Quick Answer
Allowing leaves to decompose in your yard has both pros and cons. The main benefits are that it provides free mulch and fertilizer for your lawn and garden. However, thick layers of leaves can smother grass and promote fungal growth. Moderation is key – a thin layer of shredded leaves provides nutrients, while a deep pile creates problems. Raking and composting excess leaves is recommended.
Should I Remove Fallen Leaves From My Yard?
Fallen leaves are a natural part of any landscape with deciduous trees. As autumn approaches, leaves turn vivid colors before falling to the ground. This annual leaf drop can leave homeowners wondering if they should remove leaves or allow them to remain in place. There are good arguments on both sides of this issue.
Reasons to Remove Leaves
Here are some of the reasons why you may want to remove fallen leaves from your yard:
- Leaves left on grass can smother and kill it by blocking sunlight and air circulation.
- Thick layers of fallen leaves encourage fungal growth and rotting.
- Leaves piled against foundations can lead to moisture damage.
- Large amounts of leaves kill grass and leave bare patches.
- Fallen leaves can accumulate on roofs and gutters, causing drainage issues.
- Leaves left on paths and driveways can create slippery conditions.
- Not everyone likes the natural look of leaves scattered across the lawn.
- Leaves in flower beds smother plants and affect spring growth.
- Some leaf species (like black walnut) contain juglone toxin that harms plants.
- Built-up leaves are unsightly and difficult to remove if left for too long.
For these reasons, many homeowners opt to regularly rake up and remove fallen leaves each autumn. This involves using a rake or leaf blower to gather leaves into piles for disposal. Most municipalities offer special yard waste pickup or composting services this time of year to help manage the volume of leaves.
However, it’s important to note that not all leaves need to be removed from a yard. A thin layer of leaf litter can be beneficial for your lawn.
Reasons to Leave Some Leaves
Here are some of the benefits of leaving at least a light covering of leaves in place:
- Leaves provide free fertilizer as they break down, returning nutrients to the soil.
- Shredded leaves create an insulating mulch layer that protects grass roots from cold.
- Leaves contribute organic matter to enrich lawn and garden soils over time.
- Earthworms and beneficial microbes are supported by leaf litter on the ground.
- Leaves offer food and habitat for butterflies, bees, and other helpful insects.
- Some birds like towhees use leaf litter areas to search for food and nesting material.
- Leaves scattered on planted beds reduce weeds and keep soil moist during dry weather.
- Light leaf cover on beds provides winter insulation for plant roots.
- Leaving some leaves saves time and labor compared to gathering every last leaf.
The key is not to let leaves form a dense, suffocating mat. Aim for a thin layer no more than 1-2 inches deep. This allows leaves to decompose without harming grass or smothering plants.
How Long Does it Take Leaves to Decompose?
When leaves are allowed to remain where they fall, they begin the natural process of breaking down. So how long does it take leaves to decompose if left in place? There are several factors that influence the rate of decomposition:
Leaf Type
Some leaf species decompose much faster than others:
- Soft, thin leaves (like tulip poplar, catalpa, basswood) – 1 year
- Medium leaves (like maple, sweetgum, sycamore) – 1-3 years
- Thick, waxy leaves (like magnolia, live oak, pine needles) – 3+ years
Softer broadleaf tree leaves like maple tend to decompose within a year or two under ideal conditions. Tough evergreen leaves like pine needles can take two years or longer to break down completely.
Environmental Factors
Local environmental conditions also affect decomposition rates:
- Climate – Leaves decompose faster in warm, humid climates than in cold, dry climates.
- Moisture – More moisture speeds up decomposition, while excessively dry leaves break down slower.
- Soil microbes – An abundance of fungi, bacteria, and invertebrates helps break down leaves faster.
- Aeration – Turning leaves into soil exposes them to microbes and moisture, accelerating decay.
Where winters are mild and damp, leaves can disappear within a year. In cold northern areas, leaves left on top of frozen ground can take two years or more to fully decompose. Proper shredding and mixing of leaves into topsoil drastically reduces decomposition time.
Leaf Management
Certain leaf management practices also affect decomposition rate:
- Shredding – Running over leaves with a lawnmower speeds breakdown by splitting them into smaller pieces with more surface area.
- Composting – Collecting leaves into a compost pile really accelerates decay due to the concentrated mass and extra heat generated.
- Mulching – Chopped leaves left as a loose mulch on planted beds decompose faster than compressed piles.
- Turning into soil – Tilling shredded leaves into the top few inches of soil brings rapid decomposition by mixing with soil microorganisms.
Taking steps to chop, shred, aerate, moisten, and incorporate leaves into soil can reduce their decomposition timeline.
Pros of Letting Leaves Decompose in Your Yard
Allowing fallen leaves to remain in your landscape offers some benefits:
1. Natural Fertilizer
As leaves break down over time, their nutrients are released back into the soil. This provides free fertilizer for your lawn, trees, shrubs, and garden plants. Depending on the leaf species, the nutrients made available through decomposition typically include:
- Nitrogen
- Phosphorous
- Potassium
- Calcium
- Magnesium
- Iron
- Manganese
- Sulfur
- Carbon
These leaf-derived nutrients improve soil quality and provide sustained feeding of plants from below ground.
2. Organic Matter for Soil
In addition to releasing nutrients back into the soil, decomposing leaves contribute valuable organic matter. This improves soil structure, water retention, and drainage over time. The organic matter from decaying leaves creates a loose, fertile, and productive soil environment.
3. Natural Mulch
A layer of shredded leaves makes excellent mulch around trees, shrubs, perennials, and beds. This natural mulch helps:
- Suppress weeds
- Conserve soil moisture
- Reduce soil erosion
- Insulate plant roots from temperature extremes
Allowing some shredded leaves to remain as mulch in your beds provides these perks without needing to purchase commercial mulches.
4. Food Source for Organisms
Decomposing leaves harbor fungi, bacteria, earthworms, beetles, and other organisms that form a healthy soil food web. As they break down leaves, these creatures aerate the soil and release more nutrients for plant uptake. Decomposition also provides habitat and food for valuable insects like solitary bees.
5. Cost Savings
Leaving leaves to decompose on site saves money since you avoid bagging, hauling, and disposal costs. Less time raking, blowing, and transporting leaves means more time enjoying autumn. No need to purchase commercial fertilizers either – the leaves provide free plant nutrition.
Cons of Letting Leaves Decompose in Your Yard
However, having excessive leaf accumulation also poses some drawbacks:
1. Smothers Grass
While a light dusting provides good insulation, too many un-shredded leaves piled on top of lawn grass can block sunlight. This prevents photosynthesis and leads to damaged or dead grass. Wet, matted leaves are most problematic.
2. Promotes Fungal Issues
Thick, moist layers of leaves encourage fungal growth like snow mold. Leaf spot and leaf blight fungi also overwinter in fallen leaves. These disease organisms thrive in excess leaf litter and can infect plants.
3. Harbors Slugs and Pests
Piled leaves give cover to destructive snails and slugs during winter and spring. Other pests like box elder bugs, earwigs, and rodents can overwinter in leaf litter as well. Removing some leaves can reduce these pest issues.
4. Can Look Messy
While some appreciate the natural look, not everyone wants scattered leaves dominating their neat green lawn or orderly beds. Leaf-strewn yards and beds can appear unkempt to some homeowners.
5. Drainage Issues
Leaves that accumulate along foundations, walkways, or driveways can lead to water drainage problems. Dense piles of soaked leaves can also harbor mosquito larvae. Keeping these areas clear is advised.
6. Potential Leaf Toxicity
Leaves from a few tree species like black walnut contain juglone, a natural chemical that inhibits growth of some plants. It’s best not to mulch with these leaves around susceptible species.
Best Practices for Managing Fallen Leaves
The best approach is to strike a balance between removing excess leaves and keeping some for their positive attributes. Here are some recommended guidelines:
Rake Thin Coverings Into Turfgrass
Rake any light leaf layers into lawn areas using a stiff-tined rake. This shreds them and allows faster decomposition right in the turfgrass. Their nutrients and organic matter feed the living plants.
Mow and Mulch Remaining Leaves
For moderate leaf fall, mow over the leaves using a mulching mower setting. This chops the leaves into tiny pieces that break down faster. Leave the shredded leaves in place as a beneficial lawn mulch.
Compost Excess Leaves
After mulching some into the lawn, gather extra leaves into a compost bin or pile. Mixing with green materials like grass clippings speeds decomposition into rich leaf mold compost for your garden.
Blow or Rake Leaves Off Beds
It’s usually best to remove fallen leaves from flower and vegetable beds. Blow or rake these areas clear to prevent plants from being smothered before leaves have a chance to decompose.
Keep Grass Clear Around Foundations
To avoid moisture issues, regularly clear off any leaves that accumulate right against house foundations or outbuildings. Rake or blow these leaves onto lawn areas.
Shred Leaves Using a Lawnmower
Shredding leaves by running over them with a mower helps them break down faster. Turning shredded leaves into garden beds hastens decomposition even more.
Add Decomposed Leaves to Annual Beds
Where leaves have fully broken down into leaf mold after 1-2 seasons, work this into empty annual beds to amend the soil. It lightens heavy soils and provides nutrients for the next crop of plants.
Screen Composted Leaves
For potting mixes, screen mature leaf compost through 1/2″ hardware cloth to remove sticks and debris. Mix the fine leaf mold with container potting soil or seed starting mix.
Frequently Asked Questions
Here are answers to some common questions about managing fallen leaves:
What is the fastest way to decompose leaves?
Shredding leaves by mowing or chopping makes them break down faster. Composting leaves speeds decomposition too. Turning shredded leaves into garden soil exposes them to moisture and soil microbes that hasten decay.
How long does it take for leaves to decompose in soil?
Leaves mixed into garden soil can fully decompose in about 6 months to a year. Without shredding or tilling into soil, leaves decompose much slower, often taking 2 years or longer if conditions are cool and dry.
Do all leaves need to be removed from lawns before winter?
It’s not necessary to remove every last leaf. In fact, leaving a thin layer provides insulation for grassroots during winter dormancy. But excessively piled leaves should be shredded via mowing and left as lawn mulch.
Is it okay to leave leaf mulch on garden beds over winter?
Some leaf mulch can be left on perennial and shrub beds over winter. But excessive layers should be raked off, as wet compacted leaves promote fungal issues. Screened, composted leaf mold makes an excellent soil amendment.
Can leaves cause drainage issues around foundations?
Yes, piles of damp leaves along foundations can lead to moisture damage. Make sure to regularly clear off any leaves accumulating against house walls. Rake or blow them onto lawns or garden beds to decompose.
Will composting leaves attract pests?
Basic composting is unlikely to be a major pest attractant if certain precautions are followed. Don’t add meat, oils or dairy that can attract rodents. Turning the pile regularly and keeping it moist deters pests as well.
Conclusion
Deciduous trees provide a free source of mulch and fertilizer in the form of fallen autumn leaves. Allowing leaves to decompose right in your yard offers benefits like improved soil quality, habitat for soil organisms, and cost savings from free mulch and fertilizer.
However, thick piles of leaves left in place can cause issues like fungal diseases, drainage problems, and pest habitat. The best approach is to shred and mulch some leaves into your lawn, while composting excess amounts. With proper management, your landscape can take full advantage of nature’s free bounty of leaves.