At Hermannshof, we use the German system of garden habitats to select plants according to their habitat requirements, sociability and aesthetic qualities. This is essential to achieve long-term, ecologically balanced and low-maintenance horticultural plant communities in gardens and urban green spaces. Below is my choice of plants that will be perfect for very wet soil.
Key: H = height; S = spread; C = conditions; SI = season of interest; HR = hardiness rating.
Plants for wet soil
Amosonia tabernaemontana var. Salicifolia
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An attractive, clump-forming perennial, with willow-like leaves that turn from mid-green to buttery yellow, and bronze in autumn. The open clusters of star-shaped flowers are an intense metallic-blue and appear from early May. Emerges with dark, smoky-purple shoots. H 1m. S 60cm. C Moist, well-drained soil; full sun to part shade. SI May – October. HR RHS H5, USDA 3a-9b.
Aronia melanocarpa ‘Viking’
An upright, deciduous shrub with dark-green leaves that turn an intense, dark purple-red in autumn. Profuse, large clusters of white flowers in late spring, followed by edible purple-black berries, much appreciated by birds. H 2-2.5m. S 1.5m. C Moist but well-drained soil; full sun to part shade. SI May – October. HR RHS H7, USDA 4a-8b.
Watch Cassian Schmidt deliver the winter lecture at the New York Botanical Garden
Camassia cusickii ‘Zwanenburg’
Intense blue, starry flowers in May, perfect for planting in swathes and weaving through damp meadows or around water. Enjoys both sun and dappled shade, so a good way to connect spaces and add rhythm. H 60-70cm. S 10cm. C Moist but well-drained chalk, loam, sand; full sun to part shade. SI May – June. HR RHS H4, USDA 6a-8b.
Camassia leichtlinii subsp. suksdorfii Caerulea Group
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One of the loveliest bulbs for wildflower meadows and prairie-style plantings. Its violet-blue spikes are magical on a cool, rainy morning. Bulks up nicely. H 1m. S 50cm. C Prefers a mesic-moist soil; full sun to part shade. SI April – May. HR RHS H4, USDA 5a-9b.
Carex muskingumensis
A useful semi-evergreen grass for ground cover in light shade – either in small groups or in larger plantings. Very adaptable from winter wet to reasonably dry; also useful in semi-shaded rain gardens. Self-seeds in moister soils. Can be mowed in late winter. H 1m. S 1m. C Moist to mesic loam, clay; partial shade. SI May – October. HR RHS H4, USDA 4a-9b.
Cephalanthus occidentalis
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An open-branched, deciduous shrub that’s native to damp areas along rivers in North America. Useful in retention swales and rain gardens, but thrives in normal garden soils. Compensates for coming into leaf late with scented, creamy-white flowers. H 1.5-2m. S 1.5m. C Moist to wet; full sun. SI Late summer – autumn. HR RHS H5, USDA 5a-9b.
Eutrochium purpureum ‘Baby Joe’
This new, compact Joe-Pye weed is useful in smaller prairie plantings or borders. It starts to bloom in late July with terminal heads of pinkish-purple flowers. Native to moist prairie meadows, it adapts well to normal garden conditions. H 80cm-1m. S 60cm. C Mesic-moist, loam, clay; sun-part sun. SI Late July – September. HR RHS H7, USDA 3a-9b.
Euphorbia palustris
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This clump-forming, long-lived perennial produces flowers with clusters of vibrant yellow-lime bracts in May. The fresh-green leaves often turn intense orange-yellow in autumn. Found in moist meadows, it associates well with sanguisorbas, camassias and irises. AGM. H 1m. S 90cm. C Moist but well-drained clay, loam; full sun. SI May – June. HR RHS H7, USDA 5a-10b. 72
Hemerocallis citrina
This is my favourite daylily, which I prefer to use in lush naturalistic plantings together with Lilium henryi, aconitums and thalictrums. Forms large, bushy clumps with strap-like leaves to 80cm long. The nocturnal, fragrant and elegant, star-shaped flowers with lemon-yellow sepals are produced in abundance in midsummer. AGM. H 1.5m. S 1m. C Mesic- moist, loam, clay; sun-part sun. SI July – August. HR RHS H6, USDA 3a-9b.
Iris ‘Caesar’s Brother’
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A really old cultivar but for me still the best for planting designs. It is super robust and has survived for decades in a moist, meadow-style planting at Hermannshof. The deep-violet-blue flowers appear in mid-May well above the foliage, which turns a wonderful intense yellow in autumn. H 1-1.2m. S 80cm. C Mesic-moist, loam, clay; sun-part sun. SI July – August. HR RHS H7, USDA 3a-8b.
Leucanthemella serotina
A tall, robust, clump-forming perennial with toothed, dark-green leaves, which produces large, yellow-centred white daisies from September to October. It’s native to moist, tall, herb communities, and works well planted alongside moor grasses, vernonias and
Iris sibirica. AGM. H 1.8m. S 80cm. C Moist but well-drained clay, loam; full sun to light shade. SI Late summer – autumn. HR RHS H7, USDA 5a-8b.
Leucojum aestivum ‘Gravetye Giant’
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The perfect bulb for a damp meadow garden in sun or dappled shade, where other bulbs wouldn’t survive. Great together with ferns, such as Matteuccia. With glossy, strap-like, dark-green leaves, and leafless stems bearing up to eight bell-shaped, slightly fragrant, white flowers, tipped with green. AGM. H 60-80cm. S 30cm. C Moist but well-drained soil; full sun to part shade. SI May – June. HR RHS H7, USDA 4a-8b.
Lobelia x speciosa ‘Hadspen Purple’
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This is a short-lived perennial but worth using as a vertical accent, scattered through meadow-style plantings, working especially well with Sporobolus or Molinia grasses. The fantastic, bright-purple flower racemes are attractive for a long time in summer. H 80cm. S 30cm. C Mesic-moist, loam, clay; full sun. SI July – September. HR RHS H5, USDA 5a-8b.
Lythrum salicaria ‘Swirl’
Clump-forming perennial with strongly upright, branching stems to 1m tall, clad with narrow, lance-shaped leaves that turn red in autumn. Airy spikes of rich rosy-purple flowers are produced over a long period during summer. H 1m. S 40cm. C Moist, loam, clay; full sun. SI July – August. HR RHS H7, USDA 4a-9b.
Molinia caerulea subsp. arundinacea ‘Transparent’
A deep-rooted, deciduous, cool-season grass for various conditions. Arching mounds of strap-like foliage. Transparent, airy spikelets with greenish-purple flowers emerge in late summer, turning yellow in November. Combines well with Iris sibirica, persicarias and sanguisorbas. H 1.8m. S 60cm. C Moist loam, clay; full sun to part shade. SI August – November. HR RHS H7, USDA 5a-8b.
Sanguisorba officinalis ‘Arnhem’
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A Piet Oudolf selection with tall, wiry, branched flower stalks, carrying deep rose-pink drumstick flowers in summer. This was one of the best in our trials; very floriferous and, unlike many other tall sanguisorbas, doesn’t generally flop. Cut back after flowering to prevent seedlings. H 1.8m. S 50cm. C Mesic-moist, loam, clay; full sun to part shade. SI July – August. HR RHS H7, USDA 4a-8b.
Read our guide on growing sanguisorba
Viburnum nudum Brandywine (= ‘Bulk’)
One of my favourite viburnums for woodland-edge plantings. It’s a medium-sized shrub with glossy leaves that turn wine-red in autumn. Large clusters of ornamental berries, which mature from pale-green through white, pink and blue to black, remain after the leaves have fallen. This cultivar is self-fertile. H 1.5-2m. S 1.5m. C Moist but well-drained soil; full sun to part shade. SI Late
summer – autumn. HR RHS H6, USDA 5a-9b.