Pruning rhododendron in winter
How To Trim A Rhododendron Bush
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Rhododendrons
By: Nikki Tilley, Author of The Bulb-o-licious Garden
Image by dndavis
The rhododendron is one of the most eye-catching shrubs in the home landscape, with beautiful blooms and lush foliage. Being popular shrubs in many landscapes, the topic of how to trim a rhododendron bush, including wild varieties like mountain laurel, is a frequently asked question.
Pruning Rhododendron Guide
Although there is often little need for pruning rhododendrons, especially in naturalized settings, these shrubs respond well to the occasional trimming. In fact, excessive growth may require a heavy pruning. Trimming rhododendrons is typically done for maintenance, shaping, and rejuvenation– as is the case for overgrown plants.
The most common type of pruning is maintenance pruning, which simply involves the removal of spent flowers and old, dead wood. It is important to remove the flower stems from the shrub once blooming has ceased. Allowing these dead flower clusters to remain can actually reduce the following year’s flowering. Cut near the base of the old flower cluster. Also, remove dead or diseased parts of the shrub, following the branch back to healthy wood and making your cut at that point.
Best Time for Trimming Rhododendrons
According to most professional landscapers, the ideal time for pruning rhododendrons is late winter, while the plant is dormant. However, any time between the first frost in fall and the last frost in spring (while the sap is low) will work.
Immediately following its lush spring growth, as new foliage is still hardening off, is one of the worst times for trimming rhododendrons. This will likely inhibit blooming.
How to Prune Rhododendrons
If you are considering pruning, you should probably plan to fertilize your shrub in late fall the year before. Doing so afterward may result in leggy growth. Since buds form on next year’s flowers, by the time blooming has stopped, they are already well advanced.
Therefore, as the flowers fade, trim no more than 15 to 20 inches (38-51 cm.) off the strongest branches. Cut back the plant to expose the inner branches. Follow the branch down to the last whorl of leaves you want to keep and cut just above those leaves, about 1/4 inch (6 mm.) above the topmost leaf in this cluster.
Large, overgrown rhododendrons can be cut 12 to 15 inches (31-38 cm.) from the ground when necessary. Rhododendrons often have three or more main branches rising from the crown of the plant. Each of these primary branches should be cut at a different height to produce a more natural-looking shrub. Cut about 1/2 to 3/4 of an inch (1-2 cm.) just above a latent bud. Pruning above a cluster of two or three buds is even better.
Sometimes more severe pruning may be necessary, requiring cutting to about 6 inches (15 cm.) or so from the ground. Their adventitious buds at the base of the plant will send up new shoots, but keep in mind that flowering usually will not occur for up to two or three years after this heavy pruning.
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How to Prune Rhododendrons
I learned to prune rhododendrons by destroying my prized rock garden. I had a 30-foot-tall pine that I needed to cut down. It missed the house by a wide margin, but it didn’t miss the rock garden, which I had lovingly tended for years.
When the last of the pine tree was removed, I discovered that the damage was surprisingly slight, except for a beautiful Rhododendron ‘Roseum Elegans’, now a 2-foot mound of broken branches and torn foliage. Curious to see if the shrub would recover on its own, I trimmed it back a bit, cut back the scaffold of branches to as pleasing a shape as possible, and waited to see what would happen. Four years later, the rhododendron is one of the most eye-catching shrubs in the yard, with a beautiful shape, dense branches, and plentiful flowers.
The incident illustrates how responsive rhododendrons can be to even severe pruning.
There are three common reasons for pruning rhododendrons—maintenance, shaping, and rejuvenation—and the pruning method for each is easy to learn. The result is a shrub with dense branching, plentiful foliage, and abundant flowers. And you don’t have to drop a pine tree on your shrub border to learn how to do it.
Method 1: Maintenance pruning removes old flowers and dead wood
Snip at the base of the old flower trusses to keep the plant’s energy focused on producing growth rather than seed. Also, remove dead or diseased parts of the shrub—follow the branch back to healthy wood and make a cut there.
Maintenance pruning consists of the removal of spent flower clusters, called trusses, and also of any dead or diseased wood. The trusses are not only unsightly but will eventually form seed, which uses precious energy that would otherwise be available to the plant for vegetative growth.
Maintenance pruning is the easiest type of pruning and is the only one that needs to be done every year.
To remove old flower trusses on rhododendrons, use a pruning shear to snip the truss at its base, about ½ inch above the emerging flush of new growth. Some folks just grasp the stem with their thumb and forefinger and snap the truss from the plant. This works well most of the time, but occasionally the truss breaks off, taking some of the new growth with it. By using a pruning shear, such accidents are avoided.
| Maintain your rhododendron by snipping off spent flower clusters (trusses) . . . | |
| . . . and by removing dead and diseased wood. |
Wood damaged by storms or a harsh winter should be clipped from the plant. Diseased stems, often identified by their wilted, curled yellow-green leaves, should also be removed. Make the cut below the damaged portion of the plant, taking care to cut into healthy wood right above a dormant bud.
Be sure to disinfect the shears with rubbing alcohol between cuts.
Maintenance pruning is best done when the flowers have faded and before the flush of new growth rising beneath each truss is more than an inch or so tall. Many types of rhododendrons can benefit from maintenance pruning, including some deciduous azaleas, like the Knap Hill-Exbury hybrids, and most broad-leaved evergreens, such as the popular hybrids of mountain rosebay (R. catawbiense). Some varieties of rhododendron, most notably small-leaved cultivars like ‘Elite’, ‘Northern Starburst’, and ‘PJM Regal’, rarely set seed and do not require maintenance pruning. If your flowers and flower stalks simply shrivel up and essentially disappear in the weeks after flowering, then your variety doesn’t set seed and doesn’t need to be deadheaded.
Winter damage can be common in rhododendrons. Injured branches should be removed during routine maintenance.Method 2: Pruning for shape enhances the plant’s natural habit and form
Conversely, topiary and other more formal shaping techniques prune a plant into a shape it would not naturally assume.
Shaping should not be done on leggy or very large plants, as their open habit requires a more drastic technique called rejuvenation pruning.As the name implies, shaping involves altering the shape of the plant, and it can be done for many reasons, from encouraging denser branching to controlling plant width or height. It differs from other shaping techniques, like topiary, in that shaping of rhododendrons is designed to develop the most aesthetically pleasing aspects of the plant’s natural habit and form.
Shaping improves the appearance of a plant by encouraging increased branching at its growing points. Since many evergreen rhododendrons hold their leaves for about three years, a branch will have a series of leaf whorls, each representing a year’s growth. The whorls of foliage are separated by sections of leafless stem, called internodes. In general, broad-leaved rhododendrons have much longer internodes than small-leaved and deciduous types and benefit most from shaping. To shape a rhododendron, follow the branch from the end down to the last whorl of leaves you want to keep.
Make the cut about ¼ inch above the topmost leaf in this cluster. Repeat as needed.
Shaping is most easily done in late winter, while the plant is dormant. Although this sacrifices some of the flower buds, it ensures a complete growing season for the new stems that emerge.
| To shape a rhododendron, follow the branch down to the last whorl of leaves you want to keep, and cut just above those leaves. | |
| To shape, cut just above the whorl of leaves. |
Method 3: Rejuvenation pruning calls for drastic cuts on old wood
Rejuvenation pruning involves the careful cutting back of each primary branch of the plant’s framework. Rhododendrons often have three or more main branches rising from the crown of the plant. These branches, called primary branches, form the basic scaffold of each shrub. Each branch is cut at a different height to produce a staggered arrangement that will make the shrub look natural when the new shoots mature.
Rejuvenation pruning is best used to restore shrubs that have become leggy, overgrown, or otherwise unattractive. Many rhododendron species and hybrids can be severely pruned and come back as good as new. Rejuvenation pruning removes most of the branches of the plant, initiating the rise of vigorous flushes of new growth from previously leafless old stems. The new growth matures into a new framework of branches that can then be shaped over the years to produce a stunning shrub. It’s best to perform this type of pruning in winter, while the plant is dormant.
| Cuts for rejuvenation pruning are made much farther back on the shrub. On the primary branches, make your cut just above a latent bud, or even better, a cluster of buds. In severe cases, you can sometimes cut your rhododendron to within 6 inches of the ground. |
Another type of rejuvenation pruning consists of cutting the entire plant to within 6 inches of the ground.
It is a quick method, but not all rhododendrons survive the treatment. In some instances, an apparently healthy plant may be weakened by disease or poor nutrition and cannot recover from the stresses of hard pruning. To see if your shrub can handle such a hard pruning, cut only one of the main branches back to 6 inches. Cut the others back to a height you are sure is healthy, say 2 feet. If new growth emerges from the 6-inch cut, you can cut back the rest of the shrub the following year and be confident in its return.
Regardless of the method, rejuvenation pruning works because of a special trait of rhododendrons. Look at the bark on a stem or main branch of many rhododendrons and you will see tiny buds, little pink dots about the size of a pinhead that pepper the surface of older branches. These little pink buds, called latent buds, are the key to successful rejuvenation pruning, as they will give rise to the new framework of branches.
Once you’ve determined how far back the plant needs to be pruned, take a moment and examine the area for a nice healthy bud (one that is firm and appears filled out), and cut ½ to ¾ of an inch above that bud.
Pruning above a cluster of two or three buds is better than pruning above just one bud, as this often produces multiple branches.
| Cut just above a latent bud to rejuvenate the shrub. |
All three of these pruning methods are easy to do and result in a healthier and more attractive shrub. Don’t worry about making mistakes. Rhododendrons are very forgiving—even if you drop a tree on them.
How to prepare a rhododendron for winter
PUSHKINSKY NURSERY
Perennial rhododendron shrubs have long been loved by landscape designers for their ability to unpretentiously and at the same time luxuriously decorate household plots and gardens. Pushkin plant nursery in Moscow offers to buy strong and healthy rhododendron seedlings. Our shrubs take root well, and every spring the "rose tree" pleases the eye with a scattering of delicate flowers.
How to prepare a rhododendron for winter
Seedlings are rooted in early spring or autumn. In the second case, before you come to our ornamental plant nursery and buy rhododendron here , you should learn how to properly prepare evergreen or deciduous shrubs of these plants for winter cold. Thorough preparation of rhododendrons for wintering includes:
- plentiful watering;
- bush feeding;
- autumn anti-aging pruning;
- soil mulching around strong mature bushes;
- Reliable continuous wrapping of young rhododendrons with non-woven fabrics.
Watering and fertilizing rhododendrons in autumn
Watering rhododendrons should be regular both in summer and autumn. If September and October are rainless, take care of regular watering of the plant. One medium-sized bush is watered with 1.5-2 buckets of water at a time.
At the same time, the water should be soft - from hard water, the flower may die at all. Water is poured into the hole slowly, trying not to erode the ground around the roots. Rhododendrons should be watered before the first November frosts.
Autumn top dressing of rhododendron is carried out exclusively with potash fertilizers. Colloidal sulfur, which acidifies the soil, prevents the occurrence of fungal diseases and even after wintering prevents pests from attacking flowers.
Autumn pruning of rhododendrons
Rejuvenating pruning of withered and diseased shoots helps to strengthen bushes before wintering and ensure lush flowering in the next season. Autumn pruning is carried out from late September to mid-October. In evergreen rhododendrons, old branches are slightly shortened to awaken dormant buds by spring. Deciduous flowers are cut only 30-40 cm and in no case flush with the ground.
Do not break off the branches - you need to carefully cut them with secateurs or a knife.
So that the plant does not weaken from such a procedure, it is advisable to carry out rejuvenating pruning of healthy shoots in two approaches: half of the bush is treated in the fall, and the rest of the shoots in the spring.
Covering mature shrubs
Mulching the soil around the plants helps their roots to endure winter frosts well. They cover rhododendrons with peat, sawdust, heather soil or pine needles. Of course, the higher the rhododendron, the greater the height of the mulch. When spring comes, the mulch does not have to be completely removed - part of it may remain under the bush as a natural fertilizer.
Deciduous rhododendrons prepare for frost and snow in a special way. The branches are low, but very carefully bent to the very ground and covered with mulch.
It is good to insulate the basal part of evergreen bushes with spruce branches and oak leaves. If the plant is tall, it should be hidden from winter frosts and the active spring sun under layers of large spruce branches or under burlap.
In any case, the shelter must provide excellent air permeability. They remove it when winter recedes and spring warming becomes quite stable.
Preparing young flowers for wintering
Even if you contacted the best ornamental plant nursery and purchased strong seedlings here, growing young rhododendron shrubs can hardly survive without reliable protection during severe frosts. The active sun also causes great damage, severely drying up open shoots from February to April.
A young plant can be hidden under very thick layers of spruce branches. But the first wintering of rhododendrons is ideal under a modern non-woven shelter as agril or spunbond, for example. A hut is formed from the material around the rhododendron - stakes located around the flower are wrapped around it. Do not spud young rhododendrons with sawdust or peat - this mulch can be dangerous, causing the stem and roots to warm up during warming.
The success of the first wintering of a shrub is largely determined by the initial state of the seedling.
That is why it is important to carefully choose flowers for planting. We invite you to the Pushkin plant nursery in Moscow - here you can buy rhododendrons that will take root 100%. And the correct autumn care, the intricacies of which we have already dedicated you to, will allow the plants to survive the winter safely and bloom richly in the first spring.
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Preparing rhododendrons for winter: 5 important steps
The handsome rhododendron has long been a frequent guest in our gardens. However, not everyone knows how to properly care for this plant. We will tell you in detail what work needs to be done at the end of the season and how to properly prepare the rhododendron for winter.
Winterization of deciduous and evergreen rhododendrons differs little from each other. The only difference is that deciduous varieties do not need shelter and need less water, because. no evaporation of moisture from leaf blades.
And the rest is all the same: top dressing, mulching, pruning.
Step 1. Watering the rhododendrons
Rhododendron is a hygrophilous plant, so the level of soil moisture should be monitored throughout the growing season. Do not forget about this after flowering, especially if the weather is dry. The fact is that in August-September, flower buds are laid at the rhododendron and a lack of moisture can adversely affect flowering in the next season.
In the absence of rain, water the bushes about once every 3-4 days, pouring 1-1.5 buckets under each adult plant. It is necessary to water very carefully so as not to erode the soil and not expose the roots of the rhododendron, which are located near the surface of the soil.
Despite their need for moisture, stagnant water is not well tolerated by rhododendrons. For this reason, take care of good drainage of the area where the rhododendron will grow, even at the planting stage. This is especially important in places with a high level of groundwater.
In case of frequent and heavy rains, make grooves around the bush to drain water.
In late autumn, when the temperature drops below 2°C, water the rhododendrons with water. To prepare well for winter, the plant must be saturated with moisture as much as possible. To do this, pour at least 3-4 buckets of water under each adult bush. After such a "feed" it will be easier for the rhododendron to endure severe frosts. If the autumn was rainy and the earth in the flower garden is damp to a depth of more than a shovel bayonet, this procedure is not necessary.
Not only evergreen, but also deciduous species of rhododendrons need watering, but for evergreen varieties, spraying can also be added to watering - so the plants will quickly get the moisture they need.
Step 2. Pruning the rhododendron in autumn
Nature endowed rhododendrons with a beautiful crown, so many people think that they do not need pruning. However, this is not quite true. How to prune rhododendrons?
First, all seed pods are removed immediately after flowering so that the plant does not waste energy on seed formation.
They are cut off by hand or cut with secateurs.
Secondly, every few years, in autumn, rejuvenating pruning is carried out. In the process of its implementation, all old, ugly growing and bare branches are removed. In the same period, dried or broken shoots are also removed.
Step 3: Mulching
Mulching is one of the most important steps in preparing rhododendrons for winter. As mentioned above, rhododendrons have a superficial root system. A layer of mulch is needed in order to protect it from drying out in the frozen ground during the winter. In addition, under such a shelter, the roots will not freeze even in the most severe frosts.
However, for rhododendrons - lovers of acidic soil - not every mulch is suitable. The better to mulch rhododendrons:
- peat - take high-moor peat, because it has a higher acidity level;
- coniferous litter - it is fallen, not green needles that are suitable;
- bark of coniferous trees - most often they use pine, if there is no bark, you can take sawdust of conifers.
Before mulching the soil, remove all debris and weeds from the trunk circle. The fallen leaves of the rhododendron itself do not need to be removed: lay a layer of mulch directly on them. Under small bushes, the height of the mulching layer should be at least 4-5 cm, for tall rhododendrons - at least 10 cm. all roots are further away.
Step 4. Autumn feeding of rhododendron
If summer is over and your rhododendrons still don't have flower buds, you need to urgently look for the cause and correct the situation. The reason for the lack of flower buds in rhododendron may be improper feeding. If you applied a lot of nitrogen fertilizer, the bush will continue to grow and will not begin to prepare for winter.
How to stimulate the formation of flower buds in rhododendron? A phosphorus-potassium fertilizer, such as potassium monophosphate, will help you. Dilute 1 tbsp in 10 liters of water. fertilizer and pour it over the bushes directly over the mulch layer.
Thanks to top dressing, in which there is no nitrogen, the growth of green mass will stop in the rhododendron, and the plant will direct all its forces in the "right direction": the formation of flower buds and increased growth of the root system will begin.
Step 5 Covering the rhododendron
The last step in preparing a rhododendron for winter is the creation of a shelter. Do I need to cover rhododendrons for the winter, because most varieties can withstand frosts down to -30 ° C?
- Shelter is essential for young bushes that are not yet 4 years old: their roots may not withstand severe frosts.
- Evergreen rhododendrons are also sheltered because they are not as hardy as deciduous varieties, which can overwinter without protection.
- In addition, rhododendrons need shelter not only to protect them from frost. These plants can also be severely damaged by the bright February or March sun and strong winter winds.
How to properly cover rhododendrons for the winter?
Use only breathable materials for cover, such as lutrasil, spunbond, burlap, etc.
It is not recommended to use the film, because. often condensation forms inside the film shelter, which leads to increased humidity and negatively affects the development of the shrub.
In snowy winters, a large amount of snowfall can lead to the breaking off of lignified shoots of rhododendron. To avoid this, make a shelter in the form of a pyramid or cone. To do this, install supports (such as wooden stakes or metal pins) around the bush, and then connect them at the top. Pull the spreading branches of the rhododendron with twine so that they do not touch the cold walls of the shelter.
Wrap the frame with covering material and tie it with a rope. Such a shelter will protect the rhododendron from heavy snowfall, and from winds, and from bright sunlight, which can lead to burns on the leaves.
You can start covering rhododendrons only when the air temperature drops below -8-10°C. Too early shelter can harm the bushes, because. they will start to rot, which can eventually lead to rotting of plants.
