LOW MAINTENANCE PERENNIALS FOR CLAY SOILS

Barbara J. Bromley, Mercer Co. Horticulturist 2004

There is a wide variety of flowers available for the perennial garden, but when dealing with a problem soil, it becomes more difficult to select plants that are sure to survive most years. Subsoils and heavy clays can be a challenge. These are the soils on which water just sits rather than soaking into and can puddle for longer periods of time. When dry they are like brick; when wet they are sticky. The bed preparation is most important in cases like this.

A soil test is necessary to determine the amount of limestone needed to adjust acidity and fertilizers to supply plant nutrients. Coarse builder’s sand and large amounts of compost or other organic matter turned into the soil will improve both its texture and its tilth. Using the techniques of creating raised beds or berms and of double digging (working the soil to twice the normal bed depth) is also helpful. It is possible to plant some of the perennial flowering plants that follow directly into unprepared clay soil, but long term survival is less likely.

To help ensure survival of new plants, the amount of available light must be considered also. The plants listed below have been selected for sun, partial shade (ps), and shady (shade or sh) areas.

The plants listed below are just some of the perennial flowering plants that should adapt well to clay soils. Most are moderately to very pest resistant and are easy to grow. Good perennial reference books will supply additional information on propagation and maintenance requirements. Experiment to determine which are best for your sun and moisture levels.

Botanical Name	Common Name	Color	Bloom	Light	Water	Comments
Achillea tomentosa	woolly yarrow	yellow	Jun-Jul	sun	average/dry	Do not overwater, tolerates poor dry soil well.Stake in windy areas. Attracts beneficials.
Achillea filipendulina	fernleaf yarrow	yellow	Jun-Jul	sun	average/dry	3’, do not overwater, tolerates poor dry soil well.Good for drying. Attracts beneficials.
Arisaema spp.	Jack-in-the-pulpit	green/purple	May-July	shade	moist	Red berries. Great for a moist shade garden.
Aruncus dioicus	goatsbeard	white	Jun or Jul	ps/sun	moist	Shrub-like, 3-6’ tall. Long lived, not invasive.
Asclepias tuberosum	butterflyweed	orange et al	Jun-Aug	sun	average/dry	Non-invasive, drought tolerant. Attractsbutterflies and hummingbirds. Nice pods. Do notoverwater or move once established.
Astilbe arendsii & var.	false spirea, astilbe	white-pink-red	Jun-Aug	ps	moist	Needs moderate fertilization – a “gross” feeder.
Bergenia cordifolia	heartleaf bergenia	pink	Apr-May	s/sh	adaptable	18″ tall. Large leathery leaves,
Brunnera macrophylla	Siberian bugloss	blue	Apr-May	sun/sh	adaptable	12″ tall. Water in extended dry spells, does bestwith watering and fertilizing, but veryadaptable. Large heart-shaped leaves.
Echinacea purpurea	purple coneflower	pink	Jul-Oct	sun	average	Feed in summer. Japanese beetles may be aproblem. Very tough once established.Seeds popular with goldfinches.
Helenium autumnale‘Moerheim beauty’	Sneezewort	bronze red	Jul-Sept	sun/ps	average	Water in dry weather. Support stems inexposed sites. Vigorous.
Heliopsis scabra	Heliopsis	yellow	Jul-Aug	sun	adaptable	Long lasting flowers
Hemerocallis spp.	daylily	many	summer	sun/ps	average tomoist	Water in very dry weather. Few pests.
Heuchera hyb.	coral bells	white-pink-red	Jun-Aug	sun/ps	average	Mulch to prevent frost heaving. Good edgingplant.
Hibiscus spp.	rose mallow	white-pink-red	Jul-Sept	sun/ps	average tomoist	Shrub-like. Each flower lasts one day, but openover 4-6 weeks. Japanese beetles. Bold.Use as accent plants.
Hosta spp.	plantain lily	lavender	Jul-Aug	ps-sh	average	Slugs and deer are problems.
Houttuynia cordata’Chameleon’	houttuynia	white	June	sun/ps	moist/wet	Grown as a ground cover. May become invasive. Leavesgreen with white, pink, and red bands.
Iris sibirica, pseudo-acorus, versicolor, etc.	Siberian and blueand yellowflag iris	blue, violet,yellow et al.	variable	sun/ps	average tomoist	Many species adaptable to heavy soils andwet areas.
Liatris spicata	gayfeather, blazingstar	pinkish	Jul-Aug	sun/ps	average	Must have good drainage in winter. Attractsbutterflies and other pollinators.
Liriope muscari	lily turf	lavender-mauve-white	Aug-Oct	ps/sun	average	No lime. Tolerant of shade, drought, heat , andhigh humidity
Lysimachia spp.	Yellow loosestrife,gooseneck loosestrife, etc.	yellow-white	Jul-Sept	sun/ps	moist	Range in height from ground cover to 3′ tallVarying with species. Perfect along streamsor heavily irrigated areas.
Perovskia atriplicifolia	Russian sage	Lavender	Summer	sun	average – dry	3-4 feet tall. Aromatic gray foliage.
Primula spp.	primroses	many	Mar-Jun	ps/sh	moist	Go dormant in hot weather. Plant in clumpsor drifts.
Rudbeckia fulgida‘Goldsturm’	Goldsturm rudbeckia	yellow	July-Sept	sun/ps	average	Cut to the ground after flowering.May get powdery mildew.
Salvia spp.	salvia, sage	blue-violet	Jul-Oct	sun/ps	average	Gets leggy in too shady or moist soils. Verydrought tolerant.
Sedum spectabile var.	stonecrop, sedum	pink-red	Aug-Oct	sun	average-dry	Drought and pest resistant. Attract butterflies.
Tradescantia virginianavar.	spiderwort	blue-violet-white	Jun-Sept	sun/ps	moist-dry	Long-blooming. Grows almost anywhere. Formsdense clumps.
Yucca filamentosa	Adams’s needle	white	summer	sun	average/dry	Do not overwater. Plants are bold in textureand flower.