Pruning Rhododendrons: When & How?

Rhododendrons are a genus of shrubs and small trees that contain over 1,000 different species of flowering plants and trees, including azaleas and crepe myrtles. Rhododendrons come in all different colors and can add a beautiful landscape to your home or garden. Rhododendrons are easy to maintain as long as you know how to prune and plant these flowering trees.

Rhododendrons often require little maintenance to produce a healthy plant with blooming flowers. Because of this, rhododendrons can quickly require some pruning to keep the plant both under control and beautifully landscaped. To do this, you will need to know when and how to prune rhododendrons.

When to Prune Rhododendrons

Rhododendrons require little maintenance to produce healthy and wholesome blossoms, but this does not mean they are a low-maintenance shrub. In fact, neglecting to maintain the overall shape and size of your rhododendron can cause the shrub to grow irregularly and out-of-control.

Because of this, you will need to remember to prune your rhododendron each year to keep your shrub clean and well-maintained. (But don’t worry if you are reading this after years of neglect. We can help with that, too!)

When pruning rhododendrons for yearly maintenance, they will need to be pruned in late winter while the plant is dormant. Maintenance pruning simply means that the plant is pruned to maintain its health while removing the dead flowers and wood. Leaving these dead flowers and wood on the plant can reduce the number of flowering blossoms that are produced the following year.

Pruning rhododendrons during late winter while the plant is dormant will allow flowers to bloom the following year. Pruning rhododendrons during a time when energy is still being distributed throughout the plant to different flowers, blooms, and wood will likely result in little to no blooms in the following year.

If it is not possible to prune in late winter, you can prune dead wood, leaves, and flowers any time after the first frost of fall. Once the first frost has occurred, the rhododendron will be dormant, which means there is no energy being distributed throughout the plant to the different blooms, flowers, or wood. This means the rhododendrons will bloom the following year. You will likely need a couple of tools for this, anvil pruners for the thinner branches and stems, and bypass pruners for the thicker branches.

For the really thick branches, a small chainsaw or polesaw may be required.

Do not prune rhododendrons during the spring or summer months as the rhododendron will still be producing flowers, blooms, and new growth. You will need to wait until the first frost of fall has occurred to prune your rhododendrons with late winter being the best time to prune.

If you prune during spring and summer when blooms and branches are still growing, they will not produce blooms the following year. This makes it imperative for rhododendrons to be pruned during cold months, preferably late winter, while the shrub is dormant.

How to Prune Rhododendrons

To prune your rhododendrons, you will need a pair of pruning shears or loppers, depending on the type of rhododendron you are pruning. For example, azaleas can typically be pruned with handheld pruning shears as the wood of azaleas is small and thin. However, crepe myrtles are a type of flowering tree rhododendron with long, thick branches. These flowering trees require loppers that can extend and cut through the density of the branches.

Each fall, you should fertilize your rhododendrons so that the new growth that comes from pruning can be rich and full. Failing to fertilize your rhododendrons can cause new growth to be leggy. Leggy rhododendrons will only have blooms on the outside branches of the plant, rather than deep within the shrub. This causes your shrub to look sparse rather than full.

To perform yearly maintenance In late winter, take your pruning shears and cut off all of the dead flowers. Depending on how big the rhododendron is, you may be able to cut back 15 to 20 inches of each branch of the plant. Because rhododendrons are not meant to be cut in a shape, each primary branch that you cut should be cut at different heights to make the shrub appear natural.

When making your cuts, you should cut between ½ to ¾ of an inch above or before a dormant bud. This will help the shrub produce more flowers in the following year.

Pruning Old Rhododendron

As we mentioned, it is easy for your rhododendron to overgrow due to years of neglect. Even forgetting to prune rhododendrons for just one season can cause overgrowth in the following year.

Without routine maintenance, rhododendron can become overgrown and leggy. The rhododendron will have taken growth into its own hands by sprouting new shoots, branches, and blooms wherever the energy of the shrub tells it to grow.

While this is indicative of a healthy plant, it can quickly become overgrown and unsightly. Therefore, you will need to cut back the old rhododendron so that the shrub retakes an attractive and clean shape.

To do this, you will first need to prune all of the old wood. These pieces of wood may be dead or old wood that is growing irregularly. Depending on how out-of-control the rhododendron is will determine just how much pruning the old rhododendron you must do. Pruning old rhododendron may entail cutting back the old wood or irregular branches similar to routine maintenance.

Some rhododendron may be so overgrown that you will need to cut back all of the branches of the shrub. This is known as rejuvenation pruning. Rejuvenation pruning means that you cut off all of the dead and irregular branches so that most of the shrub is cut back to a small, basic shrub.

The best place to cut the rhododendron branches when performing rejuvenation pruning is about ½ to ¾ of an inch above a healthy bud. This will allow new healthy branches to form in the following year because the energy of the shrub is being told where to go rather than deciding on its own where it should grow new branches.

Severe Pruning of Rhododendron When They Are Too Big

Oftentimes, a rhododendron that has been neglected for years and has become so overgrown that it requires severe pruning.

Severe pruning means that you cut the entire rhododendron down to the primary branches of the shrub, as low as 6 inches off the ground, if possible. Some species rhododendron can survive being cut back to 6 inches, while other species cannot.

To severely prune your rhododendron, you will want to prune in late winter, just as you would prune for routine maintenance. However, before cutting your entire rhododendron down to 6 inches and hoping the entire shrub does not die, we recommend leaving one branch in place while cutting the remaining branches back to 6 inches.

If the branches you cut back to 6 inches sprout new growth, then you know that your rhododendron can survive being severely pruned. Should you cut all of the branches down to 6 inches and it not survive, you have no healthy branch to help the rhododendron regrow the following year. For this reason, we recommend cutting all but one branch down to 6 inches to make sure the rhododendron can survive the severe pruning.

Severe pruning of rhododendron will not produce any flowers the following year. Severe pruning of rhododendron is done to correct years of neglect that has led to overgrowth and leggy flowers.

When severe pruning your rhododendron, it is important to remember to be patient. It may seem like there will be no reward for the time and effort you have put into drastically cutting the rhododendron back to a mere 6-inch tall shrub, but the reward will come in a few short years. You will have a well-maintained and lush flowering shrub that you will be able to easily and routinely maintain each year.

What Zones are Suitable for Rhododendrons?

Zones are assigned by the USDA to each climate and soil hardiness that is found throughout the United States. These zones are numbered 1 through 13, and each zone is separated by 10 °F. The colder the climate, the lower the number. The hottest and most tropical climates are from 10 to 13.

Most rhododendrons are suitable for growing in USDA hardiness zones 4 to 8. Rhododendrons can survive both cold climates and warm climates, but they do not do well in extreme cold or extreme heat. For this reason, they thrive in zones 4 through 8, but may still be able to live in lower or higher zones depending on the conditions in which they are planted.

For colder zones, from zone 3 to zone 6, rhododendrons will need to be planted in early spring and full sun so that it can receive at least 6 hours of direct sunlight each day. As rhododendrons cover over 1,000 different species of flowering shrubs and trees, you will need to make sure the rhododendron you choose can survive in these zones. The Northern Light Series of azaleas are ideal for colder zones as they can survive temperatures that fall well below 0.

Rhododendrons that are planted in zones 7, 8, and 9 do not require full sun and can be planted at any time of the year. In fact, they thrive when there is afternoon and evening shade, as full sun in warm climates can often overheat the shrub and cause it to wilt, dry out, or become diseased.

Tropical climates in zones 10 or above do not require any sunlight for the rhododendrons to survive and can also be planted at any time of the year, with fall being the most preferable. Because the climate is so warm, the rhododendron soil is warm enough to keep the rhododendron healthy and wholesome.

When planting rhododendrons, you will need to dig a hole deep and wide enough to sit the root ball inside, but not so deep that the soil will cover the entire root ball. If the root ball is planted too deep, it will likely because the soil is too heavy and saturated, which often leads to root rot. You will want to place the root ball in a hole and leave the top of the roots above the surrounding soil. This will help your rhododendron flourish when planted.

After placing the root ball into the hole, fill the hole half full with soil. Water the soil that you have placed in the hole with an ample amount of water before filling in the hole with the remainder of the soil.

Conclusion: Why You Should Plant Rhododendrons and How to Keep them Maintained

Rhododendrons are a beautiful adornment to any home or garden. Rhododendrons provide both scenic and ecological benefits to homes and gardens.

When used for landscaping, rhododendrons are ideal for adding privacy and pops of color to both residential and commercial properties. Rhododendrons come in all different colors, shapes, and sizes for you to achieve any landscaping goal you have in mind. Rhododendrons can be planted as flowering trees, like crepe myrtles, to give you both character and privacy at any type of property.

Rhododendrons are also ideal for gardens and farming as the flowers attract many bees. The bright colors and abundance of blooming flowers will attract bees. Once the bees are in the vicinity of your garden or farm, they will land on the flowers of the crops you are harvesting and carry pollen from one crop to another. The pollination from male to female flowers is what makes the flowers produce crops.

Oftentimes, the flowers of these crops can pollinate by wind alone, but when that cannot be achieved, they rely on bees to help carry the pollen from flower to flower. Rhododendrons are ideal for adding to any farm or garden because of the bright, colorful flowers that the plant produces.

If adding rhododendrons to your home or garden, you should plan to prune them each year in late winter so that they stay full without becoming leggy.

In the event they are neglected and become overgrown, you should cut back the old growth by taking off several inches of the rhododendron branches. If rhododendron overgrowth is too severe, cut the rhododendron down to around 6 inches tall, leaving one primary branch of the rhododendron intact in case it cannot survive the severe pruning.

Leave a Comment

Your email address will not be published. Required fields are marked *

Scroll to Top