Mandevilla blooms are truly a charm. But it’s even more charming when the vine is strong & all the leaves are green. But sadly, Mandevilla often disappoints us with leaf yellowing.
I know, yellow leaves are not desired but, the good thing is- you can solve this problem by yourself.
From now on, you & I, both are plant doctors. We will walk together & diagnose every single issue that may result in turning your Mandevilla leaves yellow.
And finally, we will come up with exact solutions to get our Mandevilla back on track.
So, let’s start the walk.
What's On the Page
- 1 Why Do Leaves Turn Yellow?
- 2 Why Mandevilla Leaves Turning Yellow?-Reasons & Solutions
- 3 Miscellaneous
- 4 Conclusion
Why Do Leaves Turn Yellow?
Before starting the diagnosis, let’s know the fundamental reason behind leaf yellowing-
You know, chlorophyll is responsible for the green coloration of leaves. In the plant world, losing the normal green coloration is termed “Chlorosis.”
Interestingly, there are other pigments present in leaf cells that can cause colors like yellow, orange, red & many more. Due to the abundance of chlorophyll, we only see the green color.
But if somehow the chlorophyll production gets interfered with or loses the abundance, yellow or other colors start appearing gradually.
Why Mandevilla Leaves Turning Yellow?-Reasons & Solutions
1. Pot Size
As a plant doctor, you want to look for potential causes with signs & trust me, it’s always good to start with pots. Why? Let’s see-
Causes & Symptoms
You know, most of the reasons behind leaf yellowing arise from the soil or rooting medium. Unfortunately, the pot contains a tiny share of it & thereby causes plenty of limitations.
Now the question- How can the size of the pot cause yellowing of Mandevilla leaves?
Well, Mandevilla or Rocktrumpate is a fast-growing plant. Hence, roots get crowded due to limited space in the pot.
Crowded or pot-bound roots fail to provide water, oxygen & nutrients to the plant. As a result, new chlorophyll synthesis gets reduced or, existing chlorophylls get degraded & turns Mandevilla leaves to yellow.
Anyway, crowded roots often exhibit such symptoms-
- Roots coming out from drainage holes
- Soil or rooting media is coming out from the pot
Repotting is the only efficient remedy for compacted roots.
To start, the ideal pot size for Mandevilla is 12-14 inches. But to grow them for several years, repot every year with one size bigger pot.
2. Compacted Soil
After diagnosing the pot, pay heed to the soil next. I can think of multiple issues related to the soil but compactness tops among them.
Causes & Symptom
A surprising but true fact is, you may feel difficulty while inserting a screwdriver into compacted soil. So, how come you expect your Mandevilla to survive in such a condition?
However, the soil gets compacted for several reasons like underwatering, increased root mass, presence of too much clay, heat, etc. And the result?
Compacted soil provides poor drainage & less aeration. Thus it interrupts water & nutrient supply & green Mandevilla vine leaves turn yellow.
Initially, you can loosen the topsoil by poking it with a fork. But try not to damage the stem or roots.
The next step should be adding organic matter over the topsoil as it gradually reduces soil compaction.
Mandevilla requires well-drained sandy soil with an abundance of organic material.
You can make the best soil mix for Mandevilla by mixing two parts of peat moss or potting soil into one part of sand. Otherwise, you can buy organic potting mix directly from the marketplace. (Our Pick: Espoma Organic Potting Mix)
You have checked your pot, checked your soil & now it’s time to fix the watering issues.
Causes & Symptoms
You know, plants uptake nutrients in a water-soluble form. That’s why every plant requires an exact amount of water for perfect functioning.
And that means both over-watering & under-watering is quite a big deal for Mandevilla.
In overwatered soil, oxygen gets replaced by water molecules and creates a soggy condition. In consequence, plants face breathing problems & roots also start rotting. Thereby, Mandevilla roots fail to supply nutrients, oxygen & water results in leaf yellowing & falling off.
The same symptom is displayed while underwater because roots don’t get enough water to supply nutrients.
You may ask, how much water does Mandevilla need?
From my experience, Mandevilla doesn’t require a lot of water but it thrives in moist soil.
In the case of soggy soil, you may have to think about repotting. But there is a possibility to revive your Mandevilla if you first dry the soil totally & then water thoroughly again.
And if the soil is dry, follow the watering schedule strictly.
Many Mandevilla growers often ask the question- How often should I water Mandevilla?
Well, growers are advised to water Mandevilla thrice per week from spring to fall.
But wait, many environmental factors also act behind soil moisture like rain, humidity, temperature, etc. So, it is better to water after monitoring the soil moisture. And that’s when you feel the need for a moisture meter (Our pick: Atree Soil Soil Tester Kits with Moisture, Light, and PH Test for Garden)
4. Nutrient Deficiency
You know, nutrients are profoundly involved in Mandevilla leaf yellowing or chlorosis as they interfere in chlorophyll synthesis or damage. And here is the more in-depth discussion-
Causes & Symptoms
Normally, you will notice five types of yellowing in your Mandevilla leaves caused by several nutrient deficiencies. Such as-
- Nitrogen deficiency– Inner & older leaves turn yellow & yellowing moves outward.
- Iron deficiency-New leaves turn yellow between dark green veins.
- Manganese deficiency-Yellow spots between veins with elongated holes.
- Magnesium deficiency-Lower leaves start yellowing from leaf lip.
- Potassium deficiency-Leaf tips & edges turn yellow but the middle remains dark green.
Interestingly, a high zinc percentage prevents your Mandevilla from uptaking Iron & that’s why over-fertilizing is a terrible mistake. So, how would you treat yellow leaves on Mandevilla?
Before starting treatment, you must know the reason for the deficiency. Deficiency can either occur due to a poor supply of nutrients or due to an imbalanced pH level.
Low or high pH of the soil alters nutrients available form & makes them unavailable for plants. Though Mandevilla is okay with a pH range of 6.6-7.8 but neutral pH suits the best.
So before applying the perfect fertilizer for Mandevilla, you might want to check the pH of the soil by a pH meter
However, here’s a tip for you- potted Mandevilla loves liquid fertilizers while granular fertilizers are good for grounds. (Our Pick: Miracle-Gro Water Soluble Bloom Booster Flower Food)
First of all, you have to find a fertilizer that contains most of the macro & micronutrients.
And then, you have to fertilize your Mandevilla as needed, especially during its growing season– Spring & Summer. But remember, always stay concerned about precise doses.
So far, we have covered most of the issues related to the root that can cause the yellowing of your Mandevilla leaves. Now it’s time to think about some environmental factors & pathogens.
5. Insufficient Or Excessive Sunlight
Proper sunlight is a mandatory requirement of Mandevilla. They don’t even bloom without the required sunlight, let alone leaf yellowing.
Causes & Symptoms
Though Mandevilla needs 6-8 hours of direct sunlight, extreme heat can damage leaves. If you notice upper Mandevilla leaves are turning yellow with brown spots, excessive sunlight can be the reason here.
You know, extreme sunlight can burn sensitive leaves causing brown spots. But before the leaves get completely burned, excessive heat denatures chlorophyll & causes yellowing.
On the other hand, sometimes the inner middle leaves or leaves opposite to the sunlight start yellowing. As these leaves get inadequate sunlight, they stop producing chlorophyll & gradually turn yellow.
You can cut off the yellow leaves as they are no longer needed. And make sure that your Mandevilla is getting enough sunlight & also partial shading during excessive heat.
As sunlight is not something you control, you don’t have much to do here. But I don’t mind if you are thinking about a greenhouse.
6. Insect & Mite Attack
Interestingly all the frequent visitors of Mandevilla have something in common & that particular nature causes leaf yellowing. Get more details-
Causes & Symptoms
The most frequent visitors of Mandevilla are Aphids, mealybugs, scale bugs, spider mites, etc & all of them are sap-sucking pests. These insects reduce cell sap by sucking & thus, chlorophyll content also gets reduced.
Moreover, they damage chlorophyll by their mouthparts while sucking. Therefore, damaged & reduced chlorophyll content results in yellowing of leaves.
To control these pests, you must identify them first. For example-
- Aphids– try feeling sticky substances on the downside of the leaves
- Mealybugs– look for white eggs
- Spider mites– silky waves on the downside of the leaves.
- Scale bugs-look for brown clusters at the downside of the leaves.
But unfortunately, without experience, it is hard to identify them. But don’t worry, you don’t need to identify the insects. If you notice any kind of insects activity, apply an insecticide that can work all those insects.(our pick: Garden Safe Brand Ready-to-Use Garden Insect Killer)
The good news is, you can easily make the perfect remedy at your home. Here are some homemade recipes for you-
#Neem Oil Spray
Neem oil is a miracle as it works as insecticide, miticide & fungicide. To make it at home-
Add 2 tablespoons of neem oil & liquid dish soap with 1 gallon of water & boom! You have your remedy.
To control & repel insects, mix 1 tablespoon of chili powder & 1 tablespoon of liquid dish soap with 1 liter of water & there you are.
#Vegetable Oil Spray
Mix 16 tablespoons of vegetable oil (Soybean/Cottonseed Oil) & 2 tablespoons of liquid soap with 16 tablespoons of water properly.
Later on, mix 3 tablespoons of the mixture with 16 tablespoons of water & spray.
To prevent insect attacks, you have to keep spraying insecticide regularly. Especially during the growing season & when insects attack the most.
7. Fungal Attack
One of the dominant pathogens of Mandevilla is Fusarium oxysporum, a fungus that is responsible for wilting & yellowing of leaves.
Causes & Symptoms
Fusarium oxysporum is a soil-borne fungus & thus, it enters into the plant body through roots. Furthermore, the fungus interferes with the water-conducting system of Mandevilla.
As nutrients are also uptaken through water, the end results are leaf yellowing & wilting due to nutrient deficiency & poor water supply.
Unfortunately, once your Mandevilla gets infected by fungus, it is hard to control. But you can start with spraying broad-spectrum systemic fungicides (our pick: Bonide Copper Fungicide) to stop further attack & spreading.
Though there are plenty of effective fungicides available in the market, the good news is- DIY fungicide recipes are also available for your Mandevilla. Here I am sharing the most effective one with you-
To make 1 liter of Bordeaux Mixture-
- Mix 5g of lime dust with 500 ml water properly into a plastic bucket
- Mix 5g of Copper sulfate with 500 ml water properly into another plastic bucket.
- Leave the mixtures for 8-10 hours
- After that, pour both mixtures into another plastic bucket slowly & simultaneously. Stir to mix it properly.
And thus you will get your 1 liter Bordeaux Mixture.
To prevent a fungus attack, you have to spray fungicide beforehand. Normally, fungal attacks increase during the rainy season. So, stay aware of that.
Additionally, keeping your garden & gardening tools clean is an effective precaution to avoid fungal attacks.
Mandevilla often faces a disease called “Southern wilt” which leads to wilting & leaf yellowing. So, how does it work? Let’s see-
A bacterium called Ralstonia solanacearum causes the southern wilt of Mandevilla. It is a soil-borne Bacterium & it also causes wilting & leaf yellowing by interfering with the water-conducting system.
Like fungi, after infection, bacterias are hard to control. You can only stop the spreading of the attack by spraying a bactericide (Our Pick: Monterey Ready to Use Fungicide & Bactericide) immediately.
To prevent the bacterial attack, the first step is to choose an uninfected seed or seedling to grow. And the second & final step is taking proper care by watering, weeding, fertilizing, applying pesticides, etc.
9. Natural Aging
As your Mandevilla gets older, you may notice bottom leaves typically turn yellow and fall off.
Don’t worry. It is a common phenomenon because vines lose their older leaves to provide more energy to the new growth.
There are some other reasons which can also lead to leaf yellowing. But not very common. Such as-
Most Mandevilla growers take their plants inside during heavy frost. That’s why cold temperature is not a very common factor but can cause leaf yellowing.
Most of the time, if you fail to transplant properly, your plant will die. So, leaf yellowing is not a major issue then.
But normally, before leaf yellowing, Mandevilla gets over the shock.
It is a rare factor as most growers use pure water for their garden plants. But if your water gets chlorinated somehow, it will cause leaf yellowing.
Leaf yellowing is a common way for Mandevilla plants to tell you that something is wrong with them.
Perhaps they are not getting decent light, nutrients, or water. Possibly the roots are crowded, or insects are here & so on.
I think, after this long walk, now you have the answer why your Mandevilla leaves are turning yellow. And here’s your chance to prove yourself a good plant doctor.
I hope my research & experience comes in handy for you. Let me know the result. Happy Gardening.