Pruning

Attribute	Value
Agastache	Remove faded flowers to prevent seeding. Leave stems to overwinter. Remove new growth in early to mid spring for more flowering stems and a more compact plant.
Alam Potschke New England Aster	Pinch back stems before midsummer to promote bushiness, produce a greater number of flowers and to control the plant height (to avoid flopping by the plant). Asters may self-seed if grown in ideal conditions. Cutting back after flowering will prevent undesired self-seeding. In the first part of the summer, pinching back stems every few weeks can promote a bushier and more compact growth habit. However, stop the pinching process by August, or you might accidentally take off some flower buds. If your asters become very tall and lanky, you might need to stake them to prevent the stems from flopping over. Then, cut the asters to the ground after they're done flowering and the foliage dies in the fall. This prepares your garden bed for new growth the following spring.
Astilbe	Extremely little maintenance is required of astilbe plants. The flower heads will dry on the plant and remain attractive for many months. The flowers can be cut whenever they start to look ragged, or left up for winter interest and cut back in the spring.
Alam Potschke New England Aster	Pinch back stems before midsummer to promote bushiness, produce a greater number of flowers and to control the plant height (to avoid flopping by the plant). Asters may self-seed if grown in ideal conditions. Cutting back after flowering will prevent undesired self-seeding.
Annabelle Hydrangea	The Annabelle Hydrangea grows blooms on new wood each year. These shrubs are vigorous bloomers, and can handle aggressive pruning. However, as stated above, only prune to 18"-24" if you would like the plant to have stronger limbs. But, you can prune back all the way to the ground each year and these amazing plants will bounce back with beautiful flowers no problem. The only time you should not prune is in the spring, as that is when the shrubs are preparing to bloom.
Autumn Joy Stonecrop	If you wish, you can cut back the stems in the late spring to limit their height and promote thicker, bushier growth. Some gardeners cut down the stems in the fall after the foliage begins to depreciate, but the stems can also be left to provide winter interest and cut down in the spring before new growth starts. Birds will feed on the dried flower heads over winter. Sedum plants respond well to pruning and tend to form a bushier plant in the next burst of spring growth. Use sharp pruners or garden shears to take the stems back to within an inch (2.5 cm) of the soil in early spring. Take care to avoid the new growth that is coming up. Pinching will enforce bushier plants. Pinch off the new growth near the soil and it will form a more compact stem and thicker growth.
Balloon Flower ‘Sentimental Blue’	Pruning generally isn't necessary with balloon flowers, though you can do so for appearance. To achieve stockier plants, you can cut back tall stems by about half in the late spring. This can help to prevent the plants from flopping over. Also, deadheading your plants (removing spent blooms) will keep them looking good and repeatedly blooming. Don't remove the whole stem, just the faded flowers. The remaining buds on the stem will continue to open.
Balloon Flower ‘Astra White’	Pruning generally isn't necessary with balloon flowers, though you can do so for appearance. To achieve stockier plants, you can cut back tall stems by about half in the late spring. This can help to prevent the plants from flopping over. Also, deadheading your plants (removing spent blooms) will keep them looking good and repeatedly blooming. Don't remove the whole stem, just the faded flowers. The remaining buds on the stem will continue to open.
Balmy Beebop Bee Balm	Pick bee balm flowers frequently to encourage flower production. Deadheading, or removing spent flowers, will also promote a new flush of blooms. Cut back severely after flowering to encourage new foliage growth. If you want a bushier plant, pinch off the stem tips as new growth appears in the early spring.
Black Adder Anise Hyssop	Anise Hyssop is a fairly independent plant and won't need much attention once it has established itself in your landscape. Occasional pruning can help encourage the plant to bloom and keep the plant looking its best. Pruning is best done in early spring, using a pair of clean pruning shears. Cut back up to one-third of the plant to encourage more full, bushy growth. Remove any dead plant material just above a promising bud node.
Blackberry Lily	Although blackberry lily does not require "pruning" in the formal sense, removing the seed capsules as they form will prevent them from ripening and casting seeds into the garden, where you will need to pluck out the volunteers. Cutting back the flower stems after they fade may help prolong the bloom period with new blossoms. At the end of the growing season, remove the yellowing foliage to tidy up the garden and eliminate fungal spores and nesting areas for pests.
Bleeding Heart	No major pruning is required, though you can trim back the foliage as it becomes brown and unsightly prior to dormancy. Fringed-leaf bleeding heart varieties can sometimes get a little ragged-looking and can be sheared back to their basal growth; they will re-leaf and rebloom. Refrain from deadheading (removing the spent blooms) if you want the flowers to go to seed.
Bloody cranesbill	Remove flowered stems and old leaves to encourage the production of fresh leaves and flowers.
Blue Fortune Anise Hyssop	Anise Hyssop is a fairly independent plant and won't need much attention once it has established itself in your landscape. Occasional pruning can help encourage the plant to bloom and keep the plant looking its best. Pruning is best done in early spring, using a pair of clean pruning shears. Cut back up to one-third of the plant to encourage more full, bushy growth. Remove any dead plant material just above a promising bud node.
Blue Indigo	The only pruning required for this plant is to remove the dead stems at some point, either in the late fall or early winter, or in the spring before new growth begins. Because this plant takes on such a shrub-like appearance, you can also shape it by pruning, which is best done immediately after its flowering period is over.
Blue Jean Baby Russian Sage	Prune your Russian sage plant in early spring before new growth emerges, about six weeks after the last predicted frost date for your region. This will rejuvenate the plant, maintain a manageable size and produce heavier blooming on the new growth. Cut it back to about 6 inches above the soil.
Blue Mouse Ears Hosta	Some gardeners clip off the flower stalks when they appear, though other growers recognize the value of the white or purple flowers to bees and other pollinators. If you do allow the flowers to bloom, clip off the stalks after the flowers have faded.
Carpet Phlox	Pruning is optional on these plants. After the blooming period is over, you can trim back the foliage to create a neater form. This also will promote denser foliage, enhancing the phlox's beauty as a ground cover. Alternatively, you can skip the pruning and let the plants grow naturally.
Catmint Walker's Low	If you leave the stalks up, the birds seem to eat the seeds. Cut back just above ground-level in mid-spring after the first flush of blooms. Shear off faded flowers in June to re-bloom. Nepeta 'Walker's Low' thrives in harsh conditions.Mom - “I disagree with pruning. After first flush of bloom and it starts to look ratty, prune back by half and will get second bloom. I did this pruning and it was very successful. I will cut back in winter to couple of inches. In fact, since this is my first year, I will see what they do at Heritage since it is in the circle at the parking lot.”
Coral Bells	While coral bells don't need much maintenance, you can cut back the entire flower stalk after flowering to put the plant's energy into growing more leaves. Coral bells are short-lived perennials, so you'll want to divide the plants every three to five years in the early spring or fall to keep them healthy. If the leaves get a bit ragged looking, especially after winter, cut them back and new growth should fill in quickly.
Cranberry Lace Bee Balm	Light, yearly pruning can be done if you wish to keep this plant bushy. Simply pinch off the tips of the stems in the spring. Cut the bee balm down to a few inches in the fall to promote new growth in the spring. Heritage Plantation deadheads
Creeping Phlox	Pruning is optional on these plants. After the blooming period is over, you can trim back the foliage to create a neater form. This also will promote denser foliage, enhancing the phlox's beauty as a ground cover, and will encourage some fall rebloom. Alternatively, you can skip the pruning and let the plants grow naturally.
Double Orange Daylily	Deadheading will improve appearance, and can help reduce hemerocallis gall midge. Cut back flower stems after flowering has finished. Remove dead foliage as required
Fireball Bee Balm	Light, yearly pruning can be done if you wish to keep this plant bushy. Simply pinch off the tips of the stems in the spring. Cut the bee balm down to a few inches in the fall to promote new growth in the spring. Heritage Plantation deadheads
Frankly Scarlet Coneflower	Mom - “I leave seed heads on stems since the goldfinches LOVE to sit on the and eat. I remove stems when really ratty looking and all seeds eaten.”
Garden View Scarlet Bee Balm	Light, yearly pruning can be done if you wish to keep this plant bushy. Simply pinch off the tips of the stems in the spring. Cut the bee balm down to a few inches in the fall to promote new growth in the spring. Heritage Plantation deadheads
Goldenrod	Pruning stem tips early in the season can result in goldenrod plants becoming fuller and bushier and lead to more flowers later in the season. Deadheading spent flower heads can prolong the bloom season well into fall. Removing the flower heads before they go to seed can prevent rampant self-seeding. At the end of the season or in late winter, cut the plant stalks back to a few inches above ground level.
Goldsturm Black Eyed Susan	Deadheading will help to keep the plants blooming longer into the late summer. But leave the last flush of flowers on the plants to set seeds
Great Blue Lobelia	Let some of the flower heads go to seed in the fall, and you'll have a dozen new plants coming up next spring.
Hardy Hibiscus	Because this plant dies to the ground in winter, you can prune it down to the ground in fall or in spring before new growth emerges. The root system will survive the winter, and new growth will emerge from the root system.
Husker Red Penstemon	Allow some of the plants to set seed (don't deadhead all of the flower spikes)
Hyacinth	Let foliage die down naturally. Leaves provide nourishment for bulbs to produce future growth and blooming.
Karen Azalea	https://www.gardeningknowhow.com/ornamental/shrubs/azalea/pruning-azaleas.htm
Kudos Coral Hummingbird Mint	Remove faded flowers to prevent seeding. Leave stems to overwinter. Remove new growth in early to mid spring for more flowering stems and a more compact plant.
Kudos Gold Agastache	Remove faded flowers to prevent seeding. Leave stems to overwinter. Remove new growth in early to mid spring for more flowering stems and a more compact plant.
Kudos Mandarin Agastache	Remove faded flowers to prevent seeding. Leave stems to overwinter. Remove new growth in early to mid spring for more flowering stems and a more compact plant.
Lemon Lily	After flowering, remove spent blooms and seedpods to improve appearance and encourage rebloom. When all the flowers on a scape are finished, cut off the scape close to ground level. Remove dead foliage from daylilies as they die back in the fall.
Love-in-a-Mist	Cutting flowers for bouquets and deadheading will keep your plants flowering a bit longer, but you'll sacrifice the fascinating seed pods. Love-in-a-mist easily self-sows, so you can thin the seedlings to prevent overcrowding. Harvest for bouquets when flower buds have fully colored or pods have begun to develop.
Little Lanterns Dwarf Columbine	Prune columbine plants back to their healthy base leaves just after blooming. Doing so might promote a second set of stem growth within a few weeks enabling you to enjoy another wave of blooms later in the season. Columbines can be cut back to about one-half of their height after flowering to keep the plant attractive and green for the remainder of the summer.
My Castle Lupine	Remove spent flower spikes to encourage re-blooming, or to prevent plant from producing seeds.
Orange Daylily	If all of the flowers on a flower stalk have bloomed, you can cut the whole stalk down to the ground to keep a tidy look. Feel free to remove any unsightly foliage or seed pods as well.
Pearl Glam Beautyberry	Prune, if desired, in early spring, and remove any dead wood at that point as well.
Penstemon 'Blackbeard'	Beardtongue doesn't need pruning but can benefit from cutting off the spent flowers down to the stem to encourage new blooms.
Rose Campion	Deadhead spent flowers to prevent undesired self-seeding. Cut back flower stems after flowering and leave the basal foliage on display for the rest of the season.
Rose of Sharon	This shrub grows naturally in an attractive form, so it doesn’t need much pruning. But you can tidy up its growth each year to maintain the size and shape you desire. Rose of Sharon blooms on new wood, so it should be pruned in the late winter or early spring to avoid cutting off any flower buds. Pruning back the stem tips will encourage more branching and thus more flowers. Remove any damaged or diseased branches as they arise.
Ruby Slippers Dwarf Oakleaf Hydrangea	Oakleaf hydrangea shrubs usually require little pruning, unless you are trying to fit them into a location that is too small. In ideal conditions, this plant may shoot up to 10 feet, which may require that you trim it down. This is a shrub that blooms on old wood, so when pruning is necessary, do it immediately after it is done flowering and blooms start to fade, which will likely be late summer into September or even October. Damaged or diseased branches can be cut away whenever they appear. This plant spreads through suckering, so you may want to remove spreading ground shoots to control the spread of the shrub.
Rudbeckia Maxima “Dumbo Ears”	You can prune or deadhead your cabbage leaf coneflower so that new blooms appear during bloom time.
Russian Sage	Some gardeners choose to prune Russian sage annually. The argument for pruning is that the plant will grow to be bushier as a result of this care. At the very least, it's a good idea to cut off any dead branches to keep this perennial tidy. The normal time to prune Russian sage is early spring or mid-spring, depending on the strategy you adopt. One reason why spring is the best time to prune (as opposed to trimming in fall) is that leaving the silver branches adds interest to the winter landscape. Another is that if you trim in the fall and don't get a hard freeze, the plant could start producing new growth. If it does, a hard freeze could kill the new growth. There are two basic trimming strategies: One is to prune down to within a few inches of ground level in early spring and just be done with it. The other approach is to wait until mid-spring and allow the plant stems to start to fill in with leaves. You'll be able to identify the dead stems as the ones that aren't filling in, and you can proceed to cut them off. Then, make a judgment regarding the remaining branches. For example, if you want to start out with stems that are 1 foot tall, make your cut at 1 foot. The taller the plant starts out in spring, the taller it will end up in fall.
Snowflake Oakleaf Hydrangea	Oakleaf hydrangea shrubs usually require little pruning, unless you are trying to fit them into a location that is too small. In ideal conditions, this plant may shoot up to 10 feet, which may require that you trim it down. This is a shrub that blooms on old wood, so when pruning is necessary, do it immediately after it is done flowering and blooms start to fade, which will likely be late summer into September or even October. Damaged or diseased branches can be cut away whenever they appear. This plant spreads through suckering, so you may want to remove spreading ground shoots to control the spread of the shrub.
Stiff Goldenrod	Pruning stem tips early in the season can result in goldenrod plants becoming fuller and bushier and lead to more flowers later in the season. Deadheading spent flower heads can prolong the bloom season well into fall. Removing the flower heads before they go to seed can prevent rampant self-seeding. At the end of the season or in late winter, cut the plant stalks back to a few inches above ground level.
Swamp Milkweed	Swamp milkweed does not need any pruning during the growing season. After the plant has died back in the winter, you can remove the dead stalk, just make sure to mark the location, as swamp milkweed is slow to emerge in the spring.
Sweet Autumn Clematis	This group blooms later and from new growth. These should be pruned in February or March as new leaf buds begin to show low on the plant. Also remove all dead material above the buds and clean out any old or mildewed foliage at this time.
Tango Hummingbird Mint	Remove faded flowers to prevent seeding. Leave stems to overwinter. Remove new growth in early to mid spring for more flowering stems and a more compact plant.
Threadleaf Coreopsis	Deadheading of spent flowers will keep the plant blooming. Mid to late summer shearing should help tidy up the plant and promote a fall rebloom.
Tiger Lily	Foliage on the lower part of the stalks will fade first (in late summer). These yellow leaves won't be as noticeable if the plants are growing in the back row of a garden bed. Once all of the leaves have yellowed by late fall, cut the stalks down to ground level, and dispose of them.
Witch's Moneybags	If you wish, you can cut back the stems in the late spring to limit their height and promote thicker, bushier growth. Some gardeners cut down the stems in the fall after the foliage begins to depreciate, but the stems can also be left to provide winter interest and cut down in the spring before new growth starts. Birds will feed on the dried flower heads over winter. Sedum plants respond well to pruning and tend to form a bushier plant in the next burst of spring growth. Use sharp pruners or garden shears to take the stems back to within an inch (2.5 cm) of the soil in early spring. Take care to avoid the new growth that is coming up. Pinching will enforce bushier plants. Pinch off the new growth near the soil and it will form a more compact stem and thicker growth.
Yellow Evening Primrose	Mom - “it does become invasive only if you are not willing to nip it in the bud and remove runners as they appear. Decide on the outside perimeter you want and then remove all that stray outside. lBe sure the cut back stems well after blooming so it doesn't go to seed or toss seed heads behind fence and let them grow wild.”