In most British gardens, ferns begin to stir in late February and March, and the single most useful job of the year comes just before they do. Deciduous ferns — the shuttlecock fern (Matteuccia struthiopteris), the royal fern (Osmunda regalis) and the many Dryopteris species — hold their old fronds right through winter, and those tired, papery leaves can smother the new croziers pushing up beneath them. Cut them back to within a few centimetres of the crown as soon as you see the first tight fiddleheads appearing. Evergreen ferns are different: leave hart's tongue (Asplenium scolopendrium) and the shield ferns (Polystichum) alone except for removing any fronds that have gone brown or flattened.
Once the old material is cleared, feed the soil rather than the plant. A generous mulch of leafmould, composted bark or well-rotted garden compost, spread 5cm deep but kept clear of the crown itself, gives ferns exactly what they want: cool, moist, humus-rich ground. A light scatter of general-purpose or seaweed feed as the fronds unfurl will keep container-grown specimens looking strong without pushing them into soft, floppy growth.
Late spring, once the ground has warmed but before the driest weeks arrive, is the ideal window for dividing congested clumps. Lift the entire crown with a fork, prise it apart with two garden forks back to back, and replant the healthy outer sections, discarding the woody centre. Water thoroughly and keep the divisions shaded for a fortnight — a sheet of fleece or an old piece of shade netting works well.
It is also the best time to plant. Ferns settle quickly when the soil is warm and moist, and they will have the whole summer to root in before winter. Plant so the crown sits just level with the soil surface, never buried, and water in well even if rain is forecast.
Ferns fail in British gardens far more often from drought than from cold. A dry, hot July will scorch fronds at the edges and turn a lush clump brittle within days. Water deeply and less often rather than little and often — a good soak twice a week in dry spells beats a daily sprinkling. Container ferns may need water every day in a heatwave, and they benefit from standing in a saucer that you empty after an hour or two.
Keep adding mulch through the season to hold moisture. If your garden is small and hot, group ferns together so they create their own humid microclimate, and let a few woodland companions — epimediums, hellebores, cyclamen, wood anemones — fill the gaps between them. Watch for vine weevil in pots, whose grubs hollow out the roots, and for slugs grazing soft new croziers in damp weather. A nightly patrol with a torch is remarkably effective.
Many gardeners consider autumn the true fern season. The shield ferns flush fresh, glossy fronds that hold their colour through winter, and Dryopteris erythrosora turns shades of copper and bronze as the nights draw in. Resist the urge to cut everything down. Leave deciduous fronds standing where they look good, because they protect the crown, feed the soil as they collapse, and offer shelter to overwintering insects and amphibians.
Autumn is arguably the finest time of year to plant or move ferns. The soil is still warm, rain is reliable, and roots establish steadily with no demand for top growth. Plant now and your ferns will grow away strongly the following spring.
Most hardy British ferns shrug off frost without help. Problems arise with tender tree ferns, with ferns in exposed positions, and with plants sitting in waterlogged ground. For Dicksonia and similar, gather the fronds upward and tie them into a loose cone, then pack the crown with dry straw or bracken and wrap the trunk in fleece or hessian. A handful of straw over the crowns of marginally hardy ferns is cheap insurance during a hard spell.
Pots are the real risk. Raise them onto feet or bricks so drainage holes never sit in a puddle, and wrap the outside of the pot with bubble wrap or sacking. Group pots together against a sheltered wall. Evergreen ferns such as hart's tongue keep their foliage all winter; avoid cutting them back now, as the old fronds shield the new ones emerging in spring. Water sparingly but do not let pots dry out completely under the eaves.
Fern care is rarely dramatic. A cut-back in early spring, a mulch, steady watering through summer, a light tidy in autumn and a little protection in the coldest weeks are all it takes to keep woodland planting looking lush for decades. Do these small jobs at the right moment and your ferns will repay you with that soft, green, unfurling magic that makes a shady British corner feel like a forest floor.
The Autumn Fern shares practical, down-to-earth guidance on shade gardening, ferns and woodland plants for british gardens for readers across the UK.
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