Your observation that moss only grows on the
north side of trees tells me you haven't looked
for moss near trees in the southern hemisphere.
Moss is a simple plant and likes to grow in
shady locations so it does not dry out.It is
pretty simple to picture why this is the north
side of trees here and the south side of trees in
Australia for example. The sun's rays strike the
earth's surface nearly perpendicular close to the
As you move away from the tropics, the suns
rays intersect the earth at an angle. Here in
Santa Barbara, California, the sun is not directly
overhead, but to the south, so the south side of
any object will get more sunlight than the north.
This is why moss likes the north side of trees.
The fuzzy texture and shade-loving
characteristics of moss are in part due to it
being a non-vascular plant.
Mosses belong to a group of plants called
Bryophytes. These plants do not have
roots, or the xylem and phloem of vascular plants,
but rather have rhizomes that hold the moss in
place and collect water and nutrients the moss
The "fuzzy" texture you mention helps to keep
the plant from drying out and also helps diffuse
the light used for photosynthesis.
Good question! Actually, moss doesn't only
grow on the north side of trees,it just MOSTLY
grows on the north side. Also, that rule
only applies in the northern hemisphere--in
the southern hemisphere, moss mostly grows on the
south sides of trees. The reason is that in the
northern hemisphere, because of the tilt of the
Earth on its axis, the sun almost always appears
to be a little south of directly overhead. That's
why rooms with windows facing south are brighter
than rooms with windows facing north. This is
important for the mosses because the north sides
of trees (in the northern hemisphere)are shadier
and therefore moister. The south sides of trees
get more sunlight, so water evaporates faster
Mosses need a lot of water for two
reasons. One is that they're not"vascular"
plants --that means that they don't have the
plant version of a circulatory system, and they
can't move water around inside their bodies. All
cells in a moss's body need to have easy access to
water from the environment.
The second reason they need water is because
their male reproductive cells can only survive by
swimming in droplets of water. The
only way these cells can get from one plant to
another is to hope that a raindrop will cause the
water they're swimming in to be splashed onto a
neighboring plant. If the surface that they live
on (like a tree trunk)dries out, the moss will be
unable to reproduce, and it will dry out. That's
much more likely to happen on the sunnier side of
a tree trunk than on the shadier side.
The same rule applies to rocks, fallen logs, or
anything else that mosses might grown on. If it
has a sunny side and a shady side, the moss
will mostly grow on the shady side. In the
northern hemisphere, that's usually the northern
side, and in the southern hemisphere, it's usually
the southern side. If you look closely enough,
though, you'll see exceptions.
The texture of mosses is usually (but not
always!) fuzzy because their leaves have many
little projections on them, like the finger-like
projections on a maple leaf. The moss leaves and
their projections are so small, though, that they
seem fuzzy to us. These projections are probably
to help the moss cells deep inside the leaves to
be as close as possible to external water sources.
Keep asking great questions!
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