"The grass is always greener on the other side of the fence."

Revised, 6-25-08. Copyright 2008, Clay Robinson, PhD.
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Objectives:
Is the grass really greener
on the other side of the fence?

Or are these animals demonstrating
the natural desire to have what is
kept from them?

In this picture, it does not appear
there is more, or greener, 
food available.
 

But sometimes,

(Click on the images for larger images in which the color 
differences are clearly seen.)		 cattle grazing through fence
The grass really is greener, as in 
these photos taken along an eastern
New Mexico highway by a fence.

close-up of grass on either side of fence
Notice the greener grass is on the south (left) side of every fence (including snow fences) and in the lower points on the landscape.

Notice the snow fence
in the distance to the right of the road. 
(It is clear in the 
larger image.)		 distant shot of grass on both sides of fence
So, we have seen there are
sometimes greener pastures. 
The question is ...		 WHY?
To hypothesize, we need to know 
a few facts about grass.		 There are a few common factors that affect the color of grass.
  1. The type of grass: cool or warm season, annual or perennial, biotype, etc.
  2. Time of year
  3. Supply of water
  4. Supply of nutrients
Let me answer a few of the 
questions you might now ask.		 The most common grasses on these New Mexico rangelands are buffalograss (Buchloe dactyloides) and grama grasses (Bouteloua spp.).  These are warm-season perennial grasses.

The pictures were taken in June, in the middle of the growing season for these grasses.

The rainfall was plentiful in the early spring, but tapered off in June.

These native prairies seldom require additional fertilizer, or respond to added fertilizer under normal rainfall conditions.
With this information, 
we can now form 
a reasonable hypothesis:		 The most likely reason the grass is greener is 
it has more water for some reason.
snow in snow fence
close up of grass on both sides of fence		 The green areas have more water because
  1. Winds in the winter are commonly from the north.  When the snow blows, it collects on the south (left) side of the fences.  When it melts, more snow equals more water in the soil. (Photo at left was taken in January.)
  2. The lower points on the landscape (especially ditches) receive some water that runs off the road or higher topographic features.
  3. More water available to growing grass equals greener grass.
This change in conditions over a small distance creates a microclimate.  When the microclimate remains different over time, the plant community responds, and here we see different grasses.
Other microclimates you can commonly observe are the types of plants (and their condition) that grow on north-facing versus south-facing facing slopes, or plants that flourish in the sun versus full shade.
These landscape features (even human influences) have been present for more than 40 years.  The presence of more available water on the south side of the fences and in the ditches brought an unexpected result. The grass species are different on the south side of the fence.  The north side has vegetation common to rangelands of the area; buffalograss and grama grasses.
The south side of the fence has grasses that are more commonly found in playas and other wetter environments; primarily wheatgrasses (Agropyron spp) and a few others. wheatgrass on wet side of fence
cool-season grasses The picture to the left was taken in a lawn in Canyon, TX in late February.  Wintry weather and cold temperatures, especially at night are still common.  The green grasses in this picture are cool-season grasses, primarily fescues (Festuca spp.) and some bluegrasses (Poa spp.).  The yellowish-brown (or gray) grasses are buffalograss (Buchloe dactyloides) and Bermudagrass (Cynodon dactylon). 
The picture to the right was taken the same day on the south side of a building.  It shows the blend of cool-season and warm-season grasses in the lawn.

Cool-season grasses stay green most of the winter, but require much more water in the summer than warm-season grasses.

 cool vs. warm season grasses
moss garden in shade Moss is a popular groundcover in Japan, as seen in this garden landscape.  This picture was taken in July.  Notice the only occurrence of green moss is in the shade along the right side, and a small area along the top.

There are two probable reasons. 

  • The shade protects the moss from heat and decreases transpiration from the plant.
  • These areas are adjacent to the roof and may receive some additional runoff.
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