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Sensitive Fern
Onoclea sensibilis
Description & Overview
Getting its name from its sensitivity to frost and drought, Sensitive Fern capitalizes on wet and humid environments. The large textured leaves create a grand green expanse to an understory or north side of a foundation. Sensitive Fern is the perfect addition to a shady native garden, or along the roadside or bog.
Core Characteristics
Suggested Uses:
Sensitive Fern’s fan-shaped leaves create a perfect flowing mass for a wet-shady understory, it does well in swampy areas, along rivers, or in bogs, to name a few options. The light, soft-green foliage makes it a great companion to flowering shade plants. Sensitive Fern, as its name suggests, has strict siting requirements. It cannot withstand drought or frost. Therefore, the planting location should be a sheltered location, void of prevailing winds and direct sunlight. It is crucial to check soil moisture during the dry months of summer to ensure the fern is receiving enough water.
Sensitive Fern will colonize a location; however, this happens slower than most other ferns. The root system is comprised of a hefty rhizome with numerous fibrous roots. Although not necessary, it may be beneficial to plant in a visible location.
Throughout winter, bead-like spores cover the showy fertile fronds awaiting spring. And as a sure sign of winters end, observe pale red fiddleheads emerging in spring. Cut fronds can also be a wonderful accent to a floral or container arrangement.
Wildlife Value:
Sensitive Fern has a surprisingly significant impact on native and non-native wildlife. Since this fern is only tolerant of specific humid sites, it attracts many animals with the same opinion. Salamanders and frogs will take shelter underneath the foliage and in the cool soil. Deer find themselves a nice bed amongst the fern masses and in fact, the Cayuga word for Sensitive fern means ‘Deer, what they lie on.’
Above the foliage, birds and Wild Turkeys will take advantage of the fertile fronds still standing with a great snack of spores.
There are insects that will feed upon the fronds and rhizomes, including the Sensitive Fern Borer Moth (Papaipema inquaesita), Silver-spotted Fern Moth (Callopistria cordata), Olive Angle Shades Moth (Phlogophora iris), the fern aphid Amphorophora ampullata, and the larvae of the sawfly Stromboceros delicatulus. Some aphids will suck on the juices of the fern, but it poses no health concerns.
Sensitive Fern is poisonous to horses if eaten in large amounts. Deer like to nibble on the infertile fronds, but usually not to a debilitating extent.
Maintenance Tips:
Sensitive Fern doesn’t require much maintenance in optimal locations. Over time, the fern can begin to get crowded, in which case, space it out by separating the rhizomes in the spring and re-planting. This can be a good routine to execute every couple of years to prevent any unwanted disease from taking advantage of the dense, humid environment. Once the first frost comes and the fronds wilt, you may cut and dispose of them. Or simply do nothing – let them drop and become part of the fern-understory and an addition to the organic matter in the soil. This is very subjective and can depend greatly on the visibility of the ferns in your landscape. The upright fronds should be left over winter so the spores release and afford birds a winter snack.
Pests/Problems:
Onoclea sensibilis has no major pest or disease problems. Many common problems develop over time because of the consistently moist environment. In this case, thinning can provide more airflow. The vibrant green foliage may begin to fade during the hot months of the summer which is normal given that this fern is sensitive to any amount of drought.
Leaf Lore:
The Sensitive Fern is monotypic, meaning it is the only species in the genus Onoclea. Another common name for the Sensitive Fern is ‘Bead Fern’ that originates from the appearance of the bead-like spores that appear on the fronds over winter.
Onoclea is a Greek name for another plant, possibly borage, but applied here because of its meaning: ‘onos’ – a vessel; and ‘kleio’ – to close; referring only to the closely rolled fertile fronds of these ferns. The specific epithet sensibilis means ‘sensitive; responding quickly to touch, changes in light, etc.’ – giving way to its common name, Sensitive Fern. It’s sensitive to temperatures and with the first frost, the fronds will die back.
The Iroquois had used an infusion of the root to help with pain after childbirth, to stimulate milk production, to help with menstrual pains and cramps, or for the early stages of tuberculosis. The fiddleheads were cooked and eaten like a vegetable. Fronds were used to make pillows and placed them under children to help prevent bed wetting. A decoction was used as a hair wash and taken for the blood which caused the hair to fall out or used the plant for arthritis and infection.
Sensitive Fern has an affinity for water, giving it the Wetland Indicator Status of FACW (Facultative Wetland Hydrophyte).
Human toxicity is not well known. In general, studies defer to the statement that ferns, in general, may contain natural carcinogens and/or the enzyme thiaminase. Thiaminase is dangerous in high concentrations. Cooking the plant eliminates the thiaminase content.
Companion Plants:
Many other native plants can go along with Onoclea sensibilis. Native plants that do well in “rain garden conditions” are a perfect fit. This includes prospects such as: Red Milkweed (Asclepias incarnata), Asters (Aster spp.), Purple Prairie Clover (Dalea purpureum), Pale Purple Coneflower (Echinacea pallida), Spotted Joe-Pye Weed (Eupatorium spp.), Common Spiderwort (Tradescantia ohiensis) and many other perennials.
Larger shrubs that could be paired with the Sensitive Fern include Dogwoods (Cornus spp), Common Ninebark (Physocarpus opulifolius), Common Snowberry (Symphoricarpos albus) and Viburnum (Viburnum spp.).
