Ferns can make excellent ground cover in shaded and woodland-style parts of a garden, but the best choices are not simply the shortest ferns. What matters most is how the plant spreads. Some ferns extend through the soil on creeping rhizomes or stolons and gradually form a colony. Others remain as distinct clumps and only create a continuous planted effect when several are repeated together.

That difference affects both appearance and maintenance. A low, creeping fern can soften bare soil beneath shrubs or along a woodland edge, while a taller running fern can fill a large damp area with a strong mass of foliage. The same spreading habit can become inconvenient beside paths, small perennials or narrow borders where every plant needs to stay within a fixed space.

This guide focuses specifically on ferns that can cover ground or be used in mass planting. For the wider selection process covering shade, soil, mature size and other garden uses, see our guide to choosing ferns for Irish gardens.

Best ferns for ground cover

1. Common polypody, Polypodium vulgare

Polypodium vulgare is one of the clearest choices where you want a low evergreen fern that can gradually spread. It usually stays around 15 to 30 cm high and grows from creeping rhizomes rather than forming a tall central crown.

It is particularly associated with moist shade and acidic soils. The fronds are simple by fern standards, with a narrow outline and evenly arranged divisions, so a colony creates a relatively calm, low layer rather than a dense mass of highly dissected foliage.

Common polypody is not the choice for instant, aggressive coverage. It establishes and spreads more steadily, which can be an advantage near the front of a woodland border, beneath shrubs or where a lower fern needs to mingle with rocks and other shade plants without overwhelming them.

Best for: low evergreen cover, acidic moist shade and naturalistic planting where gradual spread is preferable to rapid colonisation.

2. Common oak fern, Gymnocarpium dryopteris

Common oak fern is a small deciduous fern with slender, long-creeping rhizomes. Its triangular fronds are held separately along the rhizome, so the plant can spread through a shaded area while keeping a light, airy appearance.

It grows well in low to medium light where the soil remains moist. At roughly 15 to 25 cm high, it is useful where a tall fern would hide neighbouring plants or make the front of a border look too heavy.

The main consideration is its ability to move. In favourable soil it can spread strongly enough that some gardeners find it too enthusiastic. That is useful in a larger woodland floor where a colony is wanted, but less useful beside slow-growing treasures that could eventually be surrounded by its rhizomes.

Best for: low deciduous cover, cool moist woodland conditions and larger shaded areas where a freely spreading fern is welcome.

3. Northern beech fern, Phegopteris connectilis

Phegopteris connectilis is another low creeper, usually reaching around 20 to 38 cm. It spreads on short- to long-creeping rhizomes and is naturally associated with cool temperate woodlands, mountain slopes and mossy rocks.

Its soft green deciduous fronds make it useful for the foreground of a border, around stumps and logs, or wherever a light summer layer is wanted beneath taller woodland plants. It prefers moist acidic soil, although established plants can be more adaptable than their delicate appearance suggests.

This fern also produces fresh fronds through the growing season, which helps a colony retain a soft green appearance rather than relying on one early flush of foliage.

Best for: low woodland ground cover, moist acidic shade, stumperies and softening the foreground of a fern planting.

4. Ostrich fern, Matteuccia struthiopteris

Ostrich fern is ground cover on a completely different scale. It is a large deciduous fern with upright vase-shaped fronds and stolons that produce new plants away from the original crown. Over time it can develop into a substantial colony.

This makes it useful for a broad, moist area where the aim is to create a bold sweep of foliage rather than a low carpet. It grows particularly well in moist to wet soil and can exceed a metre in height in good conditions.

Its vigour is also the reason to position it carefully. A young plant may look contained, but the stolons can carry new crowns into neighbouring planting. Avoid using it as filler in a narrow mixed border or beside small plants that need their own space.

Best for: large moist borders, woodland edges and naturalistic areas where a tall expanding colony is an advantage.

5. Sensitive fern, Onoclea sensibilis

Sensitive fern is a medium to large deciduous fern that spreads through creeping, branching rhizomes. It is especially useful in wet temperate conditions and can form a loose colony rather than remaining as one isolated clump.

The broad, coarsely divided fronds give it a stronger texture than the finer foliage of oak fern or beech fern. Separate fertile fronds become darker and more persistent, giving the planting a different appearance later in the season.

Use sensitive fern where the ground is reliably damp and there is room for movement. It fits a wet woodland edge, pond-side planting or broad damp border much better than a small, tightly organised bed.

Best for: damp to wet naturalistic planting, medium-height cover and places where gradual rhizome spread is useful.

Spreading ferns and clumping ferns do different jobs

The underground stem of a fern is the rhizome. Its form is one of the best clues to how the plant will behave after planting.

• Long-creeping or branching rhizomes allow new fronds to appear away from the original plant. Over time these ferns can knit into patches or colonies.
• Stolons can travel farther from the parent and form separate new crowns, as happens with ostrich fern.
• Short or erect rhizomes tend to keep the fronds concentrated in a recognisable clump. These ferns enlarge, but they do not automatically fill the surrounding ground.

A clumping fern can still be used as ground cover in a design sense. Repeating plants such as soft shield fern, Polystichum setiferum, through a shaded bed can create a continuous layer of foliage while keeping each crown relatively distinct. That approach is often easier to control beside a path or among other perennials than relying on a running fern.

If you are planning how spreading and clumping ferns should sit together, our guide to designing a fern garden looks more closely at grouping, texture and long-term composition.

Match the ground-cover fern to the moisture in the soil

Ground-cover habit does not override a fern's normal growing requirements. A species that spreads well in moist woodland soil will not necessarily cover dry ground beneath mature trees, and a moisture-loving fern will not automatically tolerate stagnant, airless soil.

Common polypody and northern beech fern suit the lower, shaded end of the ground-cover spectrum where the soil remains moist and well aerated. Common oak fern also needs dependable moisture, especially while establishing. Ostrich fern and sensitive fern belong towards the wetter end and make much larger colonies when moisture is plentiful.

In an Irish garden, regular rainfall can make a site look reliably damp while the root zone tells a different story. Tree canopies intercept rain, established roots remove moisture quickly, and an exposed position can dry foliage and surface soil. Check the ground itself rather than assuming shade plus Irish rainfall will provide enough water.

Check soil reaction as well as moisture

Several useful creeping ferns have clear soil preferences. Common polypody is particularly associated with acidic soil in moist shade, and northern beech fern also favours moist acidic conditions. If your soil is strongly alkaline, they are not automatically the best choices simply because their growth habit suits the space.

Drainage matters too. Fern roots need both moisture and air. Heavy compacted ground can remain wet after rain but still be a poor rooting environment. Improving the wider structure of the soil is more useful than placing a spreading fern into one small pocket of rich compost surrounded by compacted clay.

Decide how tall you want the ground cover to be

"Ground cover" can mean a 20 cm layer beneath shrubs or a metre-high colony filling a broad woodland edge. Decide which effect you want before choosing the plant.

• For a low evergreen layer: common polypody is one of the strongest options.
• For a low, light deciduous carpet: common oak fern or northern beech fern can form a softer colony.
• For a medium-height damp planting: sensitive fern can create a broader, coarser mass.
• For a tall dramatic colony: ostrich fern can fill a large moist area, but needs substantially more room.
• For controlled repeated cover: use clump-forming ferns in groups rather than choosing a running species.

Height is especially important around paths and small borders. A fern does not need to be invasive to become inconvenient if mature fronds repeatedly arch over a walkway or shade smaller plants.

Do not choose the fastest-spreading fern by default

Rapid spread sounds useful when the aim is to fill bare ground, but speed is only an advantage when the plant has somewhere appropriate to go. The same rhizomes that create an attractive colony can travel into neighbouring perennials, through a mixed woodland border or towards a path edge.

For a large informal area, a stronger spreader can reduce the need to plant many individual crowns. In a small garden, a slower creeping fern or repeated clump-forming plants may give a better long-term result.

Think about the boundary before planting. Paths, lawn edges, substantial roots and changes in growing conditions can all help define a colony. Where there is no natural limit, allow enough access to thin or lift unwanted growth later.

How to establish a fern ground-cover planting

A spreading fern still needs to establish before it can cover useful ground. Newly planted roots are confined to the original planting area and are more vulnerable to drying than an established colony.

• Prepare the whole planting area where practical. A broad root zone with workable, moisture-retentive soil gives creeping rhizomes somewhere suitable to move.
• Keep new plants evenly moist. Pay particular attention beneath trees and shrubs where established roots compete for water.
• Use an organic surface mulch. Leaf mould or well-rotted organic matter can help conserve moisture and support the loose woodland-type surface conditions many ferns favour.
• Leave the growing crown clear. Do not bury the centre of clump-forming ferns beneath a deep layer of mulch.
• Allow time for the habit to develop. A creeping rhizome does not mean the plant will create a solid patch immediately after planting.

Once the ferns are established, let their natural growth habit do most of the work rather than repeatedly disturbing the soil between them.

How to control a spreading fern

Control is easiest when it is part of the original planting decision. Put vigorous colony-formers where their spread is useful, and choose slower or clumping ferns where boundaries matter.

If a creeping fern moves beyond the space you want it to occupy, unwanted rhizome sections can be lifted or cut back. Stolons from ostrich fern can produce separate rooted plants that can be removed while they are still young. Periodic thinning also prevents one vigorous species from taking over a mixed fern planting.

Avoid describing every spreading fern as invasive. Some simply have an energetic garden habit. The practical question is whether the rate and direction of spread suit the space you have given the plant.

Choosing ground-cover ferns for an Irish garden

Start by deciding whether you want a low carpet, a medium woodland layer or a tall colony. Then check the site's light, soil moisture, drainage and soil reaction. Finally, decide how much movement you are prepared to manage.

For a low evergreen effect in acidic moist shade, Polypodium vulgare is a strong choice. For light deciduous cover, Gymnocarpium dryopteris or Phegopteris connectilis can spread through a cool woodland-style bed. In larger damp areas, Onoclea sensibilis gives a broader medium-height colony. Where the ground is moist to wet and there is room for substantial plants, Matteuccia struthiopteris can create a much taller sweep of foliage.

Once you know the type of cover your site can support, you can browse our fern collection and compare plants by moisture, size and growth habit. For a wider range of plants that can fill and connect larger areas of a border, see our ground-cover plants.

Frequently asked questions

Do ferns make good ground cover?

Yes. Ferns with creeping rhizomes or stolons can gradually form patches or colonies, particularly in shaded and woodland-style areas. Clump-forming ferns can also be mass planted to create continuous foliage, but they will not spread across the soil in the same way.

What is a good low evergreen fern for ground cover?

Polypodium vulgare, common polypody, is a useful low evergreen option. It has creeping rhizomes, usually stays around 15 to 30 cm high and is particularly suited to moist acidic shade.

Which ground-cover fern is best for a large damp area?

For a tall colony, ostrich fern, Matteuccia struthiopteris, is useful where the soil remains moist to wet and there is plenty of room for stolons to spread. Sensitive fern, Onoclea sensibilis, is another strong option for damp naturalistic planting at a lower scale.

Will ground-cover ferns spread too much?

Some can. Common oak fern, ostrich fern and sensitive fern all have growth habits that allow them to move beyond the original planting position. That is valuable in a broad woodland or naturalistic area but can require thinning in a smaller mixed border.

Can I grow ground-cover ferns beneath trees?

Yes, provided the root zone has enough moisture. Tree cover can create suitable filtered light while the tree roots themselves make the soil unexpectedly dry. Check moisture below the surface and give new ferns enough water to establish before expecting them to spread.