and Tahiti. Good for edging, containers and window boxes.
• Intermediate (16 to 24 inches): Chimes, Crown, Freesong, LaBella and Montego, plus Snaptastic, which branches well and needs less staking.
• Tall (24 to 30 inches or more): Panorama, Rocket and Sonnet. Cornell singles out Rocket as a good cut flower.
• Trailing: Candy Showers was the first trailing series from seed and suits hanging baskets.

In Florida, UF/IFAS reports that Floral Showers, Aromas, Snapshot and Twinny perform well even in warm spells, though no snapdragon is truly heat-tolerant. For high-tunnel cut flowers in New York, Cornell found intermediate-season series such as Animation, Apollo, Overture and some Potomac the most productive in spring and fall.

Starting seed indoors

Cornell and UF/IFAS say to sow 6 to 8 weeks before planting out. Nebraska Extension allows 8 to 10 weeks to get good-sized transplants. The seed is tiny, at about 6,000 to 9,000 seeds per gram, and needs light to germinate, so press it onto the surface of a seed-starting mix and do not cover it. Keep the mix moist under a clear cover.

Sources give a range of germination temperatures. Cornell lists 60 to 70°F with emergence in 10 to 14 days. UF/IFAS gives 7 to 10 days at 64 to 68°F. Nebraska Extension reports two to three weeks at 55 to 60°F and notes that cooler growing gives shorter, sturdier seedlings. UF/IFAS adds that chilling the sown seed at 40 to 47°F for 3 to 5 days before warming it makes germination more even.

Once seedlings are up, give them strong light. UF/IFAS warns that low light produces weak, stretched stems and fewer flowers.

Planting out

Snapdragons tolerate frost, so they can go out before your last frost date. Nebraska Extension plants them in early spring with pansies and violas; the dates for your zone above show when that is. Harden the plants off first.

Choose full sun. The plants tolerate light shade but flower less. Any soil works if it drains well. Illinois Extension notes they like soils that lean alkaline, and Nebraska Extension says adding organic matter to heavy clay builds better roots. UF/IFAS spaces plants 6 to 12 inches apart. Penn State’s seed-spacing table gives 8 to 18 inches.

In the North, a second planting in mid to late summer is well worth it. Illinois Extension says these plantings perform very well and keep blooming until a hard freeze. Cornell’s Zone 5 schedule for a fall cut-flower crop sows seed in late May and transplants in mid-July.

Pinching, staking and a second crop

Pinch the growing tips when plants are 2 to 4 inches tall to get more flower spikes. Cornell’s tunnel trials found that pinching at six leaves raised stem yields by 30 to 50 percent at wide spacing but delayed the first harvest by 2 to 3 weeks.

Tall varieties need support. Stake them or run horizontal netting over the bed. Texas A&M AgriLife in San Antonio, where wind often breaks Rocket types, suggests growing one plant in a 5-gallon container inside a tomato cage.

Keep cutting or deadheading spent spikes to push out side shoots. When the first flush finishes, UF/IFAS recommends cutting plants back to 5 or 6 nodes above the ground and feeding them when the new buds show, for a second crop.

Water and feeding through summer

Snapdragons have low drought tolerance, so water during dry spells. Flowering slows in the hottest weeks. Nebraska Extension’s fix is steady watering, a weekly water-soluble fertilizer and regular deadheading, cutting stems back to a sturdy point that can hold up new growth. Bloom picks up again as nights cool, and Cornell notes snapdragons flower well into fall.

Snapdragons in warm-winter regions

In Florida, along the Gulf Coast, in the low desert and in coastal California, snapdragons are a fall-to-spring flower. UF/IFAS lists October through February for zone 9 and November through February for zones 10 and 11. University of Arizona’s Phoenix-area chart runs from mid-September to early February. Plants bloom through winter and fade by April or May. UF/IFAS notes that heat, not day length, is what stops them. North Florida gardeners may need to cover plants on the coldest nights.

UF/IFAS suggests pairing them with pansies and sweet alyssum for a cottage-garden look. That is a design choice, not a pest benefit.

Cutting snapdragons for the vase

Cut spikes when 5 to 7 of the lower florets are open. UF/IFAS warns that cutting earlier gives weak color and smaller flowers. Cut before bees work the lower florets, because pollinated florets drop early. Stand the stems upright in water. Cornell notes that spikes laid flat curve upward at the tip.

Expect a vase life of 7 to 10 days, though bright colors fade by about day 5. Stems hold 3 to 4 days in water at about 40°F. Keep them away from ripening fruit, because snapdragons are sensitive to ethylene.

Common problems

• Rust: small yellow swellings on leaves and stems that burst open to release rust-colored spores. Grow rust-resistant strains and pull infected plants.
• Powdery and downy mildew: white or gray growth that stunts plants. Improve air flow and keep foliage dry.
• Botrytis gray mold: brown, fuzzy rot on spikes and stems in damp weather. Remove affected parts.
• Stem and root rot: seedlings wilt and collapse in wet soil. Improve drainage.
• Aphids and spider mites: aphids cluster on new growth, and mites leave bronze stippling in hot, dry weather. Treat early.