7 Signs You're Overfertilizing Your Plants, Plus How to Help Them Bounce Back

Fertilizer helps plants grow better and produce fresh leaves, as well as potentially fruit and flowers. However, if you accidentally apply too much fertilizer or fertilize your plants too frequently, your houseplants, garden, or lawn can suffer from fertilizer burn and other adverse effects of overfertilization. If you suspect that you’ve applied too much fertilizer, or you just want to avoid making this costly mistake, here are some signs of fertilizer burn to watch for—and ways to treat and prevent overfertilized plants.

Signs of Overfertilization

The time it takes plants to exhibit signs of fertilizer burn depends on the plant and the type of fertilizer used. If you applied a rapid-release synthetic fertilizer, your plants may show signs of stress within a few days of application. However, if you used a slower-release product or overfertilized the plants with granular fertilizer or manure mixed into the soil, it may take several weeks for symptoms of overfertilization to appear.

No matter what type of plant you’re growing, here are some of the ways plants let you know they’re stressed by too much fertilizer.

1. Visible Fertilizer Salts

Fertilizers contain salts that may form a white crust on the top of the soil or the exterior of plant pots. Salt buildup can also occur due to the contaminants in some tap water, though, so this is not always a clear sign of overfertilizing.

2. Discolored Leaves

Overfertilized plants may develop yellow or brown leaves or leaves with bright yellow veining. This is one of the first signs of fertilizer burn, indicating that you need to take action to save your plants.

3. Brittle Leaf Edges and Leaf Drop

As fertilizer burns progress, plant leaves can become dry and brittle at their tips and edges. Plants may also begin to drop their leaves, flower buds, or fruit.

4. Slowed Growth

Fertilizer salts make it harder for plants to absorb water, which can slow their growth.

5. Wilting

As plants lose their ability to take up nutrients and water, their leaves may wilt. Like leaf discoloration, wilting usually begins on the plant’s lower leaves.

6. Rotted Roots

Overfertilized plants can develop fertilizer burn on their roots, causing the roots to appear unnaturally dry or dark. This may predispose plants to problems like root rot and damping off disease.

7. Pest Issues

If plants receive too much nitrogen, they’ll often produce lots of fresh leafy growth that attracts sap-sucking insects, like aphids.

How to Fix Overfertilized Plants

Taking action as soon as you suspect your plants have been overfertilized can limit damage and increase the chances the plants will recover. Lawn grass and any indoor or outdoor plant can potentially develop fertilizer burn. However, the steps to fixing overfertilized plants can vary somewhat, depending on where the plants are growing.

1. Stop Fertilizing

If you suspect that your plants are overfertilized, stop your fertilizer regimen immediately and don’t apply any additional compost or manure.

2. Leach the Soil

Scrape as much of the leftover fertilizer or salt buildup as possible from the soil. Then, flush the soil with water to remove the excess fertilizer.

• For houseplants, slowly run water through the plant’s potting mix until the water runs freely through the pot’s drainage hole. Allow the plant to drip dry before returning it to its saucer, and flush the soil with water again in a few hours or the following day. Since some tap water contains salt and other additives, it can be beneficial to flush your plant’s pot with distilled or rainwater instead of tap water.
• For garden plants, leave your hose on low and slow until water pools around the plant, washing excess fertilizer down through the soil and past the plant’s root system. This process can take around 30 minutes and may need to be repeated in a few days to flush out all the fertilizer that’s built up in the soil.
• For lawns, leave your hose or sprinkler running until the soil in the area where you’ve overfertilized is thoroughly saturated, but avoid watering so much that water forms puddles. Allow the soil to dry out a bit, and repeat this process in two to three days.

3. Consider Repotting or Transplanting

Leaching potting mix or garden soil with water may be enough to remove excess fertilizer and help plants recover. However, if your plants are struggling or you mixed too much granular fertilizer, manure, or compost throughout the plant’s soil, you may want to consider repotting or transplanting.

If you go this route, remove as much of the old soil as possible and give the plant’s roots a rinse in water. Then, use sterilized pruners to trim away any dead, damaged, or mushy roots, and replant the plant in fresh potting mix or soil without adding any fertilizer, compost, or manure. Remember, most healthy plant roots should be plump and white in color.

4. Remove Damaged Leaves and Stems

After leaching and repotting the plant, trim away any dead or damaged leaves to help it conserve energy and recover faster. Avoid removing more than two-thirds of the plant’s leaves at one time.

5. Provide Supportive Care

Not all plants recover from fertilizer burn, but you can improve your plant’s chances by providing supportive care during its recovery period. This includes ensuring your plant receives the right amount of light for its needs, watering regularly, and withholding all fertilizer until your plant begins to produce new, leafy growth.

Ways to Avoid Overfertilizing Plants Again

Researching the fertilizer needs of the plants you grow and reading the instructions on the fertilizer packaging can help you avoid overfertilizing your plants. You can also reduce the risk of overfertilizing by:

• Testing the soil. Testing the soil in your lawn or garden before applying fertilizer will help you avoid unnecessary applications.
• Selecting organic products. Synthetic fertilizers are more likely to cause fertilizer burn than applications of aged manure, compost, or organic fertilizers. For added safety, opt for organic fertilizers and dilute them with water before application.
• Using the right fertilizers. Always use fertilizers that are intended for the plants you’re growing, and avoid combining different types of fertilizer unless you’re certain you know what you’re doing. 
• Fertilize during the growing season only. Plants absorb fertilizer most effectively in spring and summer, and should usually not be fertilized in fall or winter.
• Applying fertilizer in the right way. Less is more with fertilizer, and it’s better to underfertilize than overfertilize plants. To further reduce the risk of fertilizer burn, water the plants before fertilizing. Avoid applying granular fertilizers directly to the stems of plants. Additionally, flush the soil of potted plants with distilled water or rainwater every three to four months to prevent fertilizer levels from building up.