AAS Winner. 65 days. Recommended by Utah State University, Organic Buttercrunch is the most popular of the butterhead varieties. Approx. 16,000 seeds/oz. These non-GMO Buttercrunch seeds grow into vibrant, green heads of lettuce that are ready to harvest in 60 to 70 days. The Buttercrunch lettuce can be grown in most zones, including colder zones. The leaves of the Buttercrunch have a mildly sweet, buttery flavor.