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Growing Calendar for Perennials

Note:   The Ohio State University Pocket Gardener will link you to good information on a limited number of plants. The entire database can be downloaded (4.3 mb). See Garden Links.

January through April

See Garden Tips Archives for those months.

May

>  Dahlias can be set in the ground after the frost-free date.  Ours are in pots on a screened porch, so they can get a jump start on the season.  (See March Archive)  Ours need to be pruned as soon as they begin to grow, then staked or caged, or they'll become top heavy and collapse.

>  A dose of fertilizer right before rhododendrons, azaleas, and roses bloom will produce stellar blooms.  After they bloom, clip the dead blooms, but be careful, because the new leaf growth are right below the dead buds.  Their lower branches can be propagated by layering.   

>  If you have a ladder and the time, (HA!) prune lilacs and forsythia after blooming.  Pruning later in the summer may result in flower bud loss for the following year.

>  Plant hollyhocks, foxglove, and delphinium.   Russian sage, globe thistle, and 'Foxy' foxglove should be planted  in front of 'Pacific Giant' delphiniums.    'Sensation' cosmos also look nice with hollyhocks; when the latter are fading, the former are often peaking.

>  Plant a rudbekia in front of a daylily and a 'Torch Light' gaillardia behind it.  When the daylily dies back, the gaillardia will flop over the daylilly, and the rudbekia will also hide the faded leaves.  This triage will provide color throughout the growing season and, since they  tolerate poor soils, can be naturalized in a meadow.  The annual dwarf cosmos, 'Brite Lights,' also looks good with these perennials.

June

According to the local nursery where I purchased Hydrangea macrophylla, 'All Summer Beauty', this cultivar is a hardier hydrangea.  I learned later this variety blooms on old growth and should not be pruned, which may account for lack of blooms the past 3 years.  If we get no bloom next year, I might consider moving it to a sunnier spot.   Winter injury and lack of sufficient sunlight are listed as the most common reason for lack of flowering.  A neighbor has a healthy looking one growing on their east wall, so I know they will bloom here.  This shrub is worth the effort if it blooms.

Black Cohosh (Cimicifuga racemosa; Bugbane) takes several years to germinate outdoors, so we broke down and bought one to plant in our shade garden.  We will try seeding in some clay pots this fall and bury them in the same garden where they will receive adequate moisture.  The roots are used as an expectorant and to control tinnitus (ringing in the ears).

Our Astilbe,  purchased last year at a garden club sale for our shade gardens, are flourishing under pine trees.

July

Perennials prefer to be transplanted in the fall, so this month is the best time for seeding them indoors.  See March Archive in Garden Tips.

In early to mid summer, thyme forms small tubular flowers that are very attractive to bees.  Harvest some before they flower for drying.  Wooly Thyme grows between cracks in cement or bricks.  The beauty of these types of thyme is that they tolerate a fair amount of traffic and they release a fragrance at the same time.

August

Bee balm, gaillardia, rudbekia, globe thistle, Shasta Daisies, Lambs' Ears are in peak bloom.  Tiger lilies should also be peaking now.

The best time to cut flowers (and herbs) is in the morning before the dew dries.  They should be 'cured'  in water in a dark place for about 8 hours before arranging.

                     delphinium_vase.jpg (10948 bytes)

One of this gardener's favorite lilies  is the very fragrant 'Casa Blanca' Oriental lily.  This bulb is worth the labor of surrounding it with hardware cloth during planting.  In a meadow are like ours, pine voles, ("meadow mice") will make short order of bulbs.

Prepare beds for a September planting of spring-flowering bulbs, ornamental grasses and shrubs, perennials, including chrysanthemums.  (Regions south of Zone 4-5 should wait till October to plant.) 

September

Cultivating

The spikey centers of  perennials echinacea, gaillardia, and globe thistle offer enough for sharing as the photo below demonstrates.  Bees and butterflies seem to prefer them to other members of the daisy family, e.g.,  rudbekia or Shasta daisies. 

bee_thistle.jpg (16463 bytes)

Globe Thistle

butterfly_echin.jpg (27116 bytes)

Echinacea

* Watering may still be necessary if temperatures are warm enough.

*  Annuals in container gardens are a bonus in the fall, when you can move pots around to track the sun. 

Pepperpot

Geraniums, petunias, and basil next to our south-facing cement porch remain impervious to low nighttime temperatures because the porch stores heat during the day. 

*  Calendula, sulking during the summer heat, now enjoys a comeback when temperatures cool down.

flowers_calendula_small.jpg (3341 bytes)

*  To harvest sunflower seeds, wait until the seeds are fully grown and firm, then cut the head leaving one foot of stem. Hang heads in a dry, airy spot to finish ripening. Do not store sunflowers one on top of another or they may rot.  (Va Tech Extension)

sunflower_yellow.jpg (18812 bytes)'Valentine'   Autumn Sunflower 'Autumn Harvest'

Pruning and Dividing

*  Perennials should be pruned systematically after blooms have peaked, leaving some leaves for plants to continue producing food for a healthy root system.   

* Give them a rest before dividing.  This is a committment to finding a suitable new planting site.  Something to keep in mind when purchasing them!  One plant can go a long way, if given the right growing conditions.

October

 

Source of Table:  Clemson University, Home and Garden Center, Prepared by Karen Russ, HGIC Information Specialist, and Bob Polomski, Extension Consumer Horticulturist, Clemson University

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
  • Anemone species
  • Aquilegia species Columbine
  • Arum italicum Painted Arum *
  • Asarum species 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
  • Chelone obliqua Turtlehead
  • Chrysogonum virginianum Green and Gold
  • 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)
  • Galium odoratum Sweet Woodruff *
  • Geranium maculatum Wild Cranesbill
  • Gillenia trifoliata Bowman’s Root
  • Helleborus foetidus Bearfoot Hellebore
  • Helleborus orientalis Lenten Rose
  • Heuchera species Coral Bells
  • Hosta species Plantain Lily
  • Iris cristata Crested 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 Wild Sweet William
  • Phlox stolonifera Creeping Woodland Phlox
  • Polygonatum species Solomon’s Seal *
  • 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
  • Thalictrum species Meadow Rue
  • Tiarella species Foam Flower *
  • Tradescantia virginiana Spiderwort *
  • Tricyrtis species Toad Lily *
  • Trillium species Wake Robin *
  • Viola species Violet *

Perennials for Hot, Dry Conditions

  • Achillea species Yarrow
  • Agapanthus africanus Lily-of-the-Nile
  • Agave parryi Hardy Century Plant
  • Andropogon species Bluestem Grass
  • Artemisia species Artemesia
  • Asclepias tuberosa Butterfly Weed
  • Baptisia species False Indigo
  • Belamcanda Blackberry Lily
  • Coreopsis species Coreopsis
  • Cortaderia selloana Pampas Grass
  • Delosperma cooperi Hardy Ice Plant
  • Festuca ovina Blue Fescue
  • Gaillardia species Blanket Flower
  • Gaura lindheimeri Gaura
  • Helianthus species Perennial Sunflower
  • Hemerocallis species and hybrids Daylily
  • Hesperaloe parviflora False Red Yucca
  • Iris hybrids Bearded Iris
  • Kniphofia uvaria Red Hot Poker
  • Lantana species 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
  • 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
  • Stachys byzantina Lamb’s Ear
  • Verbena species Verbena
  • Yucca species Yucca

Tolerant of Moist or Damp Soils

Those marked with a * will tolerate wetter soils.

  • Acorus gramineus Sweet Flag *
  • Aster novae-angliae New England Aster
  • 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
  • Filipendula species Meadow Sweet
  • Galium odoratum Sweet Woodruff
  • Helianthus angustifolius Swamp Sunflower *
  • Hemerocallis species Daylily
  • Hibiscus species Rose Mallow, Confederate Rose
  • Hibiscus coccineus Texas Star *
  • Iris ensata Japanese Iris *
  • Iris virginica Blue Flag*
  • Iris laevigata *
  • Iris hybrids Louisiana Iris *
  • Ligularia species Golden Ray *
  • Lobelia cardinalis Cardinal Flower *
  • Lobelia siphilitica Great BlueLobelia *
  • Matteuccia pensylvanica Ostrich Fern
  • Monarda species Bee Balm
  • Myosotis sylvatica Forget-me-not
  • Osmunda regalis Royal Fern *
  • Physostegia virginiana Obedient Plant
  • Primula species Primrose
  • Tradescantia virginiana Spiderwort
  • Zantedeschia aethiopeca Calla *

Perennials for Poor, Sandy Soil

  • Achillea species Yarrow
  • Anthemis tinctoria Golden Marguerite
  • Asclepias tuberosa Butterfly Weed
  • Baptisia species Wild Indigo
  • Belamcanda chinensis Blackberry Lily
  • Euphorbia species Spurge
  • Gaillardia species Blaket Flower
  • Gaura lindheimerii Gaura
  • Hemerocallis species Daylily
  • Hesperaloe parviflora False Red Yucca
  • Lantana species Lantana
  • Plumbago auriculata Plumbago
  • 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
  • Chrysanthemum pacificum Gold & Silver Mum
  • Cynara cardunculus Cardoon
  • Delosperma cooperi Hardy Ice Plant *
  • Dianthus gratianopolitanus Cheddar Pink *
  • Helleborus orientalis Lenten Rose
  • Heuchera species Coral Bells
  • Hosta species and hybrids Plantain Lily
  • Iris pallida ‘Variegata’ Varigated Sweet Iris
  • Lamium maculatum Spotted Dead Nettle
  • Marrubium incanum Silver Horehound *
  • Opuntia humifusa Prickly Pear
  • 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
  • Artemisia ludoviciana Western Mugwort
  • Arundinaria species Bamboo
  • Arundo donax Giant Reed
  • Bambusa species Clumping Bamboo
  • Campanula rapunculoides Creeping Bellflower
  • 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
  • Iris pseudocorus Yellow Iris
  • Lantana camara Lantana
  • Lychnis coronaria Rose Campion
  • Lysimachia species Loosestrife
  • Lythrum salicaria Purple Loosestrife
  • Miscanthus sinensis Silver Grass; Zebra Grass
  • Macleaya species Plume Poppy
  • Mentha species Mint
  • Oenothera species Evening Primrose
  • Persicaria virginiana Tovara
  • Phalaris arundinaceae var. picta Ribbon Grass
  • Phyllostachys species Japanese Bamboo
  • Physostegia virginiana Obedient Plant
  • Polygonum species Knotweed
  • Tanacetum vulgare Tansy
  • Vernonia species Ironweed