How much mulch per tree

Mulching Landscape Trees

Mulches can also improve soil structure and fertility. This is important in urban landscapes where soils are often compacted and lack organic matter, especially on new construction sites.

Mulching mimics the natural environment found in forests where leaves and branches blanket the soil surface, replenishing nutrients as they decompose and creating an ideal environment for root growth. Urban landscape trees and shrubs typically grow in much harsher environments with soils modified by human activities (e.g., construction, lawns, and compaction). A 2- to 4-inch layer of mulch can re-create aspects of a forest's soil environment. According to the International Society of Arboriculture, mulching, when done correctly, is one of the most beneficial practices a homeowner can do for the health of a tree or shrub.

Mulches are available in two major forms, organic and inorganic. Tree care professionals prefer organic mulches, such as wood chips, pine needles, hardwood and softwood bark, cocoa hulls, leaves, and compost mixes, since they decompose, improving soil structure and increasing soil fertility. The various organic mulches decompose at different rates and require periodic reapplication. Inorganic mulches, such as gravel, stone chips, river rock, and rubber, do not provide the same benefits as organic mulches as they do not decompose.

The benefits of proper mulching include the following:

  • Conserves soil moisture by increasing water infiltration and slowing evaporation
  • Improves soil structure, fertility, and aeration as it decomposes
  • Moderates soil temperature, protecting roots from extreme summer and winter temperatures
  • Eliminates potential tree damage from mowers and trimmers
  • Prevents soil compaction by reducing foot and vehicle traffic, allowing roots to “breathe"
  • Impedes growth of weeds and grass that compete with tree roots for water and nutrients

Inorganic mulches, such as this stone, do not provide the same benefits as organic mulches like bark and wood chips

The benefits of mulching are well documented. However, excessive or improperly applied mulch can adversely affect plants. The International Society of Arboriculture advises to apply mulch properly; if it is too deep, piled against the trunk of the tree, or the wrong material, it can cause significant harm to trees.

Proper Mulching Method

  • Organic mulches are preferable due to their soil-enhancing qualities. Hardwood bark makes very good, inexpensive mulch, especially when it contains a blend of bark, wood, and leaves.
  • Mulch can be applied to landscape trees at just about any time of the year. However, the best time to apply mulch is in the middle of spring, once soil temperatures have warmed enough for root growth to begin.
  • Mulch as much of the area as possible, preferably to the outermost edge of the tree's canopy, referred to as the “drip line." Keep in mind, the drip line moves out as the tree grows.
  • Apply a 2- to 4-inch layer of organic mulch and no more; use less if the soil is poorly drained. More than 4 inches may harm the tree's root system. If using finely textured or double-shredded mulch, use 1 to 2 inches since these materials allow less oxygen through to the root zone.
  • For tree health, keep all mulch material away from the trunk. Allow the root flare (where the trunk meets the soil) to show. The root flare is at or near the ground line and is identifiable as a marked swelling of the tree's trunk where roots begin to extend outward.

This is a properly mulched tree. Note the mulch is only a few inches deep, not mounded around the trunk. The root flare is visible and the mulch extends to the edge of the tree's crown, or the drip line.

Other tips

  • Finely shredded mulches decompose faster and require replenishing more often.
  • Before replenishing the mulch each season, check the depth. Some old mulch may need to be removed before adding a new layer.
  • Applying new mulch over old mulch in successive years is the same as applying too deep a layer all at once.
  • The appearance of old mulch can be “refreshed" by breaking up any matted layers by hand or with a rake.

On newly planted trees, mulch more than just the root ball. The goal is to promote root development away from the tree. Mulch wide, not deep.

Avoid Overmulching

Overmulching landscape trees is common. This is most obvious when mulch extends up the trunk, smothering the root flare and root zone. This practice, known as “volcano" mulching, is never recommended and should not be utilized. As beneficial as mulch is, too much mulch is harmful. Deep mulch may suppress weeds, but it wastes time and money and can cause major health problems that lead to tree decline and possibly death.

Avoid piling mulch in the appearance of a volcano cone around trees. Volcano mulching, or piling mulch against the trunk, can cause major tree health problems.

Problems Associated with Overmulching

  • Oxygen starvation and root suffocation. Tree roots need oxygen to grow and function properly. When too much mulch covers the soil surface, air may not penetrate the mulch layer and the underlying soil becomes depleted of oxygen. In addition, excessively deep mulch can inhibit water loss through evaporation. Once soil pore spaces become filled with water, diffusion of oxygen into the soil is essentially blocked. When soil oxygen levels drop too low, root growth declines, making it impossible for the plant to take up water and nutrients. Plant death may result if too many roots decline.
  • Inner bark death. The inner bark, also called the phloem, carries photosynthates produced by the leaves to the rest of the tree. When mulch covers the root flare and trunk tissues, they stay constantly wet. This tissue is much different from root tissue and cannot survive under these conditions. Continuous moisture also interferes with respiration by limiting gas (oxygen and carbon dioxide) exchange between living cells in the trunk and the atmosphere. If wet conditions continue long enough, phloem tissue dies and roots are starved of essential carbohydrates.
  • Disease. Most fungal and bacterial diseases require moisture to grow and reproduce. Overmulching creates conditions where trunk diseases can gain entry through constantly wet, decaying bark, especially if there are trunk wounds under the mulch. Once established, these plant pathogens can cause fungal cankers and root rots. Cankers caused by these diseases can encircle the tree, killing the inner bark, ultimately starving the roots, and possibly killing the tree.
  • Insects. Mulch piled against the trunk favors moisture-loving insects, such as carpenter ants and termites, which could colonize and expand decayed areas of the trunk.
  • Rodent damage. Voles and mice may tunnel under deep layers of mulch for shelter. These pests may gnaw on the nutritious inner bark of young trees, girdling the stem. If girdling is extensive, tree death may result. This often goes unnoticed until the following spring when the tree doesn't leaf out.
  • Excessive heat. Similar to composting, thick layers of wet mulch may heat up once decomposition begins. Temperatures within mulch piles may reach as high as 140 degrees. This high heat may directly kill the inner bark/phloem of young trees or delay the natural hardening-off period that plants must go through in preparation for winter.

Correcting Overmulched Trees

If you believe you have a problem with overmulched trees, carefully dig with a hand trowel to assess mulch depth. Remember, 2 to 4 inches of mulch is sufficient on well-drained soils, less on poorly drained soils. A light raking of existing mulch may be all that is necessary to freshen old mulch and break through the crusted or compacted layers that can develop.

If mulch is piled against the trunk of the tree, visually look for the presence of the root flare where the tree meets the soil line. If the flare is buried, it is essential to uncover it. Begin by carefully pulling mulch back from the tree's trunk until the root flare is exposed, taking care not to damage the bark. A good rule of thumb is to pull mulch 3 to 5 inches away from young trees and 8 to 10 inches away from mature trees. Spread excess mulch evenly out to the tree's drip line, checking to ensure the depth does not exceed 4 inches. Research has shown that most trees respond rapidly with improved color and vigor once the root flare is exposed and excess mulch is redistributed.

Below is a series of photos showing where excessive mulch was pulled back from the trunk of a young red maple and redistributed to the tree's drip line. No mulch was removed from the site; it was simply spread out to the proper depth and kept from directly touching the tree's trunk. It is important to note that the amount of mulch used to create the mulch “volcano" was sufficient to properly mulch the tree.

Excessively mulched tree with mulch piled against trunk.

Hand trowel used to pull mulch back and redistribute.

Tape marking the original depth of the mulch.

Excess mulch spread evenly, 2–4 inches deep, out to tree's drip line.

Mulch pulled back from trunk, exposing the root flare.

Tree properly mulched using the same amount of mulch.

A word of caution: you may want to consult with a certified arborist before proceeding with any root flare excavations. Trees are often planted too deep and may have the root flare buried under soil rather than just excess mulch.

In Summary

  • Mulch out, not up! No deeper than the heel of your hand, generally 2-4 inches. Mulch less if soil is poorly drained or using finely textured mulch.
  • Back off from the trunk! Keep all mulch away from the trunk of the tree, allowing the root flare to show just above ground level.
  • Mulch to the tree's drip line, if possible! Remember, the drip line moves out as the tree grows.
  • Go organic! Arborists recommend organic mulches. They provide tree health benefits as they decompose.
  • Keep the trunk dry and the roots moist!

How to Determine the Amount of Mulch You Need

Mulching is an essential spring chore for every gardener. Whether you’re mulching the vegetable garden to cut down on watering, dressing up your flower beds, mulching a playground, or hoping to keep weeds at bay in shrub plantings, it’s important to know how much mulch you need for the job. Getting stuck with too little mulch – or worse, too much! – due to poor estimations has caused plenty of gardeners to scratch their head in confusion. This article introduces mulch calculator formulas you can use to purchase the perfect amount of mulch for your garden each and every time.

Step by step mulch calculator

Follow this simple plan to calculate how much mulch you’ll need for your garden and landscape. The only tools you’ll need are a measuring tape or a measuring wheel and the calculator on your cell phone.

Step 1: Decide on the type of mulch to use

There are many different types of landscape mulch to use on planting beds, from shredded bark chips and wood chips to compost and pine straw. It’s a smart move to base the type of mulch you use on which plants are growing in the area and what’s available to you on the local level. If you’re unsure of which type of landscape mulch to use, you can read all about different kinds of mulches and where to use them in this article.

Once you’ve decided which type of mulch you’ll be using, the following mulch calculator formulas will help you calculate how much you’ll need for any type of mulch.

There are many different types of mulch for planting beds, including pine bark nuggets and arborist wood chips.

Step 2: Determine the square footage of the garden area.

After you’ve settled on which type of mulch you’re going to use, it’s time to determine the dimensions of your landscape bed.

  • To calculate the square footage of a square or rectangular shape garden area, multiply its length (in feet) times its width (in feet).

Length x Width = square footage of a rectangular area

  • To calculate the square footage of a circular area, measure the distance from the center of the bed to the outer edge (this is the radius, R). Then multiply that number by itself. Then multiply the total by 3.14 (π)

R x R x 3.14 = square footage of a circular area

If your garden bed is an odd shape, such as a kidney bean or a wide oval, that’s okay. Just do your best to divide it into a series of imaginary rectangles and circles put together to make that shape. Then calculate the square footage of each of those pieces and add them together.

***If you have multiple areas you’d like to mulch in different parts of your yard, determine the square footage of each separate area and then add those numbers together to get the total square footage you want to cover.

For oddly shaped garden beds, mentally divide them into standard shapes to calculate their square footage.

Step 3: Decide how deep you want the mulch layer to be

Now that you know the total square footage of your bed, determine how deep you’d like your organic mulch layer to be. For tree and shrub beds, I suggest a 3 to 4 inch layer of mulch (when it comes to mulching these plants, more is never better since thick layers and restrict oxygen flow to the root zone). For vegetable and flower gardens, 1 to 3 inches is best.

To make the process easier, I’m now going to give you two different options, based on whether you plan to purchase your mulch in bags or buy it in bulk.

Bagged mulch vs a truckload of mulch

Here in the US, bagged mulch is sold in bags that are measured in cubic feet (cu ft), but mulch sold by the truckload is measured in cubic yards (cu yd). So, how do you know whether it’s more cost effective to purchase bags of mulch or order a bulk delivery that arrives in the bed of a truck? I’ll give you a mulch calculator formula for both bagged mulch and bulk mulch to make the process easy. Once you’ve determined how much mulch you need using both bags and bulk, you can then price them both out to see what’s less expensive.

Bulk mulch amounts are calculated by following the steps below.

Step 4: BULK mulch calculator formula

Use this mulch calculator formula to figure out how much mulch you need when buying in bulk.

Now that you know your square footage and your desired mulch thickness, it’s time to crunch the numbers to determine the volume of mulch you need (don’t worry, it isn’t hard).

To determine how much mulch you need if you’re buying it by the truckload:

1. Multiply the square footage of the bed by the number of inches of mulch you want on top of it
2. Divide that number by 324

Now you have the amount of mulch needed in cubic yards.

For example, if your bed is 50 feet long by 10 feet wide, the square footage is 500 square feet. If you want the mulch to be 2 inches deep, you’ll need 3 cubic yards of mulch.

50 x 10 x 2 = 1000. Then 1000 divided by 324 = 3. 08 cubic yards.

Calculating the amount of mulch bags you need to purchase is easy when you follow the steps in the next section.

Step 5: BAGGED mulch calculator formula

Use this mulch calculator formula to figure out how much mulch you need when buying by the bag.

To determine how much mulch you need if you’re buying it in bags measured in cubic feet, follow this step:

1. Multiply your square footage by one of these numbers, based on how deep you want the mulch to be:
1 inch deep = .083
2 inches deep = .167
3 inches deep = .25
4 inches deep = .33
5 inches deep = .417

Now you have the amount of mulch needed in cubic feet.

For the sample bed that was 50 feet by 10 feet (500 square feet), if you want the mulch to be 2 inches deep, you’ll need 83.5 cubic feet of mulch.

50 x 10 = 500. Then 500 x . 167 = 83.5 cubic feet of mulch.

If the bag of mulch holds 2 cubic feet, you’ll need to buy 42 bags (83.5 divided by 2)
If the bag size holds 3 cubic feet, you’ll need to buy 28 bags (83.5 divided by 3)

Some bags of mulch inform you of the size of area covered by the bag, but most do not.

What’s more cost effective, mulch by the bag or in bulk?

Now that you’ve used the mulch calculator, it’s easy to determine whether it would be more economical to buy your mulch in bags or by the truckload. Using the above example, I think it would be a bit ridiculous to purchase 42 bags of mulch, simply for the amount of plastic bags headed to the landfill. But, it’s also more expensive, too. Here’s why:

  • A 2-cubic-foot bag of shredded hardwood mulch costs an average of $3.99 where I live. At that price, 42 bags would cost $167.58.
  • A cubic yard of bulk shredded hardwood mulch from our local landscape supply yard costs $32.00. For the 3 cubic yards I’d need for my 50 ft x 10 ft bed, the total price would be $96. 00.

You don’t need to be a math whiz to see that, in this example, buying in bulk is substantially cheaper than buying bags. In some other situations, buying bags may be cheaper. The only way to find out is to compare the two options.

For your own garden, do the calculations both using bags and using bulk and price them out before you spend a single cent on mulch this spring. When used right, this mulch calculator system keeps you from blowing your entire gardening budget on mulch…. and leaves you more $$$ to spend on PLANTS! And everyone needs more plants, right?!?

Pin this infographic and you’ll always have this information on your favorite Pinterest board!

For more information on mulching and other garden maintenance tasks, check out the following articles:

Types of landscape mulches 
Pruning blueberries 
Organic weed control methods
Reasons to skip a fall clean up

Do you use a mulch calculator at the start of each season? Has it made you more cost-conscious? Tell us about your experience in the comment section below.

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Why mulch is needed ?

  • Keep soil moist
  • Prevent soil compaction and overheating
  • Weed control
  • Enrich the soil with organic matter, microelements
  • Acidify soil for heathers and conifers
  • With decorative purpose
  • In winter - as an additional shelter

What type of mulch is ?

The most popular types of mulch are shredded pine and larch bark, as well as wood chips. Hardwood bark and chips alkalize the soil, make it more fertile, enrich it with humus and microelements. Softwood bark and wood chips also enrich and slightly acidify the soil. Particularly well suited for heather and coniferous plants. Not suitable for plants requiring alkaline soil - saxifrage, edelweiss, etc.

What are the benefits of larch bark mulch ?

Siberian larch bark looks very similar to pine bark, but has a noble reddish crimson hue. In addition, the bark of Siberian larch is more durable and, accordingly, will retain its original appearance longer.

Basic recommendations for its use are the same as for pine bark.

Which fractions to use ?

On the soil surface, it is better to use fractions up to 40 mm, and on top, if desired, larger fractions. Thus, a double effect is achieved: a fine mulch enriches the soil, while a larger one protects the fine mulch from blowing and performs a decorative function

What should be the layer of mulch ?

For plants in the ground, 5-7 cm is sufficient. For container plants, 1-2 cm. In this case, in most cases, the mulch should not be poured close to the root neck and the stem of the plant. This is permissible only for plants that can withstand a slight depth - currants, gooseberries, clematis, lemongrass, derains, etc.

How much mulch should I plan for when planting ?

The recommended consumption for the main application of mulch is 1 pack (50 liters) per 1 sq. m.

Do I need to use underlay geotextile ?

If only a decorative effect and weed control is important to you, you can use an underlying geotextile. But to improve the structure, composition, microbiology of the soil and to acidify it, you need to use mulch directly on the soil surface

How often should be re-mulched or re-mulched?

Mulch gradually “leaves” into the soil, enriching it. Once every 1-2 years, it is enough to add a layer of 1-2 cm.

Painted wood chips. Is it the same ?

From the point of view of decoration - you be the judge. What do you like best in terms of texture and color? Wood chips also have a beneficial effect on the structure of the soil and enrich it. But according to some reports, coloring particles can negatively affect the microbiology of the soil.

Rules and terms of mulching. How to properly mulch the soil? What size mulch is best. Mulching tree trunks

At first glance, it may seem that mulching is difficult? It's simple: I threw sawdust or some other material on the soil and no problems. However, this is far from the case, mulching is a rather serious job that requires certain knowledge and skills, otherwise it can, on the contrary, harm the soil and plants. Consider the basic rules of mulching and analyze some important points.

Preparing the area for mulching

Before spreading the mulch on the selected area, it must first be prepared:

  1. clear the area of ​​debris and weeds;
  2. Loosen the soil well so that it does not become compacted.

It is recommended to lay the mulching material on the beds 5-6 hours after rain or watering, and in no case should it be trampled into the soil.

Last year's mulch

In spring, last year's mulch should be removed and replaced with a new one, even if it has not had time to completely rot during the winter. The fact is that pests and pathogens of various diseases can be in the old material, so it is imperative to get rid of it.

Last year's material should also be removed because it prevents the soil from warming up. When the threat of return frosts has passed, bulbous plants will also need to be freed from such a shelter, otherwise they will not have enough sunlight for normal growth and development.

Timing of mulching

The soil must be mulched throughout the summer season from spring to autumn. However, in the spring, before doing this, you need to wait for it to warm up completely. Mulch does not allow heat to pass through and, if laid too early, immediately after the snow has melted, the soil will remain cold inside. The optimum temperature for laying mulch is +12 degrees.

In the fall, mulching is done to help plants survive the winter, but timing is also important. After all, if you delay the introduction of mulch, the ground may freeze, and there will be little benefit from such a technique.

Mulch size

Fine mulch is better than coarse mulch:

  • rots faster;
  • pests settle in it less often;
  • it is more convenient to work with.

So chop organic mulch if possible, but that's up to everyone. Some people prefer large mulch.

Layer of mulch

The layer of mulch should not be very thick and dense, so as not to block the access of oxygen to the roots. The optimal thickness is 5-7 cm. However, everything here also depends on the type of soil, for example, heavy loamy soils are mulched with a thin layer - no more than 2-3 cm.

If the soil is too wet, it is better not to mulch at all. in this case, natural topping will not overheat, but rot. Or the layer of mulch in this case should not exceed 2 cm. But gradually, as humus accumulates, the thickness of the layer can be increased.

In autumn, the mulching layer can reach 8-15 cm, while the shaded areas of the garden are mulched with a thin layer, and the sunny ones with a thicker one.

How to mulch

Do not mulch with a pyramid or mound, the mulch should not come into contact with tree trunks, shrubs and plant stems. This will contribute to excessive soil moisture, which in turn can lead to the development of various diseases and rot, as well as the spread of pests (insects and rodents). So the circle of mulch should look like a donut with a hole in it.

Mulching tree circles

Mulch around the tree should be spread in a layer 6-12 cm thick, while the distance from the trunk to the material should be at least 12-15 cm. nutrition will receive the roots of the tree. Thus, the diameter of the circle of mulch should be equal to the span of the tree crown, it is in this area that the roots are located underground. If you do not have the opportunity to mulch the desired area, then it is possible to mulch on a smaller area, but not less than 1.5 m in diameter of the circle.

Mulch and weeds

If weeds have managed to grow through the mulch, although this is extremely rare, cut them as soon as possible before the seeds are ripe and leave to rot right in the garden. Thus, every year the use of weed mulch on the site will be less and less.

Leave mulch for the winter or not?

Organic mulch can and should even be left in the garden over the winter as it stimulates the growth of beneficial soil microflora. Worms and bacteria process organic matter and turn it into humus. In addition, autumn is the ideal time for mulching, the abundance of organic matter after harvesting will allow you to cover at least the entire summer cottage with mulch.

Results of mulching

Mulching is very beneficial for the soil and plants and is considered to be one of the most effective methods of improving the fertility of a site.

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