A Guide to Pruning Perennials

A Guide to Pruning Perennials

Pruning is typically defined as removing growth from an herbaceous or woody plant to maintain health and vigor. However, pruning can also be highly beneficial for your perennials. 

Benefits to Pruning Perennials: 

• Maintain shape and regulate size of plants. 
• Control flowering and fruiting. 
• Promote new growth and flowers. 
• Controls pest and disease. 

Tools that can be used for pruning are by-pass pruners, pruning scissors and hand-held shears. By-pass pruners make a clean cut through the stem of the plant, a great tool for deadheading and cutting back perennials. Avoid anvil type pruners as they can crush and damage the stem of the plant. Hedge shears are useful for pruning several stems at one time, a great tool for fall and spring cleanup. Smaller pruners should be used when doing more delicate and detailed pruning. And of course, the best pruning tool of all, your fingers. 

Deadheading

Deadheading perennials refers to the removal of spent flowers. Removing the old flowers is beneficial for the plant because it promotes the growth of new flowers. If the flowers are left on the plant they will eventually go to seed. The production of seeds consumes a great deal of a plant's energy. When the plant's energy is not being used to produce seeds, the energy is focused on producing vegetative and root growth, resulting in a stronger plant. 

Methods of deadheading differ depending on species and the growth habit of the plant. The main thing to look for when deadheading is new buds and flowers. Remove only the dead flowers from the plant. Most perennials should be pruned to the lateral flower, bud or leaf. Pruning in this matter masks the cut that you have made and does not mar the attractiveness of the plant.

Some plants are best not deadheaded to promote self-seeding. Columbine, Achillea, Aegopodium, Ajuga, Alchemilla, Aster, Dianthus, Echinacea, and Violas are some of the more common plants that self-seed. Deadheading is a useful method to keep plants confined to their designated space. However, some plants tend to be weedy and spread to unwanted ares of the garden by seed dispersal such as Mallow. 

Some perennials such as Hydrangea and Baptisia are not deadheaded due to their beautiful seedheads. If you are looking to provide a great food source for birds, leave seed heads on Echinacea, Eupatorium, Sunflowers, Liatris, Monarda, Rudbeckia, and Hosta. 

Cutting Back

Cutting back may be considered a drastic form of pruning in the garden. Cutting back refers to pruning a plant to renew its appearance, encourage new growth and flowering. Cutting back can be done either before or after flowering. Cutting a plant back to the ground is beneficial for certain spring blooming perennials. Cutting back perennials can control the flowering time and height of the plant. When cutting a plant back, buds, flowers, and leaves may all be removed. Approximately two inches of stem should be left of the plant when cutting to the ground. Hedge shears are the best tool for cutting back plants. 

Disbudding

Disbudding perennials refers to the removal of the plant's terminal or side buds. Removing the terminal bud of a plant will cause the side buds to produce more flowers. The flowers will be smaller, but more numerous than if the terminal bud was left intact. 

Removal of the side buds will cause the terminal bud to produce a larger flower on a longer stem. Disbudding is a pruning technique that is commonly used on dahlias, mums, carnations, and peonies. Disbudding should be done before the buds are too large. Waiting too long to disbud can cause scars along the plant's stem.  

Thinning

Thinning perennials refers to the removal of stems from a plant. The benefits of thinning perennials are improved appearance, increase flower size, and disease prevention. To thing a plant, cut the stems to the ground in spring. A rule of thumb is to thin one in three stems. The following plants are prone to rot or mildew, and thinning improves the air circulation around the plant: aster, delphinium, morado , phlox, lady's mantle, bugleweed, bee balm, and lamb's ear. 

Pruning Spring-Flowering Perennials

Pruning spring-flowering plants can be beneficial in several ways. Many of the lowe-growing rock garden and edgin gplants will benefit from being cut back to one-half the size of the plant after flowering. Prunin gback by one-half the size of the plant will prevent it from opening up at the center, which looks unattractive in the garden. Rock garden plants that benefit from this type of pruning are evergreen candy tuft, maiden pink, and moss phlox. Some plants such as catmint will rebloom after pruning. 

Pruning Summer Flowering Perennials

The main difference between pruning spring versus summer-flowering perennials is the amount of cutting back that is required after flowering. Depending on your objective, some perennials should be pruned before flowering and others should be pruned after flowering. Pruning after floweirng improves the aesthetics of the garden. 

When the weather has been very hot and dry, the plants usually look a little weather beaten. Depending on the species, some plants should be cut to new basal foliage, and others should be cut to the ground. Some plants look best if they are cut back by one-half or one-third of their mature height. When pruning perennials, cutting out the brown parts of the plant will stimulate growth of fresh green foliage. 

The following perennials benefit from cutting back in the summer: lady's mantle, false indigo, geum, sunflower, daylily, dianthus, garden phlox, and spiderwort.