Perennials for Wet Sites

If you have a spot where your shoes always get muddy and skunk cabbage grows thick and lush, you’re in luck. You have a bog.

Let the skunk cabbage (Symplocarpus foetidus) grow. It’s the first harbinger of spring, and its flame-shaped spathes, containing flower-covered spadices, produce enough heat to warm holes through the snow. The spathes are a promising sight in late winter, and are followed by big, decorative, cabbagelike leaves in spring and summer.

Why not enhance and prolong the display by taking advantage of the many gorgeous perennials that enjoy a boggy spot? With their varied flora, including aquatics, small woody plants, and grasses, bogs are among the most biologically diverse places on anyone’s property; adding the beauty of perennials simply enriches the mix.

A bog isn’t one narrowly definable kind of place, but rather a continuum of wet places. At one extreme is shallow standing water, hosting watercress, horsetail, water arum, and pickerel weed. Above-water zones range from continually wet marshes to boggy meadows that can dry out in periods of summer drought. Some perennials will thrive in continually wet marshes, but most of those that tolerate wet feet prefer the slightly better drained boggy meadow.

Boggy places can occur naturally for several reasons. First, a piece of land may be poorly drained and contain a shallow basin where rainwater collects. Second, the bog may mark a transitional area between a pond or stream and drier land. Third, the bog may be caused by springs coming to the surface. The last two kinds of bog are by far the most common.

Pathways

If your bog is a large one, chances are you’re going to want some means of access through it, the better to appreciate the plants. A path through a natural bog, however, requires some planning. Water moves slowly through natural bogs, finding an outlet somewhere, even if it’s down through the soil. If you construct a raised path, you run the risk of damming up the water flow on one side or the other of the path, where it will turn stagnant (and stinky) and attract mosquitoes.

The solution is to construct a small bridge every 10 to 12 feet, so that water can flow underneath and find its escape. A bridge can be as simple as a sturdy plank laid over a three-foot-wide break in the path, supported by stones flat enough to keep footing secure. Or it can be a Japanese footbridge—a simple but attractive affair. Bridges make excellent viewing points, since they funnel traffic along a specific route. Walk around your bog to see if there are any other natural viewing points. You might want to site a bench there.

Plants and design

At my former house in Pennsylvania, my back deck looked out over a marshy area about 100 by 60 feet where two springs came to the surface. From the deck down to the ground was at least 10 feet, so close to the deck I planted tall perennials—specifically queen of the prairie (Filipendula rubra ‘Venusta’) and Eupatorium ‘Gateway’. The filipendula is a stunning sight when it blooms from mid-June through July, opening fluffy, cotton-candy plumes of rich rose pink on four- to seven-foot stems. ‘Gateway’ can reach six feet, with puffy heads of reddish purple to mauve florets from August to October. Looking down onto these marsh plants, I had a continual display of bloom from June through October.

Natural viewing points in most bog gardens, however, are at eye level. As you survey your boggy area, think about planting the perennials to form tiers, with the smallest plants in front and the largest in back, so that each one is easily seen. Vary the pattern, however, just as you would in an ordinary border, by mixing in large clumps of grasses, sedges, or other foliage plants.

Where there is shallow standing water, the three-way sedge (Dulichium arundinaceum) is a possibility, along with the clumps of shaggy tussock grass (Carex stricta), which likes the same conditions as skunk cabbage. Another exceptionally pretty sedge is

Bowles’s golden sedge (Carex elata ‘Aurea’), which grows into a fountain of slender golden leaves by midsummer and holds its shape and color until fall. The cloudlike masses of fine-flowering tufted hair grass (Deschampsia cespitosa) make beautiful companions to larger-leaved perennials, and are especially effective against a background of dark conifers. Variegated manna grass (Glyceria maxima ‘Variegata’) mixes well with darker-leaved bog plants like rodgersias. The graceful, upright stems of the common rush (Juncus effusus) belong in the bog garden, too.

Among other foliage plants for the bog garden, one would think hostas appropriate, since they like consistently moist soil, but they thrive only where drainage is good. The solution is to plant them upslope a bit from the real boggy areas. Ferns are a natural choice for damp soils. Cinnamon fern (Osmunda cinnamomea) and shield fern (Polystichum braunii) like the same moist yet well-drained conditions as hostas. For constantly wet, marshy areas, consider lady fern (Athyrium filix-femina), crested wood fern (Dryopteris cristata), and the glorious royal fern (Osmunda regalis), which grows up to six feet tall and can anchor the back of a boggy perennial border as well as—or better than—any other plant.

In cold areas, cleanup is often best carried out during freezing weather; by that point, deciduous shrubs will have shed their leaves, herbaceous plants will have died down, and the ice underfoot will keep your feet from getting muddy. Unless, of course, you like galumphing through the mud of your gorgeous bog garden, like a kid delirious with the joy of it all.

 

A selection of moisture-loving perennials:

TWO FEET OR LESS
Astilbe chinensis var. pumila: Zones 4–9. Bright rose-pink flower spikes to 12 in. in August-September. Semishade.
Caltha palustris/marsh marigold: Zones 3–9 Opens clusters of yellow flowers on 12–18-in. stems mid-April-June. Semishade.
Dodecatheon jeffreyi/shooting star: Zones 5–9 Likes wet conditions in late winter and spring; bears distinctive blossoms on 1- or 2-ft. stalks in June, followed by quick dormancy. Semishade.
Doronicum columnae/leopard’s bane: Zones 4–9 Toothed leaves send up foot-tall flower stalks early May-June, topped with bright yellow daisies; disappears by late summer. Full sun-semishade.
Gentiana septemfida var. lagodechiana: Zones 4–9 Easier to grow than most gentians; bears blue flowers July-August on trailing stems up to a foot tall. Full sun to semishade.
Geum rivale/water avens: Zones 3–8 Produces small, drooping purple and orange-pink flowers late May-mid-July on 18-in. stems. Semishade.
Liriope spicata/creeping lilyturf: Zones 5–9 Makes fine. 8-in.-tall, grasslike patches of foliage with lilac to white flowers late in season. Semishade.
Myosotis scorpioides var. semperflorens/forget-me-not: Zones 3–9 Grows 6–10 in. tall; continues to open tiny bright blue flowers May-frost. Full sun to semishade.
Polemonium reptans/Jacob’s ladder: Zones 3–9 Grows to just a foot tall; makes clumps of fine-looking foliage and light blue flowers. April-July. Semishade.
Trillium grandiflorum/white trillium: Zones 3–8 Makes a low-growing trio of pointed leaves that produce a stem to a foot or more tall with a single white flower on top. late April-May. Full shade.
TWO TO THREE FEET
Aquilegia longissima/yellow columbine: Zones 3–9 A beautiful, pale yellow columbine that flowers June-August; spurs are 4–6 in. long on a 2-foot plant. Full sun.
Chelone lyonii/turtlehead: Zones 4–9 This swamp denizen produces 2- to 3-ft. stems topped with short spikes of hooded pink flowers August-mid-September. Full-semishade.
Dicentra spectabilis/bleeding heart: Zones 3–9 One of the prettiest perennials, with heart-shaped pink and white blossoms below arching 2-ft. stems May-June. Semishade.
Iris ensata/Japanese iris: Zones 5–9 Flat, beardless flowers appear July-August and come in most colors except pink, surmounting 2-ft. swordlike leaves. Full sun.
Liatris spicata/blazing star: Zones 3–10 In July-September sends up 3-ft. wands of bright rose-purple florets that open from the top down. Plant where winter drainage is good. Full sun.
Lobelia cardinalis/cardinal flower: Zones 2–8 Opens 30-in. spikes of intense scarlet flowers late July-September. Likes marshy soil. Full sun-semishade.
Platycodon grandiflorus/balloon flower: Zones 3–9 Should be more widely planted. In June-July produces many closed-ended flowers on 3-ft. stems that open into flat-faced, lilac stars. Full sun.
Thalictrum aquilegiifolium/meadow rue: Zones 5–9 Forms an open, 3-ft. structure of columbine-like leaves and puffy flowers May-July in light violet to pink. Self-sows vigorously. Semishade.
THREE TO FOUR FEET
Ligularia dentata ‘Desdemona’: Zones 4–9 Bears large, spotted leaves and sends up 3-ft. stems of bright orange daisies with brown centers. Semishade.
Lilium canadense/meadow lily: Zones 4–8 Sports bright orange to red nodding flowers on sturdy 3- to 5-ft. stems in late June to August. Semishade.
Phlox carolina: Zones 4–9 In June-July opens clusters of typical phlox flowers in pink, purple, or white on 3- to 4-ft. stems. Full sun.
Rudbeckia laciniata ‘Goldquelle’/coneflower: Zones 3–9 Typically grows 3–4 ft. tall, with clusters of metallic yellow daisies atop the stems August-September. Full sun.
Trollius chinensis ‘Golden Queen’/globeflower: Zones 4–7 Sends up sturdy stems to about 3 ft. May-June, topping them with pretty, bowl-shaped, double flowers. Semishade.
FOUR FEET OR MORE
Aruncus dioicus/goatsbeard: Zones 4–9 Creamy white plumes rise above ferny foliage and reach 4–6 ft. in June-July. Male plants have showier but shorter-lived flowers. Semishade.
Cimicifuga racemosa/black cohosh: Zones 3–9 Forms a basal clump of finely divided leaflets; in early July-August produces wands of creamy white florets from 6 to 7 ft., Semishade.
Eupatorium ‘Gateway’/joe-pye weed: Zones 4–7 Makes a dazzling display of rounded, pinkish lilac flower heads to 5–6 ft in August-October. Reddish stems need no staking. Full sun-semishade.
Filipendula rubra ‘Venusta’/queen of the prairie: Zones 3–9 Tops its long, sturdy, 6-ft. stems with shaggy, puffy, rose-pink plumes in June. An outstanding plant to mix with joe-pye weed. Full sun-semishade.
Hibiscus moscheutos ‘Lord Baltimore’/rose mallow: Zones 5–9 The 4- to 6-ft. stems never need staking; opens huge, 7-in., brightly colored rose-red blossoms July-October. Looks decidedly tropical. Full sun.
Cardiocrinum giganteum: Zones 5–8 One of the most magnificent of flowering perennials, with stalks towering to 10 ft. in midsummer crowned with tubular white lilies. Semishade.
Thalictrum rochebrunianum/meadow rue: Zones 4–9 A majestic perennial up to 8 ft. tall that produces tiny lavender-purple flowers along the top third of its tall stems July-September. Semishade.
Veronicastrum virginicum ‘Album’/white culver’s root: Zones 3–9 Looks like a large (5–6 ft.) veronica, with tall spikes of small florets in a dazzling display early August-late September. Full sun.

Plants to avoid

Some grasses and grasslike plants are too invasive for the carefully planted bog garden. Avoid the common reed (Phragmites australis) and its cultivars, for they are horribly invasive on newly turned wet soil, spreading by strong rhizomes, much like bamboo. Reed canary grass (Phalaris arundinacea) is a European import that has become a major threat to marshlands in the northern United States, where it chokes out native species. Cattails (Typha spp.) can also be aggressive colonizers of marshes. The tall species, T. angustifolia and T. latifolia, will quickly take over your bog and elbow out other species. You can safely get away with the miniature cattail, T. minima, though, which grows to about two and a half feet tall and is much better behaved than its larger cousins. One plant to avoid for sure is purple loosestrife (Lythrum salicaria), which is overwhelming native species throughout the wet areas of the northern states. In fact, it’s against the law to plant it in some places. Despite its beauty, it’s a first-class pest.

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