Students at the Colorado State University studied varieties of lettuce seeds to determine which were most resistant to bolting. Batavian lettuce varieties, a cross between leaf lettuce and head lettuce, came out on top. The most resistant Batavian cultivars were Nevada, Sierra and Tahoe. Butter lettuce varieties also showed good resistance to bolting. The study also showed that red romaine lettuces were good for individual leaf harvest and picking as baby leaves.