What is that?
What good is it?
- Mulching refers to the placement of any material on the ground
- Mulches can be divided into organic and inorganic
- Organic mulches break down over time and become part of the soil,
inorganic ones do not.
- There are so many benefits to mulching trees, it is hard to
even count them.
- Almost all mulches make significant contributions:
- protect trunk from mowers, weedwhackers, etc.
- conserve soil moisture
- impede weed growth
- reduce soil erosion
- restrict soil cracking
- limit salt build-up
- Most organic mulches add further features:
- protect the roots from traffic
- cut down soil compaction
- improve soil fertility & structure
- moderate soil temperatures
- A "green mulch" such as pachysandra or vinca also brings many
of these benefits, although it will compete with the tree to some extent
for water and nutrients.
- When possible, do not grow grass beneath trees, especially young
trees, because it is highly competetive against them and will restrict
- And, oh yes, all mulch looks good.
Mulch ring over the root zone
of a newly planted tree
What problems can mulch cause?
What is the best mulch to use?
- Except for needing to be renewed now and then, mulches give
very few problems.
- Avoid fresh organic mulches, i.e., those that have
not been leached or composted. They often 1) deplete soil nitrogen, especially
if small in size and thickly applied, and 2) can be toxic, especially mulch
made of conifer (cedar, for example) sawdust and bark.
- Many mulches, if put on too thick or against the trunk,
actually tend to increase stress, disease and insect troubles, especially
on poorly drained clay soils.
- Geotextile fabrics can lead to higher temperatures, and
it is hard to get weeds out of them. If you use them, be sure to cut
slits for air and water movement.
- Black plastic and peat moss should be avoided altogether
as tree mulch.
How do you put it on?
- There is no single best mulch, but organic mulches such
as partially composted bark, branches, and leaves are much better for the
tree and often cheaper as well.
Where can I get more information?
- To the tree’s dripline, if possible. Remember, the
dripline moves out as trees grow.
- No higher than the heel of your hand. Anything from
2-6" will benefit the tree, though 4" has proven optimal.
- Not against the trunk. The mulch should look like
a donut when you are through.
ISA, 2002. "Proper
Mulching Technique." For other information, advice and help on
this topic, call offices of your State Urban Forestry Coordinator or University
Extension service, or visit urban forestry web sites.