Plumerias are resilient plants, and most of their issues are caused by over-watering or over-feeding. While they require regular support, giving them too much of anything can cause problems, with one of the worst being plumeria stem rot.
Stem rot occurs when the plants are too wet, too humid, or attacks by common plumeria pests have caused over humidification inside the stem. In this article, we’ll talk about common causes, and the best ways to treat stem rot, as well as the important difference between stem rot and black tip fungus.
What is Plumeria Stem Rot
Plumeria stem rot is a fungal disease that can kill plumeria by stopping any water from reaching its leaves, and destroying the rigidity of the plumeria stem. It usually starts from the roots but can travel up damaged parts of the stem where water has built up due to fungal disease.
Plumeria stem rot affects mature plumeria as well as causing rot in young plumeria and cuttings, and while the differences are slight, they are worth paying attention to, so we’ll try to break down how to identify stem rot at each stage of plumeria growth.
Identification of Stem Rot on Plumeria Plants
Stem rot occurs due to over-humidification, which is often tricky to avoid as most of us grow plumeria indoors or in greenhouses due to their tropical nature. These tropical plants with their beautiful flowers give us signs that they are not happy though – before it’s too late!
The first signs of stem rot are leave dropping. Leaf drop occurs for one of two reasons in Plumeria, blacktip fungus, or stem rot. Both are the result of over wet soil, and over wet leaves, so the early prevention for both is simple: waterless.
To prevent these fungal diseases, you first need to know what they are, as foliar feeds are definitely the wrong choice, even though supporting the plant’s top growth might seem like a good idea when it’s struggling.
Identification of stem rot on mature plumeria plants
If it’s too late for prevention, stem rot becomes noticeable through hollow centers and squishy black stems. Before the entire stem becomes blackened, a spot or stain on the main stem indicates early stem rot. At this point, fungicidal sprays are the only chance of saving the stem, but if you have a multi-stemmed plumeria, with new growth below the point of rot, it is often better to just cut everything off from an inch below the infection. I’ll talk more about that drastic treatment later!
If black stains appear on the outside of the stem, they indicate a hollow center, which could either be caused by parasites, or by root rot that has traveled up the stem.
If root rot is your issue, then urgent action is needed! You’ll be able to tell the difference in where the rot started pretty easily though, as stem rot caused by root rot is, understandably, just above the soil line as it has traveled up from the roots.
Infected plants with signs of rot higher up are usually caused by pests, so treating the pest along with the fungus is essential.
Identification of stem rot on plumeria cuttings
In the first year of planting, or rooting plumeria cuttings in water, your plumeria is much more susceptible to stem rot than a mature tree.
The reason for this is that plumeria cuttings rooted in water, like all tropical plants, have an adaptation that causes them to send out specialized water roots, that allow damaged plant material to transform its cells into the optimum roots for their habitat. Bwecvuiase those roots are adapted for water your plumeria will be safe, and incredibly resistant to rot until you put it in soil.
As soon as you place your plumeria cutting in soil, the roots can be shocked, and they search for water by growing long thin roots. these roots are weaker than soil roots, and far more susceptible to disease.
As a result, your young plumeria will begin to rot from the base, turning the entire stem brown, and its leave will discolor and drop.
Misdiagnosing Stem Rot in Plumeria Plants
Is it winter burns or stem rot on plumeria?
Winter burn is an irritating problem for plumeria, as it occurs while the plant is dormant (usually while you have it stored away for winter).
It causes brown legions and dried rot around the plumeria stem, causes, literally burns. The humidity, plus the heat of low winter sun, or even just being in close proximity to a boiler, can dry out the stem to the point that it spits, and lets in fungus. The biggest visual difference is that winter burn is almost always contained to a small area, and the treatment is to cut off the affected area of the plant as it won’t recover, or continue sending goodness to the leaves or plumeria blooms above.
Is it black-tip fungus or stem rot on plumeria?
Blac tip fungus is another fungal disease, which, like stem rot, can be caused by pest damage, allowing humidity and fungus into the stem. Black-tip fungus is easier to treat though, as a few treatments of fungicide, coupled with cutting off the affected tips will usually solve the problem. Read our full article about the treatment and prevention of black-tip fungus here.
What Causes Plumeria Stem Rot?
Plumeria stem rot is caused by fungal growth in hollow cavities in the stems of plants. These are often caused by spider mites who eat the cellulose within plumeria stems, petioles, and leaves. They cause small cavities which grow if any fungal spores land near them.
Stem rot at the base of your plumeria plant, just above the soil line, especially if you have soggy soil, is caused by rot in the plumeria roots. Plumeria roots, especially root cuttings, are really susceptible to rot as they can become easily pot bound, and only take up water in spring, summer, and autumn. Watering in winter leads to soggy soil and sitting water that stagnates in the pot.
There are two ways to identify root rot. Number one: smell. The smell or root rot in tropical plants is incredibly distinctive, like wet cabbage leaves, and if root rot is really bad in containers indoors, the smell can be noticeable all over the house.
If root rot hasn’t fully set in, the best sign is falling leaves. Leaves fall either due to over humidifying, which leads to pest damage like black-tip fungus, or root rot, leading to wilting, as the roots aren’t passing water up the stems.s
As the root rot intensifies, it leadup the stem, hollowing it out and creating crevises for fungus to grow in the now humid decomposing stems.
These stems can be treated with a fungicide if you catch it early, and by severe root trimming, but if it’s too late, all I can say is good luck.
Some pests damage can lead to cavities in the stem that leads to stem rot, without any fault of the roots. The difference here is that you will see black squishy stems above the soil line, at any point on the plant. The closer these are to leaves, the more likely it is to have been caused by spider mites. Accidental damage can also lead to fungal infection in the same way, where any cut to the stem can grow bacterial infections. Therefore, maintaining a generally healthy, pest-free plant in a clean environment can help eliminate some of these causes.
Treating Plumeria Stem Rot
Root pruning is the most common approach to curing plumeria stem rot. By pruning roots, especially on containers indoors, where they can be easily accessed you remove diseased rotting roots, and prompt the plant to start growing new healthy roots in their place.
This is something you should do with plumeria every two-three years anyway, in much the same way as pruning olive trees or potted citrus.
Treating stem rot ion plumeria with fungicides
After inspecting the stem thoroughly, checking for any squishy, soft, or mushy areas on the stems, or black blotches on the leaves (particularly lower down near soil and water level), make sure to clean your plumeria in any areas where you suspect fungal growths or pests to be a problem.
For me, I prefer to swab using rubbing alcohol, as this dries out the areas and reduces humidity. It also has the benefit of cleaning bacteria and killing pests safely without risking harm to other beneficial insects.
Once you have cleaned your plumeria, if the stem rot is in a very early stage, make sure to keep it dry, and water only if the soil completely dries out, and apply a weekly fungicide – neem oil is particularly effective as it helps to prevent pests at the same time.
Sadly, if the plumeria rot has extended and spread, the only option is to cut off any affected materials with clean secateurs as quickly as possible, immediately disposing of the affected stems and leaves in a trash bag.
Treating plumeria stem rot with root pruning
Root pruning is prevention as well as a cure. It helps to establish stronger plants and better-adapted roots, but it is also a necessary stop if you suspect any signs of stem rot in your plumeria plants.
Tip: If the fungal growth above ground is bad, then prune these stems off first to prevent them from rubbing against other stems while your plant is on its side
First, tip the plumeria on its side, and gently remove the pot. If the soil is oggy then you definitely have a problem. If it smells, then you have N even worse problem. Either way, the process here is the same.
Root rot is visible, and the roots will be black and mushy due to too much water, or stagnant water.
This next step might seem extreme, but remember, these infected roots are already gone and draw no water or nutrients into the plant whatsoever. So, with a clean pair of secateurs (and I mean clean!) cut off every last bit of affected root. If that means the entire root ball then so be it!
If the root rot has taken over the entire plant’s underground system, the only option remaining is to create a new rooted cutting from any healthy growth that is left above the soil level.
How to Prevent Plumeria Stem Rot?
Firstly, never take a cutting from growth that is anywhere close to stem rot. The rot might not be visible, but it can spread inside the stem without any outward signs before it shows itself.
Other than that, the only ways to prevent plumeria stem rot are through proper (meaning limited!) watering.
If the soil is wet, don’t water, no matter what. To help dry out the soil, repot the plumeria into a container with better drainage, and shake off any compost to replace with the new, lighter, better-drained mix.
And, as above, regular root pruning every 2-3 years will provide a stronger root system that is better adapted to its container, making it much more resistant to stem rot, root rot, and a whole host of other diseases.
Recommended Products for Treating Plumeria Stem Rot
1. Solimo Hydrogen Peroxide
Hydrogen peroxide works by breaking down the proteins that connect fungus DNA. By directly dabbing the peroxide onto the affected stems, the fungus is forced to dry out and stop duplicating. Peroxide is also an effective way to kill the most common pests on plumeria.
2. DEBUG – Organic Pest Control for Plants – Neem Oil + Azadirachtin & More
DEBUG is of great value and helps to prevent future fungal build-ups in plumeria stems by removing the pests that cause the problem, as well as attacking the fungus with its unique antibacterial blend.
This organic pest control is safe for children and pets once dried but can be mildly toxic if ingested while wet, so avoid contact with eyes, mouths, or cuts to avoid irritation. The biggest benefit of DEBUG is that, like most insecticidal soaps, it also cleans the plant of any honeydew that might attract pests, so stops future fungal infection in its tracks.
3. Arm & Hammer Pure Baking Soda, 8 oz
Arm & Hammer baking soda is an effective fungicide, which dehydrates the fungus within the stem. Obviously, baking soda will dehydrate anything it touches, so use it sparingly by spot spraying a solution of baking soda and water for targeted control of stem rot
To help baking soda stick, mix it with a solution of warm water and dish soap. This helps it stick to the affected area without dripping down the plant.
4. Grower’s Ally Fungicide
Grower’s Ally is an approved fungicide with limited insecticidal effects. It targets fungus to treat stem rot on plumerias quickly and effectively. Use away from pets or children though as it can be toxic while wet, but is safe once it has been allowed to dry.
While it is not organic, it is certified as safe for domestic use.
5. Organic Neem Oil
Neem oil is great at treating pests and fungus in one application, as it has strong antibacterial properties, which helps the fungus dry out in its early stages, and destroy any pests that might cause repeats of the same problem.
The other benefit of neem oil is that while is it is toxic to pests, it is only toxic while wet. So as long as you use it indoors you won’t accidentally harm other wildlife.
Other Useful Tools for Treating Plumeria Stem Rot
Large 10 Inch Terracotta Plant Pot
A new pot with a large drainage hole will help prevent root rot and ultimately stem rot. It’s worth investing in a good terracotta pot for any house plant, but particularly plumeria where waterlogging is an issue. Terracotta helps drainage as the material is porous, so allows transpiration of excess water through the drainage holes at the base, as through the walls of the pot.
Cylinder pots like this are ideal for plumerias too as they don’t collect water in their base as readily as tapered pots.
Carbon Steel Pruner/Secateurs
A really good pair of secateurs is essential, if you don’t already have a pair, secateurs like these by SunJoe are brilliant. Carbon steel stays sharper for longer meaning cleaner cuts, and they can be easily sterilized in boiling water before use.
Plumeria Stem Rot FAQs
How do you fix a plumeria stem rot?
Plumeria rot is often caused by root rot, so the best treatment is root pruning. Make sure the plant is placed back in full sun, and watering is limited after pruning to promote healthier more resilient roots.
How do you treat stem rot?
Damaged plumeria stems aren’t easy to treat, but organic fungicides will help in the early stages of infection, and can occasionally cure it without the need for drastic action. However, in really bad cases, you may need to prune any affected material harshly, until you have no signs of stem rot.
Why are my stems rotting?
Plumeria stems rot when they are over-watered, over humidified, and bacteria is allowed to enter damaged or hollow plant materials rotting stems can be caused by pests, root rot, and unhygienic conditions, so cleaning the pots, refreshing the roots, and cleaning your plant regularly will help reduce the risk.
Final thoughts on Plumeria Stem Rot
I hope you’re reading this to find a preventative measure rather than a cure because it’s never fun having to cut back huge portions of a beloved plant, but if you are, good luck with your new treatment regime.
Plumeria stem rot can be a difficult problem to tackle, but with the right care, and right tools it can be treated and your plumeria can be saved.