Succulents struggle to grow in the rocky outcrops of alpine regions. Sparse rainfall and thin or non-existent topsoil helped them evolve with thick, fleshy leaves that hold water and help them withstand drought. Shallow root systems, important in an environment where the ground is primarily solid rock, may dry out while the leaves continue to hydrate the plant. Because of their origin high in the mountains, many succulents are winter hardy in all but the most extreme northern climates in the United States, and many are reliably hardy throughout the state of Maine.
Made up of over 400 cultivars, according to the Colorado State University Extension, sedum (Sedum spp.) is native to alpine regions and and will grow throughout the state of Maine. It is hardy through USDA Zone 3, depending on the variety. Most varieties have large leaves in proportion to the tiny star-shaped flowers. The flowers begin to bloom late in summer and gradually deepen in color in most varieties. The most popular in home gardens is S. herbstfreude or 'Autumn Joy' sedum. Its flowers begin as a deep pink, deepen to maroon and finally deep red. They will remain on the plants right through winter.
Hen-and-chicks or houseleeks (Sempervivum spp.) are low-growing, spreading succulents that are hardy through USDA Zone 3 with winter protection. Houseleeks comes in varieties with foliage in all shades of green; some varieties have a burgundy tint. Mature plants may send up a flower stalk and produce a cluster of red, pink or yellow flowers. Eventually the mother plant will fade and die, leaving the chicks to take over. Hen and chicks will grow in most any type of soil as long as it is well-drained. They prefer full sun but will also grow well in partial shade.
Hardy through USDA Zone 5, the beaked yucca variety (Yucca rostrata) will survive winter along the coast of Maine, but may die without winter protection in the interior of the state. It will slowly grow to an 8- to 10-foot tree with a thick trunk and a globe of blue-green, 2-foot long leaves. Plant yucca in full sun and well-drained soil. Mature specimens often develop dual heads atop their shaggy trunks.