Do Ferns Like Sun or Shade?

If you'd like to add a woodland look to a shady or semi-shady garden spot, then plant ferns to fill in the area with their graceful fronds, or leaves. Although thousands of fern species exist, some do especially well in a garden, and most also can grow in the proper environment indoors. A varied group of plants, ferns need moist soil, and most grow best in partial to full shade. Certain types, though, also handle some sunlight, and a few even tolerate full-sun exposure.

Because they're native to natural woodlands, most ferns thrive in a moist, shady environment and do well in a shaded spot near taller plants or trees, or in shade cast by the north side of a building or porch.

Examples of ferns that thrive in shade include the cinnamon fern (Osmunda cinnamomea), which is perennial in U.S. Department of Agriculture plant hardiness zones 3 through 9, where it can reach a height and width of 3 feet. A low-maintenance plant, it gets its name from the rust-colored fibers at the base of each of its fronds.

Some ferns tolerate short periods of filtered, morning sunlight, and a few do well in full sun when grown in a spot that is consistently moist. The lady fern (Athyrium filix-femina) is an example of the latter, though it grows best in partial to full shade. Hardy in USDA zones 4 through 8, lady fern grows up to 3 feet tall and nearly as wide, and it needs shelter from wind to protect its stiff fronds.

Another fern that can grow well in a sunny spot is the Argentine false maidenhair fern (Adiantopsis chlorophylla "Tucuman"), which also grows in partial sun. It reaches about 2 feet tall and has especially lacy fronds with dark central stems. It becomes a 2-foot-wide clump and is hardy in USDA zones 7b through 10.

All ferns need organically rich, well-drained soil to grow well. If your planting area's soil contains clay, then mix about a 2-inch-thick layer of composted pine bark into the top 10 inches of the soil to increase its drainage. If the planting site has sandy soil that drains rapidly, then incorporate a 2-inch-thick layer of compost or other organic material with the top 10 inches of soil to help retain moisture.

Most ferns also prefer acidic soil, with a pH level of 4 to 7, although a few prefer a more neutral-to-alkaline soil with a pH of 7 to 8. They include the ebony spleenwort (Asplenium platyneuron), which is hardy in USDA zones 3 through 8. Determine soil pH with a commercial soil test kit, available at home and garden centers, and follow its directions to adjust your soil's pH level as needed; add ground limestone to raise pH or make it more alkaline, or add sulfur to lower pH for more acidity. For example, incorporating 0.4 pounds of sulfur with 10 square feet of soil that has a pH level of 7 lowers the soil's pH level to 5.

It's best to purchase ferns from a reputable dealer who certifies the plants are healthy and disease-free. Although you might see a desirable fern growing in the wild, never collect it for planting at home.

A fern doesn't grow from a bulb but has fibrous roots that may grow into a ball as the plant matures.

In regions with cold winters, ferns are best planted outdoors in spring after danger of frost has passed; in areas without winter frost, plant ferns in fall so their new growth isn't stressed by hot summer weather. Space ferns according to their mature width; for example, allow 4 feet between plants that attain a final width of about 4 feet, and plant a fern in a hole that's about twice the size of the plant's root ball, but keep the fern at the same soil depth it was in its nursery pot.

Ferns also can be houseplants, growing in any type of container, including a hanging basket. When indoors, ferns usually do well in indirect light, such as in front of a northern window that is covered by a sheer curtain. Some types, including the bird's nest fern (Asplenium nidus), can grow in brighter light as long as they are not in direct sunlight, which can burn the fronds. About 3 feet high and 2 feet wide, bird's nest fern has undivided, shiny green fronds and can grow outdoors all year in USDA zones 11 through 12.

When growing a fern indoors, it's important to raise the humidity in its environment to no lower than 30 percent. Mist the plant often with water, increasing the watering frequency when the air is dry from heating or air conditioning. Placing the plant's pot on top of pebbles that fill a tray containing water also helps raise humidity, but keep the water just below the tops of the pebbles.