Will Fertilizer Make Weeds Grow?

When you are caring for your lawn and garden it can be frustrating to try to balance fertilizing and weed control. 

Plan to deal with weeds chemically or manually before applying fertilizer to your lawn or garden. The fertilizer will feed weeds and plants at the same time. Nitrogen fertilizers which are often recommended for lawn growth can particularly encourage the growth of weeds like chickweed but may discourage crabgrass and dandelions. 

Soil chemistry can be as simple or as complex as you want it to be. There are generally 3 nutrients that we measure in the soil; nitrogen, potassium, and phosphorus. 

Most lawn fertilizers are heavy on quick-release nitrogen. 

Nitrogen is known to feed leaves and green-spreading plants, so it makes sense that it would be higher in fertilizers for green lawns. 

Some weeds love nitrogen-rich soil, but some do not grow as well in rich soil. Dandelions and crabgrass do not generally grow in rich soil and may be stunted or killed by the application of nitrogen fertilizer. 

When selecting products for your lawn or garden be sure to consider your needs, your soil test results, and the season in which you are applying the products. 

Soil test results can be very helpful when planning your lawn or garden care. The results often come with a recommended plan of action. 

Some herbicides contain components that prohibit seed germination and these should be applied before weed seeds germinate, fall or spring depending on the type of weed. 

Will Fertilizer Make Weeds Grow?

Will Fertilizer Feed Weeds?

Fertilizers can have many formulations and some of those formulations will feed weeds like chicory, amaranth, and chickweed. Generally, high nitrogen fertilizers will discourage the growth of clover and dandelions. 

So, being familiar with your lawn and your specific weed challenges can help you choose fertilizers for your lawn. 

Many experts recommend that you apply weed killer before or at the same time that you are applying fertilizers. 

This will keep the weeds from robbing your grass of the nutrients you are adding with fertilizer. 

You can do this by applying weed-killing products or by pulling weeds manually. 

Many “Weed and Feed” products contain a mix of fertilizer and herbicide that may seem like the perfect solution. 

Weed and Feed products can be applied in spring or fall depending on the combination of products in your individual weed and feed. 

Check the NPK ratio of your weed and feed problem and be sure it is appropriate for your application. Weed and feed products can vary widely in their formulas.

Later in the article, there are some specific recommendations for weed and feed products for each season and each weed problem. 

It is not always necessary to put down weed killer or put down fertilizer. Grass can be very hardy once it is established, so before you buy all the products, be sure you have a clearly defined problem you are trying to solve. 

If your lawn has isolated weeds in some areas you may want to do a spot treatment instead of spreading the whole lawn. 

Test your soil, if there is no nitrogen deficiency, it may not be necessary to apply nitrogen. 

Be sure you are watering your lawn regularly to encourage strong roots and establish growth.  

Should I Fertilize Or Kill Weeds First?

Kill your weeds before adding fertilizer to ensure your fertilizer is going to your plants, not the weeds. You can apply most herbicides at the same time as fertilizers. 

You may consider mixing the chemicals for application as long as the labels do not prohibit mixing. Be sure to read all the labels and information available on all products before mixing them to be sure they will not react with one another. 

Rather than choosing a general “weed and feed” product, be sure to choose a herbicide that matches your weed problems and your application time. 

Some herbicides contain compounds that keep weed seeds from germinating. These herbicides must be applied in early spring or late fall to be effective against seeds that have not yet germinated. 

The same goes for fertilizers. Choose the fertilizer that best matches your lawn type and your soil. 

While some gardeners apply regular quick-release nitrogen each season or several times a season. This can help boost a lawn for a short time, but it does not build the soil. 

Organic fertilizers, like bone meal, compost or manure are generally slower releasing and can offer other benefits that will build your soil over time. 

How to Use Weed and Feed Products

Weed and feed is a term that is used by many companies to describe a product that is designed for lawn care and contains a combination of fertilizer and herbicidal weed killer. 

These products are available from many companies with various combinations of fertilizers and weed killers. 

When choosing a product, consider both the “weed” components and the “feed” components. 

The NPK ratio will be listed somewhere on the bag. This is the combination of Nitrogen, Phosphorus, and Potassium in the fertilizer component of the product. 

Most of the products contain Urea Nitrogen which is a quick-release nitrogen that can boost your lawn’s green color for longer in the season. 

When you apply nitrogen depends on the type of grass you are growing. As a general rule, cool weather grasses can be fertilized in fall and spring and warm weather grasses can be fertilized in the summer. 

The herbicidal component in weed and feed is generally best applied in early spring before weed seeds germinate. 

Some weeds germinate in the fall, so an application could be done at that time as well. 

You can see that depending on your lawn type you may not find weed and feed beneficial for your lawn. 

Tips for Using Weed and Feed

  1. Be sure you are using the correct spreader settings for granular products. It will be listed on the package. 
  2. Know your grass type and be sure you are using a product approved for your grass. If you are unsure of your grass type you can ask a neighbor with a great lawn or contact your local extension office. 
  3. Use weed and feed when weed seeds are germinating in your area, usually early spring or fall. 
  4. Test your soil regularly to be sure it is not overburdened with nitrogen. 
  5. Read all safety information before applying, some of these products can be harmful to dogs or other animals. 
  6. Choose a weed and feed product that is formulated for your grass type. 

Nitrogen Fertilizer and Weeds

Nitrogen is the main ingredient in almost every weed and feed fertilizer that I have seen. It is generally urea nitrogen which is a very quick-release fertilizer. 

Nitrogen fertilizers feed some weeds and discourage others. 

Many gardeners are told to pay attention to weeds as they can be good indicators of your soil composition. 

Weeds that Love Nitrogen






Weeds That Will Be Discouraged By Nitrogen



As a general rule, keeping well-nourished, balanced soil will discourage weeds in your lawn. If you have a problem with some of the more nitrogen-loving weeds, be sure to remove them before fertilizing your lawn or garden. 

Can You Spray for Weeds After Fertilizing?

As a general rule, you should apply weed killer before applying fertilizer to allow all the nutrition to go to your lawn instead of weeds. If you have already applied fertilizer to your lawn you should wait a few days to a few weeks before applying weed killer. 

Give your lawn a week to absorb the weed killer that you applied so that it can be most effective, after that time you can apply fertilizer according to the package directions. 

Lawn care can be very simple, but some planning can make it much easier. 

If you are establishing a new lawn you may want to start by applying weed killer in early spring to prevent weed seeds from germinating. This can give your grass a good chance of getting established. 

If you are maintaining already established grass, apply herbicides in early spring or fall depending on when the weeds in your area spread their seeds. 

Fertilize your lawn in spring and fall for cold weather grasses and a few times in summer for hot weather grasses. 

The user’s manual or product label will tell you the varieties of grass that the product is designed to work with, use this information to choose the best products for your lawn. 

Managing Weeds in a Vegetable Garden After Fertilizing

You have worked hard to create rich soil for your vegetable garden and you may notice that weeds love that rich soil too. 

When you have applied fertilizer in your garden you may notice higher weed growth, but there are some things you can do to keep weeds down. 


Mulching is often recommended for weed control, but be careful with your mulch choice. 

Mulching with sawdust or wood chips can rob your soil of nitrogen over time. As the wood rots and breaks down in your soil it soaked up any available nitrogen in the soil. 

Be sure to test your soil regularly to identify any problems quickly. 

You may choose to use a weed barrier, paper, or pine mulch in your garden, just be sure to choose one that fits your soil and plant needs. 

Regular Weeding 

After fertilizing your soil you may notice that you have to weed more regularly for a few weeks. 

Be sure to plan your fertilizer application at a time when you will be able to devote a few extra minutes to weeding. 

Choosing organic slow-release fertilizers like bone meal, compost, feather meal or manure can make your soil healthier over time which can discourage some types of weeds. 

Dandelions and clover dislike rich soils. 

Test Soil

Test your soil regularly and address any deficiencies to create a healthy soil balance. This can discourage weeds that typically grow in poor soil. 

A soil test can help you plan to address garden problems you may have had in previous years. This may include an early spring herbicide to help stop weed seeds from germinating. 

Conclusion: Will Fertilizer Make Weeds Grow?

Lawn care can be very complicated when you are working to establish a lush green lawn, but once you have established a lawn it is very hardy against weeds and only needs occasional fertilizing and regular watering. 

Weeds should be killed before applying fertilizer whenever possible. This ensures that the nutrition from the fertilizer will be used by the grass, not the weeds. 

Fertilizers can be applied without the use of weed killer or the products can be applied at the same time. 

When you are addressing your lawn problems you should identify what type of grass you are growing and what types of weeds you are fighting. 

Apply weed killer in early spring, and if your grass type benefits from spring fertilization you can use weed and feed products to do this at the same time. 

Weed killer should generally be applied before weed seeds germinate which is in early spring or fall, depending on the weed. 

Fertilizers, especially nitrogen fertilizer, need to be applied in spring and fall for cool weather grass and in summer for hot weather grass. 

Be sure that your weed killer and fertilizers are matched to your specific lawn needs. 

If you apply these products at the wrong time it is unlikely that they will do any harm, but they will not be effective against weeds or to fortify your grass. 

The most important thing you can do for your lawn is to water it regularly. Many lawns will do well with watering alone. 

Fertilizers can extend the green color of your lawn for a few weeks or months, but these quick-release products will not improve the long-term health of your soil.