Off With Their Heads!

As early as 1592 Shakespeare used the phrase "off with their heads" in many of his plays.  Later, Lewis Carroll became the best-known user of the phrase "off with their heads" when he included it in Alice's Adventures in Wonderland (published 1865).   The Queen of Hearts shrieks the phrase several times in the story - in fact she doesn't say a great deal else.  "Off with their heads" is the mantra of many a fine modern gardener as well - referring, of course, to deadheading perennials.
 
One of the best ways to keep color in your perennial border a little longer is to deadhead spent flowers.  Reasons for deadheading generally falls into three categories:  to encourage reflowering of some perennials; to limit seed production and/or self-seeding of other perennials; and to improve the overall appearance of the plant.
 

Some of the common perennials that may rebloom after deadheading include (Disabato-Aust):

• Allwood pinks  (Dianthus X allwoodii cvs.)
• Baby’s breaths  (Gypsophila paniculata and cvs.)
• Bee balms  (Monarda didyma and cvs.)
• Blanket flowers  (Gaillardia X grandiflora cvs.)
• Butterfly weed  (Asclepias tuberosa)
• Checker mallows  (Sidalcea malviflora and cvs.)
• Cheddar pinks  (Dianthus gratianopoIitanus and cvs.)
• Columbines  (Aquilegia spp. and cvs.)
• Culver’s root  (Veronicastrum virginicum)
• Dame’s rockets  (Hesperis matronalis and cvs.)
• Delphiniums  (Delphinium spp. and cvs.)
• False sunflowers  (Heliopsis helianthoides and cvs.)
• Foxgloves  (Digitalis spp. and cvs.)
• Garden phloxes  (Phlox paniculata cvs.)
• Gauras  (Gaura lindheimeri and cvs.)
• Geums  (Geum spp. and cvs.)
• Globe thistles  (Echinops ritro and cvs.)
• Golden marguerites  (Anthemis tinctoria and cvs.)
• Hardy begonia  (Begonia grandis ssp. evansiana)
• Hollyhocks  (Alcea rosea cvs.)
• Italian bugloss  (Anchusa azurea)
• Jupiter’s beard  (Centranthus ruber)
• Lavenders  (Lavandula spp. and cvs.)
• Lilyleaf ladybell  (Adenophora liliifolia)
• Lupines  (Lupinus spp. and cvs.)
• Masterworts  (Astrantia major and cvs.)
• Meadow phloxes  (Phlox maculata and cvs.)
• Monkshoods  (Aconitum spp. and cvs.)
• Mountain bluet  (Centaurea montana)
• Painted daisies  (Tanacetum coccineum and cvs.)
• Patrinia  (Patrinia scabiosifolia)
• Penstemons  (Penstemon barbatus and cvs.)
• Perennial salvia*  (Salvia nemorosa and cvs.)
• Pincushion flowers  (Scabiosa spp. and cvs.)
• Purple coneflower  (Echinacea purpurea)
• Purple toadflaxes  (Linaria purpurea and cvs.)
• Queens-of-the-meadow  (Filipendula ulmaria and cvs.)
• Rose campions  (Lychnis coronaria and cvs.)
• Shasta daisies  (Leucanthemum X superbum cvs.)
• Sneezeweed  (Helenium autumnale)
• Spike speedwells  (Veronica spicata cvs.)
• Spiderworts  (Tradescantia X andersoniana cvs.)
• Stokes’ asters  (Stokesia laevis and cvs.)
• Sweet violets  (Viola odorata and cvs.)
• Tickseeds  (Coreopsis spp. and cvs.)
• Upright hollyhock mallow  (Malva alcea var. fastigiata)
• Yarrows  (Achillea spp. and cvs.)
• Yellow corydalis  (Corydalis lutea)

How to deadhead will depend on the particular growth habit of the plant.  According to Tracy DiSabato-Aust (The Well-Tended Perennial Gardener), "choosing the exact point to make a deadheading cut can seem confusing, since perennials have different flower forms. Because deadheading, like other types of pruning, is so species specific, it can be difficult to group plants into categories. For most plants, however, all you need to remember is to prune spent flowers and stems back to a point where there's a new lateral flower or bud. If no new flower is apparent, prune the stem back to a lateral leaf."

Not all perennials will rebloom after deading, but they sure will make the garden look much better.  Some of these perennials include (Disabato-Aust):

• Baskets of gold (Aurinia saxatilis and cvs.)
• Bearded irises (Iris spp. and cvs.)
• Bergenias (Bergenia cordifolia and cvs.)
• Clustered bellflowers (Campanula glomerata and cvs.)
• Common rue (Ruta graveolens)
• Coral bells (Heuchera spp. and cvs.)
• Daylilies (Hemerocallis spp. and cvs.)
• Goatsbeards (Aruncus dioicus and cvs.)
• Hellebores (Helleborus orientalis and cvs.)
• Hostas (Hosta spp. and cvs.)
• Jacob's ladders (Polemonium caeruleum and cvs.)
• Japanese anemones (Anemone × hybrida cvs.)
• Lady's mantles (Alchemilla mollis and cvs.)
• Lambs' ears (Stachys byzantina and cvs.)
• Lavender cottons (Santolina chamaecyparissus and cvs.)
• Lungworts (Pulmonaria spp. and cvs.)
• Mulleins (Verbascum spp. and cvs.)
• Obedient plants (Physostegia virginiana and cvs.)
• Pearly everlastings (Anaphalis triplinervis and cvs.)
• Peonies (Paeonia spp. and cvs.)
• Red hot pokers (Kniphofia spp. and cvs.)
• Rodgersias (Rodgersia aesculifolia and cvs.)
• Rose mallows (Hibiscus moscheutos and cvs.)
• Scotch thistles (Onopordum nervosum and cvs.)
• Sea thrifts (Armeria maritima and cvs.)
• Wall germanders (Teucrium chamaedrys and cvs.)
• Wall rock cresses (Arabis caucasica and cvs.)
• Western bleeding hearts (Dicentra formosa and cvs.)
• Western mugworts (Artemisia ludoviciana and cvs.)

Whether or not you allow your perennials to set seed will depend on whether you want to spend your time deadheading or removing seedlings.  Some seedlings are a welcome  gift to the gardener while others can be a gardener's nightmare.  Some seedheads are very attractive (sedum Autumn Joy) while other actually detract from the overall appearance of the garden (daylilies).  Be aware that in some cases, too many seedheads can rob the plant of energy and affect the following year's flowering (Siberian iris).   Many short-lived perennials (Lychnis coronaria) can perpetuate themselves by self-sowing.

Off with their heads?  It all comes down to the personal  choice of the gardener and knowing the growing habits of each individual perennial.   Two excellent online resources are:

http://www.gardengatemagazine.com/extras/58deadheadingGuide.php
http://www.finegardening.com/how-to/articles/off-with-their-heads.aspx

If you are a perennial gardener,  I highly recommend two books that need to be in every perennial gardener's library:  The Well Tended Perennial Garden by Tracy DiSabato-Aust and The Perennial Care Manual by Nancy J. Ondra.