Euphorbia Ascot Rainbow is a popular evergreen subshrub loved for its variegated foliage and unique greenish flowers with tiny, colorful petals. This variety of euphorbia is also known as Euphorbia x martinii, or Martin’s spurge.
Euphorbias, in general, are considered tough and fairly easy to grow. However, certain undesirable growing conditions can make them vulnerable to fungal diseases, causing discoloration and damage to their foliage. If your Euphorbia Ascot Rainbow is dying, it is most likely due to the fungal species Rhizoctonia or Fusarium, or due to sunburn.
Let us discuss how to detect these issues and what solutions are available to save your plant.
Euphorbia Ascot Rainbow turning brown and dying
Browning foliage and stems is a common sign of plant distress. There are several underlying issues that can induce this discoloration, as listed below:
Corking is a natural process in plants, wherein the outer layer of the plant’s skin or epidermis is replaced. The affected plant parts tend to display brown discoloration and thickened outer layers.
It is generally undesirable for euphorbias to develop corking, but know that this condition is not a sign of disease or pest infestation. More often than not, it is a part of your euphorbia’s aging process and should not be a cause for serious concern.
There is no treatment available to stop or prevent corking, and unfortunately the condition might alter your plant’s beautiful appearance. But give it enough time to heal and your lovely plant might be able to replace the damaged tissue.
Euphorbia comes in several stunning varieties, some of which have variegated white stripes while others have yellowish stripes on their bright green leaves. Rest assured, however, that no healthy euphorbia leaves, regardless of the variety, have brown spots or discolorations on them.
Brown spots on the leaves are typically signs of sunburn. Also known as leaf scorch or sunscald, sunburn is the negative result of abrupt exposure to full sunlight.
So, if you are planning to move an indoor plant outside, or if you have just brought home a new plant from the store, remember that proper acclimatization is important to protect it from sudden light or temperature changes. The right way to go about it is to start by placing your euphorbia in a slightly brighter location for a few hours each day, and gradually increase its sunlight exposure over a few weeks. You can also use a shade of cloth or umbrella to protect your plant until it is ready to face the full sunlight.
3. Rhizoctonia disease
Rhizoctonia stem rot is most prevalent in euphorbias that are constantly exposed to moist and humid environments. The disease is caused by the soil-borne fungus Rhizoctonia solani, and causes stem lesions, root rot, and crown rot in infected plants.
Hot temperatures ranging from 70 to 90 degrees Fahrenheit, combined with moderate moisture, are the most favorable conditions for this pathogen to thrive. Frequent misting, a lack of airflow, and close spacing between plants can soon result in brown webbing on the stems and open wounds on the plant.
The browning and limpness of the plant in the early stages of the disease are often mistaken for the signs of an underwatering problem. Without the proper diagnosis, an inexperienced gardener might react by watering the plant more, thereby causing further rotting and fungal growth. As the infection progresses, the brown lesions will become increasingly larger until the entire stem collapses.
Fungicide drenches are your best weapon to suppress or reduce the progression of Rhizoctonia disease. Applying solutions that contain bacillus bacterium, in conjunction with proper care and preventive measures, can go a long way to treating and preventing the incidence of Rhizoctonia.
4. Fusarium rot
Similar to Rhizoctonia disease, Fusarium rot is another fungal infection that causes stem and root rot in euphorbias. Aside from brown discolorations and lesions, the affected plant will also wilt, drop its leaves prematurely, and possibly die.
There are several fungal pathogens that cause Fusarium disease, the most common ones being Fusarium solani and Fusarium oxysporum. These pathogens infect plants by entering through an open wound caused by pest infestation or physical damage. If you are not careful, the infection can quickly spread through contaminated soil and unsterilized gardening tools.
Your best chance of winning against Fusarium rot is by establishing proper gardening practices and hygiene. As with other fungal diseases, avoid overwatering as well as leaving the stems and foliage wet for long periods. Instead of misting, use a humidifier to improve the humidity in your indoor garden.
Unfortunately, there are no known chemical fungicides that can eradicate these fungal pathogens.
5. Plant dormancy
The browning of euphorbia leaves does not always mean your plant is dying. It could also be that your plant has gone dormant for the winter season. In this case, it is simply reserving its energy to survive the harsh weather conditions. Most of its metabolic activities will come to a halt and the dormant plant will allow some of its leaves to brown.
Since dormancy is considered normal, there is nothing much you can do but wait for the mild weather to return. Limit your watering and avoid fertilizing your plant as the roots will be less likely to absorb and use all the nutrients. Once the cold months are over, your euphorbia should return to its former glory.
6. Normal aging
If your euphorbia has received all the right care and there are no apparent underlying issues that could be causing the browning leaves, then perhaps the discoloration is linked to the plant’s aging process. If this is the cause, the browning is more likely to occur on the older, lower leaves of the plant. Along with browning and yellowing leaves, you might also notice your euphorbia dropping a few leaves. In this case, the symptoms are considered normal and expected.
Mature plants have indeterminate growth, meaning they will likely continue growing and producing new leaves for as long as the conditions are right for them. So, let the old leaves drop naturally and they will be soon replaced with new, healthier growth.
Other signs to look out for
A potentially dying plant will not only display brown leaves. Your Euphorbia Ascot Rainbow can show several other symptoms of distress, and it is critical to understand these so that you can pinpoint and correct any issues.
Check out the signs below, and from there you should be equipped to know when your lovely ornamental needs to be rescued:
1. Euphorbia leaves turning yellow
Yellowing leaves are often related to water stress. Aside from the unsightly discoloration, you might also notice your plant shriveling and wilting as a result of extreme dehydration.
Watering your Ascot Rainbow roughly once a week is ideal to keep it hydrated. Watch the soil condition as well, especially during the hot and dry season, as you might need to increase watering at this time. You can use a soil probe to test the moisture level of the soil from time to time, to keep your watering in check.
Other factors that trigger yellowing are:
- Poorly-draining soil or pot
- Too much fertilizer
2. Dropping and wilting leaves
Dropping and wilting leaves are another classic sign of an underwatered euphorbia. All plants need water to keep their stems and leaves turgid, so do not leave your euphorbia too dry for too long. When you water, do so thoroughly and deeply to keep the soil moist for several days. Just be careful not to overwater, though, as waterlogged soil can be bad for the roots and increase the risk of fungal infections.
3. Euphorbia not flowering
Euphorbias may not flower for a number of reasons, but this does not mean your plant is doomed. More often than not, the lack of flowers is linked to watering issues, lack of sunlight, or temperature stress.
Hence, to encourage flowering, make sure that the right growing conditions are met. Euphorbias generally thrive in bright light – preferably about three to four hours of direct sunlight exposure each day. The soil must be well-draining and lightly moist (but never watery). Temperature-wise, most euphorbias are happy within the range of 65 to 75 degrees Fahrenheit.
Lastly, fertilize your evergreens from spring through fall. Dilute the fertilizer to half-strength to prevent root burn.
How do you revive a dying euphorbia?
Reviving a dying Ascot Rainbow might seem an impossible mission. Often, it is easier to just discard the plant and start over with a new one.
But do not lose heart – rescuing a dying plant is often completely possible if the underlying issue is detected at an early stage. Time is of utmost importance and your quick response will go a long way to preventing further damage and reviving your euphorbia.
Here are some helpful tips to get your plant back to its healthy state:
- Euphorbia Ascot Rainbow is most often killed by fungal diseases such as root rot and stem rot. There is no quick fix when it comes to eradicating this kind of disease, but with patience and proper care your plant can recover. As mentioned previously, your best chance at fighting off the fungus is through the use of fungicides. Do your research well, as there are many fungicides available on the market.
- Provide your plant with the best care possible. That includes proper lighting, adequate watering, moderate fertilizer, correct temperature and humidity, and well-draining soil.
- Remember that the effectiveness of fungicides can only be maximized in conjunction with proper gardening practices. This includes sterilizing your gardening tools, proper spacing between plants, and not leaving their foliage wet overnight.
- Protect your plants from potential injuries, as open wounds create entry points for fungal pathogens.
- Avoid soil contact with your plants and containers as this could spread soil-borne fungi.
As with other ornamental plants, your Euphorbia Ascot Rainbow can be vulnerable to fungal infections if it is not properly nurtured. And, as the saying goes, prevention is better than cure. So do not wait for Rhizoctonia and Fusarium diseases to attack your plants. Follow proper gardening hygiene and establish preventative measures to keep your lovely evergreens healthy and thriving!
Image: istockphoto.com / John Caley