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When to Prune Hydrangeas

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Hydrangeas make beautiful specimen plants in the garden. Many have interesting foliage and bark, but most are grown for their large showing blossoms. So, it is very disappointing when hydrangeas don’t bloom for a season. 

To complicate the issue, different types of hydrangeas need pruning at different times.

Hydrangea arborescens: Smooth Hydrangea

  • It is a rounded shrub with leaves that are somewhat rounded with a pointed end and paler on the lower surface than on the top. These hydrangeas do not usually have any problems blooming because the flowers are set only on new growth. This is a good thing because it is very susceptible to winter injury and is often killed back to the ground in colder areas. If winter injury is not that bad, you can prune slightly in early spring by removing some branches to the ground and cutting others back to shape the plant.

Hydrangea macrophylla: Mophead Hydrangea

  • The popular mophead hydrangea is sometimes easy to recognize because it is the one whose flower color changes with the soil pH: blue in acid soil, pink in alkaline.
  • Mophead type hydrangea set their flower buds at the ends of the upright or lateral branches, during late summer to early fall. Pruning Bigleaf hydrangea in the spring or even late fall, after the buds have been set, will remove the flower buds and any chance of getting flowers that season.
  • Mopheads should be pruned as soon as the flowers have faded. You should begin to see new growth coming in from the base of the plant. To keep the plant vigorous, selectively prune out the dead and weaker stems, both old and new. Do not prune out all the old wood, since this is what will keep flowering as the new growth matures.

Hydrangea paniculata: Panicle Hydrangea

  • This is the most commonly grown hydrangea variety and have massive conical shaped flower clusters in mid to late summer. The flowers can start out white and slowly turn pink, drying and remaining on the plant long after the leaves have fallen. These are also the varieties you see trained into standards that look like small trees.
  • Paniculata’s do not require hard pruning to the ground. New flower buds will be set on new spring growth. Some gentle pruning in late winter or early spring will not only keep the plants from becoming overgrown, it will also encourage more new growth and hopefully more flower buds. You can remove dead flowers, as soon as they become unattractive and clean up the overall shape of the plant.

Hydrangea quercifolia: Oakleaf Hydrangea

  • It’s probably not surprising that oakleaf hydrangea is easily recognized by its oakleaf shaped foliage. Since its major attraction is its foliage, loss of bloom is less disappointing than in other varieties.
  • Oakleaf hydrangea also blooms on new season growth and can be pruned in late winter or early spring, while dormant, to remove dead wood. If it has experienced winter dieback, prune back to below the point of injury.

Hydrangea anomala petiolaris: Climbing Hydrangea

  • The stunning climbing hydrangea is the type you see slowly making its way up a tree or support. It is actually a vine, not a shrub and requires little to no pruning. Once climbing hydrangeas become established, they can grow quite vigorously and may need occasional summer pruning to stay in bounds.

Tree and Shrub Maintenance Calendar

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Spring and Autumn: Time to Plant Trees & Shrubs

In most parts of North America, early spring, while deciduous trees are still leafless and dormant, is the best time to plant. Autumn or winter planting is recommended in areas where summers are extreme and winters are mild, such as parts of the South and West.

  • Spring is the only time you should plant bare-root trees in northern climates.
  • Balled and burlapped trees should be dug from nurseries in early spring and can be planted in yards in spring or early summer.
  • Container-grown trees can be planted successfully almost any time of the year, except when the ground is frozen.
  • There are a few exceptions. Trees with active, late-winter sap flow, such as birch and sugar maple, should be planted after their sap flow ends, just as the leaf buds begin to unfold.
  • Fleshy-root trees such as magnolias should be planted after their leaves have expanded slightly.
  • Evergreens are best planted in early autumn, after summer heat is gone but early enough to get established before winter sets in.
  • Although you can plant trees and shrubs almost any time the ground can be worked with a spade, avoid planting in late spring, right before hot summer weather, and in very late fall, because roots may not have enough time to get established before winter weather.

Spring, Summer, and Autumn: No Staking Necessary

Although you may see some staked trees, in general you should avoid staking.

Here’s why:

  • Trees need to move and bend with the wind to develop strength. When they are staked, they do not develop strong trunks from the stake on down. They also are more subject to breakage from wind because the entire tree is not allowed to move as much. Rubbing and girdling from stakes and ties can affect the trunk as well, creating wounds that are susceptible to attacks from diseases or pests. The tree may also grow too fast with an underdeveloped root system.
  • There are a few exceptions. Bare-root and large balled and burlapped trees may not be able to support themselves at first, especially in windy settings. After planting, watch the tree to see if it tips or leans; if so, it may need temporary anchor staking.
  • Each tree needs at least three stakes. Broad, soft tie materials (such as nylon stockings or elastic webbing) are fastened from the tree to the stake. Avoid using wire, string, or other materials that can cut into the trunk.
  • Remove the stakes as soon as possible. Research shows that almost all trees staked for more than two years have a higher probability for breakage.

Spring, Summer, and Autumn: Watering

During the first year after planting, water is the most important element in tree and shrub survival. Always water deeply and thoroughly, even if less frequently; avoid frequent, shallow watering, as the roots will travel to the surface to receive the water and won’t establish themselves deeper.

  • Water during the growing season during periods of drought, particularly the first year or two while the plants are getting established.
  • Place a hose at the base of the tree and allow a slow trickle of water to flow for at least 5 minutes. Shrubs can be watered for less time. If you have sandy soil, water more frequently; if you have heavy, clay soil, allow more time between waterings.
  • Autumn is the most important time to water trees and shrubs, especially evergreens. Water well before freeze up. Moisture is crucial to the survival of plants over the winter; when we experience a dry season, the success of your plantings will rely on the additional provision of water to reduce the occurrence of winter burn and die back.
  • For evergreens, the application of an anti-desiccant such as Wilt Pruf is a beneficial practice to aid in the reduction of moisture loss. Applied before temperatures drop below freezing, Wilt Pruf acts as a coating on the needles and foliage, sealing in the moisture for the winter.

Spring, Summer, and Autumn: Fertilizing

Good news: Fertilizing is one thing you probably don’t need to do! Most soils have enough nutrients to grow trees and shrubs. Only fertilize for specific elements when a soil    test indicates nutrients are missing.

Spring, Summer, and Autumn: Mulching

  • A 2” deep ring of mulch that extends to the drip line of a tree (the reach of the branches) is a great way to conserve moisture and suppress weeds that compete with tree roots for water and nutrients. Keeping the depth of the mulch at 2” or less will avoid trapping too much moisture, which can kill roots. Also avoid direct contact with the trunk or crown.
  • DO NOT create mulch “volcanoes” – where mulch is placed in a cone shape directly against the trunk of a newly planted tree. Too much mulch directly against the bark causes rot, circling roots, and disease problems.
  • Organic mulches such as shredded pine decompose, adding nutrients to the soil.
  • Mulch is also helpful in keeping lawn mowers and other equipment away from trunks.

Autumn and Winter: Wrapping

  • Tree wrapping in winter months protects against sunscald, not cold. It’s unnecessary for most trees, but it’s helpful in protecting young, thin-bark trees, such maples and fruit trees, for the first winter or two after planting.
  • A rule of thumb is to wrap the tree at Thanksgiving and remove the wrap at the spring equinox. Always remove tree wrap in spring to avoid a spot where insects can gather and disease can take hold.
  • To protect established trees from winter critters, create a barrier fence a couple of feet away from the trunk using stakes and mesh screen or plastic tree wrap. You can wrap the trunk itself with chicken wire or plastic wrap that has air holes for circulation, or a plastic drainage tube slit down the side to loosely cover the trunk. Again, always remove any barriers in the spring.
  • Protect evergreens from drying winds and sunscald with burlap screening or wrapping on the south, southwest, and windward sides. Anti-desiccant sprays can help but may not be fully effective in all cases.

Perennial Maintenance Calendar

March

  • Finish cutting what was left from fall
  • Test soil

April

  • Gradually remove winter protection
  • Weed, mulch, and edge (to prevent rot, be careful not to mulch over crowns)
  • Thin and divide plants
  • Plant bare root plants
  • Prepare stakes and cages

May

  • Weed
  • Time for planting – water newly-planted plants thoroughly
  • Finish mulching not completed in April
  • Pinch plants back or thin out
  • Stake
  • Fertilize as per soil test when establishing new beds or planting new plants

June

  • Weed and water as necessary
  • Scout for pests
  • Pinch, deadhead and cut back
  • Stake

July

  • Weed and water as necessary
  • Scout for pests
  • Fertilize heavy feeders such as ever-blooming daylilies and mums
  • Deadhead (stop pinching mums in mid-July)

August

  • Weed and water as necessary
  • Deadhead

September

  • Edge beds
  • Weed and water as necessary
  • Move and divide plants
  • Good time for fall planting of trees and shrubs

October/November

  • Cutback as personal preferences dictate
  • Mulch – to prevent rot, be careful not to mulch over crowns
  • Winterize after first frost

General Perennial Care

Most perennials benefit from lifting and dividing every three to four years. However, some perennials resent being disturbed and are better off being propagated by cuttings or seed. When dividing plants, rejuvenating the soil by incorporating organic matter such as leaf mold or compost is important.

Watering

Soak the plants immediately after planting and check regularly to prevent drying out. The rule of thumb is to add one inch of water per week for established plants. Less frequent but deep watering encourages perennials to root deeply. Perennials that are said to tolerate drought are drought tolerant only after they have become established. The addition of mulch will help to reduce the need for frequent watering.

Fertilization

Most perennials do not need much fertilizer. Many overfertilized perennials will produce excessive soft growth and produce very few flowers. A soil test will help to determine the amount of fertilizer needed. Fertilizers with a formulation of 10-10-10 or 5-10-5 are sufficient, unless a soil test indicates otherwise.

Staking

Some plants, such as delphiniums, hollyhocks, and peonies, need staking to prevent flopping over in the garden. Plants with heavy flower heads or long thin stems tend to blow over or are beaten down by heavy rains. Staking should be done early in the spring to allow the plants to grow through and around the stakes, usually hiding the stake by midseason.

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Perennial Maintenance

  • Many perennials are better left standing over the winter than cutting them down. There are several reasons for this. In addition to many of the perennials having attractive foliage and/or seed heads, they offer food resources for birds. Many birds find the seeds of perennials particularly tasty. The stems of perennials also offer a place for some birds to shelter during the winter. 
  • With some marginally hardy perennials, leaving the stems up for the winter aids in overwintering. The foliage helps to insulate the crowns. Mums seem to benefit a great deal from this practice. Another reason to leave stems stand is that if the perennial is a late riser in the spring, the stems will help to mark the spot and prevent any accidental digging in the area that might harm the underground portions of the plant.
  • Cutting back perennials in the fall may be something you would want to do especially if you were bothered by foliage diseases. Removing the old foliage would be a positive in this case as it helps to reduce the amount of inoculum present to re-infest next year’s foliage. 
  • Removing foliage can also be one of pure aesthetics. Some gardeners like to see standing perennials in the winter and others do not. 
  • When perennials are cut down, do so after they have gone dormant. This is usually after the plants have experienced several hard frosts. Cut the plants down to within 3-4 inches of the crown. Cutting too close can result in winter injury on some perennials due to the fact that the buds for next year’s growth are right at the surface or higher and not below the soil line.
  • Most perennials simply need a good layer of mulch applied late in the fall. The purpose of mulching in this case is to protect the crowns of the plants from the alternate freezing and thawing that occurs very late in fall and in early spring. It is important that the ground be allowed to get cold before mulching, so wait until early to mid-November before covering the plants. Ideally an inch or two of frost in the ground is best. Likewise in the early spring, be sure to clear the mulch from the crowns to prevent rot.
  • Some gardeners leave mulches in the beds, just pulling them back away from the crown of the plants. This adds organic matter and helps suppress weeds.