The Complete Guide to Landscape Design, Renovation,
by Cass Turnbull
HERBICIDES: Tales of Hope and Tales of Horror
In the following section on herbicides, I often use trade names
as well as the chemical names. I have done this to simplify presentation.
No endorsement of brands is implied or given.
Tales of Hope
While working for the Seattle Parks Department, I took care of an
urban park sandwiched between the freeway and a porno theater. It
had become so overgrown and nasty it deserved not the name of Park.
This park had perhaps fifteen years of grass, morning glory, horsetail,
fireweed and--you name it--growing unchecked on sun-baked clay soil.
The shrubs were suffering Zable laurels, rhododendrons, a row of
great, ten-foot, double-file viburnums and some beaten and baked
trees. During one group project we dug up and pulled out the weeds,
found scores of wine bottles, litter and syringes left by prior
users of the park, and had to dodge rats as we went. Then we sprinkled
dichlobenil (Casoron) ____ granules and covered it over with bark
mulch. In addition, the antique water system was repaired and revived
and the area fertilized. It stayed neat and tidy that entire year--and
with a modicum of regular hand weeding, with water and fertilizing,
it became a pleasant place to sit and eat lunch. Casoron lasts in
the soil for about six months, preventing new seeds from growing
and preventing tiny bits of roots (like morning glory) from re-emerging.
Another tale of hope. The second year of working as a private gardener,
I had occasion to estimate the cost of restoring a landscape that
was being overcome with weeds. Others had tried and failed. Most
discouraging was the grass coming up through the vinca ground cover.
Vinca, or periwinkle, grows as a mat of criss-crossing threadlike
strands. The grass, its stalks protected by the groundcover and
its roots entwined with the vinca's, was tough to thoroughly weed
out by hand. I vividly recall hours of weeding in the rain, the
strands of vinca cutting at my cold, sore hands, and with a rematch
scheduled for next month. I estimated a day and a half a month to
keep this yard looking good--for the first year, anyway.
Then I heard about sethoxydin (brand name Poast ____) a new chemical
that kills just grass. Spray it over non-grass plants (those listed
on the label), it would kill just the grass. Expensive as it was,
I decided to give it a try. In the spring as the new shoots of grass,
as thick as turf, emerged among the vinca, I applied the new herbicide.
I came back next month to find little, if any, grass with which
to continue the fight. Maintenance dropped to one-half day a month
immediately. Poast does not kill all species of grasses or grass
gone to seed. Still it is a powerful weapon.
Another: A rockery overgrown with morning glory, grass, vetch,
dandelions and others, defied hand weeding because the roots were
too tightly crammed under and protected by the rocks. With our weedeater
we mowed down the grass to encourage soft, tender new re-growth.
Then as it grew back we sprayed the whole area with glyphosate (Roundup).
We let it bake in for a week or two, pulled off the dead yellow
tops and replanted. Glyphosate (the active ingredient in Roundup
and Rodeo) is used as a contact spray. This means it kills what
it touches. The treated weeds translocate (move) the chemical throughout
the plant to roots, stems and fruit. It interferes with biological-chemical
processes specific to plants. According to a June, 1986, registration
standard, the Environmental Protection Agency considers glyphosate
to be relatively non-toxic to most non-plant forms of life. According
to the same report, glyphosate shows little tendency to "bio-accumulate."
Data indicate that it does not cause mutagenic (mutations), teratogenic
(birth defects) or reproductive effects.
Roundup binds tightly and quickly to the clay particles in soils.
It is not, therefore, available to poison adjacent plants or leach
through the soil to the watertable. It decomposes by microbial activity
in about two weeks. The soil is then ready to replant with desirable
ornamentals. Many otherwise organic gardeners will, on occasion,
resort to Roundup for these reasons. Since Roundup does not "poison"
the soil, remaining weed seeds will germinate.
Be sure to spray Roundup on young, healthy, growing weeds. It doesn't
work on old, dusty grass and weeds. Dirt inactivates it. Roundup
is good for the un-pullable dandelion in the sidewalk crack. However,
it does not kill horsetail, clovers, and it has a tough time penetrating
the waxy leaves of ivy and holly. Oddly enough, creeping jenny is
unaffected as well. It is still a very powerful tool for the gardener.
Be sure to spray only target plants.
Some nastier chemicals exist for other weeds. For moderate success
on horsetail, Amitrol-T,___(1) For false bamboo, also called Japanese
knotweed (Polygonum cuspidatum), dicamba. Dicamba can also be used
on bamboo (or Roundup can be used instead). Dicamba is known to
move through the soil and kill roots of nearby desirable shrubs.
It is very soluble. Its residues are persistent (two months to a
year). Be careful not to contaminate ground water and don't use
it when rain is likely.
Other tales of hope include the lawn herbicides, which if used correctly
(that is to say, applied at the appropriate time and carefully following
all label directions, sprayed on a shaggy lawn area and not washed
off for two days by the irrigation system or mowed off) will eliminate
broadleaf weeds from your lawn (moss and annual grasses have to
be dealt with separately).
I once saw a fearless gardener spray the steep slope just adjacent
to a new area with "Trimec___" a potent lawn-type formulation
of chemicals. This treacherously steep slope was a maintenance nightmare
of blackberry vines that shot up to obscure the view of the city
which park users expected to see from the bench above. Each year
we were forced to use hand tools and screaming brush blades, at
great risk to life and limb, to clear the bank. The Trimec curled
and killed the young vines in a matter of days, leaving tall grass
to stabilize the slope and look nice for the public.
Tales of Horror
Tales of hope always come with tales of horror. Once a ballfield
attendant applied Casoron to the freshly weeded dirt area of the
baseball field. A rainstorm followed, washing the granules onto
the grass and down onto the neighbor's lawn. The resulting dead
grass and the affected dirt beneath had to be replaced by the city
at taxpayer expense.
In another old city park, several beds that once contained beautiful
old rhododendrons now lie empty. A maintenance laborer who was sent
out to apply Casoron to the freshly weeded bed, tripled the rate
of application to make sure the weeds stayed down. This circumstance
in combination with the fact that rhododendrons (as well as pines)
are somewhat more susceptible to damage by Casoron than other plants,
caused them to die.
Casoron, when properly used, can be a useful tool. More often than
not it is abused by homeowners and landscapers. Usually excessive
application rates just stunt the plants, causing tell-tale yellowing
at the edges of the leaves. One sees it everywhere.
Another tale of horror. A lady determined to rid herself of morning
glory, including the vines covering her rhodies, sprayed them with
Roundup--killing both vine and shrub. Roundup is non-selective--it
kills whatever it touches.
And another: A fully mature and particularly beautiful maple in
a yard next to a prominent viewpoint overlooking the city simply
failed to leaf out one year. Indeed, it was dead. Overuse of lawn
weed killer was the cause. The ingredients in lawn herbicides work
on all broadleaves, be they dandelions or trees, leaving only the
grass unaffected. Since most of a tree's roots are in the top eighteen
inches of the soil, and they extend far beyond the dripline, trees
are far more susceptible to chemical damage than one might suppose.
The potential dangers of all pesticides (herbicides and insecticides
are both pesticides) are assessed in several ways. Scientists evaluate
the relative toxicity (how much does it take to kill 50 percent
of the test animals), whether it collects in the food chain, whether
it degrades quickly or slowly, how it degrades (digested by microbes?
decomposed by light?), whether it is likely to move through the
soil to adjacent plants or to the water table, whether it causes
particular kinds of physical damage to the test animals (e.g., cancer,
birth defects, kidney failure, etc.) with either a single exposure
or through repeated exposures.
Sometimes a particular pesticide will pose a serious threat to some
non-target species. For example, dogs are especially sensitive to
2,4-D, a common ingredient in many lawn herbicide formulations,
and geese and other birds have died browsing on lawns treated for
cranefly with incorrect application of diazinon.
You should exercise caution with all pesticides and herbicides.
The fact that home and garden chemicals appear on the shelves and
are registered with the Environmental Protection Agency (EPA) does
not mean that the EPA guarantees their safety. In 1983, of the 600-odd
chemicals in common pesticide formulae, only four had successfully
submitted all the test results required to indicate relative safety
to humans and the environment. At that time the EPA estimated that
it would take twenty more years to fill the data gaps.
Many test results are based only on analysis of the "active
ingredient." The majority of a bag or bottle of herbicide is
made up of "inert ingredients," which are sometimes other
chemicals. Chemical combinations are unpredictable, and two chemicals
which alone may be relatively non-toxic can be dangerous when combined.
No testing is done on these combinations. The term "inert"
can be misleading. In 1986, sample testing of registered pesticides
turned up "inerts" which were themselves pesticides. An
EPA staffer discovered DDT--outlawed since 1972--listed as an inert
ingredient in some registered pesticides.(2) A secondary ingredient
(POEA) found in some glyphosate formulations is three times as toxic
as glyphosate itself.
There are several tales of horror concerning the validity of test
results submitted to the EPA by chemical companies, and about loopholes
which enable a manufacturer to sell pesticides before all the required
tests have been completed (i.e., conditional registration).
So, don't assume that any pesticide, or any chemical for that matter,
is safe. We simply do not know. Treat them with a healthy respect,
but not paranoia.
If you choose to wage chemical warfare with either herbicides or
insecticides, you need to adhere religiously to several common sense
rules and procedures, whether or not they are comfortable or convenient.
Using Chemical Weapons Safely
First, do your homework. Unlike other do-it-yourself projects do
not read the instructions only when all else fails. Plan to spend
some time reading and understanding the label. Bring it inside,
sit down, use good light, perhaps take notes on mixing instructions.
Take your time. The label is a legal document. If you spray pesticides
other than according to label directions, you are breaking the law.
Anything and everything on the label is there for a very good reason.
They don't make up application restrictions just to be on the safe
side. Label instructions are serious business. Home and garden pesticides
can be as much of an ecological or health danger when abused as
any of the so-called industrial chemicals.
|Suited up for chemical warfare. To use chemicals responsibly
you must dress correctly, whether or not you find it comfortable
If you do your own spraying, use two well-marked (nail polish works
well) spray tanks, one for "bugs" one for "weeds,"
it will help you avoid a serious, serious mix-up. Think about it.
Keep all chemicals in well-marked (original) containers. Never,
ever, ever store chemicals in old food or drink containers. Keep
all such materials locked or shut up in a safe place--like a garage
cupboard, and include with them all mixing paraphernalia like measuring
spoons or cups--which should also be well-marked and used for that
purpose only. Do not use aluminum gear and avoid storing chemicals
in spray tanks--they can be very corrosive.
See chart on Herbicides.
Wear protective clothing, rubber gloves--solid ones, not just kitchen
types, but not ones with cloth linings which may absorb pesticide
particles. Safety glasses and a cloth face mask are in order. This
is especially true when mixing, and pouring materials, and cleaning
equipment--which is when most accidents occur, usually involving
higher volumes and concentrations of chemicals. This may seem obvious,
but people easily forget to "suit-up" when mixing or will
absent-mindedly take off their safety glasses just before opening
the pressurized lid to the tank. Your eyes, nose and mouth absorb
fumes and particles most readily. This is followed by the palms
of your hands, soles of your feet and your forehead. So a hat may
be a wise addition.
Mix small amounts so that you run out on the job. It's unacceptable
to return to the spigot with a tank of unused material. Spray it
all out in the yard. Don't dump it next to your spigot and never,
ever, ever pour excess chemicals down drains, toilets, or sewers.
Are you crazy? Do you want to eat it in your clam chowder?
After you are through, wash your gear and your clothes and yourself--right
Don't ever, ever mix two chemicals together if it's not allowed
in the instructions. It could be a very big mistake. Don't ever,
ever, ever, ever use some "extra for good measure." Know
what plants you're spraying and/or what pests or weeds are the target.
Be sensitive to conditions that affect your spray. On very hot days
liquid pesticides will vaporize into a fine mist and can drift quite
far. Be sensitive to even small breezes. Big droplets from the spray
nozzle will not drift as far as fine mists. With herbicides, keep
that nozzle close to the plant--not waving around up high, as is
commonly shown in TV ads. Buy a shaker for your granular herbicides
to ensure even coverage and so you don't get it all over yourself
and down in your sweaty rubber gloves. Be sensitive to the presence
of pets, wildlife, children, pregnant women, waterways (even if
they just look like that old ditch), and to foraging bees.
My own policy is that chemical intervention should be considered
an option only when it is absurd to employ cultural methods (hand
weeding, mulch, etc.). Sometimes chemicals are used during an initial
cleanup. Avoid using herbicides for regular, basic shrub bed maintenance.
I guarantee that truly responsible use of herbicides is at least
as time consuming, physically demanding (the discomfort factor alone),
and expensive as mechanical control. Additionally, it is brainracking
and the potential for disaster (P.for D.) is, needless to say, considerably
greater. In the vast majority of situations, weed control using
hand-to-hand combat is equally as effective as chemical warfare.
There are specific weeds and certain situations which may be considered
exceptions, but exceptions they are. Pesticides should be the weapon
of last resort.
There are dozens of more commonly used herbicides that are available
to homeowners. I've just told tales of hope and horror about ones
I have dealt with or will use as last resort. The tales of horror
are worse for many other chemicals, especially soil "sterilants"
(I don't want anything to grow there ever!). Herbicides are tools
to use, not abuse.
Think of hand weeding as a game, not a chore. Once everything is
cleaned up, mulched and under control, weeding is not time consuming
or arduous--it just needs to be done regularly. It helps me to sing
the weed song--to the Kenny Rogers tune "The Gambler."
"You gotta know when to hoe 'em
Know when to pull 'em
Know when to walk away
Know when to run"
Read and believe the entire label on all pesticides.
Follow instuctions religiously. Wear protective clothing whether or
not you find it comfortable.
Use chemicals as the weapon of last resort. Non-chemical weed control
makes good sense economically in the long run and you will rest easier.
(1) Because of potential carcinogenic hazard, it is now a restricted
use pesticide available only to licensed applicators.
(2) Committee on Government Operations (US House of Representatives)
1984: Problems plague the Environmental Protection Agency's pesticide
registration activities. 63rd Report. Washington, D.C.: US Government
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