The West Chicago Garden Club

Spring was slow to arrive to the Kruse garden.  So rather than talk of what may be sprouting in the garden let’s look forward and ask some questions.  In August are the sedums flopping in your garden?  Are the groundcovers messy and weed infested?  Are the summer perennials falling and leaning into each other?  Are you so discouraged that you hope for an early frost?  If so we want to share some experimentation we have done at the Kruse garden in pruning, shearing, cutting back for height, longer bloom, and flop prevention.   It is a garden that has to look reasonably nice with a minimum of care.

We can start with a book.  The “Well-Tended Perennial Garden” by Tracy DiSabato-Aust, 1998, is very useful.  It provides a guide as in “should we or shouldn’t we” shear, prune, or cut.  Her motto is “Shear Without Fear”.  It gives impetus.

To start, a lawn mower or string trimmer is wonderful for cutting spent flowers of Ajuga, trimming periwinkle, ivy, winter creeper groundcovers.  It could be done any time in the growing season when the groundcovers are too tall or too weedy.

Perennials that grow from bulbs, corms and rhizomes should only be dead-headed. Other perennials that bloom early can be cut back for looks right after flowering.  It is best to prune to the very center to the new growth on plants such as Nepeta, Pulmonaria, Lady’s Mantle, Euphorbia.  The new growth will be very fresh looking and the Nepeta will not reseed as much.  Some as Dianthus, Iberis, moss phlox should be sheared by ½ after flowering to keep a neat appearance. 

Summer flowering perennials can be cut to different heights.  Low growing geraniums, as Wargraves, can be cut to the ground.  Taller geraniums such as Johnson’s Blue, Claridge Druse should be trimmed back severally to keep them from looking shabby and leggy.  Geraniums such as Roseanne and others that bloom all summer could be cut back prudently, even severely, if they become leggy.  Summer blooming perennials can be cut for height control, to stagger or extend the bloom season, to keep plants from flopping.  For example, Summer Phlox, Heliopsis, Rudbeckia, esp. Herbstone, Coneflower,  Monarda, Aster, Chrysanthemum, and many others can be cut in June when the plant is 1-1/2 feet tall.  If the plant is cut down by 1/2-1/3 of its height, the plant will grow 1/2-1/3 of its height shorter.  This will only delay the bloom time by 1-2 weeks but the plant will be bushier and may not need staking.   If only a section of the plant is cut back, this would extend the bloom time, since the cut section would bloom a bit later.  This might be nice where lower growth is desirable, as in front of the border.  Tall sedum such as Autumn Joy can also be cut or just a ring around the center can be cut by 1/2 the height.  This would extend the bloom time and keep the sedum from flopping, since the cut shorter ring would hold the taller center stalks upright. 

In the book, many plants are enumerated, and included is when and how much to prune, and how much the plant will be shorter.  We find that just a short time spent shearing in June and trimming throughout the season keeps the plants looking neater, shorter and more floriferous.  But remember, prune early so you do not remove flower buds and diminish the floral display.