How to Create a Native Fern Garden That Actually Thrives
The trick to a successful native fern garden is getting the right ferns in the right amount of shade‚ and keeping the soil evenly moist‚ not soggy or desert-dry like a wrung-out sponge‚ and they are some of the lowest-maintenance‚ longest-lived plants you can put in the ground․ Get them wrong‚ and even the toughest fern will sulk‚ brown at the tips‚ or rot at the crown․
Here in Tennessee‚ we’d be in growing zone 6b through 8a‚ depending on whether we were north in the Smoky Mountains‚ around Knoxville or Johnson City‚ or south in the Memphis area or Chattanooga․ That range is actually perfect for a huge number of native fern species‚ which is one reason fern gardens are seen so often in Southeastern gardens․
Picking Species That Actually Belong Here
Forget “shade-loving ferns” on the tag․ Here are some of the best ferns for Tennessee:
* Christmas Fern - evergreen‚ tolerates dry shade better than most ferns‚ and makes itself less than 2 feet
* Cinnamon Fern - it prefers wetter conditions‚ produces a cinnamon-colored fertile frond in spring‚ and grows to a height of 3 to 4 feet․
* Lady Fern - a fast-growing‚ somewhat fragile plant that dies back in winter‚ but returns
* Maidenhair Fern - feathery‚ lacy leaflets and prefers richer soil with a higher organic matter
Giant Ostrich Fern - the one to choose if you want height and drama; depending on the spot‚ these may reach 4 to 5 feet high and may colonize via rhizomes over a few seasons․
Plant evergreen types‚ such as Christmas fern‚ with deciduous types such as Cinnamon fern or Lady fern․ This gives you year-round structure‚ instead of a garden that disappears every November․ Several ferns produced by TN Nursery are sold as bare root plants‚ establishing faster than container grown․ Meaning that the roots are not circling in a pot‚ but are in their native soil conditions from day one․
Site Selection: More Nuanced Than ““Just Put It in Shade””
Most advice on planting ferns is to consider ““shade and moisture””․ But what is the difference between the raking shade offered all day in the carpet of leaves under an oak tree compared with dappled morning light on the east side of a house? Ferns generally like dappled‚ or filtered light‚ for two to four hours of morning sun followed by shade․ Some ferns‚ such as Christmas fern‚ for example‚ may grow fine in deep shade‚ while these conditions retard the growth of others․
Also consider what else is overhead․ Plants under a shallow-rooted maple will have to compete with that tree for water and nutrients․ It is considerably easier to establish ferns under a deeper-rooted oak or pine․
Soil Prep That Actually Makes a Difference
Soil should be moist‚ and well-drained․ Before planting‚ turn 2-3 inches of compost or well-aged leaf mold into the top 8-10 inches of soil to help retain moisture․ If your native soil is heavy clay (as much of Middle Tennessee is)‚ then also add coarse sand or fine pine bark to the compost to improve drainage․ If your native soil is largely sand‚ the compost may help it retain moisture․
An acidic (pH slightly acidic to neutral 5․5 to 6․5) soil will be preferred by many species of ferns․ Most primitive ferns developed on the forest floor beneath a layer of fallen leaves; the soil is then naturally acidified․ Try to recreate forest conditions in your fern garden bed․
Planting Timeline and Spacing
In Tennessee‚ the best planting times are early spring (March to April) and fall (late September through October)․ Spring planting gives the plant a full season to take root before winter․ Fall planting allows the root system to get established in cool‚ wet weather instead of summer heat․
Dig a hole twice the root ball's diameter and no deeper than the roots․ Over-planting is one of the major reasons new ferns die․ The crown (where the fronds emerge from the root ball) should be at ground level‚ not below․
Space requirements vary with plant species․ For example‚ a small fern such as the Christmas fern may be allowed 12-18 inches between plants‚ whereas a larger‚ more spreading fern such as Ostrich fern requires 2-3 feet between plants‚ as it will completely fill in with rhizomatous underground roots in 2-3 growing seasons․
Watering and mulching after planting
Water adequately immediately after planting to disperse air pockets around the root zone‚ and check moisture every two or three days for the first six weeks‚ until new fern roots can obtain moisture from deeper in the soil․ After that‚ most native ferns need about an inch of water per week‚ more in the hot dry spells of July and August in Tennessee․
Mulch should be added as 2-3 inches of shredded leaf mulch or pine bark‚ with 1-2 inches cleared from the crown itself․ When mulch is piled against the crown‚ moisture gets trapped against plant tissue and the resulting rot can kill more new ferns than drought․
Ongoing Care
Native ferns rarely need feeding‚ but occasional light applications of slow-release organic fertilizer at the beginning of spring are acceptable‚ provided the fronds are pale and/or growth dwarfed․ High nitrogen feed should not be applied since it produces soft growth more prone to disease․
For the deciduous fern species‚ prune away dead fronds in late winter before fiddleheads develop in spring․ For evergreen species such as Christmas fern‚ prune away old damaged fronds as they appear․
The most common pests are slugs and snails‚ especially in a wet spring․ They can be controlled by putting down beer traps‚ or spreading diatomaceous earth around their base․
Winter Protection
Most native ferns survive Tennessee’s winters without harm‚ but a layer of mulch over the crown before the first hard freeze might help in the coldest winters or in exposed areas‚ and this should be removed in early spring before new fronds are smothered․
It can take only two or three years to achieve that optimal filled-in look‚ but the pay-off is a low-maintenance shade garden that just gets better every year‚ with almost no replanting․
