Mulch to be Desired
A discussion of the mulching practices
of members of the North Central
District
3/15/2014
Summary Stuff
The idea to create this program was based upon an
article read in an organic gardening magazine. It
talked about the C:N Ratio and how different types of
mulches can have significant impacts on the soil
 In mid January , a survey was distributed to our
NCD ARS members. 24 rosarians responded to the
survey (thank you)
 Additional information presented in this program
is from “Teaming with Microbes” as well as various
internet sites
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What is Mulch?
Mulch is simply defined as a protective covering
spread around plants as well as on top of the
surrounding soil
Mulches are typically categorized as organic or
inorganic
- Organic Mulch: derived from things that were once alive, which can be
recycled back into nutrients by soil food web organisms. Examples include grass
clippings, wood chips, and coco bean shells. Generally need annual
replacement
-- Inorganic Mulch: Stones, gravel, shredded rubber and similar material. They
cannot improve soil fertility but can reduce weeds and are often used for
aesthetic appeal. Generally last for several years.
What types of Mulch are used in the
NCD?
Twenty two different types of mulch were identified; Most
commonly reported included:
 Compost
 Wood Chips
 Chopped Leaves
 Coco Beans
 Shredded Bark
 Grass Clippings
Others Mentioned:
Pine Needles
Landscape Fabric Plastic Stone
Coco Beans with Rice Hulls Ground up tires
Rice Hulls
Leaf Mold
Horse Manure
Shredded Cedar Triple Ground Hardwood
Colored wood chips
Rye Straw
Mushroom Compost
What are the benefits of Mulching?
Top 4 Benefits Identified by recent NCD survey:
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Weed Control
Keep Ground Moist
Visual Appeal
Fortify/Provide Soil Nutrients
Other Benefits Mentioned:
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Improve soil structure
Prevent fungal disease
Winter protection
Keep ground cool
Protect irrigation system from damage and sun degradation
Easier to work in the garden (less mud on the shoes)
Is one mulch better than others?
Favorite Mulches
Rosarians responded with a variety of products!
Wood Chips
Coco Beans with Compost Wild Rice Hulls
Weed Free
Shredded Chopped Leaves with Compost
Coco Beans
Horse Manure
Coco Beans with Rice Hulls Black Colored Wood Chips (Enviromulch)
Rye Straw
Cypress Mulch
Pine Needles
Compost
Leaves/Bark Mulch/Compost
Shredded Oak Bark
Hemlock
FREE
There was no clear favorite mulch identified; Some folks
use different mulches for different plants or areas in their
yard. Clearly, many different types of mulch are used and
seem to meet the needs of the gardener -- or do they??
A Closer Look
Composting is the transformation of organic material (plant matter) through
decomposition into a soil-like material called compost. Invertebrates (insects
and earthworms), and microorganisms (bacteria and fungi) help in
transforming the material into compost. Composting is a natural form of
recycling, which continually occurs in nature. Not all composts are the same.
Leaf mold is a form of compost produced by the fungal breakdown[1]
of shrub and tree leaves, which are generally too dry, acidic, or low in
nitrogen for bacterial decomposition. While not high in nutritional
content, it is a great soil conditioner.
Pine straw mulch Pine straw is a pine needle that has fallen from a pine
tree. Pine needles are used in flower beds as a ground cover for
landscaping. Pine straw helps insulate the soil from temperature
fluctuations and will not move with heavy rains. Pine straw is excellent on
hills and slopes because the needles interlock after spreading and keep the
pine straw from moving. Pine Straw is also referred to as Pine Needle
Mulch and does not exhibit all of the problems of a hardwood mulch.
What impact does mulch have on the
soil?
Organic mulches will decompose over time, feeding soil
microorganisms and releasing small quantities of nutrients
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- Recent studies released by the Ohio State researchers,
suggest that the type of organic mulch applied will impact
soil fertility and plant health
- A good mulch works wonders in imparting soil food web
benefits in to the soil.
- Worms also pull mulch material underground, resulting
in worm castings, better water retention and improved
airation.
Plants are in Control!
Plants secret e
nutrients
through roots
(Exudates)
Microbes
excrete wastes
which are
absorbed as
nutrients by
plants
Microbes
secrete nitrogen
in form of
ammonium
These Exudates
attract fungi
and bacteria
Microbes are
attracted and
eat the fungi
and bacteria
Plants are in Control!
Plants secret e
nutrients
through roots
(Exudates)
Microbes excrete
wastes which are
absorbed as
nutrients by
plants
These Exudates
attract fungi and
bacteria
Microbes are
attracted and eat
the fungi and
bacteria
Mulches can create
a feeding frenzy by
the fungi and
bacteria, and if not
matched by
additional activity by
the microbes, can
result in the
nutrients being tied
up and not available
to plants. This is
also referenced
when disscussing
the C:N ratio
Using the right mulch can establish
dominance of fungi or bacteria
A bit about Fungi and Bacteria
Dr. Elaine Ingham at Oregon State University began publishing
results of studies in the 1980’s that identified a correlation
between plants and their preference for soils that were fungal
dominated or bacteria dominated
In general, perennials, trees and shrubs prefer fungal
dominated soils, while annuals, grasses and vegetables prefer
soils dominated by bacteria
Acids produced by fungi as they begin to dominate lower the
pH and greatly reduce the bacteria
If you can cause either fungi or bacteria to dominate, or
provide an equal mix, then this will help the plants get the
kind of nitrogen that they prefer which will help them thrive
Bacterial vs. Fungal Mulch
A mulch of aged, brown organic material supports fungi; a
mulch of fresh, green organic material supports bacteria
Where and how you place the mulches also plays an important role.
Mulch laid on the surface tends to support fungi, while mulch
worked into the soil tends to support bacteria
Bury most mulch and bacteria will have an easier time. If it is on the
surface, fungi will dominate the decay activity for a while because it is
easier for them to travel from the soil to the mulch
If you wet and grind mulch thoroughly, it speeds up bacterial
colonization. Bacteria need moist environments or they go
dormant. Coarse, dryer mulches support fungi activity. If you want
fungi activity, use brown leaves or wood chips; don’t pulverize them
or wet them much. Place them on the surface
Green and Brown Mulches
The most readily available green mulch is fresh grass clippings, which
contain all the necessary sugars to attract and feed bacteria
• Avoid grass taken where weed killers an pesticides have been
applied
• Don’t pile grass clippings too thick or it will create an anaerobic
condition, interfering with the bacteria you are trying to impact
-Most popular brown mulches are made from leaves saved each autumn; These
will support fungal dominance unless ground up to fine pieces
- Leaf mulches grow more fungi (or grow them faster) than wood chips
- Peat moss is often used as brown mulch; Peat is biologically sterile and should
be mixed with other materials to introduce some microbiology
- Pine needles make a great brown mulch, but only after they have aged a bit as
they contain terpenes, volatile chemicals that are toxic to many plants; Cedar
chips also contain high levels of terpenes
- Wood chips, shredded or chipped bark and sawdust are great brown mulches
and work fine, especially if aged or mixed with organic nitrogen (i.e. green grass)
The C:N Ratio
(as reported in organic gardening)
In order to decay, mulch requires air, water, carbon, nitrogen ; If there is abundant
carbon in mulch but not much nitrogen, a ratio of 30:1 or greater, then the decaying
microbes use up the nitrogen in the mulch, and once gone, will take nitrogen from the
soils touching the mulch (also known as nitrogen robbing)
Recycled Pallets
125:1
Organic Materials
and their C:
Ground Pine Bark
105:1
Fresh Wood Chips
95:1
Hardwood bark
70:1
Fresh Wood Chips with
Foliage
65:1
Pine Straw
64:1
Fresh Fallen Leaves
55:1
Composted Wood Chips
40:1
Composted Yard Waste
17:1
Composted Manure
12:1
Since it is primarily
bacteria that tie up
nitrogen in the soil,
consider using “brown”
mulch practices to
minimize the impact
Others indicate that this
impact is only in the top
layers of soil and not
where the roots of our
roses are.
Other Comments/Notes
-Adding a layer of mulch greater than 3 inches may end up blocking
moisture and air, smothering fungi
- Do not put mulch snug up against stems or trunks, this can cause
microbial decay of the plant itself
- Mulches can excel when they are used in conjunction with compost.
Put the compost down first then cover with mulch. Compost
organisms will inoculate the mulch, and begin to decay it as well.
- You can actually grow your own microbes by soaking fresh grass
clippings, alfalfa, hay or straw in water for three to four days. Pour
this on your mulch and you will increase the nutrient cycling power .
(Remember our “tea bags” from last year??)
- Mulch can prevent weeds because the mulch ties up the nitrogen
and it is not available to the shallow weed roots. Plant roots are
deeper and not as impacted.
Resources to Find Mulch
The #1 Source: Local Rose Society!!!!!!!
Is Your Rose Society Providing this Product??
Other Sources Mentioned:
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Make my own compost
Leaf Mold from Landscape Trucking Company
Horse Farms
City Recycling Centers
Gardener Supply Catalog
Local Garden Centers
The Farms Compost, Caledonia, WI
Mississippi Topsoils, Coldspring, MN
Leftovers from Winter Protection
Triple ground hardwood – Ericsons landscape Supply/Union Grove
Problems with Mulch?
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Formation of mold on top of mulch
Nondegradable materials (tires, stone, wood chips) require upkeep to remove leaf matter
Compost alone doesn’t prevent weeds
Grass clippings/coco beans that are too thick – result in water runoff
Coco beans wash away in heavy rains
Landscape fabric makes it harder to add more roses
Stone is impossible to work with when adding new roses
Leaves didn’t hold moisture
Mushroom compost may encourage blackspot and mildew
Drawback in spring when need to pull back mulch to apply fertilizers
Other Comments from Responders
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Be mindful of what mulch can do to soil and plants
Use mulch that doesn’t need to be hauled off – creating another problem
Be aware of cost and labor to install & how often needs to be replaced
Weed garden well before application – apply Preen for weed control
Remove mulch in fall and reapply in spring
Master gardeners discourage use of bark for perennials or roses
Landscape fabric doesn’t seem to provide enough soil airation and moisture
Weed Daily
Place deep irrigation system under mulch
Be sure to wait for soil to warm up before applying
I put down a layer of worm poop before the mulch goes down
Cultivate mulch annually or it will get compacted and retain less moisture
Summary Comments
- People use a variety of mulches to meet their needs
- The type of mulch used can impact the soil composition and nutrition
- When applying mulch in your garden this year, consider the benefits to
your soil, which ultimately impact the health of your plants
- Different mulches will encourage more fungi or bacteria. Plants have a
preference for one or the other (Roses prefer more fungi).
- Fungi rich soil will provide the nitrogen in usable form for our roses
- You may want to use different mulches in different parts of your yard or
gardens
-- The management of nitrogen in your garden is fundamental to success.
Understanding the impact of mulch is beneficial