The mention of window boxes usually brings to mind cheery annual flowers in bright primary colours. However, if your window boxes are on the north side of your house or under shade trees, you may want to consider pairing smaller varieties of ferns with shade-loving annual or perennial flowers for a more natural, woodland look. There are many varieties of hardy ferns under 2 feet in height that are suitable for container gardens.
Growing Ferns in Containers
Ferns require a location in full to part shade, moist but well-drained soil rich in humus and a pH level of 6.0 to 7.0. Mulch plants with peat moss or compost, and provide regular watering during dry periods. Feed regularly during the growing season with an organic fertiliser such as fish emulsion or blood meal. Leave frost-killed fronds of deciduous ferns until spring to protect new shoots. Then trim them back to their base as the new fronds begin to grow.
Maidenhair Fern (Adiantum pedatum or A. aleuticum)
Maidenhair fern may look delicate, but it is hardy to minus 45 degrees Fahrenheit, making it a good choice for northern regions. With arching black stems and bright green leaflets, the fronds are often used in cut flower arrangements. Plants are slow growing to a height and width of 12 to 24 inches and can be divided after 4 to 5 years.
Japanese Painted Fern (Athyrium niponicum var. pictum)
This diminutive fern with its purplish stems and variegated silver and green feathery fronds makes a striking accent. Reaching a height of 12 to 24 inches with a similar spread, it works well in containers. Hardy to minus 1.67 degrees Celsius, it is deciduous in most areas but may be evergreen in milder climates. Crowns can be divided in spring every 3 to 4 years.
Lady Fern (Athyrium filix-femina)
Lady ferns have been popular since Victorian times, when they were widely used in naturalised gardens. This medium-size variety, reaching heights of 20 to 23 inches and slightly less in width, features feathery green fronds with tassel-like tips. Hardy to minus 1.67 degrees Celsius, Lady fern needs protection from strong winds, as the stems break easily. Divide plants in spring every 3 to 4 years.
Christmas Fern (Polystichum acrostichoides)
This widely grown fern is a native of Eastern North America and is cold-hardy to minus 1.67 degrees Celsius, yet it also adapts to heat and humidity. In earlier times, this evergreen fern was used as decoration during the winter holidays, from which its common name derived. Reaching a height and width of 12 to 23 inches, this fern's leathery fronds are evergreen in many regions. This compact, dark green fern with simple, deeply cut leaflets makes a bold accent for companion plants.