Phosphorous toxicity.
I have seen posts on social media of Crown of Thorns that are sick because they are over fed and most of the time, the owner does not even know it. Also, I have been asked too many times by my customers of what is wrong with their Crown of Thorns.
On this post I will tackle Phosphorous toxicity and I will address the other nutrient toxicities in my next posts.
Many gardeners seem to believe that fertilizers that contain high amount of phosphorous will make their plant bloom like crazy. Examples of high Phosphorous fertilizers are 10-30-20, 10-52-10, 12-55-6, etc. They are often marketed as bloom boosters. However, in my years of experience of growing Crown of Thorns plus hundreds of hours on researching the effects of fertilizers on plants, I concluded that too much phosphorous is detrimental to plant health. Phosphorous is the middle number written on the label of a fertilizer bottle/bag. It is the letter ‘P’ in the N-P-K components, N stands for Nitrogen, K stands for Potassium.
Plants need Phosphorous alright, but in right amounts
Phosphorous do not leach away, it stays in the soil thus, adding more P on a regular basis would be detrimental to the plant. Too much Phosphorous inhibits the uptake of other elements, it also precipitates with other elements forming insoluble compounds which plants are unable to uptake. When the plant can no longer absorb the needed elements, it would soon suffer and if not corrected, will die.
Calcium is one of the elements that gets kicked out or be unavailable for plant uptake due to excess Phosphorous. Calcium is essential for plant growth, it has also an important role in holding together the cell walls and membranes of plants thus making the plant resistant to pathogens. Hence when plants can no longer uptake Calcium, symptoms would soon exhibit in various forms. Some of the common symptoms are browning of the tips of newly emerging leaves, leaves are distorted and are abnormally small, leaf veins are yellow, flowers are distorted and small, the plant is stunted and very ugly.
Here are some things to do when you think your Crown of Thorns has been over fed with Phosphorous.
- Repot your COT using a fresh potting soil with no fertilizer in it. Shake off as much old soil.
- Remove all the distorted, browned leaves and all distorted flowers
- Wait for one month, or when the plant starts developing new leaves, before fertilizing. A 14-14-14 slow-release Osmocote or a high Nitrogen fertilizer would be fine like 21-4-8.
The newly emerging leaves will still exhibit toxicity symptoms, however as more leaves develop the sickly signs would slowly disappear until normal leaves finally will develop.