Growing Perennials

Revised by Joey Williamson, HGIC Horticulture Extension Agent, Clemson University, 12/15. Originally prepared by Karen Russ, HGIC Horticulture Specialist, and Bob Polomski, Extension Consumer Horticulturist, Clemson University. New 06/99. Images added 09/15 & 12/15.

HGIC 1153

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Herbaceous perennials generally live for three or more seasons, but usually the tops die back to the ground each fall. The crown and roots of the plant resume growth in spring. A few perennials are evergreen or keep a green rosette of leaves at the base in winter. Hardy perennials can live through the winter without protection.

Many plants, such as cannas and dahlias, are hardy perennials in South Carolina that will not live through the winter outside farther north. On the other hand, many of the perennials that grow well in the Northeast United States or England will not tolerate hot, humid summers. Since books about perennials are often written for those cooler climates, it is important to use care in selecting plants that are adapted to Southern heat and humidity.

Sunny perennial bed with red beebalm (Monarda didyma) and daylilies (Hemerocallis species).
Sunny perennial bed with red beebalm (Monarda didyma) and daylilies (Hemerocallis species).
Joey Williamson, ©2015 HGIC, Clemson Extension

Ornamental Features

Perennials provide year-round color and interest; with endless variations in colors, sizes, habits and time of bloom. Although some perennials flower for only a few weeks, the ever-changing color display forms much of the excitement of a perennial garden. Many perennials will re-bloom in the warm climate of South Carolina.

Some perennials, such as ferns and hostas, are grown principally for their beautiful foliage. Include foliage plants to extend seasonal color and texture in the garden.

Landscape Use

While the traditional English perennial border was entirely made up of herbaceous perennials, they are attractively used in combination with other plants in the total landscape. Perennials are easily used as ground covers, mixed with annuals, grown in containers, and used as accents or specimen plants.

There are perennials for full sun, part-sun or heavy shade, and for dry, moist or wet soil. Select perennials that are suited to the growing conditions where they will be planted. Select a planting area with good air circulation to help avoid diseases.

Soil Preparation

Good soil preparation is extremely important for growing perennials, since they may be in place for many years. Deeply spade the beds to a depth of eight to 10 inches. Amend clay soils by mixing in at least 2 inches of composted pine bark, composted leaf mold, or a pine bark-based soil conditioner to improve the soil drainage and aeration. Improve water retention in sandy soils by mixing in 2 to 3 inches of composted leaf mold, peat moss, manure, or a peat moss-based potting soil. Good soil drainage is critical to the success of most perennials. Raised beds can be used to ensure adequate drainage.

Base fertilizer and lime applications on the results of a soil test for best results. In the absence of a soil test, add either a complete fertilizer such as 10-10-10 at the rate of 1 pound per 100 square feet of bed area, or add either a complete slow-release fertilizer or complete organic fertilizer following label directions.

A pH of 6.0 to 6.5 is ideal for most perennials. Most South Carolina soils are very acidic (except for some areas along the coast) and require the addition of lime to correct pH. In the absence of a soil test, add 4 pounds of pelletized lime (3 pints) per 100 square feet of bed area. Incorporate lime and fertilizer into the top 4 to 6 inches of soil after mixing in the soil amendments. Rake the soil surface smooth. For more information about how to test the soil, please see HGIC 1652, Soil Testing.

Planting

Most perennials should be planted in the fall or early spring. Fall planting gives the plant more time to become established before the start of active growth in the spring. Fall-planted perennials are usually well-established before hot weather. Fall planting should be finished at least 6 weeks before hard-freezing weather occurs.

Early spring is also considered a good time to plant perennials. Planting early, just after killing frosts have passed, is better than later spring planting.

Many perennials can be grown from seed, but most gardeners prefer to start with established plants. Perennials are available grown in containers, field-grown, or shipped bare-root and dormant.

If plants are somewhat pot-bound at planting time, loosen the roots around the bottom and sides of the root ball and spread them out in the bottom of the planting hole. To encourage side root growth, make the hole twice as wide as deep. Refill the hole, firming the soil in around the plant to avoid air pockets. Be sure the crown of the plant (the point where roots and top join) is even with the soil surface.

Watering

Water the new perennials thoroughly following planting to settle the soil around the roots. Pay especially close attention to watering the first few weeks while plants develop their root systems. Adequate moisture is essential for the growth of perennials. Most perennials require at least 1 to 1½ inches of water per week from rain or irrigation. More may be needed during very hot weather.

To promote deep root growth, water thoroughly and deeply. Allow the soil surface to dry before watering again. Soaker hoses and drip irrigation are ideal watering methods since they save water and avoid wetting leaves and flowers.

Mulch perennials with a 1- to 2-inch layer of compost, pine bark or pine straw to help keep down weeds and conserve moisture. Avoid overly heavy mulching to help prevent crown rot.

Maintenance

Weed control should usually be done by hand-weeding or with the use of herbicides to avoid damaging shallow roots. Read and follow label directions before using any herbicide. Do not apply pre-emergence herbicides around newly planted perennials, as these products will stop root growth.

Maintenance fertilization should be based on the results of a soil test. In the absence of a soil test, apply a complete, slow-release fertilizer, such as a 12-6-6, at the rate of 1 to 2 pounds per 100 square feet of bed area just before new shoots emerge in the early spring. For additional growth, repeat the fertilizer application in 6 weeks. Alternatively, complete organic fertilizers may also be used. However, if a soil test reveals that the soil pH is above 6.5, use an acid-forming, complete fertilizer instead, such as an azalea & camellia fertilizer, or use an acid-forming, complete organic fertilizer. Avoid touching any emerging leaves with fertilizer to avoid leaf damage. Alternatively, apply 4 to 7 pounds of a complete organic fertilizer, such as Espoma Garden-tone (3-4-4) per 100 square feet.

Many newly planted perennials will not bloom the first year. A few, such as peonies, may take several years to bloom heavily.

Many perennials should be staked to prevent them from bending or falling over during wind and rain. When staking is done correctly, the plants grow to cover the stakes. A floppy perennial plant may be an indication that the plant is not receiving adequate sunlight and needs to be relocated.

Remove old flowers to encourage re-bloom on perennials. Many perennials should be cut back to ground level after bloom is finished to encourage new leaf growth from the base.

Remove dead foliage and stems in the fall, and mulch to protect crowns and roots from alternating mild and freezing weather.

Most perennials eventually become overcrowded and require division. Information on division is available in HGIC 1150, Dividing Perennials. Many perennials are also easily propagated in this way. Other methods of propagating perennials include stem cuttings, root cuttings and seed.

Problems

Perennials vary considerably in their susceptibility to pests. Selection of resistant species and cultivars, proper site selection, and good cultural practices will prevent many disease problems.

Perennials for Various Uses

Many perennials are available in several cultivars with different color, height or other attributes. Some, such as the heat-and humidity-tolerant cultivar of lamb's ears called 'Big Ears,' are better suited to our climate than the species. Consult with a local nursery person or Extension specialist for cultivars that are especially suited to your area.

Perennials for Shade

Those marked with a * will tolerate the most shade.

Acanthus mollis - Bear's Breech
Alchemilla mollis - Lady's Mantle
Amsonia tabernaemontana - Blue Star

Blue Star (Amsonia tabernaemontana) grows well in partial shade with deep, moist soil. It is a native, spring blooming perennial. It is a native to the Southeast US. The flowers are soft blue.
Blue Star (Amsonia tabernaemontana) grows well in partial shade with deep, moist soil. It is a native, spring blooming perennial. It is a native to the Southeast US. The flowers are soft blue.
Joey Williamson, ©2015 HGIC, Clemson Extension

Anemone species
Aquilegia species - Columbine
Arum italicum - Painted Arum *
Asarum species - Wild Gingers *

Please see HGIC 1113, Wild Gingers

Aspidistra elatior - Cast Iron Plant *
Astilbe x arendsii - Astilbe
Begonia grandis - Hardy Begonia
Bergenia cordifolia - Heartleaf Bergenia
Brunnera macrophylla - Siberian Bugloss
Carex elata - Golden Sedge
Ceratostigma plumbaginoides – Plumbago

Please see HGIC 1180, Perennial Leadwort

Chasmanthium latifolium – Upland River Oats
Chelone obliqua - Turtlehead
Chrysogonum virginianum - Green and Gold

Please See HGIC 1186, Green & Gold.

Green & Gold (Chrysogonum virginianum) flowers best in partial shade, and is a slow spreading perennial that blooms in spring. It is a native to the Southeast US
Green & Gold (Chrysogonum virginianum) flowers best in partial shade, and is a slow spreading perennial that blooms in spring. It is a native to the Southeast US.
Joey Williamson, ©2015 HGIC, Clemson Extension

Cimicifuga species - Bugbane
Convallaria majalis - Lily-of-the-Valley *
Cyclamen species - Hardy Cyclamen
Dicentra species - Bleeding Heart
Digitalis species - Foxglove
Epimedium species - Barrenwort *
Ferns * (most)

Please see HGIC 1176, Hardy Ferns

Galium odoratum - Sweet Woodruff *
Geranium maculatum - Wild Cranesbill
Gillenia trifoliata - Bowman's Root
Helleborus foetidus - Bearfoot Hellebore
Helleborus x hybridus - Lenten Rose

Please see HGIC 1185 Lenten Rose

Hexastylis species – Gingers

Please see HGIC 1113, Wild Gingers

Lenten Rose (Helleborus x hybridus) has flowers that range from white to mauve and purple. This perennial is evergreen, blooms in the very early spring, and slowly spreads by seeds.
Lenten Rose (Helleborus x hybridus) has flowers that range from white to mauve and purple. This perennial is evergreen, blooms in the very early spring, and slowly spreads by seeds.
Joey Williamson, ©2015 HGIC, Clemson Extension

Heuchera species & hybrids - Coral Bells

'Caramel' Coral Bells (Heuchera 'Caramel') is an example of a hybrid and one of the many foliar colors that are available. One species, Heuchera americana, is a native to the Southeast US. Flowers are typically pink or red.
'Caramel' Coral Bells (Heuchera 'Caramel') is an example of a hybrid and one of the many foliar colors that are available. One species, Heuchera americana, is a native to the Southeast US. Flowers are typically pink or red.
Joey Williamson, ©2015 HGIC, Clemson Extension

Hosta species - Plantain Lily

Please see HGIC 1165, Hosta

Iris cristata - Dwarf Crested Iris

Please see HGIC 1167, Iris

Lamium maculatum - Spotted Dead Nettle *
Lobelia cardinalis - Cardinal Flower *
Lobelia siphilitica - Great Blue Lobelia *
Mertensia virginica - Virginia Bluebells *
Myosotis sylvatica - Forget-me-not
Phlox divaricata – Woodland Phlox

Woodland Phlox (Phlox divaricata) is a beautiful, spring blooming, native perennial. The species has blue, fragrant  flowers, but other cultivars are available in white and pink.
Woodland Phlox (Phlox divaricata) is a beautiful, spring blooming, native perennial. The species has blue, fragrant  flowers, but other cultivars are available in white and pink.
Joey Williamson, ©2015 HGIC, Clemson Extension

Phlox stolonifera - Creeping Woodland Phlox
Polygonatum species - Solomon's Seal *

Solomon’s Seal (Polygonatum species) are spring blooming perennial for partial shade. This variegated form is Polygonatum odoratum 'Variegatum', which blooms in the spring and is an extremely drought tolerant plant.
Solomon’s Seal (Polygonatum species) are spring blooming perennial for partial shade. This variegated form is Polygonatum odoratum 'Variegatum', which blooms in the spring and is an extremely drought tolerant plant.
Joey Williamson, ©2015 HGIC, Clemson Extension

Primula species - Primrose
Pulmonaria species - Lungwort *
Salvia koyame - Japanese Yellow Sage
Saxifraga stolonifera - Strawberry Begonia
Shortia galacifolia - Oconee Bells *
Sisyrinchium angustifolium - Blue-Eyed Grass
Smilacina racemosa - False Solomon's Seal
Spigelia marilandica - Indian Pink

Please see HGIC 1188, Indian Pink

Thalictrum species - Meadow Rue
Tiarella species - Foam Flower *

Please see HGIC 1183, Foam Flower

Tradescantia virginiana - Spiderwort *
Tricyrtis species - Toad Lily *
Trillium species - Wake Robin *
Viola species - Violet *

Tolerant of Moist or Damp Soils

Those marked with a * will tolerate wetter soils.

Acorus gramineus - Sweet Flag *
Amsonia tabernaemontana - Blue Star
Aster novae-angliae - New England Aster

New England Aster (Aster novae-angliae) is a late summer-blooming perennial that is native to the Eastern US. The species has violet-purple flowers, but cultivars are available in white or various shades of pink.
New England Aster (Aster novae-angliae) is a late summer-blooming perennial that is native to the Eastern US. The species has violet-purple flowers, but cultivars are available in white or various shades of pink.
Joey Williamson, ©2015 HGIC, Clemson Extension

Astilbe x arendsii - Astilbe
Canna species - Canna *
Carex species - Sedge *
Chelone species - Turtlehead *
Cimicifuga species - Bugbane
Colocasia esculenta - Elephant's Ear *
Crinum species - Milk and Wine Lily, Crinum
Cyperus alternifolius - Umbrella Sedge *
Eupatorium purpureum - Joe-Pye Weed
Ferns, many

Please see HGIC 1176, Hardy Ferns

Filipendula species - Meadow Sweet
Galium odoratum - Sweet Woodruff
Helianthus angustifolius - Swamp Sunflower *
Hemerocallis species – Daylily

Please see HGIC 1163, Daylily

Hibiscus coccineus - Texas Star *
Iris ensata - Japanese Iris *
Iris virginica - Blue Flag*
Iris laevigata  - Japanese Water Iris*
Iris hybrids - Louisiana Iris *

Please see HGIC 1167, Iris

Joe-Pye Weed (Eupatorium purpureum) is a tall, native perennial with soft mauve-pink flowers held in large flower clusters. It typically blooms in October.
Joe-Pye Weed (Eupatorium purpureum) is a tall, native perennial with soft mauve-pink flowers held in large flower clusters. It typically blooms in October.
Joey Williamson, ©2015 HGIC, Clemson Extension

Ligularia species - Golden Ray *
Lobelia cardinalis - Cardinal Flower *
Lobelia siphilitica - Great Blue Lobelia *
Matteuccia pensylvanica - Ostrich Fern
Monarda species - Bee Balm
Myosotis sylvatica - Forget-me-not
Osmunda regalis - Royal Fern *

Please see HGIC 1176, Hardy Ferns

Physostegia virginiana - Obedient Plant
Primula species - Primrose
Tradescantia virginiana - Spiderwort
Zantedeschia aethiopeca - Calla *

Perennials for Hot, Dry Conditions

Achillea species – Yarrow

'Coronation Gold' Yarrow (Achillea 'Coronation Gold') is an excellent hybrid cultivar that resists flopping after rains. Golden, plate-like flower clusters appear in late summer. Plants are very drought tolerant.
'Coronation Gold' Yarrow (Achillea 'Coronation Gold') is an excellent hybrid cultivar that resists flopping after rains. Golden, plate-like flower clusters appear in late summer. Plants are very drought tolerant.
Joey Williamson, ©2015 HGIC, Clemson Extension

Agapanthus africanus - Lily-of-the-Nile
Agave parryi - Hardy Century Plant
Andropogon species - Bluestem Grass
Artemisia species - Artemesia
Asclepias tuberosa - Butterfly Weed

Butterfly weed (Asclepias tuberosa) grow in sunny locations and blooms in late summer. It is a nectar source & a larval food source for the Monarch butterfly.
Butterfly weed (Asclepias tuberosa) grow in sunny locations and blooms in late summer. It is a nectar source & a larval food source for the Monarch butterfly.
Joey Williamson, ©2015 HGIC, Clemson Extension

'Lucifer' Crocosmia (Crocosmia x Curtonus 'Lucifer') is a relative of iris and is a full-sun perennial that blooms in summer with brilliant scarlet flowers.
'Lucifer' Crocosmia (Crocosmia x Curtonus 'Lucifer') is a relative of iris and is a full-sun perennial that blooms in summer with brilliant scarlet flowers.
Joey Williamson, ©2015 HGIC, Clemson Extension

Baptisia species - False Indigo

Please see HGIC 1184, Baptisia

Belamcanda - Blackberry Lily
Coreopsis species - Coreopsis
Cortaderia selloana - Pampas Grass
Crocosmia x Curtonus ‘Lucifer’
Delosperma cooperi - Hardy Ice Plant
Festuca ovina - Blue Fescue
Gaillardia species - Blanket Flower
Gaura lindheimeri - Whirling Butterflies
Helianthus species - Perennial Sunflower
Hemerocallis species and hybrids – Daylily

Please see HGIC 1163, Daylily

Hesperaloe parviflora - False Red Yucca
Iris hybrids - Bearded Iris

Please see HGIC 1167, Iris

Kniphofia uvaria - Red Hot Poker
Lantana species – Lantana

Please see HGIC 1177, Lantana

Lavandula x intermedia - Provence Lavender
Liatris species - Gayfeather
Limonium latifolium - Sea Lavender
Nepeta species - Catmint
Oenothera species - Evening Primrose, Sundrops
Opuntia humifusa - Prickly Pear Cactus
Perovskia atriplicifolia - Russian Sage
Phlomis species - Jerusalem Sage
Phlox subulata - Thrift
Rudbeckia species - Black-eyed Susan
Ruellia brittoniana - Mexican Petunia
Salvia greggi - Texas Sage
Santolina species - Lavender Cotton
Sedum species - Stonecrop
Sempervivum tectorum - Hens & Chickens
Solidago odora - Sweet Goldenrod

Please see HGIC 2326 Goldenrod

Stachys byzantina - Lamb's Ear

Verbena species – Verbena

Please see HGIC 1175, Verbena

Yucca species - Yucca

Perennials for Poor, Sandy Soil

Achillea species - Yarrow
Anthemis tinctoria - Golden Marguerite
Asclepias tuberosa - Butterfly Weed
Baptisia species - Wild Indigo

Please see HGIC 1184, Baptisia

Belamcanda chinensis - Blackberry Lily
Euphorbia species - Spurge
Gaillardia species - Blanket Flower
Gaura lindheimerii - Whirling Butterflies
Hemerocallis species – Daylily

Please see HGIC 1163, Daylily
Hesperaloe parviflora - False Red Yucca
Lantana species – Lantana

Please see HGIC 1177, Lantana

Plumbago auriculata – Plumbago

Please see HGIC 1180, Perennial Leadwort

Salvia greggi - Texas Sage
Setcrasea pallida - Purple Heart
Yucca species - Yucca

Attractive Foliage

Those marked with a * are gray or silvers that tolerate heat and humidity.

Acanthus species - Bear's Breech
Alchemilla mollis - Lady's Mantle
Artemisia 'Powis Castle' - Wormwood *
Baptisia species - False Indigo

Please see HGIC 1184, Baptisia

The white-flowered false indigo (Baptisia alba) forms a 3 – 4 foot, multi-stemmed clump and blooms in April.
The white-flowered false indigo (Baptisia alba) forms a 3 – 4 foot, multi-stemmed clump and blooms in April.
Joey Williamson, ©2015 HGIC, Clemson Extension

Chrysanthemum pacificum - Gold & Silver Mum
Cynara cardunculus - Cardoon
Delosperma cooperi - Hardy Ice Plant *
Dianthus gratianopolitanus - Cheddar Pink *
Helleborus x hybridus - Lenten Rose

Please see HGIC 1185, Lenten Rose

Heuchera species - Coral Bells
Hosta species and hybrids - Plantain Lily

Please see HGIC 1165, Hosta

Iris pallida 'Variegata' - Variegated Sweet Iris

Please see HGIC 1167, Iris

Lamium maculatum - Spotted Dead Nettle
Marrubium incanum - Silver Horehound *
Opuntia humifusa - Prickly Pea
Ornamental Grasses

Please see HGIC 1178, Ornamental Grasses

Phlomis fruticosa - Jerusalem Sage *
Polygonatum species - Solomon's Seal
Pulmonaria species - Lungwort
Santolina chamaecyparissus - Lavender Cotton *
Sedum species - Stonecrop
Sempervivum tectorum - Hen-and-chicks
Stachys byzantina 'Big Ears' - Lamb's Ear *
Teucrium fruticans - Silver Germander *

Perennials That Can Be Invasive

Aegopodium podagraria - Goutweed
Ajuga – Bugleweed

Please see HGIC 1102, Ajuga

Artemisia ludoviciana - Western Mugwort
Arundinaria species - Bamboo
Arundo donax - Giant Reed
Bambusa species - Clumping Bamboo

Please see HGIC 2320, Controlling Bamboo

Campanula rapunculoides - Creeping Bellflower
Chasmanthium latifolium – Upland River Oat

Upland River Oats (Chasmanthium latifolium) spreads by seed production. This is one of the few ornamental grasses that will grow well in shade. It is also called Northern Sea Oats.
Upland River Oats (Chasmanthium latifolium) spreads by seed production. This is one of the few ornamental grasses that will grow well in shade. It is also called Northern Sea Oats.
Joey Williamson, ©2015 HGIC, Clemson Extension

Chrysanthemum leucanthemum - Ox-eye Daisy
Coronilla varia - Crown Vetch
Cortaderia jubata - Purple Pampas Grass
Equisetum hyemale - Horsetail
Euphorbia cyparissias - Cypress Spurge
Elymus arenarius - Blue Lyme Grass
Eupatorium coelestinum - Hardy Ageratum
Hemerocallis fulva - Common Daylily, Ditch Lily
Houttuynia cordata - Chameleon Plant
Imperata cylindrica - Japanese Blood Grass

Please see HGIC 2318, Cogongrass

Iris pseudocorus - Yellow Iris

Please see HGIC 1167, Iris

Lantana camara – Lantana

Please see HGIC 1177, Lantana

Lychnis coronaria - Rose Campion
Lysimachia species - Loosestrife
Lythrum salicaria - Purple Loosestrife
Miscanthus sinensis - Silver Grass, Zebra Grass

Please see HGIC 1178, Ornamental Grasses

Macleaya species - Plume Poppy
Mentha species - Mint
Oenothera species - Evening Primrose
Persicaria virginiana - Tovara
Phalaris arundinaceae var. picta - Ribbon Grass
Phyllostachys species - Japanese Bamboo

Please see HGIC 2320, Controlling Bamboo

Rose Campion (Lychnis coronaria) is a clump forming, short-lived perennial that freely spreads by seed. It flowers during the summer months with rose-magenta blooms that contrast well with its gray-green foliage.
Rose Campion (Lychnis coronaria) is a clump forming, short-lived perennial that freely spreads by seed. It flowers during the summer months with rose-magenta blooms that contrast well with its gray-green foliage.
Joey Williamson, ©2015 HGIC, Clemson Extension

Physostegia virginiana - Obedient Plant
Polygonum species - Knotweed
Tanacetum vulgare - Tansy
Vernonia species – Ironweed

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