Despite being known as one of the hardiest and cold-tolerant shrubs, you may see your Rhododendrons all brown and withered up one day. The question is: is it dead?
The ‘Bark Scratch’ test is the easiest way to check if a rhododendron is dead or alive. Using a sharp knife or the back of your fingernail, scrape parts of the bark off the main trunk. If there’s a green cambium layer, the plant is still alive and will recover. However, if it is brown, it is dead.
Below, I elaborate on this further with the causes and helpful insights from The American Rhododendron Society (Thanks ARS! – Shasha):
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How to Check if My Rhododendron is Alive or Dead?
There are two ways you can do to check the status of your Rhododendron:
- The ‘Bark Scratch’ Test – this is where you scratch/scrape 1-2 inches of bark off the central stem and other larger branches. You can skip checking thin stems as they are the likeliest to have been severely damaged. Here’s what you need to look out for:
- If there’s a green layer underneath the bark, your Rhododendron is still alive.
- If it’s brown, the plant is unfortunately dead.
- Leave the plant as is and observe whether it develops new growth. This is more of a ‘watch and wait’ method. It requires you to be patient, watering regularly, and not pruning off any damaged or dead parts of your Rhododendron. Here’s what to keep an eye on:
- If there are new leaves and side shoots developing from the primary trunk or big stems, your Rhododendron is still alive and thriving. You can trim off the dead branches by late summer so the plant will look and grow better.
- If the plant looks the same with no new side shoots or leaves, it’s definitely a goner.
While the first method is an instant way of checking, most gardeners do the second one. Glen Jamieson from ARS shared a story about how two of his potted Rhododendrons lost their leaves last summer. But they have since developed new growth this September after regularly watering!
So you got to remember that it takes a lot to kill off Rhododendrons. Most of the time, they’ll pull through. But if they don’t, don’t let that stop you from trying again. Take this as an opportunity to learn about the probable causes and preventive measures to protect your plant best the next time.
What Caused My Rhododendron to Die?
Typically, there are four common reasons why Rhododendrons perish:
1. Lack of water. Rhododendrons have shallow roots that grow near the surface. Unlike other established trees and shrubs, it doesn’t have a tap root to dig deeper into the ground in search of moisture, especially during dry periods. This means the plant needs to be watered often, about once or twice a week, and even more so during hot spells. Otherwise, the plant will eventually wither away if you leave it to dry out for too long.
2. Too much water. Like other plants, Rhododendrons can suffer from overwatering and root rot, eventually leading to plant death. Since the plant requires frequent watering, this increases the risk of waterlogging the soil. So always check the ground before watering at 1-2 inches deep. If it’s damp, don’t water it; but if it’s dry, then give the plant a good glug.
3. Extreme cold temperatures. Different Rhododendron cultivars have various hardiness – some of which can tolerate down to -35°F/-37°C. However, that doesn’t mean they are invincible because they will still suffer if temperatures get too low and cold for them, especially if it’s windy. Glen Jamieson from ARS says, “… if the non-deciduous plant is overwintered with no leaves, it is likely dead. The cause could be disease, prolonged lack of water and drying out, and so on.” Non-deciduous or evergreen plants are essentially ones that keep their green foliage all year long. But if it’s a deciduous Rhododendron, it’s normal to see the leaves turning red, purple, or yellow before falling off.
4. Pest & disease problems. It’s worth noting that these rarely cause Rhododendrons to collapse unless the plant was cultivated from an infected or infested cultivar. Instead, they often appear when the plant is already suffering from other ailments. Say you save your plant from an infestation of Rhododendron borers or an infection of Ovulinia petal blight. It’s worth looking deeper into the soil, sun, water, and fertilizer aspects to see if they were the initial cause of its weakened state.
Helpful Tips to Prevent Rhododendrons from Dying
Here are some valuable things to remember to keep your Rhodendrons in tip-top shape:
- Give Rhododendrons plenty of bright, indirect sunlight. They’ll still grow in deep shade, but they would produce very few flowers. And too much sun will cause leaf scorch.
- Grow Rhododendrons in acidic soil with pH 4.5-6 for best growth. The foliage will turn yellow with green veins if the pH is too alkaline, especially when planted near concrete structures. As time progress, the plant will suffer from poor overall growth. If it’s too much of a hassle to amend the soil with sulfur to lower the pH, it’s best to use raised beds or containers. Because this way, you can give them the right potting mix from the start.
- For potted Rhodendrons, use loose, well-draining, and nutrient-rich soil with plenty of organic matter like compost.
- For a raised bed, the best soil mix is a mixture of potting soil and organic material like sphagnum moss, chopped leaves like oak leaves, and pine bark.
- Plant the Rhododendrons with the top of the rootball sticking out at 1-3 inches above the surrounding soil. The plant has short roots, so planting it near the surface allows it to extract moisture easily as it is being watered.
- Water Rhododendrons once or twice per week. As mentioned before, they have shallow and fibrous roots. They may also need more water than usual when there hasn’t been enough rainfall or during hot, blistering summers to keep the plant going. But again, be careful and check the soil first before watering.
- Apply a 2-4 inch layer of mulch around the base of the plant, spaced 3-5 inches away from the main trunk to help retain moisture and heat in the soil. Not only does it help prevent weeds, but it also protects the delicate surface roots from drying out in the sun.
- Water Rhododendrons thoroughly before applying mulch to preserve as much moisture as possible before the ground freezes in late fall. It’s encouraged to use additional protection, like the following:
- an anti-desiccant to preserve as much water as possible;
- a windbreak for dry winds;
- a burlap sack to cover the plant from frost
- Don’t prune Rhododendrons often. If you need to remove damaged or dead branches, only do it after the plant has stopped flowering or developed new growth in late summer.
- Do a biweekly pest & disease check around the plant. Being on top of this practice will allow you to spot anything out of the ordinary with your Rhododendron.
Frequently Asked Questions about Rhododendrons
A Rhodendron can recover if there is still living plant tissue in the main trunk. This requires scratching the bark off to see if it’s still green underneath. If there is, wait for the plant to develop new growth before pruning off the old, damaged, and dead parts. If there isn’t, discard the plant entirely.
A dead Rhododendron has no chance of bouncing back if there is only a brown layer underneath the bark of the primary stem. However, if it is green, the plant is still alive and may recover. Water it frequently and let the plant be until late summer to develop new growth.
There are several causes as to why a Rhododendron has turned brown:
– It is dehydrated from inadequate watering, especially during hot weather.
– Its roots are drowning in oversaturated soil (Too much water, not enough oxygen).
– It has cold damage from being exposed to windy and freezing temperatures in winter.
– It is experiencing temperature shock.
– It is receiving too much direct sun resulting in scorched leaves.
– It is suffering from a pest infestation or a plant disease infection.
Whichever the case, the first thing to check is whether the plant is still alive or not by scraping a section of bark off the main trunk. If it’s brown, then your Rhododendron is dead. But if it is green, it’s still alive. Here’s how you can save it:
– Water the plant frequently, making sure not to overwater by checking whether the soil is dry beforehand.
– Wait to prune the damaged or dead parts of the plant until late summer after new growth has developed.
– Ensure the plant is shaded from the excess sun but receives enough indirect sunlight to grow.
– For pest & disease problems, use organic solutions like Neem oil spray sparingly to eliminate them. But keep in mind that this is a last resort type of situation.
Deciduous Rhododendron cultivars shed their leaves to go into dormancy before winter. However, if non-deciduous/evergreen types drop all their leaves, they may suffer from severe dehydration or a plant infection. Water your plant first, then investigate the possible pest or disease problem before grabbing the nearest pesticide.
Some Rhododendron variety loses their leaves in winter, especially if they are still young, which is normal. However, it also depends on the cultivar’s hardiness. Some are deciduous, meaning they shed their leaves before winter in late fall. Some are evergreen, retaining their leaves throughout the cold season. 
Regularly water and don’t prune any branches off a half-dead Rhodendron. It’s better to wait until the plant develops new side shoots before trimming dead and damaged parts. Most Rhododendrons are pretty hardy and will bounce back – give it time, and you’ll see it come back to life in no time.
Rhododendrons with a green cambium layer underneath their bark have the potential to recover. They only require regular watering and no pruning until the plant has developed new growth. However, if the main stem only shows a dried and brown layer below the bark, it’s dead and has no chance of bouncing back.
Burnt Rhododendrons result from excess sunlight exposure, causing crisp and scorched leaves. It’s best to provide shade with enough indirect sunlight to allow the plant to grow better. You can also place them in deep shade, but this will result in fewer flowers.
Rhododendrons benefit from yearly pruning to remove old, damaged, dead branches and flower buds. It’s advisable to do this after the plant has finished flowering in mid to late summer. However, take care to prune only 1/3 of the whole plant.
Final Words
Overall, don’t be quick to discard your Rhododendron before checking. Just because it looks dead, it doesn’t mean it has given up on recovering. When in doubt, leave the plant and water as you usually would and watch it claw its way back to life. Happy planting!
A quick word on The American Rhododendron Society:
I want to extend many thanks and appreciation to the establishment for giving the time to answer our queries and provide valuable insights for this Rhododendron article. Special thanks to Bill Meyers, the President, and Glen Jamieson, the Chair and Editor of the ARS Journal, for his personal experience with this particular Rhododendron issue.
The ARS is currently open for new members to join them. If you are interested, visit them and sign up at www.rhododendron.org! They also have an impressive database and collection of resources on Rhododendrons for the public to peruse. You can just go to their site, look around, and start reading.
References:
- Rhododendron. (n.d.). PPO Home. Retrieved September 26, 2022, from https://ppo.puyallup.wsu.edu/sod-home/education/pr-symptoms/rhododendron/
- Soil Information for Growing Rhododendrons and Azaleas. (2020). Rhododendron.org. https://www.rhododendron.org/soil.htm
- Rhododendron and Azalea Weather Protection. (n.d.). Www.rhododendron.org. Retrieved September 26, 2022, from https://www.rhododendron.org/protection.htm
- Irrigating Rhododendrons and Azaleas. (n.d.). Www.rhododendron.org. Retrieved September 26, 2022, from https://www.rhododendron.org/irrigation.htm
- Azaleas and Rhododendrons: Identify and Manage Problems | University of Maryland Extension. (n.d.). Extension.umd.edu. Retrieved September 26, 2022, from https://extension.umd.edu/resource/azaleas-and-rhododendrons-identify-and-manage-problems
- Support, E. W. (2005, March 25). Give rhododendrons and azaleas an annual check-up each spring. Extension Communications. https://extension.oregonstate.edu/news/give-rhododendrons-azaleas-annual-check-each-spring
