- Hydrangea arborescens – Hills of Snow Hydrangea
- Hydrangea macrophylla (excluding Endless Summer types) – Big Leaf, Snowball, or House Hydrangea
- Hydrangea macrophylla (Endless Summer types) – Reblooming Big Leaf Hydrangeas
- Hydrangea serrata – Mountain Hydrangea
- Hydrangea quercifolia – Oakleaf Hydrangea
- Hydrangea petiolaris – Climbing Hydrangea
- Hydrangea paniculata ‘Grandiflora’ – P. G. Hydrangea, Tree Hydrangea
- Pruning Hydrangeas
- When Cutting Back Hydrangeas Can Be Helpful:
- Pruning Mophead, Lacecap, and Oakleaf Hydrangeas
- Pruning Hydrangea Trees
- A Pruning Story:
- Deadheading Hydrangeas
- Solving the Hydrangea Puzzle
- Wood Pruning Methods: What Is Old Wood And New Wood In Pruning
- What is Old Wood?
- What is New Wood?
- Distinguishing Between Old and New Wood
- Wood Pruning Methods on Old Wood Bloomers
- Wood Pruning Methods on New Wood Bloomers
- Where, Oh Where Have my Hydrangeas Gone…..?
There are many different kinds of Hydrangeas, from vines, to shrubs, to small trees. The following list encompasses the species that we carry at Natureworks with information about their growth habits and pruning techniques.
Hydrangea arborescens – Hills of Snow Hydrangea
These are the old fashioned farm yard hydrangeas with white snowball flowers on 4-5’ plants. They are hardy to zone 4 and bloom on current year’s growth. They can be pruned back hard in late fall or spring. They spread rapidly to form huge clumps and can be divided when they become too large. Hills of Snow Hydrangeas tolerate deep shade and will also grow in full sun! Their flowers dry a greenish-cream color. The variety ‘Annabelle’ has larger flowers up to 12” across. Both varieties bloom in June. Native to North America.
H. a. ‘Incrediball’ This new introduction has enormous white flowers on very strong stems that will not flop. A Proven Winner Color Choice shrub selection.
H. a. ‘Invincibelle Spirit’; ‘Bella Anna’– These are soft pink forms of Hills of Snow! A true breakthrough.
Hydrangea macrophylla (excluding Endless Summer types) – Big Leaf, Snowball, or House Hydrangea
These are the most common types with large, rounded flower heads appearing in July and August. The tops are hardy to ZONE 6 which means that they may suffer damage in a severe winter in Ct., the roots are hardy to zone 5. This hydrangea will bloom on new shoots growing off last year’s wood. DO NOT cut them to the ground in the fall or spring. In the spring, remove some of the older, thicker canes to the base to thin the plant out. Wait for the new growth to sprout and then trim the tops of the canes to encourage branching. In midsummer, cut new vigorous shoots to a spot lower than the height of the old wood so they will branch and won’t hide the flowers. If they continuously don’t bloom well for you, the tender one-year-old shoots may be getting winter killed. Move to a protected spot or wrap the plant each winter OR replace them with repeat blooming varieties that bloom on both old and new wood.
Hydrangea macrophylla ‘Cityline Venice’
— Their flowers are pink if the soil is alkaline (i.e. PH 7.0+). Add aluminum sulfate to change the color to blue and make the soil more acidic.
— Their flowers are blue if the soil is acidic (i.e. PH 5.5-6.0). Add lime if you want to change the color to pink and make the soil more alkaline.
They prefer a rich, humusy soil that retains moisture. Plant in morning sun or dappled shade. If in full sun, be sure that the soil does not dry out. Deep shade may reduce flowering.
H. m. ‘Nikko Blue’
The standard blue hydrangea in the trade. Enormous round blue heads. Grows 5’ x 5’.
H. m. ‘Cityline Series’ (‘Paris’, ‘Mars’, ‘Vienna’, ‘Rio’ are examples)
Wonderful dwarf varieties with incredible blooming power. Large blossoms on 2-3’ plants. Because they are so compact, leaves piled around the base of the plants (or good snow cover) will protect the one year old wood. Developed in Germany.
H. m. ‘Wedding Gown’
Double flowers start out pure white and transform to brilliant red in the fall. Compact habit, growing only 2-3’ tall. Blooms on old wood with some reblooming later in the season. Exceptionally hardy. Bred by Ball Horticulture, part of the Double Delights series.
Hydrangea macrophylla (Endless Summer types) – Reblooming Big Leaf Hydrangeas
Hydrangea macrophylla ‘Endless Summer’ is a breakthrough in plant breeding. This plant produces flowers off of old wood AND new wood! That means that even if the old wood is pruned or killed to the ground, you will still have flowers! Prune the same as any H. macrophylla types. If old wood dies in winter, cut it to the ground and the current year’s wood will replace it with flowers beginning later in the summer.
H. m. ‘Endless Summer’ , ‘Bloomstruck’
These plants bloom on both old and new wood! That means they flower EVERY year, even if we have a hard winter. Grow to 5’ tall. ‘Bloomstruck’ is an improved ‘Endless Summer’ with deeper blue, larger flowers.
There are MANY new varieties of repeat blooming Hydrangeas that flower on current year’s wood being introduced each year. Examples include ‘Penny Mac’, ‘Mini Penny’, ‘Blushing Bride’, and ‘Twist and Shout’.
Hydrangea serrata – Mountain Hydrangea
A very hardy species. Roots and stems are zone 5 hardy, making them reliable bloomers in CT even after a hard winter. Flowers are slightly smaller than mophead types. Leaves and stems turn burgundy red in the fall.
H. s. ‘Acuminata Precioza’ – Pink Beauty Hydrangea
Flowers are rosy pink deepening to almost red in the fall. Grows 4’ x 4’.
H. s. ‘Bluebird’, ‘Blue Billow’
Two exceptionally hardy varieties of lacecap hydrangeas with profuse blue flowers covering the plant. Grow to 5’ tall and wide with an excellent dense habit making it a real asset to the foundation planting or the perennial border. Flower interest begins in late June and continues until October.
Hydrangea quercifolia – Oakleaf Hydrangea
Oakleaf Hydrangeas have beautiful, striking foliage that resembles giant oak leaves. The leaves alone make this plant a true garden asset. They turn a rich red in the fall. The flowers are pure white pointed panicles up to 10” long and appear in July. Oakleaf Hydrangeas can tolerate quite a bit of shade or will grow in full sun. They are hardy to zone 5 and bloom on the TIPS of last year’s wood. Pruning involves opening up the plant and creating an architectural, picturesque form. The bark is exfoliating (peeling) and a good winter feature. If you want to reduce the height, prune immediately after flowering. An invaluable shade shrub growing 5-6 feet tall. Native.
H. q. ‘Snow Queen’ A new and wonderful hybrid with much larger pure white flowers than the species.
H. q. ‘Snowflake’ A beautiful double flowering form, very sought after for exceptional flowers.
H. q. ‘Sike’s Dwarf’ A dwarf form reaching only 3-4’ tall.
Hydrangea petiolaris – Climbing Hydrangea
This is a vine which attaches itself by holdfasts. It will climb on walls, chimneys, tree trunks, fences, or any surface. Although they grow slowly at first, after 2-3 years they begin to grow rapidly and cover a tremendous area in one year, eventually growing to 25’ long! The flowers are creamy white lacecap types, 6-10” in diameter. They are hardy to zone 4 and can tolerate deep shade or sun.
Hydrangea paniculata ‘Grandiflora’ – P. G. Hydrangea, Tree Hydrangea
P. G. Hydrangeas have enormous panicles of creamy white flowers in the summer which gradually fade to creamy pink as the fall progresses. They are the most popular for drying. Standard varieties will grow 12-15′ tall; the new dwarfs reach 6-8’. All can be trained as a tree by selecting out strong trunks at an early age. They bloom on current year’s growth and should be pruned back hard each spring to develop a strong, woody framework to support the huge, heavy flowers. They need full sun or dappled shade. Hardy to zone 4.
H. p. ‘Quickfire’, ‘Pinky Winky’ Dwarf forms of “P.G.”, start blooming earlier, usually early July, starting white, quickly fading to pink or deep rose.. Great for smaller gardens and yards.
H. p. ‘Limelight’ Late blooming with pure white, upright, pointed flowers that are much longer than “P.G.”; flowers and do not hang down! A definitely different variety that adds a distinctive, dramatic look to the fall garden; grows 8’ tall, up to 10’ wide.
In an effort to provide horticultural information, these educational documents are written by Nancy DuBrule-Clemente and are the property of Natureworks Horticultural Services, LLC. You are granted permission to print/photocopy this educational information free of charge as long as you clearly show that these are Natureworks documents.
First, it’s important to know that mophead hydrangeas do not have to be pruned back – ever – unless they are very old. Removing dead stems is the only pruning that must be done for the health of the plant, and these can be removed at any time. Dead blooms can also be removed at any time.
But if your hydrangea is getting much too large (or old), and you simply must prune it, use one of the following methods.
Use Method One if you have mophead or lacecap hydrangeas (these are the only type hydrangeas that are usually blue or pink) or if you have oakleaf hydrangeas (leaves shaped like large oak leaves, white blooms).
Use Method Two if you have paniculatas (PeeGees) or ‘Annabelle’ (arborescens). Both PeeGee and smooth hydrangeas bloom white.
Before pruning, be sure to know what type of hydrangea you have.
When Cutting Back Hydrangeas Can Be Helpful:
(1) All dead stems should be removed from hydrangeas every year.
(2) After the plants are at least 5 years old, about 1/3 of the older (living) stems can be removed down to the ground each summer. This will revitalize the plant.
(3) In addition, if it becomes necessary to prune a plant to reduce its size, it may be cut back in June or July without harming the next year’s bloom. But it will return almost immediately to it’s former size. This is one reason why it’s best to plant a hydrangea where it does not have to be pruned.
Pruning Mophead, Lacecap, and Oakleaf Hydrangeas
Prune these hydrangeas only in the summer before August (to be safe). Some experts believe these hydrangeas may be pruned even into August, but this might be risky. The hydrangeas may already have set their bloom buds for the next year.
Method I is for hydrangea types that bloom on old wood. “Old Wood” are stems that have been on the hydrangea since the summer before the current season. “New wood” are stems that developed on the plant during the current season. This group of hydrangeas produce flower buds on hydrangea stems around August, September or October for the following summer’s blooms. If those stems are removed (pruned) in the fall, winter, or spring, the bloom buds will be removed, and there may be little or no bloom the following summer (usually June/July for the northern hemisphere).
Note that pruning is not the same thing as removing the dead blooms. (See below “Removing Old Blooms.”) There exists a small group of mophead hydrangea that will bloom no matter when they are pruned. Endless Summer is this type of hydrangea. But for the vast majority of hydrangeas, pruning after July will likely result in fewer blooms the next summer.
EXCEPTIONS: For all mophead hydrangeas, the above method of pruning (Method I) will work very well. However, one may become confused when a neighbor or friend prunes his or her hydrangea at the “wrong” time, i.e. in the fall or spring, and then his hydrangea blooms just fine.
Unlike most mophead hydrangeas, there are a few that will regenerate the bloom buds they are cut off (destroyed). These hydrangeas are known as ‘remontant’. They seem to be found most abundantly in gardens in the northern regions of the U.S. and Canada. Therefore, on these special hydrangeas, if the bloom buds are killed by frost or pruned off at the wrong time, they will regenerate the bloom bud and bloom as usual. Endless Summer is the best example of a hydrangea that does this.
Pruning Paniculata (PG) & Smooth Hydrangeas
This method is used for hydrangea arborescens, smooth hydrangeas, and hydrangea paniculata (PeeGee types) hydrangeas. These types of hydrangeas bloom on new wood (new stems). It is a joy to grow these type hydrangeas because they are determined to bloom every single year, no matter how they are treated. The only time they cannot be pruned is in the spring (‘Annabelle’) or in the summer (PG) when they are preparing to bloom.
Many people grow hedges with smooth hydrangeas and cut them within a few inches of the ground each fall so they will not be an eyesore during the winter. They will still bloom beautifully in the spring/summer, however this drastic pruning may not allow stems to increase in size, and they may need staking to hold up the large heads.
Paniculatas (PG/Limelight types) can be pruned in the fall, winter, or spring. However, it is not necessary to prune them every year. It is suggested that one trim out crossing branches and those that do not contribute to an attractive form whenever necessary.
Pruning Hydrangea Trees
Paniculata hydrangeas are the only hydrangeas that can be pruned into a tree-form. If one is attempting to grow a paniculata as a tree, the developing trunk and main top branches should not be removed. If a panicultata that is trained into a tree-form is cut or broken off close to the ground, it will grow back as a shrub unless the training and pruning is started again from the new shoots.
A Pruning Story:
Gail, from Trussville, Alabama, has a beautiful blue hydrangea (actually she has several). The picture on the left, below, shows this hydrangea in early summer, at the height of its glory. As the summer progressed, it became increasingly loose, and the blooms were easily brought down in inclement weather.
Gail thought her hydrangea would be much more compact and attractive if it could be pruned. Unfortunately, it was still covered in bloom. If she waited until fall or winter to prune it, the hydrangea probably wouldn’t bloom the following year at all. So, after we’d discussed the situation by email, Gail decided to prune it right then and there, since some of the bloom was starting to fade. The picture on the right was taken the morning Gail finished pruning. When I saw this picture, I gasped.
The summer after the pruning, this hydrangea was covered in bloom . But, I have to admit, it took a lot of nerve to pull this off.
Removing old blooms on a plant is called “Deadheading.” Fortunately, we can remove the old blooms at any time of the year without harming the bloom for the following year. In June and July you may remove them in any way you would like (long stems or short stems). Here are some tips for deadheading:
(1) When you cut blooms for arrangements in June or July, you can cut them with long stems because the bloom buds haven’t set for the following year.
(2) When you cut the blooms after the first of August, it would be safest to remove them with very short stems so you won’t disturb any developing bloom buds for next year. As long as you cut above the first set of large leaves, the blooms will be fine.
Hydrangeas are popular, but understandably confusing! There are about 25 species, though only five are primarily grown in the U.S. There are literally thousands of cultivars. Some species are classified as either mophead (all large, sterile florets) or lacecap (fertile, center florets surrounded by larger, sterile florets), depending on cultivar. The showiest part of the flower cluster is actually the bracts rather than petals. The bracts persist long after the petals drop and are often cut for dried floral arrangements.
Initiation of flower buds and when to prune
-Some hydrangeas bloom only on old wood (last-year’s growth); prune after bloom.
-Some bloom only on new wood (current season’s growth); prune late winter.
-A few bloom primarily on old wood but can also bloom on new wood.
Smooth hydrangea (H. arborescens)
Native species features large clusters of pale, greenish blooms, changing to white and then drying to papery brown; blooms on new wood. Often best to prune back to a few inches in late winter for sturdier stems.
Annabelle – huge blooms, very showy and popular
Incrediball – larger blooms than Annabelle!
Invincebelle Spirit – pink flowers, breast cancer fundraiser
White Dome – lacecap form
Oakleaf hydrangea (H. quercifolia)
A dramatic native species, foliage is shaped like an oak leaf, with outstanding fall color; cinnamon-brown, peeling bark visible in winter. Showy blooms in late spring and early summer; blooms on old wood. It is generally a large, coarse shrub, though some compact cultivars are available. Prune, if needed, after blooming.
Alice – Large, white flowers maturing to a rose pink; outstanding purple color in fall
Snow Queen – Upright, white flower clusters maturing to pink, burgundy fall foliage Little Honey – Compact plant with yellow foliage in spring, chartreuse in summer, changing to red in fall
Pee Wee – Compact shrub, white flowers turn pink, red fall color
Snowflake – Large, double white flowers maturing to purple-pink, burgundy fall foliage
Panicle hydrangea (H. paniculata)
Large shrub, native to Asia, most with cone-shaped clusters of white flowers; blooms mid-summer on new wood, can prune end of winter.
Bobo – dwarf Pee Gee type, large cone of white blooms, may fade to pink
Grandiflora aka Pee Gee (PG) – huge cone of white blooms changing to pink
Limelight – lime green flowers changing to greenish-white to pink
Little Lamb – small, white florets on compact shrub
Pinky Winky – white flowers changing to deep pink
Bigleaf Hydrangea (H. macrophylla)
This most popular species is native to Japan, but most selections bloom only on old wood and foliage usually is killed to the ground in Zone 5, frequently in Zone 6. A few cultivars will also bloom on new wood (remontant) but are showiest on old wood. Flowers are blue in acidic soil, pink in alkaline soil (availability of aluminum is the key factor which is related to soil pH.) If your hydrangea never blooms but produces lovely foliage every year, it is likely this species and flower buds were winter killed.
Selected Remontant Cultivars (can bloom on new wood):
‘All Summer Beauty’
‘Lemon Wave’ Variegated foliage attractive even without blooms.
Mountain Hydrangea (H. serrata) (a.k.a H. macrophylla var. serrata)
Flower buds hardier and earlier than bigleaf but more demanding of cool, moist soil.
‘Tiny Tuff Stuff’ Compact form of ‘Tuff Stuff’.
‘Tuff Stuff’ Reblooming lacecap type, blooms can be pink, blue or white (based on soil pH)
Climbing Hydrangea, (H. anomala petiolaris)
Also native to Asia, this striking clinging vine (root-like fastholds) with fragrant, lacecap flowers on current season’s growth and has interesting cinnamon, peeling bark. Needs sturdy support. Hydrangea-vine is a separate but related genus (Schizophragma spp.).
‘Skyland’s Giant’ has large white flower clusters.
‘Firefly’ has variegated foliage of green and bright yellow in spring but less contrasting as foliage matures.
Solving the Hydrangea Puzzle
Pruning hydrangeas is a subject that baffles many gardeners – novice and experienced alike. Before you even think about grabbing your pruning tools, you need to identify which species you have in your garden. There are several species of hydrangeas commonly grown in New Hampshire, and all of them have very different growth habits and pruning requirements. While some plants bloom on new growth, others primarily set flower buds on old wood. Follow the brief guide below to determine how and when you should prune your hydrangeas.
Bigleaf hydrangea (Hydrangea macrophylla)
Bigleaf hydrangeas are the quintessential hydrangeas most gardeners are familiar with. Also called mopheads or lacecaps, bigleaf hydrangeas are characterized by shiny, dark green foliage and large colorful blooms. They generally bloom on old wood and can be difficult to get to flower in New Hampshire. Cold winter temperatures and drying winds often kill flower buds, leaving plants with lush foliage but no sign of flowers.
Flower buds are produced at the tips of stems on old wood of the previous year. If those buds are killed or damaged over the winter, the hydrangea’s flowering potential is reduced; although lower buds along the stem have the potential to develop flowers too. Wait to prune your bigleaf hydrangeas until new growth appears in the spring. Make pruning cuts one quarter inch above the first set of live buds. Hint: stems with live buds will be green on the inside, while dead stems will be brown. Entirely dead stems should be cut flush to the base.
If you have trouble getting your bigleaf hydrangea to bloom year after year, consider replacing it with a “remontant” (reblooming) type. A number of cultivars have been released in recent years that flower readily on new shoots.
Mountain Hydrangea (Hydrangea serrata)
Mountain hydrangeas look very similar and are closely related to bigleaf hydrangeas. Mountain hydrangeas have a more delicate branching structure and flowers that are slightly less showy than their relative. Flowers only develop on old wood, so do not remove stems until new growth begins in the spring and you can determine which buds are still viable.
Smooth hydrangea (Hydrangea arborescens)
Smooth hydrangeas are native to Eastern North America and are well suited to most New Hampshire gardens. They have a mounded growth habit and white to pale pink flowers that bloom mid-summer. Unlike bigleaf and mountain hydrangeas, smooth hydrangeas bloom on new wood and will tolerate heavy pruning. Old flowers from the previous year can be removed in late winter through spring. Old stems will flower, but the flowers will be small. For larger, more robust flowers, prune stems to the ground in the spring.
Panicle hydrangea (Hydrangea paniculata)
Undoubtedly the most common hydrangea grown in New Hampshire, panicle hydrangea is incredibly cold hardy and flowers reliably season to season. It grows as an upright, low-branched small tree or large shrub whose branches tend to arch under the weight of numerous, large conical flowers. Panicle hydrangeas bloom on new growth and should be pruned in late winter to early spring before leaf emergence. Remove spent flowers and prune to improve overall plant structure and habit. Make cuts one quarter inch above live buds or to the branch collar of stems.
Oakleaf hydrangea (Hydrangea quercifolia)
Oakleaf hydrangeas are native to the Southeastern part of the United States. Although this shrub may suffer some winter damage and flower bud loss in northern gardens, its striking foliage and exfoliating bark are enough justification to grow it. Oakleaf hydrangeas also bloom on old wood, so only remove dead or damaged branches in the spring. In general, oakleaf hydrangeas do not require much pruning. As needed, thin stems and reduce plant height after new growth has begun.
Many well-meaning gardeners reduce their hydrangea’s blooming potential through simple pruning errors. Fortunately, hydrangeas are really quite simple to care for, as long as you understand their growth habits and follow these simple pruning guidelines.
A classic bigleaf hydrangea shows its softball-sized blue blooms in a normal June.
Q: I read your article in Thursday’s Patriot-News about hydrangeas not blooming this year, and indeed, mine are like that great-looking plant pictured that has no blooms. My question is how and when do I prune my hydrangeas to get the best blooms for next year?
A: Hydrangea pruning is tricky because the job varies by type. The main difference is whether you’ve got a hydrangea that blooms on old wood (i.e. the flower buds form on branches the preceding fall) or on new wood (i.e. flower buds form on shoots grown earlier in the same season).
Most people have bigleaf hydrangeas (Hydrangea macrophylla), the type that gets those softball-sized blue or pink balls in June. Bigleaf hydrangeas bloom on old wood, which means that either a cold winter like we had this year, or a fall, winter or early-spring pruning will eliminate their flower buds. No live buds, no flowers.
You can’t do much about deep freezes, but you can avoid pruning this type of hydrangea between August and June of the following year. Obviously, that leaves July as the only good time to prune these and still get flowers.
The best solution is to simply not prune bigleaf hydrangeas at all. Some of the best blooming bigleaf hydrangeas I’ve seen are those that the gardener never touches, except for snipping off the spent flower heads after they brown.
The problem is most people don’t give hydrangeas the space they need to grow up and out, and so they end up needing to do size control – often every year. If you have to do that, do it in July. For mature bushes, remove about one-third of the shoots right down to the base and then shorten the rest by one-half to one-third.
If big, old bushes are starting to get so dense that they’re not blooming as well or developing leaf diseases, this same thinning and shortening can help them.
Breeders have recently introduced several new series of bigleaf hydrangeas that bloom on both old wood and new wood, so that no matter what happens with winter or pruning, you’ll likely get at least some flowers at some point every year.
Oakleaf hydrangeas also bloom on old wood.
The other common type of hydrangea that flowers on old wood is the native oakleaf hydrangea (Hydrangea quercifolia). These also are best not pruned at all or pruned right after they’re finished flowering (primarily July).
Oakleaf hydrangeas are cold-hardier than the Japanese-origin bigleaf hydrangeas, and so these usually don’t run into the same winter dieback trouble that the bigleafs sometimes do. Oakleafs, in fact, bloomed normally even after this frigid winter.
Panicle hydrangeas (Hydrangea paniculata) and smooth hydrangeas (Hydrangea arborescens) bloom on new wood and so also were largely unaffected by this past winter, although like almost everything else, their flowering is happening a little later than usual.
Panicle hydrangeas flower in summer on new wood, with cone-shaped flower heads of white, pink or rose.
Panicle hydrangeas, also known as “PeeGee” or tree-type hydrangeas, are best pruned at the end of winter (in other words, before new growth begins). They can get cut back very hard – almost to the ground – and they’ll bloom the same year. Or they can be left unpruned to grow into the size of a small tree. Most bloom white, pink or rose with cone-shaped flowers.
Smooth hydrangeas are woodland natives that bloom either white or pink on big, round balls that are so big and heavy that they typically cause the stems to droop. ‘Annabelle’ is the best known variety of this type.
Smooth hydrangeas are best pruned at the end of winter, cut back as far as you like to maintain the size you prefer. Be aware they grow very fast and can easily shoot back up to 6 feet tall the same season after you’ve cut them nearly to the ground.
Wood Pruning Methods: What Is Old Wood And New Wood In Pruning
Keeping shrubs and small trees healthy is vital not only to their appearance, but also their ability to fight disease, insect infestations and extreme weather. Plant pruning encourages new growth and blooms and is necessary for many species of shrubs and small trees. If left unpruned, many plants become woody and do not produce enough new wood to support blooming.
However, when it comes to plant pruning, many questions arise as to what is old wood and what is new wood? Distinguishing between old and new wood is crucial in understanding the correct wood pruning methods for your plants.
What is Old Wood?
Spring flowering shrubs such as forsythia bloom on last year’s stems, which are known as old wood. The best time to prune these types of plants is right after they bloom. Flower buds will form during the summer and fall in preparation for spring blooms.
What is New Wood?
Stems that develop during the present season are known as new wood. Many hydrangeas and summer blooming spirea bloom on new growth. Trim new wood bloomers in late winter or early spring before blooming to encourage growth.
Distinguishing Between Old and New Wood
Most plants develop what is known as a vegetative bud at the end of a year’s stem growth. The expansion of the bud, the following spring, leaves a noticeable scar. The scar is the place where old growth ends and new growth begins. Many times, there is also a slight difference in the stem color of old and new wood.
Wood Pruning Methods on Old Wood Bloomers
Prune old wood bloomers to thin and control size. All dead or crossing stems should be cut as close to the ground as possible.
Since buds will form on old wood, it is important to remember that the more wood that is removed, the less prolific the bloom will be.
Also, be sure to sterilize your pruning shears before cutting.
Wood Pruning Methods on New Wood Bloomers
Plants that bloom on new wood will handle severe pruning, if necessary, in their dormant season.
Most new wood bloomers need to be shaped and thinned, just like old wood bloomers. Be sure to cut back any dead or damaged limbs or any that cross.
As always use clean and sharp pruning shears.
Where, Oh Where Have my Hydrangeas Gone…..?
Q: We’ve had ten hydrangeas in our yard for many years; and every summer they’ve produced beautiful bouquets for me to bring to work. This is the first year that not one of the bushes has bloomed, regardless of their location in my yard. Could it be because of the cold winter we had? Also, some years I cut the hydrangeas back in the fall and some years I don’t. Is Fall when you’re supposed to cut them back?
—Pat in Huntingtown, Maryland
A. We’ll take the pruning part first, because it seems like I can’t give this warning out often enough: No perennial plant should ever be cut back in the fall—ever, ever, ever. It interferes with them going dormant for the winter, which could cause permanent harm. And fall pruning can accidentally remove lots of flowers-to-be from blooming plants.
Now, you’re always going to get a bad result when you prune Spring blooming plants, like azaleas, rhododendrons, and forsythia in the Fall. These early bloomers have produced all of their flower buds for the following year by mid to late summer, and people who ‘clean them up’ in the fall remove those buds and wind up with few to no flowers in the Spring.
But hydrangeas bloom in the summer, right?
Right. And most other summer bloomers—like crepe myrtle and butterfly bush—do best if they get a nice pruning in the Spring, about a week or two after all risk of frost is gone. But most hydrangeas bloom on what’s called ‘old wood’—growth from previous years, and not the current season. So when people prune their hydrangeas in the Fall or in the Spring, they’re inadvertently removing the old wood that was poised to produce summertime flowers.
Now, I have to admit that the temptation to prune is pretty strong. Hydrangeas don’t look very nice in the winter. And they look even worse in the Spring! The old branches look dead at the end of winter (even though they’re almost always just dormant); and they are unattractive for a while. But the people who resist temptation and leave them alone will absolutely have the most flowers that summer.
Which begs the question: Can you ever prune them?
Yes, and it’s one of my favorite cheap and sleazy gardening techniques. You leave them alone until all the flowers have formed early in the Summer, and then you go in and remove all the barren, non-flowering branches that are hiding the blooms from view. It’s a great trick that makes the plants look like they have twice as many flowers, and there’s no risk of harming future displays.
Now, to actually answer the question: Did these hydrangeas fail to bloom because of the fall pruning? The answer is a qualified use of the weasel-word maybe—because Nature has to share at least some of the blame. Lack of flowers is the rule this year in the mid-Atlantic, Northeast and other regions that experienced the crippling ‘once-in-every-twenty-year’ winter we barely survived, and not the exception. I repeat: It isn’t you (this time, anyway); few to no hydrangeas are blooming in those regions this summer. Boo-hoo! Mean Mother Nature!
I know this for a fact, because we have gotten lots of emails about the problem—and similar sad queries about crepe myrtle and fig trees. The emails fall into three categories:
1)    The plants are stone cold dead; no sign of green growth late in the season.
2)    The top parts are completely dead, but there is some green growth coming out of the ground. And:
3)    The first email we receive says “my hydrangeas or figs or whatever are dead”. But when I email them back and ask if there’s any green growth at the bottom, they say ‘yes’. So apparently I thought I knew what the word ‘dead’ meant, but I was wrong.
At any rate, the vast majority of hydrangeas in especially-harsh winter areas were slow to do anything this Spring, and then finally, some green growth appeared at the base. That’s what happened to mine, and from all the emails I’ve gotten, it seems like my plants were poster children for this season.
So In June, when we saw the new growth that reassured us that the plants themselves were still alive, ‘we’ (which means my ace intern/helper/hired man Matt, who did all my chores while I recovered from rotator cuff surgery) carefully pruned back the old growth by just a few inches to see if that would stimulate the old branches into doing something.
We waited a couple of weeks, and when nothing sprouted, we removed all of the old branches that were crispy, snappy dead. Then we finally cut the rest of the old sticks back so we could enjoy this year’s new growth—which is very lush and full; the plants are exactly the height they should be.
But no flowers. Not a one. Zip; nada; bupkiss. I do miss those big flowers, but I’m happy that the plants themselves are lush and healthy—and they don’t look bad just as foliage plants. They’re actually very attractive in full leaf—and a heck of a lot better than the dead sticks of May.
So, to all those whose hydrangeas are in the same place: Enjoy the lush greenery that reveals that the root systems survived; and don’t you dare prune them until the flowers form—hopefully—next summer. Because the new growth you have now will be the only old wood the plant will have to produce flowers on NEXT year.
And if your hydrangeas—or other perennials—are really, most sincerely dead, I would urge you to replace them without worry. Those kind of winters should continue to be rare.
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