How to Plant and Grow Native Ferns: A Complete Care Guide
Most native ferns will make good ground cover in an moist‚ dappled shade if you plant them (try Christmas fern‚ cinnamon fern or lady fern) one season‚ and then by the following season sufficient fronds will have spread to provide good fern cover․ Fail to do this and you will be replacing crispy brown fronds every summer․
It is a blessing that most of Tennessee falls within USDA hardiness zones 6b - 7b‚ within easy access of dozens of species and forms of native woodland ferns․ A small shady slope‚ a wee shady bit under a stand of mature oaks‚ a damp little corner by a downspout: all you need to do is to turn the soil․
Select the appropriate fern for your site․
Not all "native" ferns have the same preferences; Christmas fern (Polystichum acrostichoides) is evergreen through the winter in Tennessee and established plants tolerate drier conditions․ It is considered to be one of the easiest ferns to grow․ Cinnamon fern and royal fern prefer consistently moist to boggy conditions‚ such as on the edges of a pond or on a depression (such as a kettle hole) with water run-off․ The fern grows quickly and fills out well‚ but dies back in winter․
Choose a fern according to the nature of the soil in your yard‚ rather than a fern which looks attractive in the plant catalog‚ for ferns which grow in wet‚ boggy ground will die when put in well-drained ground which dries out․ A fern that will tolerate dry shade will not tolerate standing water and will die‚ however‚ TN Nursery sold other native ferns of the South‚ such as the Christmas fern and cinnamon fern that did not require the gardener to hope that the plants would grow outside of their climate zone․
Site selection: shade is more important than most people think․
Native ferns evolved in the understory of forests‚ and prefer under a deciduous forest canopy (intermittent sun and shade) or morning sun and afternoon shade (rather than the deep shade of fully-conifer-dominated forests)․ Even a healthy plant would burn within two or three days if exposed to full-afternoon summer sun in Tennessee․
Because the maples are shallow-rooted‚ the fern will compete for moisture with them‚ and it may be necessary to water the fern for the first year․
Soil Preparation and Planting
Ferns prefer well-drained but moisture-retaining soils rich in humus; compost or well-rotted leaf mold 2-3 inches deep over 8 inches of soil is optimum․ If using pure clay (such as found in the Nashville basin and most of Middle Tennessee) amendments must be made‚ as excessive water will rot the crown and root system․
Most Tennessee soils have a pH between 5․5 and 7․0‚ which is ideal‚ but do still have your soil tested; especially if your lawn or vegetable garden has been limed․
For best results‚ get a spring planting in (April and May in Tennessee) so that the plants can get a good start before the summer heat; however‚ the ferns will accept a fall planting (early October best)․
Watering: The Most Overlooked Garden Detail
Everyone says keep ferns moist‚ but what does that mean? For the first month or so‚ water 2-3 times per week unless there is sufficient rainfall․ Water enough to keep the top 6 inches of soil well watered․ Once ferns are established (in 6 to 8 weeks)‚ most require an inch a week of water‚ like a lawn․ In Tennessee‚ during hot summer months (July and August)‚ ferns may need to be watered twice weekly unless there has been adequate rainfall․
To prevent fungal spotting (dark splotches on the leaves)‚ it is necessary to water from below and keep them under a moist environment‚ as Tennessee has more humidity than elsewhere․
Feeding and Maintenance
Ferns grown in compost amended soil require little or no fertilizer in the first year․ It may be helpful to apply a light annual dressing of a slow release balanced fertilizer each spring when the new fronds first start to appear․ Fall fertilizing‚ producing soft‚ palatable new growth that can be damaged by frost‚ is undesirable and can weaken the plant․
Minimal pruning is employed: dead and damaged fronds are cut back to the root mass‚ but living green fronds‚ although ragged‚ are not pruned to allow photosynthesis to continue to feed the root mass․ For evergreen species such as the Christmas fern‚ last year's fronds are cut back when new fiddleheads appear in spring; old fronds are often left for winter protection of the crown․
Winter Care in Tennessee
Most native ferns can survive the Tennessee winters outdoors‚ but it can help to put 2 in (5․1 cm) of mulch over the roots in late November․ In East Tennessee‚ the elevation and the winter weather are different from the rest of the state and deciduous ferns such as lady fern and cinnamon fern can die back to the ground in winter․ Pruning off the fronds is not necessary but can help․ They can also catch leaf litter and snow and thus form an insulating blanket around the crown․
Common Problems and Fixes
Orange‚ yellow or brown fronds (foliage) may indicate either too much direct sunlight or standing water‚ and should be investigated before pest infestation․ Pests are rare‚ but aphids may infest new fiddleheads early in the season; they can be removed simply using insecticidal soap‚ which does not harm the plant․ Slugs may damage very wet plantings by eating young unfurling fronds; they can be effectively trapped using beer traps or a ring of diatomaceous earth (diatomite) around individual plants‚ and unlike many commercial slug baits not be harmful to helpful species․
An Ancient Plant Family
So fern evolution began 200 million years before flowering plants diversified․ They grow well in darker‚ moist forest understories‚ meaning that fern would have been present in a wide distribution by the time of the dinosaurs‚ giving them a long time to specialize․ So‚ next time you are on your knees in the mulch‚ trying to get that darn crown depth just right‚ it is rather nice to know that you are connecting your garden to one of the most ancient lineages of plants on earth․
If planted in suitable sites and watered in the first season‚ native ferns require little maintenance‚ have a long lifespan and improve with age․ Woodland ferns make excellent ground cover and in the shade can cover the same area for more than 20 years․
