How to make a bog garden

Spring is the best time to start a bog garden, so that the plants have plenty of time to establish once the soil warms up. 

• Start small if you’re new to bog gardens, or use an existing boggy area. You can always expand it!
• The soil needs to be reliably moist all year round. If your soil is well drained, use a liner with a few holes in it to reduce drainage underneath your chosen spot. Although bog garden plants require plenty of moisture, they don’t like to sit in stagnant water.
• Sun or shade are also important: hostas and some ferns like moist soils in full or part shade, while other plants can only tolerate damp conditions if they are in full sun.
• Think about structure and winter interest – some shrubs and evergreens tolerate wetter conditions, such as Cornus ‘Midwinter Fire’, Leucothoe and winterberry (Ilex verticillata).
• Some plants are invasive in the right conditions. Don’t plant giant rhubarb (Gunnera manicata or Gunnera tinctoria), skunk cabbage (Lysichiton americanus) or giant butterbur (Petasites japonicus) in bog gardens or near ponds and streams.

10 best bog garden plants

2. Ornamental rhubarb

Rheum palmatum

Towering flower spikes, foamy panicles of creamy white or pink flowers, large and lush dark red leaves that turn dark green as they mature: what’s not to like about ornamental rhubarb?

A statement plant requiring a fair bit of space, this seemingly tropical plant is extremely hardy, tolerating temperatures as low as -20C!

It doesn’t like to dry out, so plant it at the edge of a pond or stream. Notable cultivars include ‘Atrosanguineum’ and ‘Hadspen Crimson’. H2-3m; S1.5-2m.

3. Marsh marigold

Caltha palustris

Marsh marigold or kingcup is a bog garden favourite for its bright yellow flowers, which start blooming in early spring and sometimes go on well into winter.

It’s reliable, self-seeds (though not invasively) and brings a welcome pop of colour when the rest of the bog garden is still dormant. A bonus is that it’s a UK native (it even gets mentioned in Shakespeare!), beloved of bees and other beneficial insects.

Here at Eden we have a double form, ‘Plena’, and a white-flowered cultivar, ‘Alba’. H40cm; S30cm.

4. Darmera peltata

Everything about this plant is weird, from its tall flower stems that come up long before the plate-sized leaves, to its fleshy, creeping rhizomes that sit on the soil surface, bearing a close resemblance to alligator skin.

It’s in the Saxifrage family, which will come as a surprise to anyone familiar with its usually diminutive alpine relatives, as Darmera peltata can reach 1.5m in height. It does gradually spread, but is easily kept in check by chopping the rhizome off with a sharp spade.

Take care weeding underneath it after the rain – the large leaves have a dip that holds quite a bit of water – as you’ll find out when they tip it all over you!

5. Snake's head fritillary

Fritillaria meleagris

Named for the shape of its flowers just before they open in March and April, this beautiful and unmistakable spring favourite is one of only a few bulbs to really enjoy damp conditions.

The blue-grey foliage emerges before the flower heads, which start off slumped on the ground before rising a foot or more above the soil.

Most of the flowers are purple and mauve, with a distinctive chequerboard pattern, but occasional snow-white flowers pop up to contrast with the purple. Admire them with the sun behind them to fully appreciate their lovely markings. When happy, they self-seed freely; the bulbs also bulk up into large clumps over several years.

7. Astilbes

Plumes, spires, sprays – however you describe the flower heads of these stunning bog garden perennials, they are a must-have. Colours run from deep claret reds through breathy pinks and mauves to sparkling whites. Some are tall, others dwarf, while the fern-like foliage ranges from fresh green to burnished bronze.

They keep themselves to themselves, slowly forming clumps that are easily divided. Their only requirement is a sunny spot in moisture-retentive soil, for which they will reward you with extensive flowering during the summer and persistent seedheads for autumn and winter interest.

For a taller display, choose ‘Red Sentinel’, whose dark red plumes can reach 1m. ‘Bronce Elegans’ is a smaller (to 30cm), white-flowered cultivar whose leaves are bronze when they first emerge.

8. Plantain lily

Hosta sp.

Many people are wary of hostas because of their reputation as slug food, but their lush foliage adds such wonderful colour and texture to the bog garden that it’s worth the odd sacrifice.

Some cultivars are more resistant to slug attack, such as the dark, glossy-leaved Hosta ‘Devon Green’ (which also lends a tropical look), H. sieboldii ‘Elegans’, with corrugated, grey-blue leaves, and the cream-edged H. ‘Sleeping Beauty’, which is one of the few variegated hostas less palatable to slugs. All of these prefer damp soil in partial or full shade.

9. Ligularia przewalskii

Dramatic yellow flower spikes, deeply toothed dark green leaves and an Award of Garden Merit to boot: Ligularia przewalskii is a prime choice for brightening a shady area at the back of your bog garden.

It will also grow in partial shade as long as it never dries out. Originally from northern China, it likes plenty of organic matter so give it a good mulch over the winter and it will reward you with a firecracker display from mid to late summer.

10. Globeflower

Trollius sp.

Its lovely bowl-shaped flowers in shades of yellow and orange may look delicate, but in reality the globeflower is a sturdy plant for dependably damp soil.

Some 30 species grow around the world, but those most commonly grown in gardens are cultivars of Trollius europaeus, Trollius x cultorum and Trollius pumilus.

Best in sun or partial shade, they gradually seed themselves around when happy. Orange-flowered Trollius ‘Dancing Flame’ has long sepals that point straight up like flames, hence its name. ‘Golden Queen’ is similar but more yellow in colour. 

Trollius pumilus has flat yellow flowers, while Trollius x cultorum ‘Alabaster’ has beautiful pale yellow blooms. 

'How to make a bog garden' written by Emma Pearce, Horticultural Scientist (Conservation) at the Eden Project