Note: Descriptions are shown in the official language in which they were submitted.
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3276~5
This invention relates to a horticultural ground
sheet for preventing the seeding and growth of undesirable
weeds in gardens or in any cultivated area reserved for the
growth of desired vegetation.
Gardeners frequently use ordinary polyethylene
film, known in the building trade as vapour barrier, as a
ground cover. This film, which is usually black and imper-
meable to light r is spread over the garden area and ope-
nings are cut in it with a sharp utensil where one wishes
to plant either seeds or seedlings. The seeds or seedlings
are then pushed through the openings into the soil below.
This sheet, while it is moderately successful in preventing
the growth of weedis, is unsuccessful in promoting growth of
the desired vegetation for the following reasons. First
~5 the small space between the stem of the seedling and the
edges of the opening in the sheet often prevents adequate
water flow to the soil underneath. Thus seedlings are
deprived of water, which is of course essential to their
growth. Further if the seedling does grow, sooner or later
the stem will itself begin to seal the opening cut in the
sheet, further compounding the problem. Enlarging the
opening in the sheet is not a worthwhile solution as the
hole reqjuired would become so large as to allow for the
germination of weeds, thus negating the purpose of the
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sheet in the first place.
Secondly beneEicial air circulation in and around
the seedlings and soil is greatly reduced.
Owing to the above conditions souring or acidity
of the soil occurs and undesirable mildew and moss growth
is promoted, principally due to the lack of proper air cir-
culation. The amount of opacity oF a thin plastic sheet
is sometimes insufficient to prevent the growth of weeds
that can survive even in the presence of small amounts of
water. Indeed the inventor has found that weeds or any
other common vegetation require a minimum of about 500 foot
candles of light to grow. Some of the sheets currently
used do not permit this much light to pass. Allowing more
than 500 foot candles of light to penetrate the surface can
~5 allow undesirable weed growth beneath the cover.
The present invention seeks to overcome the
problems with the prior art by providing a thin but opaque
sheet, for example polyethylene, interspersed with a plura-
lity of slits, over its surface.
More specifically the present invention is a hor-
ticultural ground sheet comprising a flexible, sheet of an
opaque material, the sheet being formed with a plurality of
slits, the slits being of such dimensions that water and
air can pass through the sheet but plant shoots cannot grow
up through the sheet and plant seeds cannot pass down
through the sheet.
:
,
In a desirable embodiment the sheet may be formed
with larger openings, to be cut in the sheet when it is
placed over a garden, so that seeds and seedlings may be
pushed through these holes into the soil below. It should
be emphasized that such larger openings can, if desired, be
provided on the production line.
The sheet will typically be made of a plastic
that is as cheap as possible yet able to carry out the
required function. Polyethylene has been found to be
ideal. A black polyethylene sheet has been used in
experiments. Such a sheet is substantially completely opa-
que to light and the slits formed in it was such that the
light that passed through did not exceed about 500 foot
candles. Any colour of sheet that is opaque will generally
be adequate. Black will, of course, absorb heat and it may
be desirable to heat the soil so that the use of a black
horticultural ground sheet according to the present inven-
tion will provide advantages. In other circumstances a
lighter coloured, but still opaque, sheet may be used in
order to avoid heating the soil. Thus the colour can vary
from black through gray to white to vary heat absorption
characteristics.
Aspects of the invention are illustrated in the
drawings in which:
Figure 1 is a general view showing a ground sheet
according to the present invention in use;
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Figures 2 and 3 illustrate various patterns of
openings that may be used; and
Figure 4 illustrates a means of locating and
maintaining ~he larger openings necessary to permit
planting of the desired plants.
The drawings show a horticultural ground sheet 2
comprising a flexible sheet of an opaque material, typi-
cally polyethylene. The sheet is formed with a plurality
of slits 4 that are of such dimensions that water and air
can pass through the sheet but plant seeds cannot.
The opacity of the sheet is such that it will not
allow more than 500 foot candles of light to pass.
Figures 2 and 3 illustrates various patterns of
slits 4 that have proved useful In Figure 2 the slits 4
are regular elongated slits and in Figure 3 relatively
irregular slits. It has been found that slits of approxi-
mately 2 to 6mm, preferably 3mm, in length are desirable.
Figure 4 illustrates the formation of larger ope-
ning~ 6. These larger openings 6, which are for the
planting of desired plants 8 (see Figure l), are maintained
by the use of clips lO. These clips 10 comprise wire
bodies having limbs 12 extending downwardly to penetrate
the soil 14. They maintain the position of the sheet 2 and
thus prevent the sheet 2 from interfering with the growth
of the desired plant 8. As illustrated in Figure l the
sheet may, of course, be retained in position by use of
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weights 16, for example stones.
To use the sheet of the present invention an area
of cultivated ground is covered with the sheet 2 according
to the invention. Openings 6 may be formed, or will
already be formed, to receive desired plants 8. Once the
desired plants 8 are planted rings 10 are positioned to
maintain the openings 6.
In trials conducted the sheets 2 have proved a
considerable success. In a spring growing season an area
of approximately 900 sq. ft. was covered with sheet 2.
Openings 6 were formed and tomato plants planted. During
the whole growing season four weeds were observed. One was
a blade of grass and the three others weeds were of a type
wlth which the area planted was previously infested.
~S The sheet according to the present invention may
be made by conventional methods well known to the plastics
manufacturer. The slits 4 may be formed in the sheet imme-
diately after production of the sheet, for example by
passing the sheet over a roll having cutting projections
~ formed in the desired pattern.
The present invention thus provides a simple
means of greatly improving the yield from any given area of
ground. It is particularly desirable in horticultural use,
for example for domestic gardens. The sheet is such that
watering may be carried out conventionally. That is water
applied to the sheet passes through and is absorbed by the
.,
soil. The sheet may be left on in the winter to prevent
weeds re-establishing themselves. The sheet may also act
as a mulch for the soil.
The sheet may be used as a base material beneath
stones or bark mulch where its ability to allow water to
pass yet suppress weed growth is an advantage.
