Globe Artichoke

Introduction

Globe artichoke (Cynara cardunculus var. scolymus) is a plant in the Asteraceae family native to the Mediterranean region.  The harvested portion of artichokes is the immature inflorescence, or bud, of which the fleshy bases of the bracts and the heart can be eaten.  Globe artichoke is a domesticated variety of cardoon, which has edible stems instead of buds, and which is still eaten in many regions of the world.  Unharvested artichoke buds will mature into stunning composite flowers that make excellent bee forage or additions to fresh and dried flower arrangements.

Types and Varieties

In mild climates where temperatures do not remain below 50º F for prolonged periods, globe artichoke is a perennial crop that is propagated vegetatively.  In perennial systems, artichokes will produce in their first year but yields will be improved thereafter.  In colder regions like New England, artichoke can be grown annually from seed.  While most if not all varieties can be grown as annuals, some varieties have been bred that reliably produce many buds in their first year after a vernalization period (see Planting section).  

Globe Artichoke Varieties
Colorado Star (A) Romanesco
Emerald Tavor (A)
Green Globe Improved Violetto
Imperial Star (A) Wonder
Imperial Star Purple (A)  
A: bred for annual production

 

Soil Fertility

Apply lime according to soil test results to maintain soil pH between 6.5 and 7.0. Artichokes can be grown on a wide range of soils but produce best on deep, fertile, well-drained soils. Lighter soils having poor water-holding capacity should be avoided. Artichokes are moderately salt-tolerant. 

PLANT NUTRIENT RECOMMENDATION ACCORDING TO SOIL TEST RESULTS FOR Globe ARTICHOKE
Globe ARTICHOKE   PHOSPHORUS (P) LBS P2O5 PER ACRE POTASSIUM (K) LBS K2O PER ACRE
SOIL TEST RESULTS NITROGEN (N) LBS PER ACRE VERY LOW LOW OPTIMUM ABOVE OPTIMUM VERY LOW LOW OPTIMUM ABOVE OPTIMUM
Broadcast and Incorporate in fall 100 75 50 0-25 0 150 100 50 0

Sidedress 3-4 weeks later 

0-50

0

0

0

0

0

0
TOTAL RECOMMENDED 120 75 50 0-25 0 150 100 50  0

 

Planting

Artichokes should be seeded 8-12 weeks before transplanting into 50-cell trays or 3-4” pots.  Seeds take 8-12 days to emerge. Germinate at 70-80º F, using heating mats if needed. If initially seeded into smaller cell trays, they can be potted up at two true leaves.  Plants require vernalization, i.e. exposure to cold temperatures to induce budding.  The most foolproof way to vernalize plants is to move them to a cooler set to 45-50º F for at least ten days, although the amount of chilling required varies by variety.  Alternatively, transplanting can be timed so that transplants get their chilling time outdoors (use row cover if frost is expected).  However, this is less reliable than artificial vernalization and coolers should have ample space in spring for seedlings. 

Field Culture

While the vernalization process is somewhat involved, this crop is mostly trouble-free in the field with few pests, and offers New England customers a unique Mediterranean treat. Artichokes are large plants and require ample space: 2-3' between plants in 4-6' rows.  Straw mulch may reduce soil temperatures (which can benefit plants in hot weather), but recent research on straw and plastics mulch effects on artichoke production have mixed results.  Plants need an inch of water per week, for which drip irrigation is useful. Artichoke buds should begin to form in late July.  If desired, the healthiest artichoke plants with several side shoots can be split at the end of the season and planted into unheated high tunnels under row cover for an early June harvest the following year. 

Perennial artichokes have been successfully overwintered in experimental settings (see Northeast SARE project FNE 14-809) in northern New England with a combination of straw mulch and low tunnels.  While it is possible that refinement of this system could result in earlier harvests and higher yields, it is unclear whether the proportion of plants that survive winter would be large enough to warrant overwintering versus annual production. 

Harvest and Storage

Yields vary based on variety and cultural practices.  Plants commonly produce 10-20 buds each, but only 2 – 3 of these will be primary buds.  Primary buds are typically of a large enough size to market individually, greater than 3” in diameter.  The remainder of the buds are “secondaries” and will form at plant axials further down in the plant.  While these are smaller, they are equally delicious and can be sold by weight, quart container, etc.  Secondary buds can be eaten much like larger sizes, but are often more tender with a larger proportion of the bud being edible.  Artichokes are marketed in 22 lb cartons, and buds are graded in the following classes: 18s are larger than 4.5" in diameter; 24s are 4-4.5"; 36s are 3.5-4"; and 48s are 3-3.5".  Average diameters in New England tend to fall between 3 and 4". 

Buds are ready to be harvested when they feel fairly compact for their size when squeezed.  Bracts of overmature buds will begin to splay apart, and become bitter and tough.  Clip buds with 2-3” of stem attached.  Wearing gloves is recommended for guarding against spines, and because artichoke plant residue can be difficult to wash off.  After harvest, buds should be cooled quickly and stored at temperatures close to 32º F, but should not be allowed to freeze.  Artichokes can last 2 weeks or longer in storage. Weekly or biweekly harvests are sufficient, depending on size classes of the buds being produced and the time in the growing season.  Plants will continue producing (mostly secondary buds) up until a hard frost.