Grow Light for Artichoke Seedlings: Long Start Plus Cold Cue
A grow light for artichoke seedlings supports the long indoor start these plants need. University of Maine Cooperative Extension notes that artichokes grown as annuals need cool temperatures to form buds the first year. Sow early, grow under bright light plus plant out into cool spring weather.
The short answer
University of Maine Cooperative Extension advises sowing artichoke seed 6 to 12 weeks before the last spring frost. Heat mats at 70 to 80°F speed germination. Seedlings grow at 75°F by day plus 65°F at night in full light. Most varieties need about 500 hours between 35°F and 50°F to form buds.
Why do artichokes need an early start?
University of Maine Cooperative Extension advises sowing seeds 6 to 12 weeks before the expected last spring frost. Expect 6 to 8 weeks after germination to grow transplants with 4 to 6 true leaves.
Utah State University Extension suggests starting seeds in early January. Plants require 2 to 3 months to reach transplantable size, the same source notes.
University of Maine Cooperative Extension adds that heat mats set to 70 to 80°F will speed germination. Utah State gives a germination range of 70 to 75°F.
How does cool weather help buds form?
University of Maine Cooperative Extension explains that artichokes grown as annuals need vernalization. Cool temperatures are provided to ensure first year bud production.
Most varieties need approximately 500 hours of exposure to temperatures between 35°F and 50°F, the same source notes. Utah State University Extension adds that artichoke requires cool spring temperatures to start the flower stalk.
Avoid temperatures above 80°F for seedlings, University of Maine Cooperative Extension advises. High temperatures can cause the plant to lose its vernalization plus stay leafy.
| Stage | Guideline | Source note |
|---|---|---|
| Sowing | 6 to 12 weeks before last frost | Start early |
| Germination | Heat mat at 70 to 80°F | Speeds sprouting |
| Seedling growth | 75°F day plus 65°F night | Avoid over 80°F |
| Cold cue | About 500 hours at 35 to 50°F | Needed for buds |
Source: University of Maine Cooperative Extension plus Utah State University Extension.
Which lights suit artichoke seedlings?
University of Maine Cooperative Extension advises growing seedlings at 75°F by day plus 65°F at night in full sunlight. Indoors, that means bright artificial light.
University of Maryland Extension notes that the natural light from a window is seldom enough for good seedling growth. Seedlings by a window usually stretch plus lean toward the panes.
Full spectrum grow lights produce thicker stems than cool white tubes, the same source notes. Incandescent bulbs give off more heat plus less light than fluorescent tubes.
How to: step by step
- Sow seed 6 to 12 weeks before the last spring frost.
- Place trays on a heat mat at 70 to 80°F.
- Move seedlings under bright grow lights after germination.
- Hold 75°F by day plus 65°F at night.
- Pot up into 2 to 3 inch pots once seed leaves open.
- Plant out 3 to 4 weeks before the frost free date for cool weather.
Troubleshooting
Stretched plants: window light only. Move under grow lights.
No buds later: not enough cool hours. Plant out earlier into cool weather.
Plants stay leafy: seedlings above 80°F. Grow them cooler.
For related reading see cannabis seedling light schedule, potting up cannabis seedlings plus hardening off cannabis seedlings. Kind Seed Co also stocks cannabis seeds.
Sources
- Growing globe artichokes in Maine (Bulletin 2075), University of Maine Cooperative Extension
- How to grow artichoke in your garden, Utah State University Extension
- Cynara cardunculus (globe artichoke), NC State Extension Gardener Plant Toolbox
- Grow lights for starting seeds indoors, University of Maryland Extension
FAQ
Can artichokes grow as annuals?
Yes. University of Maine Cooperative Extension notes that in Maine artichokes are grown as annuals from transplants because they are not cold hardy enough to survive winters reliably. NC State Extension adds that the globe artichoke is a perennial often grown as a half hardy annual.
How long do artichoke seeds take to grow?
University of Maine Cooperative Extension notes that it takes 6 to 8 weeks after germination to grow transplants with 4 to 6 true leaves. Utah State University Extension says plants require 2 to 3 months to reach transplantable size. That makes artichokes one of the longer indoor starts.
Do artichokes need much space?
Yes. Utah State University Extension advises planting artichoke 18 inches apart in rows 2 to 3 feet wide. NC State Extension notes that the large jagged leaves give ornamental interest on their own. Plan for a roomy bed before starting seed indoors.
When should artichokes be planted out?
Utah State University Extension advises planting artichoke 3 to 4 weeks before the frost free date for your area. University of Maine Cooperative Extension adds that seedlings can be hardened for two to three days before transplanting for natural vernalization once frost risk has passed.
What is natural vernalization?
University of Maine Cooperative Extension describes transplanting seedlings early in spring so they gather enough chilling hours from cool weather. The goal is at least 500 continuous hours between 35°F and 50°F. The source notes this method involves some guesswork plus offers no guarantee.
