How does it work and how should it be planted?
When Vetiver is planted in single rows along the
contour of
the slope, it forms a dense hedge, effective
in slowing and
spreading runoff water, reducing
soil erosion, conserving soil
moisture, and trapping
sediment and farm chemicals on site.
Because of
the density of the hedge made up of shoots,
water
cannot channel in any one area and spreads evenly
along the length of the hedgerow. This results
in large scale
water absorption and provides slow
seepage of water
through the hedgerow which minimizes
water flow down the
slope and filters sediment,
minimizing soil erosion and
sediment flow. This
sediment filtering characteristic
facilitates the
growth of other species as well as reducing the
movement of sediment which would otherwise have
flown
downslope. Vetiver's characteristic deep,
thick root system
binds soil and makes it difficult
to dislodge under high
velocity water flows. This
very deep and fast growing root
system makes Vetiver
very drought tolerant and highly
suitable for steep
slope stabilization.
Initial planting may require the area to be free
of weeds.
Fortunately, Vetiver grows quickly, becomes
established
under hostile conditions, and its very
deep and extensive
root system provides structural
strength in a relatively short
period of time.
Plants will establish, on average, within 3-4
months
and will be fully effective within 9-10 months
depending on weather conditions and watering.
Ideal planting will take place in well wetted
soil. If not planted
during a rainy season, then
watering of the soil is necessary.
Inadequate watering
may stunt growth; however, this is
generally only
seen when establishing Vetiver in harsh
conditions
such as sand dunes. Plants should be planted
about
10-12cm(4-5in.) apart in erodible soils and 15cm(6in.)
apart in normal soil in a row along the contour
of the slope;
this interval will ensure adequate
hedgerow formation.
Vertical intervals between
rows may vary between 1-2m
(3-6ft.) depending on
the intensity of the slope. Dry soils
may require
periodic irrigation during the first three months.
Vetiver must be unshaded. Tolerance to shading
is minimal
and can cause growth reduction and may
not survive.
What are its advantages over alternative solutions?
Vetiver is a very low cost with very high benefit
to cost ratios.
When used for civil works protection
its cost is about 1/20 of
traditional engineered
systems and designs.
Superior
to grass, iceplant, red apple, ivy, bamboo, and
other commonly used “erosion control" plants
which are
shallow rooted, top heavy, and very invasive,
Vetiver is deep
rooted, fairly light compared to
iceplant and red apple, and
has shown no invasive
characteristics. Because iceplant and
red apple
are succulent plants, they hold large amounts of
water, making them much too heavy for their shallow
root
systems to support in the event of heavy rains;
this renders
them quite ineffective for erosion
control purposes.
Additionally, iceplant, red apple,
and ivy create fire hazards,
as the green, leafy
outer layer of the plant hides the ever-
increasing
mass of dead, fire-prone undergrowth. Regular
grass
becomes extremely heavy when wet, and frequently
slides on slopes due to its very shallow root system.
Bamboo also has major deficiencies which greatly
inhibit its
ability to control erosion. First,
bamboo is very topheavy and
has a shallow, bunch-type
root system which cannot
effectively support its
canopy. Bamboo also grows in clumps
but fails to
form a hedgerow, allowing water to easily pass
through, concentrating at the gaps between clumps
and
intensify erosion. Furthermore, the bunch root
system tends
to destabilize soil beneath it.
Other erosion control plants such as trees take
years to
develop a root structure, most of which
are not nearly as
extensive as Vetiver. Additionally,
Vetiver roots are, per unit
area, stronger and
deeper than tree roots.
Alternative,
non-living "solutions" to
erosion control may
include straw mats, jute, concrete,
and bare soil, but none
come close to matching
Vetiver's erosion controlling
properties. Straw
mats do not last very long and do very little
to
control soil erosion. Straw also introduces a multitude
of
additional problems such as fire hazard, spreading
of weed
seeds, and the fostering of rodents. Concrete
has a finite
lifespan, as it cracks and eventually
crumbles away from the
soil it was meant to protect.
In addition to its high cost and
unsightly appearance,
concrete funnels water downslope
causing more erosion
problems.
The very deep and fast growing root system makes
Vetiver
very drought tolerant and highly suitable
for steep slope
stabilization.
New roots grow from nodes when buried by trapped
sediment. Vetiver will continue to grow up with
the deposited
silt eventually forming terraces
if trapped sediment is not
removed, unlike other
plants which may smother and die.
Vetiver maintains tolerance to extreme climatic
variation
such as prolonged drought, flood, submergence
and
extreme temperature from -14C to +55C (7 to
131F)
exceeds most grass, iceplant,red apple, bamboo
and many
tree varieties.
Unlike many plants, Vetiver has the ability to
re-grow very
quickly after being affected by drought,
frosts, and fire. - See Photos
2, 3
Where
does Vetiver Grass grow?
Vetiver typically grows in tropical, semi-tropical,
and
mediterranean climates, but may grow anywhere
that does
not experience freezing temperatures
for prolonged periods
of time or where soil does
not freeze. Vetiver also tolerates a
wide range
of soil types and conditions from river banks to
sand dunes with a wide range of soil pH levels
and annual
rainfall.
Vetiver
tolerates extreme climatic variation and
temperatures
from -14 to 55 degrees C or 7 to 131
degrees
F.
In frosty
weather, the top growth dies back or becomes
domant and turns purple; however, roots
will not become
dormant from cold until soil temperature
reaches about 5
degrees C or 41 degrees F. Extreme
temperature cases
include plants in Australia where
growth was not affected by
severe frost at -14
degrees C or 7 degreesF, in Northern
China where
Vetiver plants survived for a short period at -22
degrees C or -8 degrees F, and in Georgia where
plants
survived soil temperatures that dropped
to -10
degrees C or
14 degrees F.
Vetiver will sustain growth in areas of annual
rainfall between
10 inches and 200 inches.
How
controllable is Vetiver and will it spread?
Our
plants, species Chrysopogon zizanioides, are
sterile
and completely
non invasive. These plants do not produce
seeds and will not spread.
Though
Vetiver is an extremely hardy plant, it can be
easily
controlled or removed if necessary. Vetiver
grass can be
destroyed
easily by application of Roundup or by cutting
off
the plant below the crown(the base of the
plant). |
Vetiver being implemented to stabilize a hillside
in Santa Barbara, California |
Does
Vetiver require maintenance?
Minimal
maintenance is required to establish Vetiver
grass.
Watering:
Initial periodic irrigation for the first 3 months
is recommended as is weeding. In dry
weather, plants must be watered every day during the first
two weeks after planting and then every second day. Watering
should occur twice weekly until the plants are well established.
Once established, Vetiver plants require no watering.
Replanting:
During the first month after planting, it is
necessary to replace all plants that fail to
establish or that wash away. Continue such inspections until
the plants have suitably established.
Weed
control: Control weeds, especially vines, during
the first year. DO NOT USE RoundUp
(glyphosate) herbicide. Vetiver is extremely sensitive to glyphosate,
so it should not be used to control weeds near Vetiver plants.
Fertilizing:
On infertile soil, DAP or NPK fertilizer should
be applied at the beginning of the second wet
season.
Cutting:
After five months, regular trimming is important.
Hedgerows should be cut down to 15-20cm(6-8inches)
above the ground. This reduces the volume of
dry leaves and promotes growth of new shoots.
Trimming also minimizes fire danger and improves
appearance. Cutting can be done two or three
times per year, as long as the grass has long
leaves during the wet season.
Where
is Vetiver currently in used?
Vetiver
has been used for over 100 years and is currently
widely used in Africa, Asia, the Pacific Islands,
and Latin America, and has begun to find implementation
in the United States.
Information and photos used with permission of The Vetiver Network International |
