Globe Artichoke

Sow indoors in flats at 70 to 80F, 8 to 12 weeks before your last frost date. Seedlings emerge in 8 to 12 days and need 2 to 3 months to reach transplantable size, so late starts cost you the whole crop. Artichoke is a slow, big seedling that must be sizeable before it meets the cold spell that triggers budding, and a plant started late simply grows leaves all summer and never sets a head.

Transplant 3 to 4 weeks before your frost-free date, spacing plants 18 inches apart in rows 2 to 3 feet apart. Give them deep, fertile, well-drained soil high in organic matter. Going out ahead of the frost-free date is deliberate: the cool weeks that follow finish the chilling that sets buds, and artichoke tolerates light frost. The wide spacing matters because a mature plant sprawls 3 to 4 feet and crowded plants trap the humidity that aphids and gray mold exploit.

Beginning 4 weeks after transplanting, apply about 2 teaspoons per plant of a nitrogen fertilizer such as 21-0-0, and repeat every 4 weeks through the growing season. Water it in. The edible bud is an unopened flower riding on a lot of leaf growth, and artichoke is a heavy nitrogen feeder - starve it and you get small, tough heads that open early.

Before transplanting, hold the seedlings at 35 to 50F for roughly 10 days - a cold frame, an unheated porch, or simply setting them outside during a cool spell all work. Do not let them freeze. Artichoke will not initiate a flower stalk until it has felt sustained cold, so a plant that never gets chilled stays vegetative. This cold treatment is what lets growers outside zone 7 to 9 harvest buds in the first year instead of waiting for a winter the plant may not survive.

Supply 1 to 2 inches of water per week in several applications rather than one soaking, and do not let the bed dry out while buds are sizing. Artichoke is a heavy water user, and a plant checked by drought while the bud is forming pushes the bracts open and turns the head fibrous. Once a bud opens it is inedible, and no amount of later watering reverses it.

Check leaflets weekly through the warm, humid stretch of summer. Treat when you average about 3 aphids per leaflet, using a strong stream of water to dislodge them or insecticidal soap on the leaf undersides. Destroy crop residue right after harvest to deny them a bridge to next year. Artichoke aphid outbreaks build under high temperatures with very high humidity, and the damage is honeydew rather than chewing: it coats developing buds, sooty mold grows on it, and the head is downgraded even though the plant lives. Aphids also carry the viruses that decline a perennial planting.

Harvest each bud once it reaches full size but before the bracts begin to open, cutting 2 to 3 inches of stem with it. Take the large terminal bud first; the smaller side buds follow and are worth taking too. Keep cutting until frost. The bud is an immature flower, and once the bracts loosen the tissue turns woody and the choke develops - flavor and tenderness fall off fast. Cutting the terminal head also releases the side shoots to size up.

Cut the plant back, mound 4 to 6 inches of soil over the crown, then pile 8 to 12 inches of leaves or straw on top. Pull the cover off as growth starts in spring. Where winters are too hard for that, dig the roots and store them in moist sand or peat in a cold cellar that stays above freezing. Artichoke is a tender perennial that dies at the crown, not the leaves - the growing point sits at soil level and is what the cold kills. It carries over as a perennial only in milder-winter areas, and an insulated crown gives a plant that buds earlier and heavier than any first-year seedling.

After the last buds are cut, take the plants down to ground level and leave them cut back for 2 to 3 months, then chop the tops and bury the debris under at least 6 inches of soil. Pull any thistles and related weeds nearby. Artichoke plume moth larvae overwinter inside the old stalks and crowns, and they are what tunnels into next year's buds. Cutting the planting down and burying the residue removes their shelter, and this sanitation is the primary control in a perennial planting. Thistles are the same plant family and act as a reservoir.