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Nathan Johanning
Extension Educator, Local Food Systems and Small Farms
University of Illinois Extension
402 Ava Rd.
Murphysboro, IL 62966
Phone: 618-687-1727
FAX: 618-687-1612

Vegetable Production

Vegetable Production


Globe Artichoke

     Globe artichokes (Cynara scolymus L.) are thistle-like herbaceous perennials that are grown for their immature flower bud. The “globe” is the flower bud which includes the edible parts: the fleshy bases of the outer bracts, the inner bracts, the receptacle, and interior portions of the floral stem. Globe artichokes are adapted to a wide range of temperatures with 70-75oF (day) and 50-55oF (night) optimum for the highest quality flower bud development. The suitable temperature range for production is between 45oF and 85oF. Plants can tolerate temperatures above 85oF, but high temperatures will cause faster development of the flower, which decreases flower bud quality. The silvery-green plants reach approximately 4-5 feet in height and spread outward about 5-6 feet.
     Many consumers are familiar with the globe artichoke as they can be used in a wide variety of dishes and are often thought of as a gourmet crop. Many cold-tolerant globe artichoke cultivars are available that can be grown as perennials in the lower Midwest. Vegetable growers often have problems producing crops during the early spring to fulfill their market needs during this time of year and over-wintered globe artichokes will produce edible flower buds starting in late April or early May in the lower Midwest.
     There are several cultivars suitable for the lower Midwest environment including ‘Green Globe’, ‘Imperial Star’, ‘Emerald’, and ‘Northern Star’. All can be propagated by seed. In moderately-cold climates, ‘Green Globe’, and ‘Imperial Star’ are grown as annuals, while ‘Emerald’, and Northern Star’ can over-winter and be grown as perennials with proper care. ‘Green Globe’ produces large edible buds under ideal growing conditions, but tend to be smaller in climates not well adapted to their production. ‘Imperial Star’ will produce a high quality edible bud approximately 80 days after planting if plants are properly vernalized prior to field planting. Varieties that are grown as perennials such as ‘Northern Star’ and ‘Emerald’ will need to be protected during the winter months in some manner.

Tips for Artichoke production in the lower Midwest:

1) Sow artichoke seed (¼ inch apart and ¼ inch deep) indoors about 2 months      before the date of the last spring frost, and maintain soil temperatures near 70 to 80oF for adequate germination.

2) Transplant into 3-4 inch pots or large-sized cell-paks about one week after seedlings emerge.

3) At the 2-3 leaf stage, place plants in a coldframe or similar structure to vernalize seedlings (keep plants at minimum temperatures between 35 and 50 oF) for about a month.

4) Transplant seedlings about 3 feet apart on raised beds that are about 6 to 7 feet apart.

5) Fertilize plants about three times per year (March, May and September) with a complete fertilizer applying about 50 lbs N per acre at each application.

6) Place straw mulch around plants to keep soil temperatures cooler, lower weed pressures, and to conserve and maintain constant soil moisture.

7) To over-winter cultivars such as ‘Emerald’ and Northern Star’, stems and foliage should be cut down to soil level in early December, covered with about 2 inches of wheat straw and a heavy spun-bonded rowcover (about 1.8 oz per ft2).

8) Straw and rowcovers should be removed from plants in mid- to late-March and artichoke plants will start producing edible buds in late-April to early-May for about 6 weeks.

9) This vegetable has few pest problems when grown in the lower Midwest, although weed control is essential to maintain a productive planting.

     Artichokes are ready for harvest when the edible flower bud has reached maximum size, but before the bracts open. Mature buds can be cut from artichoke plants grown as annuals from July to October or from May to June from those grown as perennials. Cut the edible buds by hand with 3 to 4 inches of the stem remaining with the bud; remove the top one first, and then the secondary ones as they mature. To avoid harvesting overdeveloped buds during high temperatures, it is best to harvest every 1 to 2 days. But during cooler periods, harvests may only need to be done once every week or so. Artichokes can be held for about 1 month if held at or near 32°F and at 90 to 95% relative humidity. Buds that are left on the plant open to 6 inch diameter purple-blue flowers and can be dried and used in floral arrangements.
     For nutritional value, a medium-sized artichoke has 25 calories and provides 6% of the Recommended Daily Value (RDV) of phosphorus, 10% of magnesium, 8% of manganese, 10% of chromium, 5% of potassium, 4% of iron and 2% of calcium and iron. In addition to all these important minerals, artichokes are a good source of fiber (12% of the RDV), vitamin C (10% of the RDV), and folate (10% of the RDV), as well as contain about 3% protein, 0.2% fat, and no cholesterol. This vegetable can be cooked in a wide variety of dishes, and artichoke hearts are considered a delicacy by many cultures. A simple and easy recipe for steamed artichokes is provided below.

Steamed Artichokes
Ingredients: 4 large artichokes, Serving Size: 1 artichoke
Yield: 4 servings

Cooking instructions:
1. Remove the stems and cut about 1 inch off the artichoke tops. Also, remove the outer leaves and cut off any hard, spiky points.
2. Put about 2 to 3 inches of water into a large pot, insert a steam rack into the pot, and bring the water to a boil.
3. Prepare an ice bath.
4. Place artichokes on the rack and steam uncovered, until the bottom is tender and the outer leaves can be easily removed – normally takes about 25 to 30 minutes.
5. Remove the artichokes from the rack with a large spoon.
6. Briefly place the artichokes into the ice bath.
7. Drain and refrigerate until serving.

Support provided by the College of Agricultural Sciences, the Department of Plant, Soil and Agricultural Systems, and the Illinois Council on Food and Agricultural Research (C-FAR).
Published June 2007