Illinois Horticulture Extension Team
Pruning perennial flowers takes the garden from looking good to looking good. Deadheading, cutting and pinching are pruning techniques that can keep perennials looking good and healthy.
Pruning perennials is a complex topic because different plants need different types of pruning. Experience, developed through practice and careful observation of plants, helps determine when and what type of pruning is needed. Fortunately, perennials are tolerant, so experimenting usually won’t cause permanent damage. Tall plants, rough leaves, or new growth at the base of the plant are signs that the plant is ready for pruning.
Many perennials bloom for three weeks or less. Deadheading is one way to encourage a longer flowering period in certain species.
After flowering, the plant expends a lot of energy to create seeds to complete its life cycle. Deadheading or removing flowers after flowering forces the plant to put more effort into making new flowers.
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Deadheading techniques depend on the species. Because growth habits vary, some plants require access to the next flower, bud or leaf, while others require the flower stalk to be removed.
Known perennials that should be deadheaded to the next side flower, bud or leaf to encourage a longer flowering time include:
• Butterfly weed (Asclepias tuberosa)
• Purple coneflower (Echinacea purpurea)
• Scarlet bee balm (Monarda didyma)
• Garden phlox (Phlox paniculata)
• Culver’s root (Veronicastrum virginicum)
Cutting back is the second pruning option for perennials. Increasing plant vigor, delaying flowering time and controlling height are some of the reasons to choose cutting plants. Cutting back when the foliage looks rough and new growth begins at the base of the plant can rejuvenate the appearance. Renewed growth also helps keep the plant healthy.
Removing old, worn-out foliage with new, healthy foliage reduces stress and can increase the life expectancy of the plant.
Cutting the plant back can also delay flowering time or control plant height. In some plants, cutting back can encourage a second flowering. It is best to cut the entire plant at once. With continuous flowering, perennials can use all their energy to flower one season and have none left to form flower buds the next season.
Some species can handle cutting better than others. It is necessary to pay close attention to signs that a reduction will be beneficial. Cutting off more than half of the foliage can cause the plant to experience some stress, so be sure to give the plant extra attention until new growth begins.
Perennials that benefit from cutting back early in the summer include:
• Sedum (Hylotelephius spectable)
• Cardinal flower (Lobelia Cardinalis)
• Goldenrod (solidagos)
The third option for pruning perennials is the pinch method. Pinching can cause the plant to produce more but smaller flowers by removing the central flower bud. On the other hand, pinching side buds can force the plant to put more energy into one large flower.
Perennials that can be pinched to benefit the plant include:
• Yarrow (Achillea millefolium)
• Chrysanthemum (Chrysanthemum x morifolium)
• Goldenrods (Solidago hybrids)
Another benefit of pinching certain stems is increased air circulation through the plant. Increased air circulation helps reduce the possibility of illness. Removing diseased or pinched stems helps keep the plants healthy.
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