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Learn About Mulch

Students learn about the importance of mulch in water conservation and soil building.

Learn About Mulch

Contact a local arborist or tree trimming company for leads on free mulch in your area.

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Roots of trees growing in a natural environment plunge into well-aerated, nutrient-dense soil. The roots of your flowers, fruits and veggies are likely planted in soil typical of urban landscapes.

Limited amounts of organic matter and large fluctuations in temperature and moisture make it difficult for your plants to survive.

The soil around forest trees is littered with bits of organic matter such as fallen leaves and twigs, eroding rocks, and decomposing critters. As these organic materials break down, vital nutrients, including carbon and nitrogen, are taken up by the soil. This layer of loose, organic matter also helps maintain soil moisture and temperature, reduces the growth of weeds, improves soil structure and aeration, and can inhibit certain plant diseases.

Mulch mimics this natural process. Sometimes referred to as composting in place, mulch is simply a 2 to 4-inch layer of organic and/or nonorganic debris arranged around the base of plants.



· Students learn the concept of evaporation in the water cycle

· Students witness ways in which to reduce evaporation and water consumption



1.h. Students know living organisms and most materials are composed of just a few elements.

3.b. Students know when liquid water evaporates, it turns into water vapor in the air and can reappear as a liquid when cooled or as a solid if cooled below the freezing point of water.

(EEI) 5.3.d. Students know that the amount of fresh water located in rivers, lakes, underground sources, and glaciers is limited and that its availability can be extended by recycling and decreasing the use of water.



Find plants surrounded by bare soil. Procure organic mulch.


· Organic mulches: straw, pine needles, wood chips, leaves, compost mixes, grass clippings, bark, straw, coconut fiber (“coir”)

· Inorganic mulches: stone, lava rock



1. For this activity have students go outside to the garden beds and water the gardens.

2. Next, apply a thick layer of mulch to all of the plants.



1. Explain the water cycle step by step.

2. What happens during the evaporation cycle?

3. Why is mulch important?

4. In an area with few plants would the air be humid (wet) or dry?



Evaporation the process where water changes from a liquid to a gas. When water vapor comes together in the sky, it forms clouds.

Mulch layer of material added to the surface around plants in order to conserve moisture, help with weeds and pests, disease management, and protect soil.

Condensation the process by which water changes from a gas to a liquid.

Precipitation the process by which the condensed water in the clouds returns to the earth. Depending on the temperature, precipitation can be in the form of rain, snow, ice or hail.

Transpiration the process by which living plants release water vapor into the atmosphere.

Percolation the downward movement of water from the surface of the earth into underground aquifers.

Accumulation collection of rain, snow, sleet, etc. (precipitation) into puddles, rivers, lakes, and oceans.

Reservoir above ground human-made lake that is used for storing water until it is needed

Molecules – the smallest possible particles of a substance, made up of atoms that have joined together

Hydrogen and Oxygen Two hydrogen atoms and one oxygen atom join together to make water. The water molecule is one of the most common molecules on earth.

Aquifers an underground storage area for water that consists of a layer of porous soil and/or rock above a layer of rock that will not allow water to percolate