Delphinium long stemmed blue flower farmer bailey cut flower plug perennial
Common Name Delphinium
Genus  Delphinium
elatum, chinesnis, grandiflorum, hybrids
Life Cycle 
Perennial, often treated as biennial in warm climates.
Tray Size  125
Plug Care
Transplant within 2 weeks of arrival or bump up into a larger cell until you can transplant.
Netting / Staking
Varies by location. Delphinium will need staking if grown in high wind and/or heavy rain locations.
Temperature Range
-35 to 75F
6-12". 18" in cool summer locations.
Soil Preference
Fertile, moisture retentive soil.
Day Length
Facultative long day.
Pinching No
When to Plant
In hot summer locations, plant 2-4 weeks before first frost for bloom the following spring. Can also be planted in a cool greenhouse in winter for spring flower, as you would grow snapdragons. In cool summer locations, plant any time and establish as a true perennial.
Harvest when 1/3 of florets are open. Cut to the ground to encourage regrowth.
Post Harvest Care
Use a holding solution. Delphinium is highly sensitive to ethylene and treatment should be considered.
Diseases / Insects
Powdery mildew should be managed at first sign of infection. Belladonna types seem to be more susceptible to mildew. Broad mites and cylclamen mites can cause puckering of the foliage and distortion of the flowers. Manage with predatory mites.
Bailey's Notes
The only thing to know is that Delphinium hate heat. If you live in a hot summer location, you need to plant in the fall or late winter and grow them like a hardy annual. In locations with cool summers they become long lived perennials. Cut back to the ground when you harvest and they will often regrow and rebloom. When established as long-lived perennials, thin the new growth to 3-5 shoots per plant to produce better quality flowers.
Resources National Garden Bureau Delphiniums, a perennial favorite

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