“Help! My 4-year-old Adenium has always thrived. Last year it put out 6 seed pods and this year the blooms were massive overpowering any green. When the blooms finally stopped all the older leaves turned yellow and dropped. But new ones were coming out. Now the new ones are all curling and while green on the top the bottoms have brown spots. It’s in the sun all day long and while we had a wet spring (before the blooms) the summer has been dry and hot. When the leaves started turning yellow (over a month ago) I noticed spider mites so I sprayed them with an insecticide soap for 2 weeks and they are gone but now the leaves are all curled and brown spots on the underside only. How can I save this plant?” Question from Julie of McKinney Texas
Answer: The good thing is the succulents like Adeniums have lots of stored energy, so once you totally rid them of the spider mites, they will bounce back quickly. To truly eradicate the mites, you will have to spray more than just the foliage.
How to Treat Plants for Spider Mites
Here are the steps I would take to completely remove spider mites from an Adenium.
- Remove damaged, yellowing leaves.
- Wipe down the base of the plant and stems.
- Wipe down the pot.
- Remove the top 2 inches of potting mix, and replace it with a quality cactus mix, such as Black Gold Cactus Mix.
- Fertilize with a water-soluble fertilizer formulated for flowering plants.
- Spray all plant parts with insecticidal soap or Neem oil.
The white-paper test is my favorite way to further test for mites. Take a clean piece of white paper, hold it beneath the leaves, then tap the leaves onto the paper. If you have mites, tiny specs will fall, and eventually, they will start crawling around. These are spider mites. Continue to do the tap test and gently wipe down leaves and stems and spray them until healthy new growth appears and remains undamaged. It may take time, but you can overcome spider mites.
Black Gold Horticulturist
“My desert roses are dropping their leaves and they have brown to blackish spots on them. I have attached an image.” Question from Charles of Sebastian, Florida
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.). Yellowing of the leaves is caused in the early stages, and then they develop black spots and splotches and fall off.
These true desert plants thrive in dry heat and cannot take high moisture and high humidity without eventually succumbing to fungal diseases. I recommend placing them away from any place where they will be subjected to rain and high humidity. An indoor sunroom or south-facing window would be ideal. Bottom water the plants sparingly (to keep water off of the leaves) and hope that this will tackle your leaf spot. In very severe cases, this disease can cause plants to die. Also, be sure to water these plant very little to none in winter to mimic the dry winter period in their native Africa and Arabia. Consider reading this other Ask a Garden Expert Inquiry: What is the Best Soil for Desert Rose?
I also encourage you to watch the video below. It covers desert rose. (Many of the other flowers will also grow well in Florida.)
Black Gold Horticulturist
“What is the best soil mix to plant my desert rose (Adenium obesum) in?” Question from Sara of National Park, New Jersey
Answer: Plant these beautiful succulents in very sharply drained soil that also retains water and has a slightly acid pH of 6.0. Of course, we recommend Black Gold Cactus Mix for planting, but you might also want to add a bit more perlite as well as some additional peat moss, which retains water and is acidic. Potted desert roses look nice when a layer of decorative pebbles is added at the top.
Plant these succulents in pots with good drainage. The water should run from the bottom of the pot at watering time. The potting soil should never become totally dry, so monitor soil moisture levels. In winter, water less. The mix should remain lightly moist to dry.