Desert rose (Adenium) varieties (as a whole) are capable of surviving a great deal of neglect, but even this tough guy has its limits. It will very quickly curl up its toes and keel over from wet feet due to poorly draining potting mix and/or too much water, particularly in colder weather.
If nothing else kills this plant, you can be sure that too much water will. Over-watering, especially during the winter (dormancy period) when less moisture is required or when the plant is kept in cooler temperatures, is lethal to this otherwise resilient garden gem. (We have included a chapter about potting mix with suggestions to overcome a lot of the issues with rot.)
There are two reasons an Adenium will get a soft trunk. They are both a direct result of the potting mix they are growing in. It will either be rot or dehydration.
This happens when the potting medium becomes excessively dry and water repellent (will not hold moisture). The plant is then unable to access the moisture that would normally be available. The caudex will soften as it struggles to provide continued moisture to leaves and flowers, which is usually replaced through the roots from the potting mix. Tell-tale signs are very similar to rot.
This problem is often seen when the Adenium hasn’t been re-potted for some time and the medium has degraded to a point that it cannot supply the requirements needed. Re-potting is strongly recommended; don’t be tempted to use a soil-wetting agent as a ‘quick fix’. This can quickly change the situation from not enough to too much moisture.
Weather plays a large role too: extreme temperatures combined with lots of wind will also dry potting mix quickly. You may need to increase watering a little to compensate for this.
As the name suggests, it is rot that appears at the tips of branches where new leaves and flower buds form. This can arise from insect damage or damage from another source. Often, the plant will self-heal and the affected rotted area will dry and easily break off. If the problem continues down the stem, cut well below this area into healthy tissue. Allow the air to dry the wound and make sure not to wet this area until it has dried.
This affects the main stem or caudex and leads to all the leaves suddenly drooping and turning yellow. The leaves tend to stay on the stem (not always) and yellow from the centre outwards.
This rot starts below soil level. If it affects the main tap root it will manifest itself with the same symptoms as caudex rot, but often only a side-root is affected and it is seen only when the plant is being re-potted or bare-rooted for export, or when it has progressed to a point of no return. There are treatments available on the market (anti-rot) that can be used to help prevent the problem occurring; however, if good drainage and hygiene is provided, there is far less opportunity for it to happen to start with.
By good hygiene, I mean care being taken when re-potting and/or pruning, not recycling potting mix from a plant that has died (as that may be the source of a disease), and pruning any damaged roots with sterile utensils, allowing the plant to air-dry before it is re-potted. Simple steps, but important ones to help you maximise the best results for your desert rose.
Remove All of the Damaged Area
It is possible to save plants suffering from root rot, providing it is caught early enough. It is extremely important to remove all of the damaged area; even a small amount left behind will allow the rot to continue further up the stem and will ultimately destroy the whole plant.
Can my plant be saved? The only course you can take (particularly if it is a prized colour) is to cut well above the damaged area and use the upper part of the plant as a cutting, or to graft onto rootstock. This is the finale when rot has reached this level.
Seedling Damp Off
Seedlings will rot and shrink just above ground level; the tops remain green and topple over. This is a typical example of damp off. It can happen very quickly.
Usually, the problem can be resolved by simply starting again, ensuring fresh seed-raising mix, new pots, and new seeds are used, while also providing the best possible growing conditions (sufficient light and suitable potting medium). Some enthusiasts get better results from sprouting seeds on dampened paper or cotton wool first, and then potting into a suitable medium.
Do not keep and recycle the seed-raising mix or put it onto the compost bin; if it contains any diseases it will simply keep the problem around and spread it to other areas of the garden. Bag the mix and growing containers and dispose of them in the rubbish.
Keep the potting medium damp but not wet and allow plenty of air circulation around the seed-raising containers.
Sunburn can occur when a large part of the upper branches has been pruned, resulting in the trunk becoming yellow/ brown; due to excessively high temperatures (heatwaves); or from a more sensitive variety (variegated) looking bleached or burned. The most simple method to start the healing process is to provide more shade to these plants in the afternoon in summer.
Fertiliser burn looks similar to sunburn. Fertiliser burn usually arises when a plant has been fertilised with a strong nitrogen or chemical fertiliser.
A sunburned desert rose can recover but it is almost impossible to bring a fertiliser-burned plant back from the dead.
As humans, we know all too well that stress can kill. The same can be said for plants. Stress is a direct reflection of something that is ‘not right’ in their environment. For example, a desert rose that has been freshly potted into a potting mix that has poor drainage and is being watered daily, will quickly show signs of stress, because it is trying to grow in an environment that it isn’t used to. It will develop rot, will shed its leaves and flowers, and look pretty unhappy. In this example, the stress was caused by poor drainage or over-watering to begin with, but has progressed to a point where the plant is so stressed that rot has set in. This plant may not recover, even if all attempts to heal it have been tried.
If you see any stress signs (yellowing, wilting, or leaf drop), act immediately. Have a good look for any obvious causes: fungus, soft trunk, etc., and do something. The most common problems are associated with the growing medium, so start there. If you find this is the case, add drainage to your potting mix so as to prevent it happening again. Remember to use new potting mix and not recycle. If the problem isn’t easily diagnosed, run through the problems listed in this article, rule out any that don’t seem appropriate, and go with your observations to work on a solution. If you still aren’t sure, contact someone locally and get their opinion.
Never fertilise a stressed plant immediately after re-potting. Allow a couple of weeks before you do and only fertilise at half normal strength.
When using any pesticide, wear protective clothing (including glasses) and ALWAYS follow the directions for that particular product.
In the warmer months of the year and when the plants are in full growth, those dreadful hungry caterpillars arrive! Butterflies lay their eggs everywhere and it’s not always possible to squash them all, so at times you may need to use a pesticide to get them under control. Whether you do or don’t use a spray, it’s always nice to see butterflies in the garden, even if we dislike the caterpillars.
These very small sap-sucking insects are usually only around during humid conditions in the growing season. Treat with a pesticide, spraying under the leaves too. Again, if the best growing conditions are provided—e.g. plenty of sun, airflow around and under the pots— there is less opportunity for these insects to hide and breed.
Worldwide, there are many thousands of different species. They look harmless enough but if you are wanting your plants to set seed, you don’t want them around. They feast on the immature seeds inside the pods and the seeds will be destroyed. Treatment is to spray with a pesticide.
These are the fluffy white bugs that appear (again, usually only throughout the warmer growing months) and attack the plant by sucking nutrients from the stem. The plant will suffer deformed growth when left unattended. Remove the areas under attack (prune) and spray with a pesticide. The mealy bug and scale belong to the same family of pests as aphids. (Hemiptera, formerly Homoptera.)
These pests look like small round spots (shiny or shelllike) and appear on all parts of a plant—the upper part and underneath of leaves, branches, and trunks. There are many, many different varieties and can at times be very difficult to eradicate. The waxy covering of many species of scale protects them effectively from contact with insecticide. Using an oil-based formula proves more effective in eradication as it suffocates them (e.g. Neem or White oil). But don’t spray an oil-based pesticide throughout the hottest part of the day; best to use early in the evening.
These are very tiny insects living on the underside of leaves. They are responsible for leaves appearing deformed (curled), mottled, or discoloured. They spin silk webbing to help protect against any natural predators.
They are the larvae of the Elephant or Rhinoceros beetle. These little critters wreak havoc on lawns, but they can also be found in pots. The beetle lays eggs in the pots or lawn and they germinate after about eighteen days. The tell-tale sign is when the potting mix starts disappearing (the level in the pot drops).
When you grow your desert roses in pots, it is much easier to get rid of them. You simply need to re-pot them into fresh potting mix. If you need to treat ground-grown plants, purchase a specialist product and only use according to directions on the packet.
All different kinds of spiders can be found throughout your garden. Some choose to use the leaves of your plants to build a house. If you have plenty of small insect-eating birds visiting your garden, they will usually keep them under control. Only use a recommended pesticide if the problem is extensive and it requires spraying.
These usually arrive at the first sign of new growth following winter, or just after the first rains of the season. They can be a huge problem when their numbers reach plague proportions, but if you only have a few, you can spray or squash them. Most of the time they don’t cause too much damage, as there are plenty of other plants in your garden they prefer to eat.
Desert roses can be prone to deformed flowers. The cause: a deficiency, insect damage, or large fluctuations in temperatures affecting growth. If you are not entirely sure of what deficiency (if any) your desert rose has, give it trace elements (a blend of all micronutrients required for growth). A drench with trace elements should supply any lacking elements, and as they are ‘trace’ the plant will only utilise what it requires. If it is caused by insect attack or fungus, treat this problem as you would for any other plant; but if it is caused by the weather, you just need to be patient. The weather will sort itself out eventually and the problem will cease.
Fungus on Leaves
During the wet times of the year (raining, dew) you may find leaves with discoloured patches that turn yellow and fall off. This is a fungus. It can grow on the leaves with the help of the extra moisture, e.g. when plants are watered overhead with sprinklers, especially in the late afternoon, or during times of continual rain. The spores of the fungus are in the air around us all the time. We never seem to notice them until they find a home with plenty of moisture and multiply. You can treat it with a fungicide if it is affecting your plants. Watering in the mornings to allow the leaves to dry and separating pots (not allowing them to touch) to allow more airflow between them will also help.
Adenium plants will shed leaves throughout the year for a few different reasons. This can be an indication of root rot, which can be eliminated by checking the root system. If they have got a fungus growing on their leaves (see previous image) they will shed leaves in an attempt to eradicate it, which is a natural occurrence and is also easily fixed. Another reason a desert rose might shed leaves is simply because when the weather cools down, they start shedding in preparation for winter. If being grown in the tropics, they may have very little to no leaf drop.
Losing leaves in most cases is no indication that anything major is wrong; however, if this coincides with a lot of rain or excessively high temperatures, you may need to check moisture levels to determine if the plant is stressed from too much/too little moisture, and work on a solution.
It is also worth mentioning that most pests can be reduced with the planting of certain herbs/plants as deterrent plants. For anyone who prefers companion planting or a more natural approach to gardening, this is a great opportunity to add more ‘good bugs’ to the garden; not to mention the chance to utilise all those herbs!
Typically, a nutrient deficiency will appear as a discolouration of the leaves, with plants appearing yellow or lighter in colour around the tips or veins. This can happen during times of heavy rain when the nutrients are leeched out of the potting medium. The easiest way to correct this is to apply trace elements. Trace elements contain all the micronutrients required for strong growth. (Iron, zinc, boron, and magnesium, to name a few.) The plant will utilise only what is needed. If there is an imbalance, the leaves are the first to indicate this. Regularly fertilised plants don’t usually suffer from this as most complete fertilisers include trace elements in the recipe—but it does happen from time to time.
This picture shows the difference between the leaf colours. Two are healthy and one needs a little fertiliser.
Yes, plants get viruses too! They can be spread by insects or unsterilised tools. From what information I can find, there are some viruses that do affect Adenium. They can either weaken the plant’s immune system to a point that another disease kills it, or the plant shows very little effect from it. Either way, they do get them. If you suspect a plant has a virus, isolate it until you can identify the problem. Mottled, curly, or deformed leaves or stems (growth that is not normal) can be symptoms, but they can also be the result of spider mites or other pests.
It is very important to exercise good hygiene, especially when you are handling a plant that has a noticeable disease/virus. The last thing you want to do is inadvertently spread the condition to another plant.
- ALWAYS wash hands after handling any plants that appears to be affected or suffering any sort of rot before you handle another.
- ALWAYS sterilise any utensils you have used. This includes knives, secateurs, cutting boards and the like.
- NEVER reuse the potting mix or put it in the compost.
- IF IN DOUBT then always throw it out. Put the plant, pot, and potting mix into a garbage bag, tie the neck, and dispose of it in the rubbish.