There is the adage that a weed is simply "a plant out of
place." There is a quotation in Celia Thaxter's "An
Island Garden" attributed to a Mrs. Getty that goes,
"A better definition would be, 'A plant which has an innate
disposition to GET into the wrong place' . . . the essence of
weed character - in plants as in men. If you glance through your
botanical books you will see often added to certain names, 'a
troublesome weed'. It is not its being venomous or ugly, but its
being impertinent - thrusting itself where it has no business
and hindering other people's business [that makes a plant into a
weed]".
The U.S. Bureau of Land Management, while not as poetic, defines
weeds as "non-native plants that have adapted to a new
area." They are in balance with nature in their native
areas where they are held in check by the various indigenous
pests and pathogens. In essence, weeds are a problem BECAUSE
they are out of place.
This section is about weeds and their place in the garden, weed
biology, weed prevention, and weed control.
Annual weeds reproduce only by seed and live just one season.
In a period as short as a few weeks or months, they germinate,
shoot up, blossom, set seed and die. Winter annuals germinate
in the fall, mature in the winter, and die early summer. The
seeds remain dormant until the fall. Summer annuals germinate
in the spring, mature in the summer, and die in the fall. The
seeds remain dormant until the spring.
Annual weeds characteristically produce a great number of
seeds. These seeds have the ability to become established in a
wide range of environments and to remain viable over an
extended period of time. Control of annual weeds, for the most
part, is dependent upon the control of the seeds.
Biennial weeds reproduce by seed and live for two growing
seasons. They sprout and undergo vegetative growth during the
first season, then flower, set seed and die in the following
season. Control of biennial weeds is centered on control of
the plant in the first growing season before it has a chance
to set seed.
Perennial weeds reproduce both by seed and vegetatively. They
are the "thugs" of the garden and they can take over
large areas of the soil in little time. They produce new top
growth from buds located on the root stock. The root stock can
be bulbs, tubers, rhizomes, stolons, crowns or taproots.
Control of perennial weeds is dependent upon the control of
the root stock buds.
This sub-section is about the ways weeds, as a group, impact
on the garden and the biology and/or ecology of specific weeds
in the home garden. Appendix B, the
Recommended Reading section of this FAQ, also lists a number
of references. Knowing the characteristics and life-cycles of
those plants counted as weeds is the starting point in their
control.
Equisetum or Horse Tail is an invasive perennial that is
closely related to the ferns. It grows on extensive and
fragile rhizomes. They are extremely difficult to remove from
the soil once they have become established. Any of the
remaining bud bearing stem or rhizome pieces have the
potential to become new plants.
Map out the area with the equisetum and plan to garden
elsewhere until the problem can be finally resolved. Remove
all of the top growth, rake up any stem pieces, and get that
material out of the garden. Dig out as much of the rhizome
system as possible. Repeat the process when you see new
equisetum stems breaking the soil surface. Be prepared to
repeat the removal of top growth and the digging out of the
rhizomes a number of times. Eventually, the rhizomes weaken
and die.
This sub-section is for materials on the various ways to
prevent or minimize weed problems in the garden. For the most
part, weed prevention involves the use of a physical barrier
to keep weeds and their seeds away from the garden soil. This
section is mostly about the different materials that are
appropriate as barriers and the ways they should be used.
Cultural practices to prevent or to minimize weed problems are
included as well.
Hot composting will kill most weed seeds. Cold composting will
not. All areas of the compost pile must heat up to at least
140 F, the "thermal death point", to kill the seeds.
Newspaper is effective as a barrier keeping incoming weed
seeds away from the soil and, at the same time, keeping light
away from the weed seeds already present. The soil is first
hand weeded, cleaned, raked smooth, and watered. Three to four
days later, the soil is again hand weeded to clean up any
weeds that might have sprouted as a result of the disturbance
to the soil and watering. Then lay down about six layers of
newspaper overlapping so there are no thin spots. Cover with a
2"-3" layer of well composted organic material as a
mulch and give a light soaking.
The compost mulch looks better, it keep the newspaper in place
and it provides a measure of protection. At one time,
newspaper ink was petroleum based and would have injured the
soil environment. The newer inks are based on vegetable oils
and are considered O.K. The use of newspaper with colored inks
should be avoided.
This sub-section is about the various ways to control weeds by
pulling or digging out, cultivating, and/or mowing. It is
about the advantages and disadvantages of these various
mechanical control methods and when their use is appropriate.
Top growth generates plant nutrients which, for the most part,
are stored in the roots. Chopping off top growth of weeds is
another way to achieve control _if_ you chop at the right
time. In the case of annuals, remove the top growth just
before it sets seed. Plant energy at that time is being
channeled into flower and seed embryo production with little
left over to replace top growth.
In the case of perennials, the removal of top growth forces
the roots to give up nutrients to develop new stems and
leaves. There is a limit to how many times roots can initiate
new foliage in a single season.
This sub-section is about the various ways to use fire and/or
heat to control weeds in the home garden. Primarily, this
includes soil solariazation and flaming. Some material on
prescribed burning is also included, not because it is
considered an appropriate control measure in home gardens, but
because some of the issues have relevance to a broader
understanding of weeds and their control.
Soil solarization is a clean, environmentally friendly and
efficient way to clean up seed infested soils prior to
planting. Flaming, if done properly, can be a clean,
environmentally friendly, and efficient way to control
seedlings and adult plants. Prescribed burning is primary for
the rejuvenation or clearing of prairies, meadows, or open
fields. . . not something to be done by the casual home
gardener!
Soil solarization is straight forward and effective. The
"thermal death point" of weeds is 140 F (60 C).
Solarization uses trapped solar energy to raise the soil
temperature to that level. Wait until the average daytime
temperatures are 85 F (29 C) or higher. Cultivate and rake the
soil level, remove the large clods, and irrigate well. Wait 2
weeks for surface seeds to germinate, again cultivate and rake
smooth. Give another deep irrigation and tarp with 2 mil clear
plastic. Bury the edges of the plastic to give a tight seal
and solarize for 4 weeks. Once the plastic is removed and the
soil has dried somewhat, it is ready for planting.
Appendix B cites a concise booklet
by Hesketh and Elmore that spells out the details.
It is well understood that weeds are a problem in gardens
because they compete with the intended plants for nutrients,
moisture, light, and site. It is also true that the intended
plants can and do compete with the weeds. Complementary
plantings have been defined as plantings that "occupy an
environment or space _not_ occupied by crop plants which would
otherwise be open for invasion...by weeds...and other
uninvited guests". Competitive plantings are those
plantings installed deliberately to reduce the nutrients,
moisture, or light to control weeds.
This sub-section is for material on the use of complementary
and competitive plants in the home garden as control agents
for weeds.
The term "allelopathy" refers to the ability of
certain plants to produce toxic substances that inhibit the
growth of certain other neighboring plants. There are a number
of plants that show alleopathic effects on weeds.
See "Common-Sense Pest Control" by Olkowski, Daar &
Olkowski.
Biological control includes the use of insects, pathogens,
fish, geese and grazing animals to suppress weeds. Goats
and/or geese have been used for centuries to suppress weeds in
gardens just as fish have been used to suppress aquatic weeds.
The practice of using beneficial insects or micro organisms to
suppress weeds is relatively new. This sub-section is for
materials on all of these biological agents to suppress weeds
in the home garden.
Mycoherbicides are living fungi or their products and they are
useful in suppressing certain weeds. Apparently they are
relatively target specific and wouldn't work in generalized
applications.
All of the synthetic herbicides are prohibited for use on the
land or crops in the Certified Organic Crop program.
Herbicidal soaps and horticultural oils are the only
herbicides that are permitted on Certified Crops or are
considered appropriate for use in organic home gardens. This
sub-section is about the various ways to use these materials.
There is no good and easy way to get rid of Poison Ivy. The
plant, _Rhus radians_, is a woody perennial that may grow as a
small shrub or a high-climbing vine. It reproduces as shoots
off of creeping roots and by seed. The toxin that causes the
blistering, urushiol, is contained in all parts of the plant.
It is very potent and the material resists composting. It can
stay active for a long time.
Physical contact with Poison Ivy should be avoided and if you
are going to work with the plant you should wear protective
clothing. If you are trying to weed by hand, keep in mind that
every last piece of remaining root with a growth bud has the
potential to make a new plant. Also, Poison Ivy shouldn't be
burned - the toxin can be carried by the soot particles and
inhaled. This could cause a strong reaction. Goats will eat
Poison Ivy but then they need to be bathed and its back to the
issue of avoiding physical contact with the urushiol.
The OCIA's International Certification Standard prohibits the
use of all synthetic herbicides on certified land. (See Appendix A). The home remedy
herbicides based on salt or acid can do serious harm to the
soil organisms and they should be avoided. On a practical
basis, spot application of Roundup may make the most sense. It
is relatively safe to use but it is certainly not organic.
If you are going to use Roundup, apply the material as a very
coarse spray to minimize drift or swab the material directly
onto the foliage. Keep it off everything except the foliage
and don't soak the soil. Apply when the plant is in the fruit
or flowering stage. The plant needs to be active to
translocate the material from the foliage to the roots. If the
ivy has grown into a large canopy, clip the vines 2-3 feet
above the ground, two weeks later spot treat the stubs and two
weeks later spot treat again. Read and follow the directions
on the label. Keep the material off of everything except the
Poison Ivy.
Wear protective clothing and avoid physical contact with the
Ivy and with the Roundup as much as possible. Cut up, bag and
seal all of the pieces and put it out in the trash. Keep it
out of your compost pile. Disinfect your tools, wash or
discard the protective clothing. Shower immediately after
working with Poison Ivy using lots of soap and water. Keep
ahead of Poison Ivy. It's the older plants that are the more
difficult.