Sean has been in the industry of gardening and landscaping since 2006. He is also a certified arborist that specializes in plant health.
Excessive fertilizing tends to be more become more of a problem than fertilizing too little. It is very easy to overdo fertilizing and there are several factors that can combine with excess fertilizer to cause negative effects. Fertilizers have high amounts of different salts that can pull moisture away from the roots in a process called reverse osmosis. If the salt content in the soil is higher than what the plant contains, then reverse osmosis will occur.
Reversing the effects of over-fertilization is possible, but time is needed before the plant returns full health. Container-grown plants can be affected more quickly compared to those grown in the ground, but excessive fertilizer damage can be corrected easier in container grown plants. The process of leaching can correct soils high in fertilizers.
Fertilizers Contain Salt
Symptoms of Over-Fertilization
There are several symptoms of excessive fertilizer application. Stunted growth, excessive growth of foliage with few blossoms, and discoloring on the edges of leaves are the most recognizable symptoms. The most severe damage occurs underground in the roots. Excess salt in fertilizers can "burn" the roots and limit moisture uptake. The combination of burns and limited water uptake will quickly lead to a decrease in plant health. The affected roots will also become weakened against disease and cultural problems.
Excess nutrients and salt need to be removed by a process called leaching. Leaching is the movement of nutrients down through the soil via watering. Leaching washes the extra nutrients out of the soil or below the root zone which allows the plant to begin the recovery process.
Plants in Containers
Check the surface of the soil around the plant for a white crust. Soluble salts from the crust can make their way to the roots and cause more harm during leaching. The crust needs to be carefully removed from the rest of the soil. Remove no more than one-quarter inch of soil from the surface. Sometimes the crust is hard enough that it can be picked out in large chunks. Be careful not to remove too much soil along with the crust. Removing too much can stress the plant even more. Leaching can begin once the crust is removed.
Saving a plant from fertilizer damage is relatively simple and quick to do. For container grown plants, use room temperature distilled water and fill the container to the top edge. Distilled room temperature water is the best water to use because it contains no dissolved minerals and will not add further stress. Filtered water can be used if distilled water cannot be obtained. Allow all the water to drain from the plant. Large containers will take quite a while to drain so have patience. Repeat this about 4 times. Excess fertilizers will be washed from the soil and drain through the bottom of the container.
Plants in the Ground
Place a garden hose at the base of the plant. Turn the water on just enough to produce a steady trickle. Allow the hose to run for a while so that adequate water runs through the soil to leach the fertilizers past the root zone of the plant.
Remove Dead or Dying Foliage
Foliage that is discolored and dying should be removed along with dead foliage. The plant will never be able to heal affected foliage and the plant should not waste any further energy on damaged foliage. New foliage will be produced once the plant begins to recover from fertilizer damage.
Fertilizer NPK Formulation
Preventing Excessive Fertilizing
When in doubt, only use half to a quarter of the amount listed on the fertilizer package. It is always better to use too little than too much. Research the soon-to-be fertilized plants before application as well. Different plants require different formulations and may be susceptible to certain formulations. Succulents cannot handle rich fertilizers while fast-growing plants can. It all comes down to the plant and adequate research to prevent fertilizer damage.
This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.
Questions & Answers
Question: My squash are rotten on the bottom before they are ready to be picked. What should I do?
Answer: Elevate the squash off the ground. Contact with the damp ground will cause rotting to occur.
Dee on July 21, 2020:
I mistakenly spayed fertilizer on my shrubs should I cut the damaged areas out?
Ash on June 13, 2018:
Hi,I have treated my plants with excess fertilizer I believe.My plants are dying I can see that ...I changed some soil keeping the original and changing like half of it just so that it doesn’t get too much of fertilizer.I was like 2 days late to notice this happening to the plants on the patio in the pots.I really wish them to re grow but Basil,Lavendar,Rosemary and other plants have all lost died.My question to you is—-If Inhave to plant new plants in the same pots should I change the soil completely or I can still use some old soil?I have made sure to pick as much fertilizer as I can...I have added part of that fertilizer soil in the regular soil I got from Walmart....to reduce the fertilizer’s effect...what do you suggest?
sreenivasarao on August 28, 2017:
thank you for suggesion