As long as a rhododendron presents itself in a magnificent floral robe, the gardener rightly doesn't waste any thought on pruning. As it gets older, the ornamental shrub becomes visibly bald and is now only a shadow of its former self. You should now note pruning in your care plan at the latest. This tutorial explains in detail when and how to skilfully cut a rhododendron bush.
How do I cut a rhododendron correctly?
A rhododendron pruning should include the following steps: flower care after flowering to remove wilted flowers; Maintenance pruning in spring to remove bare and unfavorable individual shoots; Rejuvenation pruning in late winter to revitalize the shrub and post-rejuvenation pruning to encourage new growth. It is important to always leave small cones with leaves, shoots or sleeping eyes.
Reasons for a rhododendron cut – occasions in brief
There is widespread agreement among rhododendron experts when it comes to pruning care. In the first few years you should leave the picturesque flowering shrub as it is. The opulent ornamental tree develops an inimitable habit with a stable structure and compact stature. The colorful flower clusters unfold every spring from the buds that were planted the previous year.
Planting and training cuts must be deleted from the rhododendron without replacement. Apart from summer flower care, a rhododendron does not need any pruning in the first few years. Only when the balanced growth begins to f alter with increasing age can visual disturbing factors become a reason for cutting measures. The following table summarizes what these are, which goal is targeted and which point in time is advantageous:
| Cut style | Goal Setting | Appointment recommendation |
|---|---|---|
| Cleaning | remove wilted flowers, encourage new buds | after the flowering period |
| Conservation cut | remove bare and unfavorable individual shoots | in spring before flowering |
| Rejuvenation cut | revitalize old shrub | in late winter until March 1st |
| Construction cut after rejuvenation | Promote new growth after radical pruning | in the spring before the flowering period |
For all dwarf rhododendrons (Rhododendron repens), the only thing that matters is flower care. Popular varieties, such as 'Pumuckl', remain comparatively small and compact with a height of 50 centimeters. Nothing changes even after many years, so you don't have to think about maintenance or rejuvenation cuts. The little beauties thank you for regularly cleaning out withered inflorescences with a dense flower dress that covers the green leaves.
Flower care on the rhododendron – mock cut without scissors
Two convincing arguments speak for annual flower care: When withered, a rhododendron is certainly not a feast for the eyes. In addition, the buds for the next shoot are already located beneath the faded flowers. Garden scissors are not required for the maintenance measure. How to clean out wilted rhododendron flowers by hand:
- Use your index finger and thumb to grasp the small piece of shoot under the withered inflorescence
- Tip off the flower cluster or break it off to the side
The sooner you start cleaning, the easier it will be. Keep an eye on the new buds and fresh shoots below the wilted flowers. At this early stage of growth, the plant parts are sensitive and break off quickly.
Background
Remove water bullets promptly
For the removal of cheeky water bullets, the quickest appointment is the best appointment. This term refers to steeply upward-facing branches from the wild substrate. The most beautiful rhododendron varieties are the product of horticultural refinement. A precious part is grafted onto a robust game base with great dexterity. Strong shoots regularly emerge from the wild base to overgrow the noble part and compete with it for nutrients. Wild shoots are revealed by the strikingly large distance between leaves, the internodes. If you come across a water shooter, cut or tear off the shoot immediately.
Preservation cuts target individual shoots
Sometimes bare branches protrude from a rhododendron and disrupt the well-groomed appearance. These shoots are a case for maintenance pruning. If you are concerned that the cut is not visible at first glance, we recommend this cutting technique:
- The best time is before the flowering period begins
- Examine the shoot in question for a deeper, young, unbranched shoot
- Make the cut at the fork of the branch and side branch
- Leave a small cone of 5 centimeters with a leaf on the side
The cut is a combination of derivation cut and tenon cut. With this strategy you can reliably prevent unsightly gaps and optimize the prospects of new growth at this point. The figure below illustrates the procedure. However, if you haphazardly saw off a cheeky branch somewhere, you will look in vain for young shoots and have to live with a large hole in the foliage for many years.
If individual branches protrude cheekily and bare from the rhododendron, a derivation cut brings the shoots into line. Shorten the unfavorable shoot so that a young, short side shoot takes over the new leading position. Small cones with leaves promote new growth because the nutrient supply is not interrupted.
Background
Pruning technique “on cones” cheers up tired rhododendrons
In cutting instructions for rhododendrons, a sophisticated cutting technique is regularly mentioned, which is crucial for the result. For this reason, we will deepen the procedure here. Rhododendrons rarely sprout again from old wood. By leaving a small cone with a leaf, shoot or sleeping eye when cutting, you stimulate growth. The parts of the plant mentioned maintain the supply of nutrients so that the shrub continues growth at this point. Always cut the leafy shoot “on cones” with a sideways, outward-facing leaf. On the bare branch, place the scissors 5 centimeters behind a fork to the younger side shoot. Where both are missing, look for or feel a sleeping eye under the bark and apply your newly acquired know-how here. Then practice patience. It can take more than a year for budding to start.
Rejuvenation cut reverses aging – it works in stages
If the ravages of time gnaw at a rhododendron, you are not powerless against the gradual balding. You can rejuvenate the old, aging shrub over several years. Please do not be tempted to put the sparse, bare ornamental tree on the stick in one go. In this case, total failure is inevitable. It's better if you follow the instructions in this tutorial. How to do it right:
- Best time is on a frost-free day before March 1st
- Important: Do not carry out rejuvenation cuts in accordance with the Federal Nature Conservation Act between March 1st and October 30th
- A third of the bare shoots lead to a young side shoot
- Leave 5 centimeters of cones at the interface behind the fork
- Severely aged scaffold shoots are directed to the lowest side shoot near the ground
The figure below illustrates the first stage on the path to rejuvenation. Then fertilize the cut rhododendron generously with leaf compost and horn shavings or special rhododendron fertilizer with an NPK formulation of 14+7+14. There is a one-year waiting period before the procedure continues as a combination of build-up and rejuvenation cuts. You can read how to do it in the following section.
In the first stage of rejuvenation, remove a maximum of a third of all shoots or redirect them to a lower side shoot. Leave 5 centimeter small cones again.
Excursus
Proper cutting tool is crucial
Pruning rhododendrons becomes a gardening success story when the right tools are used. As a basic equipment for uninterrupted work, you should have the appropriate scissors or saw ready for every type of cut and cutting strength. The one-handed secateurs (€47.00 at Amazon), either with a bypass or anvil mechanism, are suitable for shoots up to 2 centimeters thick. You can handle branches with a diameter of 2 to 4 centimeters with two-handed pruning shears or a folding saw. For a thinning cut on the majestic shrub with branches 4 centimeters in diameter and more, a high-quality sword or hacksaw is a must.
Build-up cut completes the rejuvenation – this is how it works
Under ideal conditions, the first cones sprout in the summer after rejuvenation. As the tree grows, cone residue dries up and can be easily removed. The following spring, cut back the next third of over-aged branches, again using the combined derivation and cone pruning method. The image below illustrates the correct procedure.
Take this opportunity to take a close look at all young ground shoots. Select the strongest specimens and cut off weak competing shoots at ground level.
If no cones have sprouted, postpone the second rejuvenation stage for another year. A lack of growth of young shoots signals that your rhododendron is still suffering from the hardships of the first stage. By refraining from further pruning, you give the shrub the opportunity to gather its strength.
If the first young shoots form at the interfaces in the year after rejuvenation, the next third of old shoots are rejuvenated. Without fresh growth, wait until next year for the next stage.
Background
Wound closure on rhododendrons is no longer up to date - with one exception
Thinning out old, thick branches or extensive rejuvenation pruning leaves large cuts on the rhododendron. Modern home gardeners leave the healing process to the shrub and no longer seal the wounds with tree wax. The latest scientific research has shown that in every tree and shrub there is tissue that can divide under the bark - the cambium. After wounding, cambium forms wound wood to cover the damaged area. This natural form of regeneration trumps horticultural measures by far. As a result, tree wax and other wound closure products are discarded in the home garden. The only exception is a thin layer of tree wax along the edges of the wound if frost could damage the valuable cambium.
Frequently asked questions
What is the difference between rhododendron and azalea?
The Rhododendron genus includes more than 1000 species, including azaleas. For this reason, botanists call the popular Japanese azalea Rhododendron japonicum. Regardless of their close botanical relationship, you can distinguish between the two flowering shrubs based on their visual characteristics. A rhododendron thrives as an evergreen, usually sprawling shrub. Azaleas, on the other hand, shed their leaves in autumn or winter and develop an upright, less expansive stature.
Are rhododendron bushes poisonous?
Most rhododendron species and varieties contain a cocktail of various toxins. Not only the leaves are dangerous to he alth, but also the roots, buds, flowers and fruits. Excessive consumption causes severe symptoms of poisoning in humans and animals, ranging from nausea and vomiting to shortness of breath and slow cardiac activity. Please only integrate a rhododendron into your garden design if the plant is out of the reach of children and animals. Protect yourself with gloves when cutting. Do not dispose of clippings in the compost or a pasture, but in the organic waste bin.
Can I use clippings for propagation from cuttings?
Propagate rhododendrons with cuttings is considered a challenge even among plant experts. Nurseries usually propagate ornamental trees through grafting. Instead of struggling with these complicated methods, we recommend the lowering method. Semi-woody shoots close to the ground are perfect. First, remove all side shoots and lightly score the tissue on the underside. Bury the piece of shoot with the wound site in the ground. Fix the end of the shoot on a wooden stick. The mother plant and offshoot remain connected until the offspring has developed its own root system.
Rhododendron buds die - what to do?
You describe the typical symptom of a fungal infection caused by the rhododendron leafhopper. When the insects lay their eggs, they cause tiny wounds on the bud, which fungal pathogens use as a portal of entry. Remove dead flower buds promptly and dispose of them in household waste. To prevent this from happening in the first place, you can use yellow boards to prevent the female cicadas from laying eggs in August and September.
The 3 most common cutting mistakes
No master for rhododendron pruning has fallen from heaven yet. Although the beautiful flowering bushes are easy to care for per se, pruning them requires attention to their special growth characteristics. The following table would like to prepare you for the three most common cutting errors with tips for prevention.
| Cutting errors | malicious image | Prevention |
|---|---|---|
| withered flowers not cleaned out | decreasing abundance of flowers | break out wilted flowers promptly |
| aged rhododendron placed on the stick | Total failure | rejuvenate old bush in stages |
| do not cut back to cones | no new shoots at the interface | Always cut branches with small cones and lateral leaves or shoots |
Tip
Transplanting rhododendrons requires a rethink about pruning. While pruning is part of the standard procedure for other garden shrubs, the measure is canceled without replacement for rhododendrons. The sap pressure is simply too low to sprout again after a change of location and pruning. Therefore, pay special attention to a transplanted rhododendron when watering and fertilizing so that it can compensate for the lost root volume on its own.