75-85 day maturity. Lactuca sativa var. asparagina ‘Summer 38 Celtuce’. Summer 38 Celtuce Lettuce Seeds. Non-GMO, cool-season annual heirloom. This variety of Chinese stem lettuce has pointed, light green leaves. Good tolerance to heat or cold and slow bolting. This celtuce can tolerate 100°F for a few days as it is slow bolting. This variety has superior stem development during the warm season. Contrary to popular belief, celtuce is not a cross between lettuce and celery; this idea rose to prevalence in the late 19th century upon its introduction to America. Approx. 18,500 seeds / oz.