Clearfield is also crossbred with higher yielding varieties to produce an overall hardier plant. Hybrids of the two are hardier and calmer, in addition to exhibiting natural hybrid vigor. It was replanted with hardier beech trees. Kumquats are much hardier than citrus plants such as oranges. Indeed, the Hampshire may be considered a larger and trifle coarser and hardier Southdown. They are significantly hardier and of higher yield than criollo. Their leaves are typically hardier and longer lived but require more energy to grow. Hardier breeds of sheep can be left on hillsides. Located just outside these farms, hardier vegetables are grown such as potatoes, carrots, and onions. Once established it is hardier and tolerates temperatures down to . Selective breeding under exposure to both chemicals and ultra-violet light produced even hardier "Caulerpa" strains. The cactus collection also extends outside the conservatory where some hardier species can be found. "Musa balbisiana", a hardier species of lesser genetic diversity than "M. acuminata". The resulting fish had longer fins, long barbells, pompom nostrils, and were hardier than koi. "Myeongi" is a specialty of Ulleung Island, where the leaves grow wider and hardier.