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Perennial pruning


If you spend any time at Sugar Creek you’re bound to hear us say “Whack it back” or “Give it a haircut” when talking about plants.

Cut off something you want to grow??

Watch your plants closely— they’ll usually tell you by their appearance what kind of pruning is in order. Following are several reasons to spend time in your garden every week with a pair of sharp shears or hand pruners:


Pruning Perennials – General Pruning. In early spring, old foliage should be removed from most plants. Many spring blooming perennials should be pruned just after the blossoms fade. Perennial plants which bloom during summer and fall should be pruned in spring to create bushier, more floriferous plants. However, although most perennials benefit from deadheading spent flowers, not all perennials benefit from pruning before flowering, as you may be cutting off the only flowers of the year. Read on to learn when to prune, what to prune, along with techniques for stronger plants, more blooms, and to time blooming.


Pruning Perennials to Extend Bloom Period and Promote Re-blooming, Deadheading Technique. Extending the bloom period and promoting repeat blooming are two of the most important reasons to prune perennials. Deadheading, the removal of faded or spent flowers, can give life to your garden through prolonged blooming or repeat blooming. In many cases, if the bloom is not allowed to go to seed, the plant will continue to put out new blooms in an attempt to complete its lifecycle. Deadheading forces the plant to put its energy into new flower production, rather than into seed production. Many perennials benefit from deadheading. Examples of plants that benefit: Columbine, Phlox, Black Eyed Susan, Stoke’s Aster. When a flower has faded pinch off the flower stem below the spent flower and above the first set of leaves. For large groups of flowers shear back the entire plant.


Perennial Pruning Technique For Compact Plants With More Flowers. Use this technique to form bushier plants with more flowers, and to reduce plant height to eliminate staking. Some perennials benefit from pinching to encourage more blooms, and to keep plants more compact. Pruning will also reduce plant height to eliminate the need for staking. Pruning encourages branching. For every stem that is cut back, two will form, doubling the number of blooms. The little bit of time it takes you to cut back or pinch perennials before flowering will reward you with more flowers, and the time of having to stake plants later. Pruned flower stalks will bloom 2-3 weeks later than normal, and flowers may be smaller than normal. Examples of plants that benefit: Phlox, Asters, Mums, Sedums, Beebalm, Joe-Pye Weed, Monkshood, Sneezeweed. Remove 1/3 to 1/2 of plant’s top growth in spring. Fall bloomers should be cut back by July 4.


Perennial Pruning Technique To Encourage New Growth. Use this technique to encourage lush new growth and re-bloom. Cutting back plants after flowering and when old growth becomes tatty promotes lush new growth from the base of the plant. This new growth contributes to the overall appearance of the garden, refreshing it and holding that spot in the overall design. Sometimes a plant will even re-bloom after being cut back close to the ground. Examples of plants that benefit: Perennial Geranium, Catmint, Spiderwort, Salvia. Look for new growth coming out of the base of the plant below tired growth. Cut the plant back to the new growth leaving the crown or at least 2” of old stems.


Perennial Pruning Technique For Double Bloom Time. Use this technique to extend bloom time with more flowers, and to stagger plant height and bloom time. For perennials growing in large groups, you can encourage the plant to mature at differing heights or to bloom at slightly different times by pinching or cutting back. This creates interesting gradations, adds additional flowers, and extends the bloom time of a planting. Flowering can be delayed on a few stems of an individual plant to provide a longer bloom period. For many perennials, pinching delays blooming by 2-3 weeks. Examples of plants that can be manipulated by pruning: Phlox, Asters, Beebalm, Mums, Chelone, Sneezeweed, Obedient Plant, Joe-Pye Weed, Veronica, Catmint, Russian Sage, Monkshood.  Cutting back the front half of a perennial grouping will result in the back half blooming first at its normal time. The front pinched section will bloom later. When the back half is finished, it will be hidden by the blooming front. Or, pinch back 1/2 of flower stalks throughout the clump. For summer bloomers pinch in spring. Fall bloomers should be cut back by July 4.


Perennial Pruning Technique to Increase Flower Size. Removing or disbudding the side buds off a plant will produce one large flower on a long stem. For certain plants, the thinning of stems can produce larger flowers than un-thinned plants.


When To Pinch Perennials. For many perennials pinching their flower stalks back will delay blooming for 2-3 weeks. With thought out pruning, perennials can be timed to bloom in continuous waves. Spring blooming perennials should not be pruned until after flowering. Summer bloomers should be pinched in early spring. Perennials that bloom in the fall should be cut back by July 4. These include: Asters, Mums, Chelone. 


Perennials that respond well to pruning: 

Achillea, Aconitums, Adenophora, Aegopodium, Alcea, Amsonia, Anchusa, Arabis, Artemisia, Asters, Boltonias, Campanulas, Centaurea,  Centranthus, Clematis, Coreopsis, Chrysanthemums, Eupatorium, Gypsophila, Helianthus, Heliopsis,  Iberis, Leucanthemum, Linum, Lobelias, Monarda, Perovskia, Phlox paniculata, Physostegia, Platycodon, Salvias, Saponaria, Stokesia, Tanacetum, Thalictrum, Tradescantia, Veronicas.

Important note: Not all perennials benefit from pruning before flowering, as you may be cutting off the only flowers of the year.

The following perennials should not be pruned until after flowering:

Acanthus, Alchemilla, Aquilegia, Armeria, Aruncus, Astilbe, Crocosmia, Delphinium, Dianthus, Dictamnus, Digitalis, Filipendula, Gaillardia, Geraniums, Geum, Hellebore, Hemerocallis, Heuchera, Hosta, Iris, Kniphofia, Ligularia, Limonium, Papaver, Polygonatum, Verbascum