Mulches on Your Landscape
Between all the plants in your gardens that you have worked hard
to place and nurture is open ground. With the help of mulch, these
spaces can be an asset for weed suppression, soil moisture retention,
aesthetic appeal, and eventual soil organic matter. Without mulch,
it can be an invitation for unwanted plants and drying soil. Mulch
is typically applied to planting beds, tree and shrub beds or rings,
walking paths, and embankments, each of which will require slightly
Mulch can take many forms, though typically it is seen as an organic
material. Here is a list of common mulches, and their advantages.
Compost – Adds soil nutrients and humus.
Wood chips/shavings – Informal/woods/functional sites
with very good moisture retention and weed suppression qualities.
Bark mulch – The best combination of adding course
organic matter, soil moisture retention, weed suppression, and oxygen
Buckwheat and cocoa hulls – Adds a trim appearance
but limited other functions.
Straw- Use for new grass seeding as it shades new blades
and limits erosion. Good under strawberry plants.
Black plastic – Only good for very long term weed suppression
in plant-less open space.
Newspaper – Good, cheap weed suppression.
Pea stone/gravel – Path and drip edge use though weeds
can still establish through it.
For the most effective mulching, the natural or naturally derived
materials or combinations of them will prove best. A compost, bark
mulch, and buckwheat hulls combination will provide very good nutrients
with a lighter appearance. Two to four inches of these materials
will last most of the season, with a light additional cover at the
end of the summer to take your beds through the fall and winter.
Remember, mulch is not directly for the plant. The one exception
is that a mulch bed or ring will keep mowers and grass trimmers
away from plants. Creating just a narrow mulch bed around fence
posts will also keep mowers and trimmers away from them as they
can suffer substantial wear over the years. Black plastic will substantially
limit soil moisture and oxygen exchange and if it is covered by
mulch or chips to mask the appearance, weeds will eventually grow
on it. Dyed mulches give an appearance of something less than natural
in a place where you might be attempting to create one.
Generally, the depth of mulch will be 1-4 inches with a lighter
application for annuals, perennials, and smaller shrubs. Larger
shrubs and trees will tolerate a maximum of about 4 inches between
them. For both plant groups, the mulch should only lightly come
in contact with the plant. At the bed edges, taper the mulch to
meet the edge. In a new planting bed, spreading mulch is a careful
process because of the small size and fragility of the plants. As
the plants increase in size and heartiness and the mulch settles
and becomes an integral part of the bed, this process will be much
easier. Especially in the first season, the mulch may settle as
much as half of the original depth, so adding more by the end of
the season will be necessary. This will also be true especially
if there are significant rains or if you have tenacious weeds.
There are some finer points to spreading mulch and it is important
to heed them as they will effect how the mulch works. As you spread
any mulch, take care not to compress it, usually by stepping on
it. Compressing it will decrease water soaking into the soils and
air movement through the mulch. You can help this situation by placing
some flat stepping stones throughout your beds. Mounding mulch against
a tree trunk, sometimes known as a mulch volcano, is an unnecessary
and harmful tree mulching technique. Within a year or two, the tree
bark will begin to rot, insects will infest, and small rodents will
have a winter home and food. In addition, it is an added expense
for extra material. If you are using wood chips or pea stone for
paths and banks, you will need a little more mulch, 3-5 inches usually.
Though it will be loose at first, these materials will settle and
pack down over time to give firm walking traction. A caveat here
is that if you use chips for paths around the home, some of it will
So step back from your new maple and think about what the base
of that tree might look like in the woods; lots of forest floor
duff, old leaves, broken branches, moss, etc. with more of this
stuff decomposing underneath the loose top layer. Though in a simplistic
way, this is what we are trying to imitate in an ornamental landscape.
Have Creative Fun!
Grounds by Design – Fine Landscapes is locally owned by Matt
Giroux, who is available for design, gardening, consulting, and
photography on your landscape project. Contact Matt
at 371-7093 with your gardening and landscape questions.