Transfer them to pots that are a minimum 3-inch diameter, and keep the soil evenly moist. Fertilized and cared for, they grow quite rapidly and will produce four to six pairs of leaves by the time they are transplanted outdoors in mid-May. Varieties of globe artichokes are limited. The longtime standard is Green Globe Improved, which always has done well, provided the plants are started early enough. Searching through garden catalogs, you also might find Violetta, a purple and very spiny variety of artichoke with good flavor but marginal yields.
Site selection is important.
They need full sun and a reasonable well-drained soil. Transplanting can be a bit of a shock, and, as they become established, the plants grow little for the first few weeks. By late June, however, the plants will take off and soon fill the area provided for them. Globe artichokes have moderate watering and fertilizer requirements, similar to that of most garden vegetables. The edible part of the globe artichoke is the newly produced flower bud.