How to Prune Perennials
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Learning how to prune perennials starts with one question: what does this plant need right now? Illinois Extension names three techniques, deadheading, cutting back and pinching, and each one answers a different need. Leggy stems, ragged leaves and new growth at the base are the signals that a perennial is ready for pruning. The guidance below draws on extension pages from Illinois and Maryland and on an article hosted by the University of California, and where those pages stop short, this guide says so.
Quick answer
- Deadhead spent flowers back to a lateral leaf, flower or bud. A single bare flower stem should be cut off close to the base.
- Cut back when foliage looks ragged or new growth is starting at the base. Illinois Extension says it is best to cut the whole plant back at one time.
- Pinch to get bushier growth, but do not pinch a lily or an iris before it blooms.
- Leave stems standing through winter if you want cover and seed for birds, then prune in early spring before bees start flying.
Read the plant before you cut
Illinois Extension is direct about the difficulty: “Pruning perennials is a complex topic because different plants need different kinds of pruning.” The same release says judgment comes from practice, and it offers a reassurance that matters for a first attempt: “Luckily, perennial plants are forgiving, so experimenting usually won’t cause permanent damage.”
The Maryland page describes the same warning signs in more detail. Over a growing season, perennial foliage “may become ragged and tired-looking from accumulated damage,” and stems can get leggy. It adds that “pruning leggy stems down to the base of the plant can stimulate new growth in some cases.”
Deadhead to keep the flowers coming
Maryland Extension defines deadheading as “the removal of spent, faded flowers.” The reason is energy. “Flowers that go to seed consume large amounts of a plant’s energy, diverting it from vegetative growth or more blooms.” Illinois Extension makes the same point from the other side: removing the flowers after bloom “forces the plant to put more into making new flowers.”
Where you cut depends on the stem. Maryland says: “When practical, plants can be deadheaded to a lateral leaf, flower or bud.” For a single flower stem with few or no leaves, Maryland says “the flower stem should be cut off close to the base.”
Illinois adds that “Deadheading techniques depend on the species.” Its examples of perennials to deadhead “to the next lateral flower, bud, or leaf” are butterfly weed, coreopsis, purple coneflower, scarlet bee balm, garden phlox and Culver’s root. Other perennials, the release says, need a different cut, since “others need to remove the flower stalk.”
Deadheading is not always the right move. Maryland says “perennials should be deadheaded after blooming, although there are exceptions when:” and names self-seeding, attractive seed heads and seeds that feed wildlife as the main reasons to leave flowers in place. Its seed-head note says coneflower, Joe-pye weed, beebalm, mountain-mint and black-eyed Susan are “considered both attractive in winter and a good food source for birds.”
The University of California article takes a similar view. “Leave old flowers on when you want them to reseed”, it says, and it names larkspur and hollyhocks as examples.
Cut back for fresh growth and height control
Cutting back is a larger cut than deadheading. Illinois Extension gives three reasons: “Increasing plant vigor, delaying bloom time, and controlling height are some reasons for choosing to cut back plants.” The timing cue is the foliage: “Cutting back when foliage looks ragged, and new growth at the plant’s base is starting can rejuvenate the appearance.”
Illinois says it is best to cut the whole plant back at one time. It also warns that “Cutting back more than half of the foliage can put the plant under some stress”, so the plant needs extra attention until new growth begins. It adds that “Some species can tolerate cutting back better than others”.
Some plants benefit from an early cut. Illinois lists sedum, asters, cardinal flower and goldenrod under the heading “Perennials benefitting from cutting back early in the summer”. Maryland describes a different use for the cut: garden phlox and ‘Autumn Joy’ sedum “can be cut back once or twice in the summer before mid-July.” Use the early cut to shape the plant, and keep the second pass for later in the season.
Pinch and disbud for shape or bigger flowers
Pinching is the most direct of the three techniques. Maryland defines it this way: “Pinching is removing the top few inches of soft growth on a stem with either a sharp, clean pair of shears or by pinching it off between your thumbnail and index finger.”
Illinois explains the trade-off. “Pinching can cause a plant to produce more but smaller flowers by removing the central flower bud.” On the other hand, “pinching away side buds can force the plant to put more energy into one large flower.” Pick the result you want and pinch to match it.
Maryland names the shape benefit: “Pinching promotes bushy growth for many species.” It suggests pinching back chrysanthemums and asters “several times before mid-July” to “produce more compact plants with stronger stems”.
Pinching has a cost. The Maryland page states that “Pinching delays flowering.” Pinching only some of the stems can extend the bloom, because “the pinched portions will bloom later” while the rest bloom on time.
Disbudding is a related cut, which Maryland defines as “the removal of small, immature flower buds.” Removing the side buds “will produce a larger flower on a longer stem”, while removing the top bud produces more, smaller flowers. The table sets out the four cuts side by side, using only what the two pages say about each one.
| Cut | What the sources say it does | Where it is described |
|---|---|---|
| Pinch the soft growing tip | Promotes bushy growth for many species; delays flowering | Maryland Extension |
| Remove the central flower bud | Produces more flowers, but smaller ones | Illinois Extension |
| Remove the side buds | Produces a larger flower on a longer stem | Maryland Extension |
| Deadhead spent flowers | Stops energy going to seed; can encourage more bloom | Maryland Extension |
Thin stems for airflow and bigger flowers
Thinning is a different kind of cut. Maryland gives the method in one sentence: “Thin by cutting some stems at the base of the plant.” It notes that thinning can be done “to increase flower size”, and it lists phlox, aster, beebalm and delphinium as perennials that benefit from being thinned.
Illinois connects pinching with airflow, noting “increased air circulation through the plant.” Thin the plants that are known to crowd, and leave the rest alone.
Pinching that should wait for bloom
Not every perennial takes pinching. Maryland is clear that “Perennials with one leafy or unbranched stalk, such as a lily, and those with leafless flowering stalks, such as iris, should not be pinched back before bloom.” Check the stem before you reach for the shears. A single unbranched stalk or a bare flowering stalk should wait until it blooms.
Spring cuts that start the season
Spring is when many perennials get their first large cut. The University of California article says: “Many perennials can now be cut to the ground or just above new shoots.” For stems that are still alive, it advises: “If old stems are alive and showing signs of growth, trim to perhaps a few inches above the ground.” Its examples include asters, Shasta daisies, many sages, yarrow, coneflower, catmint and sedum ‘Autumn Joy’.
The same article says “Most ornamental grasses, too, are ready for a major trim”. It also separates shrubs from perennials: “Prune later. Wait to prune shrubs that bloom on old or last year’s wood.” If the plant has woody stems and blooms on last year’s growth, it is not a perennial in this sense, and its spring cut should wait until after it blooms.
Fall decisions and winter cover
Fall is where many gardeners hesitate. Maryland describes the traditional habit: “Traditionally, cutting non-evergreen perennials to the ground in autumn would tidy-up the garden for aesthetics.” It then cautions that “this clean-up can also remove the winter weather protection that broken, bent stalks provide to tender basal foliage and crowns.”
Standing stems do useful work. Maryland says that perennials which are not cut back in autumn “provide shelter from weather and predators, as well as food like seeds, for birds and other wildlife in winter.” Its conclusion is practical: “It is a personal preference whether to leave the plant debris or cut it back.”
If you leave stems standing, Maryland suggests early spring: “If plants are healthy and not pruned back in the fall, prune them in early spring before bees start flying and seeking nesting sites.” It also notes that “Stems can be cut to various heights from 8 to 24 inches above the ground.” The top portions you remove can go somewhere useful: “The top portions of pruned stems can be composted or put in a pile or bundle in an out-of-the-way area of your yard to create additional nesting and shelter spaces.” For the composting side, see our guide to how to make a compost pile. For winter bed care more broadly, see preparing raised beds for winter.
Mistakes to avoid
- Pinching lilies or irises before bloom. Maryland says these plants should not be pinched back before bloom.
- Cutting back more than half the foliage at once. Illinois Extension says that much removal can put the plant under some stress.
- Pruning shrubs as if they were perennials. The UC article says to wait to prune shrubs that bloom on old or last year’s wood, including lilacs and some hydrangeas.
- Clearing every stem in autumn without thinking about winter cover. Maryland notes that clean-up can remove winter weather protection, and that uncut perennials feed birds in winter.
- Letting invasive plants set seed. Maryland advises pruning off the seed heads of invasive plants, such as fountain grass, to control their spread.
How we chose
We limited this guide to three pages that we opened with curl on 2026-10-22: an Illinois Extension news release on pruning perennials, a University of Maryland Extension page on perennial selection, planting and care, and a University of California article on trimming and deadheading that is hosted on a ucanr.edu class site. We kept only the steps that at least one of these pages states in plain words. Each quoted sentence was checked against the text we pulled. We did not compare products, and this guide does not recommend any product or brand.
What we could not verify
The three pages do not give a calendar for each perennial. Illinois Extension calls the topic complex because “different plants need different kinds of pruning.” Maryland ties its summer cut-back guidance to mid-July without a list for each species. The UC article places a second, lighter pruning pass later in the year, without a date. For your region and your plants, check the timing with your local extension office, since the Illinois release itself says to “connect with your local Extension office” for more information.
What the sources do not say
- None of the three pages gives watering or feeding instructions for the days after a cut.
- No page gives a cut height for most perennials. The UC article gives one height only for tall, floppy plants, which it says to shear “a foot or so above ground.”
- None of the pages gives a count of how many times to deadhead a given plant in one season.
- None of the pages gives frost dates or hardiness zones for your area. The UC article ties spring work to the point “When the frosts are finished,” but it does not say when that is.
Frequently asked questions
Do you need to deadhead every perennial?
No. Maryland Extension says perennials are generally deadheaded after blooming, with exceptions for self-seeding, attractive seed heads and seeds that feed wildlife. Some plants need the whole flower stalk removed instead, so check the cut point for the plant you have.
Can perennials be cut back in summer?
For some, yes. Illinois Extension lists sedum, asters, cardinal flower and goldenrod as perennials that benefit from cutting back early in summer, and it says cutting back can delay bloom or control height. Maryland’s summer cut-back window for garden phlox and Autumn Joy sedum closes before mid-July.
Should perennial stems be left standing over winter?
That is a personal choice, according to Maryland Extension. Standing stems protect the crowns, give birds seed in winter and offer nesting space for native bees, while a full clean-up removes that cover. If you do leave them, Maryland suggests cutting in early spring before bees start flying, to a height that suits the plant.
What is the difference between pinching and deadheading?
Pinching removes soft growth from the top of a stem, which Maryland says can make plants bushier and can delay flowering. Deadheading removes spent flowers so the plant does not put energy into seed. Pinching can be done with shears or between your thumbnail and finger, while the UC article says hand pruners or scissors usually work for deadheading.
Does this guide cover shrubs like lilacs?
No. Lilacs and some hydrangeas are shrubs that bloom on old wood, and the UC article says to wait before pruning them. Illinois Extension notes that different plants need different kinds of pruning, so check the plant before you cut.
Sources
- https://extension.illinois.edu/news-releases/care-perennial-gardens-3-proven-pruning-methods (opened 2026-10-22)
- https://extension.umd.edu/resource/perennials (opened 2026-10-22)
- https://class.ucanr.edu/sites/default/files/2015-09/220858.pdf (opened 2026-10-22)
