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Native to the mild climates of the Southern Mediterranean, globe artichokes (Cynara scolymus) are half-hardy perennial thistles that are easily killed by temperatures below 20 degrees Fahrenheit. Where winters are mild, you can grow globe artichokes as perennials, replacing plants every four years. In most areas, though, globe artichokes must be grown as annuals. Growing artichokes from seeds started in late winter will produce edible buds in midsummer and fall. The edible plant parts are the immature artichoke flower buds.
Types of Artichokes
Green artichoke varieties include ‘Imperial Star,’ the best variety to handle as an annual, and ‘Green Globe,’ a heavy-bearing perennial hardy to Zone 7.
Purple artichokes include ‘Violetta,’ an heirloom variety hardy to Zone 6, and the fast-maturing ‘Opera’ hybrid.
How to Plant Artichokes
Start artichoke seeds indoors in late winter, under bright florescent lights. The large seeds will germinate within a week at warm room temperatures, and seedlings should be potted into larger containers as they grow. Six weeks before your last frost date, start hardening off seedlings by gradually exposing them to bright sun, wind and cool temperatures.
Set artichoke plants out in prepared beds 3 to 4 weeks before your last frost date. Exposure to cool temperatures below 45 degrees is necessary to trigger flowering. Before transplanting artichokes, enrich each planting hole with a balanced organic fertilizer, and space plants 3 feet apart.
Globe artichokes have average fertility needs, similar to those of tomatoes. In areas where artichokes are grown as perennials, container or bare-rooted plants can be set out in spring. When setting out artichoke seedlings, plant them slightly high, so that the crown is well above the soil line.
For recommended planting dates for your local climate — and to design your garden beds — try our Vegetable Garden Planner.
A month after planting, drench actively growing artichokes with a high-nitrogen liquid fertilizer to invigorate new growth. Artichoke plants grow 3 to 5 feet tall, and their spiny gray-green foliage makes them useful as edible ornamentals. As older leaves wither, gather them up and compost them.
Harvesting and Storage
In mid- to late-summer, watch for upright flowering stems topped by artichoke flower buds. Use a sharp knife to cut globe artichokes with a 2-inch stub of stem attached when the lowest scales on the bud begin to open, but the top is still tight. Refrigerate artichokes immediately, and wash just before cooking them. After the first artichokes are harvested, plants typically produce a second crop of smaller buds.
For long-term storage, you can freeze whole washed artichokes that have been steamed until just done. When thawed, the artichokes can be cut in half and grilled.
Artichoke seedlings are not as uniform as other vegetables, and some plants are stronger producers than others. Where globe artichokes are winter hardy, superior plants should be propagated vegetatively, by cutting off the small “pups” that emerge in spring and rooting them.
Vigorous artichoke plants also may be allowed to bloom and set seed where summers are long enough for the seeds to ripen. Choose a large bud from a favorite plant and let it stay on the plant until it blooms and then shrivels to brown. Cut the dried flower and keep it in a paper bag indoors for two weeks before shattering it and gathering the seeds. Under good conditions, artichoke seeds remain viable for at least six years.For information on cooking this delectable crop, check out How to Cook an Artichoke and Many Ways to Eat ’Em. Plus, for growing advice for many more garden crops, check out our complete Crops at a Glance Guide.
Contributing editor Barbara Pleasant gardens in southwest Virginia, where she grows vegetables, herbs, fruits, flowers and a few lucky chickens. Contact Barbara by visiting her website or finding her on Google+.