How To Grow Ferns

Osmunda claytoniana showing 'interrupted' frond with sterile and fertile pinnae

Osmunda claytoniana showing 'interrupted' frond with sterile and fertile pinnae

Ferns are a widely varied group of plants. Their native habitats range from the tropics to the Arctic and from deserts to swamps. They may be coarse or delicate, succulent or filmy, crown forming or creeping, lime lovers or lime intolerant, invasive weeds or virtually impossible to cultivate. One of the first plant groups to adapt to life on land, ferns have since adapted to most conditions and environments, but relatively few are able to contend with direct sunlight and low humidity. Most species need moist soil, high humidity and enough shade to maintain these conditions.

Ferns are essentially wildlings; unlike many of the flowering plants, such as herbaceous perennials, they have not been hybridized for garden conditions. Before you begin your fern garden, observe the ferns growing naturally in your area. Most of these are available commercially. Be sure to place them in your garden where conditions are comparable to those supporting the native ferns in the wild. Be cautious in your selection. If a fern's growth in the wild is rampant, it is likely to be even more so in your garden. If the fern grows only in a specialized habitat, such as moist rock crevices, it may be difficult to grow in the garden. Grow only those plants for which you have the proper conditions. Never collect ferns from the wild. When you buy ferns, look for reputable dealers who state explicitly that their plants are nursery propagated, not collected from the wild. Selected forms with fancy fronds are always nursery propagated.

Choosing Ferns

The section of the country where you live and garden determines to a large extent the plants you can grow. Most of Florida and the southern coastal areas can grow the tropical ferns that the rest of us can cultivate only under glass or as house plants. Southwest gardeners can grow only those that have adapted to less humidity, while gardeners in the midwest, northeast, mid-atlantic and upper south can grow most woodland types.

Keep in mind, too, that some ferns have specialized requirements. It's not impossible to grow maidenhairs, hart's tongues or other ferns that prefer an alkaline soil, even if your soil tends toward the acidic; mixing crushed limestone, oyster shell grit or cement rubble in the soil will provide a constant source of lime and improve drainage. If you live in a limestone area and want to grow those that require acid conditions, it is not quite so easy. You can make the planting bed acidic by working lots of peat or humus into the soil, separating it from the subsoil with landscape fabric or a two-inch layer of granite grit and treating the soil with sulfur or ammonium nitrate. The problem is that the water in these areas is likely to be alkaline, and will gradually change the pH of the soil. Under these conditions, it's best to grow ferns that prefer limestone, or those tolerant of alkaline conditions. Most adiantums, aspleniums, polystichums, dryopteris and athyriums will grow in a wide pH range, and the organic material in a well prepared soil will help to buffer the effect of excess acidity or alkalinity.

Many ferns have a natural affinity for rocks. Some, such as polypodies and the walking fern will actually grow on the rock surface; others, such as Cheilanthes and the cliff brakes, need exceptionally sharp drainage and more sun. Almost all appreciate the protection of rocks, which help the soil retain moisture and establish a microclimate that is warmer in winter and cooler in summer than the surrounding environment. It's important to know which ferns must have limestone and which require acid conditions. Sandstone and granite rocks are generally the foundation for those needing acid, while limestone or even cement rubble will provide alkalinity. Ferns among rocks should be planted in a well drained but moisture-retentive soil.

Woodland Ferns

For gardeners in most regions of the country, species adapted to woodland environments are attractive and easy to grow. In most areas, Christmas or sword ferns (Polystichum spp.), lady ferns (Athyrium spp.) and shield ferns (Dryopteris spp.) are commonly found in the wild. These genera contain other non-native species that will grow under similar conditions in the garden. Most prefer a slightly acidic soil with 50 to 75 percent humus, good water retention and excellent drainage.To add humus to your soil, work about 4 inches of coarse compost, rotted manure or fine pine bark into the top 4 to 6 inches. All ferns require ample moisture for growth, as well as a certain amount of humidity to prevent dehydration of their foliage. Established plants of most woodland species are tolerant of periodic dry spells, but that doesn't mean they will survive bone-dry conditions. Only a very few are adapted to life in bogs or really wet conditions. Swamp, bog and streamside ferns such as the osmundas require more water than most woodland ferns.

Woodland ferns do best in high or dappled shade. The open shade of mature trees or the north side of the house or a wall, open to the sky, provide nearly ideal light conditions. Most woodland ferns will adapt to relatively low light levels, but no ferns thrive in deep shade. Evergreen species are the most tolerant of low light levels. Generally, plants will tolerate more sun and less water in the northern part of their range. The stronger the sun, the greater the need for water; conversely, the more water available, the more sun they will take.

The nutritional needs of ferns are generally met with compost or the breakdown of leaves. Small size and slow growth are more likely to be caused by limited water than lack of food. In fact, ferns are sensitive to excess fertilizer; quick-release inorganic fertilizers are likely to burn the roots. If supplemental feeding is needed, use well rotted manure, fish emulsion or other slow-release organic food. Wind protection prevents the breakage of brittle fronds and reduces dehydration. While shelter is an advantage, the lowest, most sheltered spot is also probably a frost pocket which can delay spring growth, and result in early and late frost damage to deciduous ferns and winter-kill of species with borderline hardiness.

Planting Ferns

The best time to plant varies according to geographic location. Spring planting is preferable where winters are cold and wet. If ferns are planted late in the season in these areas, the roots could very well rot before they are established. Alternate freezing and thawing may heave the rhizomes from the soil, breaking young roots and exposing them, making them prone to desiccation. In warmer climates, fall planting is preferable because the plant has time to establish itself before the stresses of summer heat and drought. If you move or plant a fern that is actively growing, cut the fronds back by half to reduce stress from water loss and help it get established. New fronds usually will be produced as soon as the plant has enough roots to support them.

To move a fern, dig a generous root ball, especially if the plant is in active growth. Next, dig a hole the same depth as the root ball and place the plant in the hole, water well, fill in the sides with good soil and firm the soil around the plant. If the job is well done, the fern may never know it has been moved.

Many ferns available for sale are grown in quart size or larger pots. These are either mature size or will grow to maturity in a year or two.To plant a potted fern, knock the plant out of the pot and gently shake or tease the roots apart. It is important to remove excess potting soil, especially if it differs significantly from the soil in your garden. Potting soils are often light and peaty and will dry out faster than the surrounding soil. This may leave the newly planted fern dry and wilted even though the surrounding soil is moist. To rectify the situation, spread out the roots, mix some of the potting soil into the root area, water well and fill in the planting hole with good soil. Keep newly planted ferns well watered for the first growing season while they are becoming established.

Never let plants growing in 4-inch or smaller pots dry out until they reach a mature size and are well established. Plant them in well prepared soil in a protected area. It is often easier to pot them up for special care. Add fine pine bark to any good potting mix to improve drainage. Do not feed until they are growing well. If the fern requires alkaline conditions, you can add a tablespoon of ground limestone to a gallon of planting mix.

Ferns sold by mail may have been removed from their pots and put in plastic bags or they may be almost bare rooted. When you unpack the plants make sure that the growing tip has not been damaged during shipping. If it has been broken or has rotted, the fern will probably not recover and the shipper should be notified immediately. Depending on size, either pot the fern or plant it in a protected spot and keep it well watered until it has had a chance to establish itself. If the roots seem at all dry, set the plant in water for one to two hours while you are preparing the planting area.

Some ferns may be purchased as small bare rooted plants packed in dry peat moss in a plastic bag. In theory, there is enough humidity in the bag to prevent desiccation of the plant; in practice, ferns do not appreciate being bare rooted, and while they will certainly rot if they are enclosed with wet peat, they are generally dry enough to need a recovery period. Unless you can actually see signs of active growth such as a crozier beginning to uncurl, bare rooted plants are best avoided. Often the growing tip has been damaged by handling, or the peat has become completely dry. If you do try ferns sold this way, soak them in water for a couple of hours and pot them using a good, well draining potting mix. Be careful to keep the growing tips at or above soil level. Keep well watered and transplant to the garden after they have become established. Another disadvantage of ferns sold bare root is that they are frequently dug up from the wild.

How far apart should you plant your ferns? Spacing depends on form, size and type of growth. Crown formers with upright rhizomes and vase-shaped form spread slowly and show to best advantage as a single crown. Goldie's fern and some of the larger growing polystichums and osmundas may need three feet or more between plants. Oak and beech ferns spread quickly and can be planted fairly far apart. Hay-scented, New York and Virginia chain fern are even more rampant spreaders, and the ostrich fern, which spreads by far-ranging runners, is best planted in an area where it can be controlled.

Caring for Ferns

If you choose plants suited to your growing conditions and practice good gardening hygiene, removing debris that may harbor pests, you may seldom have to deal with diseases or pests. Slugs and snails tend to be the most common problems; they are voracious eaters that thrive under the same conditions as ferns. Slug baits containing metaldehyde are effective, but they are toxic and especially hazardous to children and pets. Various nontoxic baits and traps are safer: Dishes of beer sunk to soil level are effective. Slugs will also collect under overturned grapefruit shells and can then be dropped into denatured alcohol for the coup de grace. Ferns are quite sensitive to insecticides. If you must use a chemical poison, test it on a few plants. Avoid the liquid emulsion sprays, as they contain oils that damage ferns. Use dusts or sprays made from wettable powders, reducing the recommended dosage by one half.

To prevent disease, start with healthy plants. Keep the crown of the plant above the soil, and don't cover it with mulch. Avoid overwatering and space the plants far enough apart for adequate air circulation. Mulching with fine pine bark, pine needles or a fairly coarse compost will help keep the soil moist, prevent weeds or at least make them easier to pull and provide essentially all the nutrients your ferns need. Replenish the mulch each year to compensate for the tendency of certain athyriums or dryopteris to raise their crowns above soil level.

Which Ferns Are For You?

Ferns For Beginners

  • Adiantum pedatum
  • Athyrium filix-femina
  • Blechnum spicant
  • Cyrtomium species
  • Cystopteris species
  • Deparia acrostichoides
  • Dryopteris dilatata
  • Dryopteris erythrosora
  • Dryopteris expansa
  • Dryopteris filix-mas
  • Dryopteris marginalis
  • Matteuccia struthiopteris
  • Polystichum acrostichoides
  • Polystichum munitum
  • Polystichum setiferum
  • Thelypteris noveboracensis

Ferns For Sun

  • Athyrium filix-femina
  • Dennstaedtia punctilobula
  • Dryopteris filix-mas
  • Dryopteris ludoviciana
  • Matteuccia struthiopteris
  • Onoclea sensibilis
  • Osmunda cinnamomea
  • Osmunda regalis
  • Polystichum setiferum
  • Sphaeropteris cooperi
  • Thelypteris kunthii
  • Woodwardia virginica

Ferns For Deep Shade

  • Asplenium rhizophyllum
  • Blechnum spicant
  • Cyrtomium falcatum
  • Dryopteris (evergreen species)
  • Gymnocarpium species
  • Osmunda cinnamomea
  • Polystichum species
  • Phegopteris species
  • Woodwardia areolata

Ferns For Wet Soils

  • Athyrium filix-femina
  • Blechnum serrulatum
  • Dryopteris celsa
  • Dryopteris ludoviciana
  • Macrothelypteris torresiana
  • Onoclea sensibilis
  • Osmunda cinnamomea
  • Osmunda regalis
  • Thelypteris kunthii
  • Thelypteris palustris
  • Woodwardia species

Ferns For Dry Soil

  • Asplenium platyneuron
  • Blechnum penna-marina
  • Cystopteris bulbifera
  • Dennstaedtia punctilobula
  • Dryopteris filix-mas
  • Dryopteris intermedia
  • Dryopteris marginalis
  • Osmunda claytoniana
  • Pentagramma triangularis
  • Polypodium species
  • Polystichum species
  • Phegopteris hexagonoptera
  • Woodsia obtusa

Ferns For Alkaline Soils

  • Adiantum species
  • Asplenium most species
  • Cystopteris bulbifera
  • Diplazium pycnocarpon
  • Dryopteris carthusiana
  • Dryopteris dilatata
  • Dryopteris expansa
  • Gymnocarpium robertianum
  • Matteuccia struthiopteris
  • Osmunda claytoniana
  • Polystichum aculeatum
  • Thelypteris palustris

Ferns For Strongly Acidic Soils

  • Asplenium platyneuron
  • Blechnum species
  • Cyrtomium species
  • Dennstaedtia punctilobula
  • Dryopteris campyloptera
  • Dryopteris cycadina
  • Dryopteris ludoviciana
  • Gymnocarpium dryopteris
  • Osmunda cinnamomea
  • Osmunda regalis
  • Polypodium species
  • Polystichum species
  • Phegopteris connectilis
  • Thelypteris species
  • Woodsia obtusa
  • Woodwardia species


Nancy Swell grows and propagates a wide variety of hardy ferns in her garden in Richmond, Virginia. She is an active member of The American Fern Society, The British Pteridological Society and The Hardy Fern Foundation and is a self-proclaimed fern fernatic.


Comments

May 8, 2010
Carlotta

I once saw a fern covered wall and I want to make one on my wall. The wall is brick cemet on the south side in Whittier Calif. A lattice wall filled mulch and not sure what else. Hope you can help?


October 29, 2011
DIANE

i recently moved into a house and outside was an abandoned fern plant in a hanging pot. it was mostly dried up up but a few leaves were growing here and there. we were able to pull apart the plant after much time and now i am not sure what to do . do i plant the root balls without any leaf and if i can how far apart should the balls be from each other. there are hundreds of rootballs. they feel like a small potato. i know nothing about planting from seed or bulbs. also can i throw these balls on the ground and cover them with fresh soil ?


May 24, 2012
Deborah Gross

What fern grows on a moist, shaded, concrete vertical wall on a Bronx, New York, apartment building? I would like to encourage the growth of the preexisting ferns and plant more in the empty crevasses. Moss is growing also. Will buttermilk, yogurt, or beer hurt the ferns? 
Thank You!


March 20, 2013
pam

Love the information !! I’m looking for ferns to grow for my sons wedding in August. Something easy, still learning about all the different kinds.
Thank you for sharing,
Pam Fouse


April 4, 2013
BBG Library Staff

Since you need the ferns by August, you should probably buy them as fairly mature plants from your local nursery. Choose ferns that are compatible with your environment. For more in depth information, the following book includes an encyclopedia section detailing features and cultural requirements for about 50 ferns for the home garden: Ferns: Wild Things Make a Comeback in the Garden, (C. Colston Burrell, editor, Brooklyn Botanic Garden, 1994). Native Ferns, Moss and Grasses, IWilliam Cullina, Houghton Mifflin, 2008) is also a good reference; the book includes a 60-page encyclopedia of ferns and how to grow each one.


April 28, 2013
Lynne

My ferns are getting way too big. Can I cut them back or will it kill them?


May 29, 2013
BBG Library Staff

Cutting back the fronds is not likely to kill your plants, but doing so won’t solve your problem. If your ferns are growing too tall, consider moving them to a site where their height is more suitable and select new ferns with less height at maturity. Before you purchase replacement ferns, check the labels for height information.

If you have clumps of ferns that are spreading aggressively, the best thing to do is to divide the ferns, either after the first fall frost or in the early spring when new growth is just showing. Different types of ferns require different types of division. Two online references from Clemson University has two helpful online references, one on ferns in particular and one on dividing perennials.


August 21, 2013
Ed Mackiewicz

I recently rescued (salvaged) a fern (Boston, I think) that had been thrown to the curb. I took some of the still green fern leaves with good roots, dipped them in root hormone, and then planted them in a pot of compost. Will I have any luck, do you think? Any tips?


May 26, 2014
Char Mason

Thank you for this thorough and most helpful site.


June 19, 2014
Rita Haag

Just purchased two Dryopteris erythrosora ferns in 4-inch pots that will be planted in containers.  Any recommendations for type of container, size, etc., would be appreciated.


August 12, 2014
BBG Library Staff

In general, larger pots, perhaps gallon size, will allow the ferns to spread their roots and achieve maturity. Your type of fern prefers moist to a bit dry, humus-rich soil and shade. The pots you use should drain any excess water well. This will not only prevent soggy roots but also prevent salt buildup. If a fern outgrows the pot and you prefer not to repot it in a larger container, you may remove the fern from the pot and trim its roots back from the tips; remove about a quarter of its length. Remove any “black” strands at this time, as such roots are dead.


September 26, 2014
Nancy Rose

I am planning to plant ferns in a shady flower bed. We live in southeastern PA.  I already have a Japanese Painted fern and have recently purchased an Autumn fern.  I would like taller ferns on either end, then lower growing ferns, in the middle.  Can you recommend varities that would do well in my area?


October 29, 2014
Beckie Uhl

There was a beautiful grove of wild ferns growing in our yard for years. However, this past winter, snow bent them down and most of them died. Brown stems plus dried up leaves were all that was left.  Will they return in the spring?



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