Maine typically experiences a continental climate, which means warm summer weather and cold winter temperatures. The coastal regions enjoy a more moderate climate than Maine's colder, drier north. The entire state sees snowfall in the winter. Maine falls under United States Department of Agriculture (USDA) Hardiness Zones 3 to 5, which means gardeners must select plants that can handle cooler weather. Various perennials, shrubs and ferns thrive in Maine gardens.
The marsh marigold (Caltha palustris), an herbaceous perennial in the Ranunculaceae plant family, generally grows well in USDA Zones 3 to 7. Native to North American marshes, stream margins and swamps, this plant prefers very wet soil in partly shady to fully sunny locations. Marsh marigolds bloom yellow, buttercup-like flowers from April through June. Yellow stems reach up to 18 inches in height. Potential problems include rust and powdery mildew. Maine gardeners often plant the marsh marigold along pond edges or in water gardens.
New England Aster
The New England aster (Aster novae-angliae) belongs to the daisy family (Asteraceae). Indigenous to eastern regions of North America (N.A.), this plant grows well in USDA Zones 4 to 8. Reaching 3 to 6 feet in height and 2 to 3 feet in width, the New England aster prefers moist soils in full sun positions. Numerous flowers bloom in August and September, featuring dark pink to purple petals surrounding yellow center disks. Aster wilt and powdery mildew occasionally affect this plant. Maine gardeners often plant the New England aster in butterfly, cottage and native plant gardens.
American Maidenhair Fern
The American maidenhair fern (Adiantum pedatum), a member of the Pteridaceae plant family, naturally occurs in eastern regions of North America. Winter hardy in Maine USDA Zones 3 to 5, this fern variety prefers humus-rich, acidic soils in full shade positions. This clump-forming plant reaches 30 inches in height and 18 inches in width. American maidenhair ferns feature frilly leaves and red-brown to black stems. The leaves sometimes turn brown during hotter summer weather. Gardeners frequently plant this ornamental fern in borders, shaded rock gardens and Maine native plant gardens.
Carolina rose (Rosa Carolina), a deciduous shrub in the Rosaceae family, is a North American native plant that grows well in Maine USDA Zones 4 and 5. This plant matures to heights between 3 and 6 feet with spreads ranging from 5 to 10 feet. The Carolina rose grows best in wet soils that receive full sun. Pink flowers bloom in May and red hips appear in the summer. The Carolina rose often suffers from numerous rose diseases, including rose rosette, powdery mildew and rust. Rose midges, spider mites and aphids often feed on the foliage. Maine gardeners often plant Carolina roses in native plant gardens, rose gardens and borders.
The shadblow serviceberry (Amelanchier Canadensis), a member of the rose family (Rosaceae), works well in Maine native plant gardens and woodland gardens. This deciduous shrub prefers well-drained soils in partly shady to fully sunny locations. Native to Eastern North America, this plant grows well in Maine USDA Hardiness Zones 4 and 5. Mature shadblow serviceberry plants reach up to 30 feet in height with spreads up to 20 feet. Fragrant, white flower clusters bloom in April and May, followed by edible, purple-black berries early in the summer. The green leaves turn orange and red shades in the fall. Possible problems include leaf spot, leaf miners and scale.