Fall, the season to reap the season's most abundant crop: leaves.
Leaves, also known as gardener's gold, are a rich source of organic matter for soil. Plus they are earth-friendly, renewable and free!
"Leaves are packed with trace minerals that trees draw up from deep in the soil." (Source: Gardeners)
According to an article by Oxford Academic on The Composition of Tree Leaves, leaves contain:
- nitrogen (primary macronutrient)
- phosphorus (primary macronutrient)
- potassium (primary macronutrient)
- calcium (secondary macronutrient)
- magnesium (secondary macronutrient)
"Macronutrients are essential for plant growth and a good overall state of the plant." (Source: AGQ Labs) To learn more about "Macronutrients Required for Plant Growth", check out this blog.
"Micronutrients are elements required in small quantities, and are essential in order for plants to complete their life cycle." (Source: AGQ Labs)
We utilize a number of micronutrients in our plant products, check out this blog to learn more.
Curious how these nutrients aid plants?
Potassium: "Potassium ... helps regulate the opening and closing of the stomata, which regulates the exchange of water vapor, oxygen and carbon dioxide. If K is deficient or not supplied in adequate amounts, it stunts plant growth and reduces yield." (Source: University of Minnesota Extension)
Calcium: "Calcium is an essential plant nutrient. ... it is required for structural roles in the cell wall and membranes, as a counter‐cation for inorganic and organic anions in the vacuole, and as an intracellular messenger in the cytosol." (Source: National Library of Medicine)
Magnesium: "Magnesium is the central core of the chlorophyll molecule in plant tissue. Thus, if Mg is deficient, the shortage of chlorophyll results in poor and stunted plant growth. Magnesium also helps to activate specific enzyme systems." (Source: University of Minnesota Extension)
Iron: "...it's mostly to help the plant move oxygen through its system. Plants only need a tiny amount of iron to be healthy, but that small amount is crucial." (Source: Gardening Know How)
Manganese: "Manganese (Mn) is an important micronutrient for plant growth and development and sustains metabolic roles within different plant cell compartments." (Source: National Library of Medicine)
Silica: "Silica increases plant tolerance to drought, frost and lodging. Silica strengthens plant cells which means reduced water loss, less frost damage, more root growth and a decrease in lodging. Silica increases plant resistance to fungal disease and pest attack because of harder epidermal cells." (Source: Ag Solutions)
Phosphorus: "The function of phosphorus in plants is very important. It helps a plant convert other nutrients into usable building blocks with which to grow. Phosphorus is one of the main three nutrients most commonly found in fertilizers and is the “P” in the NPK balance that is listed on fertilizers." (Source: Gardening Know How)
Carbon: "Plants take in – or ‘fix’ – carbon dioxide from the atmosphere during photosynthesis. Some of the carbon is used for plant growth, and some of it is used in respiration, where the plant breaks down sugars to get energy." (Source: Imperial College London)
Nitrogen: "Nitrogen in the plant is a very important subject. There is more nitrogen in plants than any other element, with the exception of carbon, hydrogen and oxygen. Nitrogen plays an important part in many essential functions and compounds necessary for life. Nitrogen is an important part of the compounds that regulate plant growth and development. Nitrogen is also an important part of the plant structure. In the roots, nitrogen is found in proteins and enzymes. They help the nutrients and water be taken up into the plant." (Source: University of Missouri Extension)
The chemical composition of tree leaves is related to soil conditions and the type of tree.
Uses for tree leaves
- Mixing shredded leaves into soil will add beneficial nutrients, improving growing conditions.
- Adding leaves to your garden will feed beneficial microbes and hungry earthworms.
- If you have heavy soil, adding leaves to your soil will help lighten it.
- If you have sandy soil, adding leaves to your soil will help it to retain moisture.
"Mulch is any material that is placed atop the soil to moderate its environment and enhance the landscape." (Source: Gardening Know How)
Leaves are a wonderful organic mulch that can be used in your flower garden and vegetable garden.
The benefits of using shredded leaves as mulch are extensive:
- Applying leaf mulch helps the soil in maintaining a consistent temperature year round, protecting plants. It will help buffer soil temperatures to keep soil warmer in the winter and cooler in the summer.
- Applying leaf mulch enriches the soil and improves soil fertility as it decomposes, which reduces the need for fertilizing.
- Leaf mulch helps control and suppress weeds. This can save time in weeding and decrease the need for herbicides.
- Leaf mulch, in some uses, can help reduce soil erosion.
- Leaf mulch can aid the soil in conserving moisture, decreasing the need for watering in dry conditions. Composted leaves can retain 6 times their weight in water.
"To use the dried leaves as mulch, spread them at a rate of 3 to 4 inches (7.5 to 10 cm.) around trees and shrubs and 2 to 3 inches (5 to 7.5 cm.) over perennial beds." (Source: Gardening Know How)
Keep in mind that if you use leaves as a mulch it will decompose (which is good for the soil!) and consequently will need to be replaced.
Compost Pile Material
Use leaves in your compost pile. Leaves are a valuable source of carbon. If you add fresh grass clippings to your compost, they are high in nitrogen; so leaves provide a good balance.
To speed decomposition of leaves, mix with grass clippings, which are high in nitrogen. And be sure to shred the leaves beforehand as well, as the smaller the leaves are, the quicker they will decompose.
According to Peppers Home and Garden, "Whole leaves can take as long as 2–3 years to decompose in a compost bin. Shredded leaves can break down in as little as 3–6 months."
For tips on composting, check out our blog, "Fall Composting Tips".
Need help with your compost pile? Check out our Compost Starter. This high quality compost starter can produce odourless, hygienic, mature compost that can be safely applied to the land for improved soil structure, moisture retention and add an additional wide range of nutrients.
Insulation for Plants
Use leaves to insulate tender plants during the cold winter months.
Tips When Using Leaves
While leaves are important organic matter, it is important to shred them before adding them to your soil or using them as mulch.
- increases the surface area, providing microbes more places to work.
- prevents leaves from clumping into layers, which block water and air from penetrating.
- reduces the volume, making them more nutrient dense.
Not sure of the quickest or most efficient method to shred your leaves? Here are a few ideas:
- Rake up leaves into long rows and run over with a lawn mower with a mower bagging attachment
- Use a leaf shredder
- Use a hand-held vacuum equipped with a shredder
- Gather leaves, put in a trash can, use a string trimmer to shred leaves in the trash can
Don't Leave Leaves on Lawn
Leaving leaves to decompose on your lawn is not recommended. A thick mat of leaves on your lawn will suffocate your lawn. Check out this blog to learn more about why you need to remove those leaves when it comes to your lawn, "Raking Leaves: Is it Really Necessary".
"If you add shredded leaves right to the soil, add some slow-release nitrogen fertilizers to help the leaves decompose and to ensure that soil microbes don't use all of the available nitrogen." (Source: Gardener's)
Consider mulching the leaves on your grass rather than raking them.
Don't Use These Types of Leaves
"Be careful with some kinds of leaves. Walnut, eucalyptus and camphor laurel leaves contain substances that inhibit plant growth. It's best to compost these leaves before using them in your garden."(Source: Gardener's)
Of course don't use leaves from diseased or sick trees.
AGQ Labs USA, Macronutrients in Plants
AGQ Labs USA, Micronutrients in Plants
Fr-Dor Inc, What is the Best Mulch for Vegetable Gardens?
Gardener's Supply Company, Put Fall Leaves to Work, How to turn fall leaves into fuel for next year's garden
Gardening Know How: Leaf Mulch Info – Learn About Mulching With Leaves
Gardening Know How, Iron for Plants: Why Do Plants Need Iron?
Gardening Know How, The Importance of Phosphorus In Plant Growth
Imperial College London, How plants use carbon affects their response to climate change
National Library of Medicine, Calcium in Plants
National Library of Medicine, Manganese in Plants: From Acquisition to Subcellular Allocation
Oxford Academic on The Composition of Tree Leaves
Peppers Home and Garden, How to Shred Leaves for Compost [5 Ultra-Fast Methods]
University of Minnesota Extension, Magnesium for Crop Production
University of Missouri Extension, Nitrogen in the Plant
University of Minnesota Extension, Potassium for crop production