Why Are My Desert Roses Leaves Turning Yellow

Adenium Desert Rose 16 May 2020

Yellow desert roses leaves may mean you're over-watering your plants. There's an easy way to notice this:

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The yellowing starts from the tip of the leaf and slowly spreading inwards. Initially, you'll see the leaves getting kind of darker–like it's slowly bruising in. Then some days after that, it will turn more yellow & dry.

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You can save it by reducing the water amount immediately. Or try sucking out the moisture using some napkin, Q-tip or sand. If your trees are bigger, get new soil for them. Be careful during the transplanting process.

The reason why people (including us) overwater the plants may be because spraying or watering  feels good & is sometimes addicting. It's easy to go overboard. We try to water less by making the spraying bottle slightly less pleasant to use.

Here's another one:

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If the yellowing starts from the inside of the leaves & spreading out to the tip, this may suggest lack of sunlight or under-watering. To make sure, check the soil condition & look at the adenium overall body. If the soil is dry & the adenium body looks wrinkled with non-glossy leaves, then it is thirsty.

When people want the adenium to go dormant in the winter, they leave it inside the house. This triggers the yellowing & dropping of the leaves.

This one is easier to save than the over-watered one. Give your babies some sprinkle of water. Then move it out to some area with more sun during the day. They will recover.

The basic idea can be simplified to this:

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If we look at the little leaf as our little water measurer, it may be telling us what's going on. If the yellowing starts from the tip in, it may be too much water. If the yellowing is from the inside out, this may mean too little water.

Now, finally:

If you try touching the yellow leaves and they fall off immediately, this means it's normal. The leaves are in its natural cycle to turn yellow after flowering & everything is okay. You don't have to worry too much in this case.

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Normal yellow leaves falling as we touch

If, however, you press down on the leaves a few times but they don't fall off instantly, then check the roots. It may be root fungal diseases or too many string roots. The good bits may not get carried up to the leaves, causing yellowing.

To save it, you can dig the plants up. Cut off some mushy roots. Then dry it under the sun. Remember to apply some sealant to help the open wound. Let them rest for 7-14 days. Replant your trees in new soil for recovery.

If you want a closer look to deal with root rot, check out this post below:

Adenium Desert Rose Root Rot: How to Save It Now?
Adenium desert rose root rot tips & how to know if your roots are rotted

Pests & Fungi

1. Red spider mites

Red spider mites are tiny red insects that can suck the nutrients out of the adenium leaves, causing them to yellow. They appear again & again each year.

You can catch these guys running up & down on the underside of the leaf like here:

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Along the spine are their white eggs. These become baby mites in about 4 days. Very fast production.

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Close-up of a red spider mite

If the condition of the leaves is not too bad, you can use a garden hose to hose them off. Or use some gloves to rub them off.

If condition is quite bad, then we might need to use some sprays. Be careful with chemical sprayers. The ones that promise to kill the eggs too are highly toxic.

To rid them off safely, try this recipe:

  • 3 parts boiling water
  • 2 parts room temperature water
  • 3 cc (3 ml) dish soap
  • Optional: mint essential oil, neem oil, horticultural oils, red wood fiber

Spray this solution on the leaves late in the afternoon when the weather is cool. You can also try soaking chopped onion in water. Then, extract that juice for spraying. The idea is to make the pests 'cry' or at least 'tear up'. Termites & ants hate red wood fiber. It may be the redwood smell that keeps them away effectively.

Cold Pressed Neem Oil
organic-neem-seed-oil
100% pure oil (no chemical additives)
Does not burn plants
Effective

When the mama mites sense the smell of the spray (the dead zone), they will think twice before landing on the leaves & laying eggs there. The soap & oils may dissolve their soft body or cuticles. It's the smell + the dissolving that work together to keep insects away. Neem oil also messes with their reproduction a bit.

If they have been scared by the spray once, they have the 'memory' not to find that spot to reproduce again. Hope they have a good memory. It's better to prevent this than treating it afterwards. Because you know they may come again seasonally.

2. Mealybug

Mealybug usually attacks the caudex & roots of adenium. It can make your adenium weak & lessen the overall ability to process water and nutrients. This also cause the yellowing & dropping of adenium leaves.

Here you can see the white little creature with 2 antennas:

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In this case, the adenium leaves may turn duller, droopy, not glossy & more yellow. The caudex may get shrunk smaller.

mealybug.jpg
The white sap on the bug when washed off shows an orange color

To save your plants, dig them up. Wash the whole body thoroughly with water. If it's really bad, use some purple insecticide like Starkle G to spray around the roots. Leave in shade for 7-10 days. Then, replant your tree into new soil. Be careful when using chemical insecticide because most of them to a degree are toxic.

If it's not too severe, you can also use some onion juice or the spray recipe above. Spray around the leaves or pour some around the roots, where these little guys usually start their lives.

Oh and to make onion juice. You just need to chop up some onion, then soak them in water. After a few days, use that extract to spray around the plants. Onion, garlic & mustard have some sulfur in them (noticeable by their unique smell). It's effective for "shooing" these bugs away while not killing them.

3. Fungi

They usually call this leaf spot. Or Anthracnose disease, caused by this long-named fungi Colletotrichum gloeosporioides penz. It looks a bit like this:

adenium-leaf-spot-anthracnose.jpg

This usually happens at the beginning of the rainy season, when the humidity is high. There's excess nitrogen around the tree & that attracts the fungi. They can spread to other leaves & flower buds on the tree, often leaving black spots on the flowers as well.

Some folks just let the leaves fall. The next season, new leaves will grow out normally even though they can be quite wrinkled. Others use fungicide to kill them.

You can move your plants somewhere more dry & with sunlight. Bottom water the plants sparingly to avoid water contact on the leaves.  Cut off some infected branches to avoid the fungi spreading into the tree.

What is Causing Leaf Spot and Drop On My Desert Roses?
What is Causing Leaf Spot and Drop On My Desert Roses? Answer: The yellowing and black blotching and spotting on your desert rose (Adenium obesum) leaves is likely caused by the fungal disease, anthracnose leaf spot (Colletotrichum spp.).

Also, watch out for these little guys:

4. Aphids (yellow bugs)

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These aphids love partying around the flower stem. But they come & go fast. You may see them today & tomorrow they're gone.

They live symbiotically with ants. They give ants the sweet honeydew juice. Ants lead them to the sweetest spot & protect them from lacewings/ladybugs. Dish soap spray & onion should get rid of them. Horticultural oils can also work.

The appearance of these little creatures may invite some other badass guys to the garden, like this one:

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A guy on Reddit told us that this is the yellow-spotted stink bug (Erthesina Fullo). We wonder if their food is the mealybugs or spider mites. This specie can be very invasive.

Recovering: For Glossy Green Leaves

Sounds like there's too much eyeing your yummy desert rose leaves. Although pest control can be quite a headache, it also means your trees are attractive. Otherwise, visitors wouldn't come visit them. This is a natural pattern.

Also, control the water amount you give your plants. All of these yellowing signs are very similar for young seedlings & bigger adenium. Once you know where the yellowing is going & some interacting factors around it, you can save your plants. Good luck! The plants will recover.

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