Marsh fern

Marsh fern: how do you recognise it?

Habit

Loose groups of upright fronds 30–60 cm tall, rising here and there from a creeping rhizome rather than from a single clump.

Fronds

Pale green, thin and soft, pinnate with deeply cut leaflets; deciduous, yellow-brown in autumn.

Spores

The spore-bearing fronds appear later in summer and are slightly taller; their leaflets have rolled-under edges covering the spore clusters. Ferns do not flower.

Roots

Thin, black, far-creeping rhizomes just below the surface: this is how the plant spreads.

Size

Up to about 60 cm tall; a group soon reaches 60 cm across, and more in a wet spot.

Plants: March–May and September–October · Pruning: March

Why grow it?

• One of the few ferns for truly wet soil: perfect for the marsh zone of a pond.
• Grows in sun, partial shade and shade, as long as the soil stays wet.
• Its creeping rhizomes quickly fill a wet corner with a loose, fresh green carpet.
• A native plant for the wildlife garden, giving cover to frogs, toads and other creatures of the water’s edge.
• Fully hardy and little work: no feeding, just a tidy-up in March.

Marsh fern: where does it grow best?

• Sun, partial shade or shade: in full sun only if the soil is always wet.
• Wet, humus-rich loam or peat, acid to neutral; it is less happy on chalky soil.
• In the marsh zone of a pond, where the soil is saturated under a few centimetres of water at most, or in a wet border or bog garden.
• Allow 40–50 cm between plants: they soon grow together.

Light

Sun, partial shade and shade

Soil type

Loam or peat

Acidity

Acid or neutral

Moisture

Wet

Size

0.6 m tall, 0.6 m wide

Hardiness

Hardy (to -30 °C)

Goes well with

• Royal fern: A large, stately fern that also loves wet, acid soil.
• Marsh marigold: Yellow flowers in early spring, before the fern wakes up.
• Meadowsweet: Creamy, scented plumes in summer, in the same wet soil.
• Purple loosestrife: Purple-pink spikes above the light fronds, loved by bees and butterflies.
• Yellow flag: Sturdy, sword-shaped leaves that contrast with the fine fronds.

Marsh fern: when and how to plant it?

Plant in March–May and September–October.

1. Plant from March to May or in September–October.
2. In a small pond, use a large aquatic basket filled with heavy, low-nutrient aquatic soil; in a bog border, simply plant into the wet ground.
3. Lay the rhizome horizontally, 2–5 cm deep, with the growing points facing up, and firm in well.
4. Set the basket so that its top is level with the water surface or at most 5 cm below it.
5. Space plants 40–50 cm apart, preferably 3–5 together for a group that fills in quickly.
6. Water in well and keep the soil wet from then on.

Care

Water

The soil must never dry out. In dry summers, top up the pond with rainwater; water a bog border generously.

Feeding

Not needed, and certainly not in or near the pond: fertiliser encourages algae.

Mulching

In a bog border, a layer of leaf mould in spring keeps the soil moist and rich in humus. Not in the pond itself.

Spread

Each spring, chop off runners that go too far at the edge, or keep the plant in a basket.

Old fronds

Leave them from autumn until March: they protect the rhizomes and give small creatures a hiding place.

Tip: Plant it where the soil is always wet: there it will even grow in sun. In a small pond, keep it in a large aquatic basket so the runners do not take over the whole bank.

Marsh fern: when to prune it?

Pruning months: March.

When: In March, before the new fronds emerge. Otherwise marsh fern is not pruned.

How:

• Cut last year’s dead fronds off just above the ground.
• Pull out dead foliage hanging in the pond water, so it does not rot there and enrich the water.
• Work carefully around the growing points: the new, coiled fronds are already waiting just below the surface.

Caution: Do not cut the old fronds off in autumn: they protect the plant through winter.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Division

In April–May, cut off a piece of rhizome with a few growing points and replant it straight away in wet soil or an aquatic basket. It almost always works.

Spores

In late summer, collect ripe spores and sow them on moist, sterile seed compost under glass. It takes a year or more to get young plants; division is much quicker.

Marsh fern: how does it get through the winter?

Hardy to −30 °C.

• Fully hardy, to about −30 °C: no protection needed in Belgium.
• The foliage dies back in autumn; the rhizomes overwinter safely in the wet soil.
• Leave the dead fronds until March as natural winter protection and shelter for insects and other small creatures.

Diseases and pests

• Drying out: Brown, shrivelled fronds in summer: the soil is too dry. Keep the soil wet or move the plant to a wetter spot.
• Spreading too far: Runners pop up among other plants. Chop them off in spring, or plant in a basket or with a root barrier.
• Scorched fronds: Yellow and brown foliage in full sun, in a spot that dries out now and then. Choose a wetter or slightly shadier position.
• Late to appear: Nothing to see in April? That is normal: the fronds only come up late in spring.

Through the year

• March: Cut off old fronds. Plant or divide.
• April: Plant and divide.
• May: The new fronds unfurl. Plant.
• June: Keep the soil wet. Chop off runners that go too far.
• July: Top up the water in dry spells. The spore-bearing fronds appear.
• August: Collect ripe spores. Top up the water in dry spells.
• September: Plant.
• October: Plant. The foliage turns yellow-brown.
• November: Leave dead fronds in place as winter protection.
• December: Rest.

Did you know?

• The spore-bearing fronds only appear in summer; the edges of their leaflets roll under and cover the spore clusters.
• The name Thelypteris comes from the Greek words for ‘female’ and ‘fern’; palustris means ‘of the marsh’.
• In open marshes and reed beds, a single plant can over the years form a large, dense stand from its rhizomes.