Snapdragon flowers on long stems grown in a greenhouse using farmer bailey plugs starter plants
 
Common Name Snapdragon
Genus 
Antirrhinum
Species
majus
Family
Plantaginaceae
Life Cycle  Tender perennial, grown as hardy annual.
Tray Size  210
Plug Care
Transplant within 2 weeks of arrival, or bump up into a larger cell until you can transplant.
Netting / Staking
1 layer of support netting
Temperature Range
Snapdragons like it cold, especially when young. Short drops to 20F or colder are tolerated well.
Spacing
Plant in clusters of 2-3 seedlings, with 6" spacing. Plugs are multi-seeded with this in mind.
Soil Preference
Well drained, generally fertile soil.
Day Length
Facultative long day
Pinching
Pinching will produces more, but smaller stems per plant. I prefer to not pinch, resulting in taller stems with larger flowers. Use a wider spacing when pinching.
When to Plant
In autumn, plant 3-4 weeks before first frost. In spring plant 3-4 weeks before last frost. These cold hardy plants prefer frosty conditions to hot conditions. Plant at the same time as Stock and Campanula.
Harvesting
Harvest when 1/3 to 1/2 of the buds are open.
Post Harvest Care
Harvest into a holding solution. Snapdragons are moderately sensitive to ethylene.
Diseases / Insects
Generally easy growing. Rust is an issue in some environments. Harlequin bugs love snapdragons in summer.
Bailey's Notes
When planted in fall or late winter, snapdragons will reach 3-4" easily. Different series bloom at different times and you can extend your harvest window by planting several series at the same time.
Resources

Mississippi State University Extension: Snapdragon for the Farmer Florist

Syngenta Flowers Snapdragon Madame Butterfly Culture Guide

American Takii Antirrhinum (Snapdragon) F1 Chantilly™ Series Culture Sheet

 

Snaodragon Madame Butterfly Rose grown from Farmer Bailey plugs at Ardelia Farm in a greenhouse