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| Photo courtesy © Darrick J. Smith |
As you’re shopping the seed catalogues and looking
for perennials and shrubs to show sprouts of life, now is also a good time to
give some thought to mulch! And there is
a LOT to think about!
There are many kinds of mulch to choose from. Recently a Bucks County Master Gardener came
up with a list of over 30 types of mulch—and each has its special features and
benefits!
Whichever you choose, there are also right and wrong
(some very wrong) ways to introduce the mulch to your garden. First:
The benefits of proper mulching:
· Weed Control: One chief benefit of mulching is the reality
that mulch prevents weed seeds from getting the
sunlight they need to germinate and grow. A layer of cardboard or wet
newspapers placed under a more traditional layer of mulch is very effective in
weed control. With this purpose in mind,
early mulching is most effective.
· Soil temperature moderation:
If an early warm spring thaw activates seeds or young sprouts, mulch (last
year’s leftovers or a new layer if you got an early start) can moderate the
soil temperature to protect tender plants and seeds from temperature variation
or extremes! This could save a plant’s
life if Mother Nature throws a late freeze/snow anomaly our way! Mulch can protect the soil from (too) early
warmth and insulate it from (too) late cold.
Temperature swings in spring can be killers---and mulch can be the
shield that makes the ultimate difference in a healthy start for a new plant.
· Moisture control—goes
hand-in-hand with the moderation of soil temperature. Bare soil will heat up more quickly because it
lacks the insulating layer of mulch; this will cause baked hard soil to lose
moisture. Alternately, during cool
evenings in early spring mulch will insulate the soil, helping it to retain
daytime warmth. At temperature extremes,
mulch can even prevent frost from heaving plants out of the ground.
· Visual garden appeal: a fresh layer of mulch enhances the curb
appeal of your springtime garden, giving a fresh tidy appearance. However, we recommend you resist the
temptation to use dyed mulch. Dyed mulches
can leach poisons into the soil and be especially damaging to new plants.
· Prevention of soil
erosion: This is especially important on
slopes or in an area where rain or drainage may cause soil erosion—heavy mulches
(think stone or pebbles) can keep soil from eroding.
· Prevention of soil splash: Splashes of mud can damage tender plant
leaves or introduce pathogens that are harmful to the plants. Especially on vegetables and fruits that are
grown for food, this benefit is most appreciated at harvest time.
· Enhanced soil
structure: Organic mulches (think finely shredded bark or wood chips,
straw, or shredded leaves) that break down over time
can improve soil structure. Although not
a substitute for fertilizer (or a reason not to test your soil for proper
nutrients), decomposed mulch can be overall beneficial to soil fertility.
So how can you go wrong?
· Depth: Mulch spread too thick, or too thin, can be
ineffective or counter-effective to the reason for spreading the mulch! If using finely ground (or textured) mulch,
2” is ideal; for coarser mulch, spread
to a depth of 4”. Deeper mulch is
ineffective in moisture utilization and may encourage rodents to take up
residence, or encourage plant diseases. Use
the 2-4” range, along with the square
footage of your garden, to calculate the cubic feet of mulch you should
order—don’t over order (and overspend) and then be tempted to spread a layer
that’s too thick.
· Proximity to plants/trees: Even
professional landscapers have done it – the dreaded mulch volcano! Mounding up soil and mulch around the base of
either deciduous or evergreen trees or shrubs can be harmful – and potentially
fatal -- to the tree or plant. A freshly
planted tree with a mulch volcano around it will be subject to girdled
roots—root growth circling the tree trunk to the point of strangling the
growing tree in the years ahead. (Sadly,
you’ll see new trees planted this way in professional landscapes each spring.) For
a mature tree, the trunk—all the way down to the where the roots flare out at
the soil line—should be above ground and exposed to oxygen which roots need to breathe. If the lower trunk is covered, the situation
encourages insects, mice, voles, moles and even diseases—enough damage to eventually
kill the tree. Wet bark can be a
breeding ground for disease, rot, and fungus.
In autumn, exposed bark down to the root flare needs to harden to
prepare for winter cold—if bundled in mulch, the hardening will be delayed and
the tree will not be ready for winter’s harshness. Always keep mulch or soil at least 3-5 inches
away from the trunk to allow proper circulation so the bark can dry out between
rain events, and so roots have proper oxygen and growth patterns, and rodents
and insects will not take up residence.
· Compaction: If last year’s
mulch is not fully disintegrated, and a new layer of mulch is added, it may prevent
moisture from sinking into the soil—and dampness from escaping. Be sure to fluff up last year’s leftovers
before adding more. You may find that only a small new layer is needed and then
do not exceed the 2-4” limit including last year’s remnants.
· Timing: Mulch is best applied in mid-to-late spring, after
the ground has warmed and dried from winter rains. If applied too early, it can
lead to water-logged soil. If applied
too late, it will be less effective for weed control.
· Type: There are many, many types mulches from which
to choose. Each has benefits and
disadvantages in certain applications.
Black polyethylene used commercially by some fruit and vegetable growers
doesn’t permit passage of water—but does protect plants from soil splash. Some mulches (wood chips and bark) are high
in carbon and actually drain nitrogen from the soil. Compost adds great nutrient benefits to the
soil, but can be a poor performer for weed control. Pick the mulch that works best for your
specific needs.
DO YOU WANT TO LEARN MUCH MORE? While NCAA fans are filing out their
basketball brackets this month, you can select from the Sweet 16 mulches to
pick your Final Four—and the ultimate winner for your garden! Yes, it’s MULCH MADNESS on Saturday,
March 18 when the Bucks
County Master Gardeners invite the public to the Extension office auditorium from
10am-1pm to view/touch/learn about
16 types of mulch and get information about the best ones for Bucks County
gardens. You’ll find out if newspaper,
aluminum foil (!) or wood chips are in your Elite 8 of mulch picks. You’ll learn about application, timing, garden
value, and mulching tools—and you’ll be a Mulch Master after taking advantage
of this opportunity. Plus, you’ll have fun
learning—perhaps an opportunity to make a ‘hoop’ to win a chance at a beautiful planter.
Light refreshments will be available,
light-hearted fun will be included, but most of all, a heavy dose of mulch
knowledge is guaranteed at our Mulch Madness event. Hope to see you there! Bucks County
Extension, 1282 Almshouse Road, Neshaminy
Manor Center, Doylestown, PA 18901.
Questions? 215-345-3283
-- Mary Ann Smith, Bucks County Master Gardener, March 2017
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