There has been discussion of the use of Cedar mulch and can
it be dangerous to the plants? Really
that depends on many variables but lets look at some of the known issues, the
process it inhibits and some alternatives.
Sensitivity -Some people may be sensitive to the cedar
fragrance, and they may find that it exacerbates allergy symptoms through
either contact or smell.
Decomposition - Cedar will draw away nitrogen from the
soil. Typically only a problem when
mulch is tilled into the soil. Some argue
this is a myth but for any of us who have used cedar extensively can attest
that shredded cedar mulch decomposes quickly and requires it to be removed each
year for fresh much. An option is add it
to a compost pile the year prior and let it begin to decay and if your compost
is ready add it to the soil your planting in.
Make sure to take a pH reading of the compost before using it and
compare it to the soil your planting in.
Acidic soil types - Cedar and pine mulches can add acid to the
soil. If you already have a low pH level
cedar mulch can cause a problem. You may
want to add wood ash or lime to the soil if amending with cedar mulch.
Wet areas - low beds or wet spots can create an addition
issue, but when adding mulch to it the problems grow significantly by promoting
root rot.
Young plants - Cedar has been found to be toxic to young
plants and seedlings. Make sure if wanting
to use cedar it is not in sawdust form or do not use on plants that have very
shallow root systems such as celery or asparagus.
Beneficial bugs - The biggest benefit to cedar is it
naturally repels insects. But not just
those pesky ones but also ladybugs and mantis, the ones we want around our
plants.
So what is happening it the soil and the hubbub about
Nitrogen. We often use words inaccurately
and using Nitrogen as it is, is one of those.
During natural decomposition you have organic material and to break down
it needs oxygen, water and bacteria. The
oxygen and water start the process of decay, but decay is not enough. Plants do not have mouths so they need to
have their food is a water soluble form.
The decaying is a mixture of organic material, oxygen and
water this process is called nitrification and creates Nitrites. Once it reaches 72-78 degrees the bacteria
move in and look for the Nitrites. It is
theses Nitrites the bacteria need to create Nitrates. Nitrates are what the plant needs.
Back to the Cedar, this process takes longer, a lot longer
and with natural inhibitors already in the wood it takes more for the process
to take hold often directing the bacteria away from materials already needing
to be converted and the essential oils in Cedar have been shown to kill these
bacteria. So now we need to amend the
soil and we find ourselves in the catch 22.
So what can you do?
Cedar mulch is fine to use but on the balance of nature, sustainability
and conservation you might want to avoid shredded cedar mulch except for trees,
and hedges and perennial gardens based on items discussed if you want to use
cedar in your vegetables choose cedar bark or chunk type mulches and be sure
that no coloring has been added. Many
cedar mulches have a red dye added to give them a red appearance, cedar is
actually an off orange, tan to brown color.
Remove the cedar before planting the next season and
compost. Replace with fresh mulch each
year. Also water the ground heavily prior to placing mulch down. After the mulch is down it will take up to
10x's more water to get it down to the roots of the plants.
Another option is to lay strips of ground fabric between
plants, about 6" away from the base of the plants and place most of the
mulch along those strips, keeping a thin layer near the plants. Square foot planting will also reduce water
consumption because the plant leaves will assist in keeping the soil at the
right temperature and maintain water levels.
A good example would be zucchini.
A plant that requires to be planted in full sun but the leaves are often
so large they shield the ground. These
large leaves serve multiple functions, photosynthesis and providing proper soil
protection for the things the plant needs.
The sun is for the flowers, once set and pollinated it has done its job and
now produces the fruit. Mulch is not a
huge help here.
If you are like me and love raised beds mulch may not be
much of a help. Often mulch will keep
soil too wet and root rot will be a big problem. My suggestion here is use leaves. If you have a leaf shredder save a pile from
the fall and use that as mulch. It retains
the same amount of water as the mulch, and it restricts weed growth.
No matter what you choose, keep in mind what you place in
your gardens can always benefit or hinder your garden and each season needs to
be addressed each year. Meaning more
rain less mulch or less rain more mulch, also keep an eye on where you get your
mulch. In recent years there have been
reports of lead in mulch coming from
China and India as well as Canada, it is always a good idea to read the label
or visit your local garden center, many of which sell locally produced mulch
products and often cost far less than a per bag from a chain store, unless you
only need to do a small area. A cubic
yard of mulch (about a ton) usually cost me about $35.
Happy gardening, farming and eating!