How to Compost Weeds

Composting weeds is a smart way to recycle garden waste while creating nutrient-rich soil for your plants. By properly managing temperature, moisture, and aeration in your compost pile, even the most persistent weeds can be transformed into valuable organic matter for your garden.

When you compost weeds effectively, you turn potential garden nuisances into a free soil amendment packed with nutrients. The key is ensuring your compost pile reaches high enough temperatures (around 140 degrees) to kill weed seeds. Chopping weeds before adding them speeds decomposition, and keeping seed heads out of your pile prevents unwanted sprouting in your garden beds later.

In this guide, I’ll share my favorite method to safely compost weeds and offer tips to achieve the best compost without unwanted surprises. 

Skill level: Beginner Length of project: From 2 weeks to 2 years, depending on your method. Hot composting can break down weeds in a few weeks, while cool composting can take several months to 2 years. Estimated cost: It will range from $0 to $150, depending on whether you buy a compost bin or use free materials and the tools you already have.

What to know before composting weeds

Weeds are often seen as garden enemies, but they can actually become valuable allies when composted. Rich in nutrients and organic matter, weeds make excellent compost material. However, keep the following in mind before you dive into composting those weeds.

Understanding weed types and their risks

Before adding weeds to your compost, it’s important to understand which types are safe and which types might cause problems.

Annual weeds: These complete their lifecycle in one year and are generally safe to compost, especially if they haven’t developed seeds. Examples include chickweed, lambsquarters, and purslane.

Perennial weeds: These live for multiple years and often spread through persistent root systems. Examples like dandelions, bindweed, and quackgrass can regrow from small root fragments.

Seeding weeds: Any weed that has gone to seed poses a risk, as seeds can survive cool composting temperatures and potentially sprout when you use the compost in your garden.

Common problem weeds

Pay special attention to these notorious types of weeds that require extra care before composting:

• Bindweed/morning glory: Its extensive root system can regenerate from tiny fragments.
• Creeping Charlie (ground Ivy): Spreads through runners that can survive in compost.
• Quackgrass: This is a grassy weed with rhizomes that continue growing unless thoroughly killed.
• Dandelions: The deep taproot can regrow if not completely removed or treated.
• Nutsedge: Underground tubers can survive and spread if not properly treated.
• Poison Ivy: Contains urushiol, which can cause skin reactions even when composted.

If problem weeds have completely overtaken your yard, professional help might be your only option. Lawn Love can connect you with a local weed control expert to safely and effectively manage invasive plants, saving you time and effort. 

Safety Considerations

Herbicide residue: Avoid composting weeds that have been treated with persistent herbicides, as these chemicals can survive the composting process and damage plants later.

Toxic weeds: Some weeds like poison ivy, poison oak, or giant hogweed contain substances that can cause skin reactions. Wear gloves, long sleeves, and long pants when handling these plants.

Diseased plants: Weeds showing signs of disease might spread pathogens to your compost. Hot composting can kill many pathogens, but particularly aggressive diseases might be better disposed of elsewhere.

Best practices for weed collection

The best time to deal with weeds for compost is when they’re young and haven’t come to seed. Removing weeds early prevents them from spreading and competing with your plants. 

For easier removal, pull weeds when your soil is still moist, such as after rainfall or watering. Damp soil loosens the roots, making it less likely that they will break off and regrow. Use a weeding tool or hand-pulling technique to remove the entire plant. 

Read more: How to Deal with Overgrown Weeds   

Step 1: Choose your composting method 

The best composting method for you depends on how much time and effort you want to invest and what type of weeds you’re dealing with. 

If you want quick results and are willing to turn your pile regularly, I recommend trying hot composting. If you prefer a low-maintenance approach, cool composting works too, but it takes longer and requires extra weed preparation. There are other methods, like vermicomposting and bokashi composting, which can also be useful for certain situations. 

Hot composting

Hot composting is the fastest and most effective way to compost weeds because it generates enough heat to kill seeds, roots, and any invasive plant material. To work properly, the pile needs to stay around 145 degrees for nearly 2 weeks.

Key factors for hot composting success:

• Material balance: Use a ratio of 3 parts browns (dry leaves, shredded paper) to 1 part greens (grass clippings, food scraps, or weeds).

• Moisture: Grab a handful. It should feel like a wrung-out sponge.
• Particle size: Chop up large pieces to help them break down faster.
• Aeration: Turn the pile every 4 to 5 days to maintain heat and keep air flowing.
• Time: Around 2 weeks to 3 months.

My tip: Make sure your compost pile is at least 3 feet by 3 feet by 3 feet in order to trap heat and ensure efficient decomposition.

Cool composting

Cool composting is a low-maintenance method where fresh materials are added continuously to the top of the pile. While you technically don’t need to turn it, strategic turning can significantly improve the process. Without turning, decomposition takes at least 6 months to 2 years for materials to break down completely.

For optimal results, consider turning your cool compost pile every 2 to 3 months during active growing seasons when decomposition is naturally more vigorous.

Important rules for cool composting weeds:

• Only compost annual weeds that haven’t gone to seed.
• Avoid perennial weeds that spread through aggressive runners.
• Pre-treat problem weeds before adding them to the pile.
• Chop or shred weeds into smaller pieces to accelerate decomposition.
• Monitor your compost and remove any weeds that begin sprouting within the pile.
• Keep your cool compost pile moist to help speed the decomposition of weeds.

Other composting methods

• Vermicomposting uses worms to break down material. Since it’s a cool process, only add weeds that haven’t gone to seed and avoid invasive roots.
• Bokashi composting uses bokashi bran to ferment waste. The acidic environment helps kill weed roots and seeds but it doesn’t fully break down the weed. This method prepares weeds to be added to a compost pile or to be buried.  

My tip: I like to combine methods by using Bokashi composting first, then add it to my hot compost pile. This double treatment ensures the weeds are completely broken down and speeds up the decomposition process.   

Read more: What can and cannot be composted

Step 2: Prepare your weeds 

As you pull weeds, it’s important to separate them into two categories: harmless weeds and problem weeds. 

Harmless weeds are typically annual plants that complete their life cycle in one season and don’t spread through persistent seeds or roots. As long as these weeds don’t have seeds, you can add them directly to your compost pile.

On the other hand, the problem weeds I discussed above require extra care before composting because they either produce seeds that can survive the composting process or have aggressive root systems capable of regrowing. 

If you opt for cool composting, pre-treating problem weeds is essential because this method doesn’t achieve the high temperatures necessary to kill seeds and stubborn roots, which can lead to weed regrowth in your garden. In contrast, hot composting effectively eliminates most seeds and roots by sustaining temperatures around 145 degrees. 

This chart details the most effective methods for pre-treating your weeds before cool composting:

Method	Best for	How it works
Drowning	All problem weeds	Soak weeds in a container of water with a lid for 1 month. This kills seeds and roots.
Drying	Weeds with strong roots	Leave your weeds in the sun for 2 to 3 weeks until completely dry. This kills roots but may not kill seeds because some seeds remain dormant.
Weed bags	Tough perennial weeds	Place in a sealed black bag for 10 days or more in the sun. The bag method deprives weeds of light and air, killing the roots, but seeds can remain viable if they don’t experience sustained heat.

My tip: Once your weeds have been properly pre-treated using an above method, chop them into small pieces before adding them to your compost pile. This speeds up decomposition, allowing microbes to break them down more easily.

Read more about weeds in our guides:

• 14 Ways to Kill Weeds Permanently
• How to Get Rid of Weeds in Flower Beds
• How to Make a Homemade Weed Killer 
• Rent a Goat: Remove Invasive Weeds Naturally

Step 3: Build Your Compost Pile

Now that your weeds are ready, it’s time to set up your compost pile. The following factors are essential for successful backyard composting. 

Choose a good location

First, you want to find the perfect spot for your compost pile. Choose a flat, well-drained area to prevent water from pooling at the bottom. The location should be accessible year-round, making it convenient to add materials and turn the compost pile about once a week in warmer months and every few weeks in colder weather.

• Moderate sunlight: A mix of sun and shade is best. Too much sun can dry out the compost, while too much shade can slow decomposition. 
• Keep a safe distance from your home: Placing the compost 10 to 20 feet away helps reduce odors and keeps pests from getting too close to your house.
• Avoid tight spaces: Setting your compost against a wall, fence, or dense vegetation can create hiding spots for rodents. 
• Shelter from strong winds: Windy locations can dry out the pile too quickly, making decomposition less effective. 

Pick your composting setup

Next, you need to decide on your structure. You can buy a compost bin or, if you want, you can build your own. There are many materials you can use. Common options include repurposed garbage cans, plastic containers, or wooden pallets. 

For a more durable structure, metal sheets, or chicken wire can be used to create an open, breathable compost bin. Just be sure that whatever you choose allows for proper airflow, easy turning, and convenient access for adding materials. 

If you enjoy DIY projects, check our guide on How to Make a DIY Compost Bin: 13 Easy Builds for Beginners.

Assemble your pile

Finally, now is the time to assemble your pile. A well-structured pile breaks down faster and prevents problems like bad odors.

Compost base: Begin by laying a base of small branches or twigs at the bottom of your compost pile. This helps with drainage and improves airflow, preventing the pile from becoming compacted and soggy.

Pile size: For successful composting, your pile should be at least 3 feet wide, 3 feet long, and 3 feet high. This size allows the compost to retain heat and maintain the necessary microbial activity for proper decomposition. 

Compost layers: To create a well-balanced compost pile, layer your materials properly. Start with browns like twigs or straw for airflow. Then alternate layers like making a lasagna and maintain the 3:1 ratio — three parts of browns (dried weeds, leaves, shredded paper) for every one of greens (fresh weeds, food scraps, grass clipping). 

Step 4: Maintain proper moisture

The perfect compost should be moist but not soggy, similar to a wrung-out sponge, with about 40 to 50% water. Too little moisture slows decomposition and can attract ants, while too much creates bad odors and may draw pests like rodents. 

Adjust moisture level: If your compost is too dry, spray water while turning the pile and add moisture-rich greens like food scraps. If the compost is too wet, mix in dry materials such as shredded newspaper, straw, sawdust, or dry leaves to absorb excess moisture.

Seasonal moisture adjustments: During hot, dry weather, compost can dry out quickly. To retain moisture, cover your pile with a tarp, cardboard, or mulch layer to reduce evaporation. During heavy rain or winter, too much water can make compost soggy. Cover the pile or, if possible, place it in a sheltered spot to prevent excess moisture. 

My Tip: To check your pile’s moisture, grab a handful of compost and squeeze it. If one drop of water falls, it’s just right.                

Step 5: Turn your pile properly

Regularly turning your compost aerates the pile, helps distribute heat evenly, and speeds up decomposition. The frequency and method of turning depend on whether you’re using hot or cool composting. 

• Hot composting: Turn the pile every 4 to 5 days to maintain airflow and ensure all materials reach a proper temperature.
• Cool composting: This method depends on a slower breakdown, so turn the pile only every 2 to 3 months to encourage decomposition. 

You’ll know it’s time to turn your compost when a few key signs appear. If the temperature drops, your pile isn’t heating enough to break things down properly. If the compost looks dense or matted, airflow is getting blocked. If you notice a bad smell, like something rotting, it clearly indicates that the pile has gone anaerobic and needs air.                   

The chart below outlines common turning techniques.

Turning technique	Description
Inside-out method	Brings outer layers to the center and moves central material to the outside, ensuring even heating and decomposition.
Layer flip method	Turns the pile into sections, flipping layers to expose fresh material to oxygen for improved aeration.
Berkeley method	Intensive hot composting method that requires turning every other day and maintaining 135 to 150 degrees for rapid breakdown, producing compost in as little as 3 weeks.

In order to turn your pile, use the proper tools, including:

• Garden forks or pitchforks: traditional and effective for small to medium piles.
• Compost aerators: Long, rod-like tools with wings or spirals that help mix compost.
• Turning bars or auger: Designed for deep mixing, good for large piles.
• Compost tumbler: If using a compost tumbler, simply spin it to mix materials without the mess. 

Step 6: Address issues

Even a well-managed compost pile can encounter issues, but fortunately, most problems are easy to resolve. Here’s how to keep things running smoothly:

Issue	Causes	Solution
Bad odor	Too much moisture and lack of oxygen. A rotten egg smell indicates anaerobic conditions, while an ammonia smell means excess nitrogen.	Mix in dry browns like leaves or shredded paper. Turn the pile to improve airflow. Use a compost aerator or insert perforated PVC pipes for better ventilation.
Pile not heating up	Insufficient aeration, large scraps, too small of a pile, or an unbalanced mix of greens and browns. A hot compost pile should reach 130 to 150 degrees.	Turn the pile more often and chop up large scrapes before adding them. Use a compost thermometer to monitor heat levels. Ensure your pile is at least 3x3x3 for proper heat retention.
Flying insects	Exposed food scraps can attract flies. Fruit flies are common but harmless, while black soldier flies actually speed up decomposition.	Bury food scraps 8 to 12 inches deep in the pile’s center. Cover the compost with a breathable material like burlap. Avoid adding large amounts of citrus peels and onions, which attract fruit flies.
Overrun by ants	The compost is too dry. A few ants are fine but large colonies mean it’s too dry.	Gradually add water over several days while turning the pile to restore moisture. Line the bottom of the bin with cardboard or newspaper to help retain moisture.
Rodents or wildlife digging in	Meat, dairy, greasy foods, or warm, dry nesting areas in winter.	Never add meat, dairy, or oily foods. Use ¼ inch hardware cloth instead of chicken wire for a rodent-proof bin. Turn the pile regularly to disrupt potential nests.
Weed regrowth	The compost pile didn’t reach or maintain high enough temperatures consistently, or the pile was not properly turned, and some materials didn’t get fully heated.	Ensure the pile is at least 3x3x3 feet to retain heat, turn it inside-out, and monitor your pile with a compost thermometer.

Step 7: Know when compost is ready

The best way to tell if your compost is finished is by examining its texture and smell. It should be dark, crumbly, and earthy, with no recognizable pieces of the original materials. For weed composting, pay special attention to any remaining roots or stems, these should be completely unrecognizable to ensure they won’t regrow in your garden. 

Composting timelines vary. Hot composting can produce finished compost in 4 to 8 weeks during warm months, while cool composting may take several months to 2 years. Winter batches take twice as long due to lower microbial activity. 

Even when compost looks ready, it’s best to let it cure for 2 to 4 weeks before using it in your garden. Curing ensures any remaining decomposition processes are complete, stabilizing the nutrients and making them more beneficial for plants.

My tip: A simple way to test readiness is the bag test: Place a small sample in a sealed plastic bag for three days. If it develops a sour smell or the bag expands, the compost is still decomposing and needs more time.

Read more: How to Use Compost in Your Lawn and Garden     

FAQ about composting weeds

Find a pro near you

If you’d rather get rid of the weeds in your yard or simply don’t have the time to compost them, a weed control pro can help manage them for you. And if you need assistance with your yard, Lawnlove can connect you with a professional nearby to help with tasks like mowing, lawn cleanup, or aeration. 

Main Photo Credit: hopsalka | Adobe Stock Free | License