1. Testing For Natural Herbicide, Eliminating The Weeds
Fabian Ho Kai Bin(Leader) , Benson Quah , Myra Koh, Amelia Jane Lim and Lee
Hui xin
Pasir Ris secondary school
The purpose of this experiment is about finding out the best household
chemical that can act as a good herbicide. Household item is tested is to prevent use
of artificial herbicides, 2-4,d. Herbicide is substance that has 2,4-
Dichlorophenoxyacetic acid which is used to kill unwanted plants but research has
shown that one of the most widely used herbicides, Atrazine, which contain 2,4-d,
has been linked to cancers in humans, and sexual deformities in frogs so chemicals
that are used are a combination of household and convenience item as they are less
harmful to the environment as compared to artificial herbicides. The materials used
are household item like distilled white vinegar, citrus oil, salt solution, coke, lime,
rootbeer, clove oil, half-boiled egg, boiled water, tap water, soap, toothpaste, bleach,
juglans which is commonly known as walnut and corn gluten meal which is also
known as cornflakes. Tap water is used for as the control for this experiment. The
other measuring materials are 100 milliliters of measuring cylinder, 200 milliliters
of beaker, filter funnel, filter paper, soil, electronic balance, universal indicator,
lighter, styrofoam cups and the weeds, Phyllantus Urinaria L. The hypothesis made
is that coke is the best household item that can act as herbicides while the other
substance that can act as herbicides are distilled white vinegar, clove oil and lime.
For alkali, soap and toothpaste are the one thought to be acting as herbicides. As
alkaline stuff had not been proven as herbicides, this became one of the aims of this
experiment. When the clove oil was substituted as the herbicide, the weeds used took
no longer than 30 minutes for it to fully become discolored, before dying. This same
result occurred for other similar tests conducted on the clove oil. Several factors
had been taken into consideration, such as cost, eco-friendliness and the speed
which the plant is killed. While bleach, half boiled egg, clove oil, citrus oil, salt
solution and toothpaste can all kill weeds, the item that is concluded as the best
herbicide is the clove oil.
The purpose of this experiment is has shown that one of the most widely
about finding out the best household used herbicides, Atrazine, which contain
chemical that can act as a good 2,4-d, has been linked to cancers in
herbicide. The reasons for the purpose humans, and sexual deformities in frogs
are as listed. Firstly, household items are so chemicals that are used are a
tested is because it is inexpensive, combination of household and
commonly found and it also serve as an convenience item as they are less
alternative for artificial herbicides. harmful to the environment as compared
Secondly, household item is tested is to to artificial herbicides. Thirdly,
prevent use of artificial herbicides, 2-4,d. preventing the use of “ugly” herbicides.
Herbicide is substance that has 2,4- Glyphosate, the ingredient in Roundup,
Dichlorophenoxyacetic acid which is is toxic to amphibians. Glyphosate is
used to kill unwanted plants but research safe for use near mammals, but there is

2. some debate as to whether it is an contaminated with the Monsanto
endocrine disruptor. Monsanto genetically modified canola blown in by
Corporation, makers of roundup, created the wind. According to the Monsanto
a genetically modified canola. The patent, farmers who use their canola
modified canola is resistant to roundup, seed must buy it every year. They cannot
making it easier to treat weeds. This store seed. The chemical will be tested
genetically modified canola can cross on a weed named Phyllanthus Urinaria
pollinate with weeds, making them L, also known as Meniran. Phyllanthus
resistant to roundup. No one knows the Urinaria L is a kind of weeds that has
possible effects of genetically modified small alternate leaves resembling those
food crops intermingling with native of the mimosa tree, disposed in two
plants. As well, Monsanto sued a ranges. The leaves are large at the tip
Canadian farmer whose canola field was and smaller towards the petiole.
Material and Methods
vinegar is 2.86, citrus oil is 4.36, salt
The materials used are household solution is 7.00, coke is 2.54, lime is
item like distilled white vinegar, citrus 2.66, rootbeer is 4.75, clove oil is 6.12,
oil, salt solution, coke, lime, rootbeer, half-boiled egg is 7.90, boiled water is
clove oil, half-boiled egg, boiled water, 7.00, tap water is also 7.00, soap is 6.74,
tap water, soap, toothpaste, bleach, toothpaste solution is 6.84, bleach
juglans which is commonly known as solution is 9.76, walnut is 6.31 in is
walnut and corn gluten meal which is powdery form, diluting with water and
also known as cornflakes. Tap water is cornflakes is 5.55 in its powder form
used for as the control for this after diluting with water.
experiment. The other measuring
materials are 100 milliliters of The pH-value of the soap,
measuring cylinder, 200 milliliters of toothpaste and the half-boiled egg will
beaker, filter funnel, filter paper, soil, be discussed later. The method used is
electronic balance, universal indicator, applying the household item to the
lighter, styrofoam cups and the weeds, weeds after putting the weeds in cups.
Phyllantus Urinaria L. This means that five grams of the
respective chemical will be poured into
The materials that are acidic are the cup that is labelled with the chemical
distilled white vinegar, citrus oil, clove name.
oil, walnut, coke, lime, rootbeer,
cornflakes. The materials that are alkali The procedure for the experiment
are soap, toothpaste and soap. Salt, goes. Firstly, hypothesis is created
boiled water and tap water are neutral before anything is done to have a rough
substance. Most of the substances are idea of what the result of the experiment
either in powdery form, diluting it with would be like. The hypothesis made is
water or it is a solution. that coke is the best household item that
can act as herbicides while the other
The pH-value of the items listed substance that can act as herbicides are
is also tested and the values respectively distilled white vinegar, clove oil and
are as listed below. Distilled white Lime. For alkali, soap and toothpaste are

3. the one thought to be acting as weeds could photosynthesise thus light
herbicides. As alkaline stuff had not is not the factor why the weeds died.
been proven as herbicides, this became
one of the aims of this experiment. Fifthly, the weeds are watered at
Secondly, one hundred gram of mixed a frequency of two days as the weeds
burnt soil is poured into cups of 15. This need it to stay alive also making sure
is to ensure that the amount of soil is the water is not one of the factor why the
same to ensure that the experiment weeds dead. Observations of the weed
would not be affected thus having a fair are recorded before and after the three
test is needed. days as to see the differences thus
having a clear eye of the changes. Last
Thirdly, one Household chemical but not least, the results are recorded on
is pour into each cup with each cup a small booklet to have a reference of the
having the same amount of chemical. result. As to minimise the experimental
This ensures that the experiment would errors that is made, the experiment is
be a fair one. Fourthly, the cups are left repeated for four times using the same
for three days facing the window at the procedures repeatedly, taking the
science lab. This is to make sure the average results in the end of the
experiment.
substances Initial length End length of pH of Did the plant
of weeds weeds soil(acidic die?
/alkaline)
Half boiled 5.0 cm 4.5 cm 7.90 No
egg
Clove oil 5.7 cm 4.9 cm 6.12 Yes
Citrus oil 5.5 cm 6.5 cm 4.36 Yes
Cornflakes 6.5 cm 4.9 cm 5.55 No
Walnuts 5.5 cm 5.7 cm 6.31 No
Toothpaste 5.1 cm 6.1 cm 6.84 Yes
lime 4.9 cm 3.2 cm 2.66 No
Coke 4.9 cm 4.9 cm 2.54 No
Boiled water 6.2 cm 6.7 cm 7.00 No
Tap water 5.5 cm 3.9 cm 7.00 No
Salt solution 4.5 cm 5.0 cm 7.00 Yes
Bleach 4.5 cm 5.6 cm 9.76 Yes
Rootbeer 4.9 cm 3.2 cm 4.75 No
Distilled 5.2 cm 5.5 cm 2.86 Yes
White
Vinegar
Lemon 4.5 cm 4.7 cm 6.74 Yes
flavored soap
Table 1

4. Results at the end of the experiment .Lime,
This table is formed from the average acting as herbicide, killed the weed once
result of all the experiment done. The out of three experiment, thus it may not
results collected have shown that there prove to be an effective herbicide. When
are some convenience items that can also soap acted as herbicide, the weed was
be used as effective herbicides, such as killed in every experiment, thus it is
salt and toothpaste. It also shows that proving to be a quite effective herbicide.
some items have positive effects on the The cornflake did not proved to be a
growth of the plant. All of the good herbicide. Through all the
carbonated drinks used in this experiments, the cornflake succeeded in
experiment aid the growth of plant , also kill one weed.
cornflakes and walnuts are also agents
that promotes growth of the plant. With This table also shows that the
half boiled egg as the herbicide, the weeds might have grown by a little
weed died once out of three experiments before it is dead.
and mould can also be seen growing on
the egg. The clove oil kills the weed In conclusion, research shown
quickly and the weed that died leaves of that acidic substance like lime, walnut
a deep brown colour. and cornflakes is not as effective as
alkaline substance like toothpaste, soap
The rootbeer does not kill the and bleach. So this research shown that
weed but instead it helps it to grow not all acidic substance is herbicides.
better, at the end of the experiment, the The table shows that Clove oil, Citrus
weed did not wilt but remain healthy. oil, Toothpaste, Salt Solution, Bleach,
The salt solution did kill the weed. The Distilled white vinegar and Lemon
weed has wilt and dehydrated .Also flavored soap are substance that killed
some of its leaves fell off. The bleach the weeds.
effectively killed the weed which wilts
quickly but also the bleach increase the Discussion
pH value of the soil by an undesirable
amount. The toothpaste killed the weeds After conducting the experiment
twice out of three experiments, the weed for four weeks, the results observed can
wilt at the end of two experiments. be categorized into 2 different groups,
namely weeds that die after 3 days,
The vinegar changed the pH weeds that are still surviving and have
value of the soil, making it more acidic, grown. However through the various
thus creating an unfavorable experiments, certain trends observed
environment for the germination of remain constant.
plant. The weed that was applied vinegar
died. The weed that was applied with When the clove oil was
coke grew well and did not die at any of substituted as the Herbicide, the weeds
the experiment. The same can be said of used took no longer than 30 minutes for
the weed that was applied with it to fully become discolored, before
cornflake. The citrus is proving to be an dying. This same result occurred for
effective herbicide, it kill the weed in other similar tests conducted on the
every experiment. The weed always wilt clove oil.

5. most likely the cause of the wilted look
Juglans nigra, more commonly and discoloration.
known as walnuts have also displayed
trends that remained constant through When coke, root beer, lime, was
the tests conducted. The walnuts when added, the leaves remained green with
grounded and applied on the soil shows some discoloration at the edges as it
no change at first, but 3 days later, a grew to an average of 10cm. it is most
layer of mold and fungi can be observed likely due to the nutrients added from
at the top of this layer of juglan the drink to the soil that the plant needs.
herbicide. This phenomenon is similar to As the coke and root beer are both
that of the cornflakes although the consumer items, it could have contained
cornflakes promote the growth of weed more amounts of nutrients as compared
rather than stunning its growth. to the level of acidity, hence caused
more growth rather than elimination of
The tooth paste and soap when the weeds.
applied on the plant caused it to wilt
downwards presumably due to the As water, (control) and boiled
weight. The same reaction happened to water was substituted as herbicides, no
the plant poured with bleach. However, visible signs of elimination happened,
in both cases, it is once again possible but rather it grew to an average of
for the 2 substances to raise the PH value 9-10cm. the most likely reason is due to
of the soil to an alkalinity that the weeds the fact that water has proven to be a
are not able to survive in, causing it to necessary essential, and that the plant
wilt before dying. would not survive without it.
The half boiled egg and citrus The agent can be split into two
oil, although killed the weed several groups, the one that promote growth or
days later had also attracted an the one that stunt growth. In between
increasingly large amount of pests, these two groups, it can be split into
hence is advisable to either use it with smaller groups to further understand
pesticide or avoid using it. what is common in the ingredient that
causing the chemical to fell into the
The salt and white distilled category after research and comparison.
vinegar also caused the weed to wilt and
turn brown. This could be because of the Firstly, the one that promotes
dehydrating agents found in both growth. Nitrogen (N) , phosphorus (P) ,
substances. Because water is a very vital potassium (K) , calcium (Ca) ,
component of what the weed needs to magnesium (Mg) , sulphur (S) , boron
survive, without it, the plant would wilt. (B) , copper (Cu) , iron (Fe) , chloride
As there is a higher concentration of (Cl) , manganese (Mn) , molybdenum
water present in the cell as compared to (Mo) and zinc (Zn) are the nutrients
the soil contents added the salt or found in soil needed for a plant to grow
vinegar herbicide substitute, water from well. But firstly, it must be noted that the
the plant cells are lost through osmosis, 13 nutrients which come from the soil,
causing the plant cell to dehydrate and are dissolved in water, and absorbed
therefore become flaccid. Hence, it is through the roots. However, there are

6. mostly insufficient amounts of these
nutrients. This is also the reason why Other chemical such as lime which also
most farmers and gardeners use has acidic properties is instead used in
fertilizers to add nutrients to the soil. maintaining the soil’s PH value. When a
soil has too much acidity, maybe due to
The mineral nutrients can be fertilizers, irrigation of acidic water or
divided into 2 groups, macronutrients decomposition of soil organic matter,
and micronutrients. liming is a common garden term to
reduce the PH value of the soil. It is
Macronutrients can then be necessary as nutrients, needed by plants
further subdivided into 2 more groups, to grow well lessens as the PH value of
known as primary and secondary the soil drops below 6.0 on the PH scale.
nutrients. The primary nutrients, Some of these nutrients include nitrogen,
consisting of nitrogen, phosphorus and phosphorus, potassium, sulphur,
potassium, are major nutrients that lack calcium, magnesium and molybdenum.
the first as large amounts of it is used by As the amount of these nutrients
plants for survival and growth. decrease, the plant will be affected in
terms of its colour, vigour, and ability to
The secondary nutrients, resist and recover from heat, drought and
consisting of calcium, magnesium and traffic stress. By adding lime to increase
sulphur, are much more abundant as the PH value above 6.0, the amount of
compared to the primary nutrients. these nutrients is also, in turn, increased.
Because it can replenish itself through However do note that an excessive
natural and non harmful ways, it is not amount of lime can cause high alkaline
necessary to add fertilizers. Through PH in the soil. If the soil PH exceeds 8.0,
liming, calcium and magnesium are important nutrients such as nitrogen,
largely produced. Sulphur is produced phosphorus, iron, manganese, boron,
during the slow decomposition of soil copper and zinc becomes lesser,
organic matter. resulting in an unhealthy less vigorous
plant.
Micronutrients are the elements
essential to a plants growth although it is In addition, by just looking at the
only used in small quantities as its name components in a raw lime juice, traces of
(micro) suggests. The remainder of the calcium (14mg) , copper (0.027mg) ,
nutrients fell under this category. It is iron (0.09mg) , manganese (0.018mg) ,
also produced by recycling grass magnesium (8mg) , phosphorus (14mg) ,
clippings or tree leaves. potassium (0.1mg) and zinc (0.08mg)
which is needed for plants to grow can
From the previous statement, it can be be found.
concluded that not all acids are able to
kill weeds such as coke and rootbeer. 11 According to researches, water
grams of phosphoric acid, And 30 grams has proven to be a necessary need for
of lime juice can be found on the plants to survive, let alone grow. As
ingredients used to make coke. Modern water acts as a solvent for minerals and
rootbeer has also shown common food, as it cannot be absorbed by the
components as coke. plant in a solid form. Another reason is

7. that the Water is used to transport the hydroxide creating soap and glycerol.
metabolic products from one part to the For bleach, chlorine gas is passed into
other where they are needed. Thirdly, for sodium hydroxide for the bleaching of
the plant to photosynthesize, water is clothing. As for toothpaste, sodium
one of the raw materials that are needed. hydroxide is use as a tooth whitening
And water lost through the stomata agent.
through transpiration actually helps to
cool the plant, in a similar way that Soap itself is a good herbicide because it
humans do through perspiration. This will destroy the weeds surface which
evaporation process also helps the will not allow the plant to photosynthesis
stomata to remain open for the intake of and thus killing it. It also helps to control
carbon dioxide. Finally, water also helps weeds due to the potassium salt of fatty
the plant cells to remain turgid rather acid
than flaccid, resulting in a healthy From the research, it says that
upright plant look rather than a wilted fluometuron; an aryl fluoride herbicide
look. is use to kill weeds in grain and cotton
fields. Therefore, it is inferable that
Cornflakes on the other hand fluoride which is found in toothpaste can
have been known to contain iron, also be named as a weed killer. As for
another essential mineral that plants bleach, due to it being highly alkaline it
require to grow. will detoriate the soil condition and thus
resulting in the death of the weeds.
In conclusion to these
comparisons, it is possible to conclude From an article, it says that using of
that water is the most important factor bleach as an herbicide is not a good idea.
for a plant’s growth but lime actually It is sodium hypochlorite and that its pH
provides the plant with the most is 11.When bleach is added, it will
nutrients it requires to grow. increase the pH value of the soil on the
PH scale, and add sodium in to the soil
However, anti-growth means that it does through the run-offs. In fact, it will be
not provide growth for the weed thus providing an undesirable condition for
making it a good herbicide. The plant to germinate.
following groups are those that are anti-
growth- Soap, bleach and toothpaste, Also another common ingredient found
vinegar and salt, half-boiled egg and in soap, bleach and toothpaste is sodium
walnut, lastly, clove oil and citrus oil. lauryl sulphate which is able to kill
weeds. In most commercial herbicide,
For soap, bleach and toothpaste, they all this is usually one of the active
contain a common ingredient of sodium ingredients used.
hydroxide also known as caustic soda or
lye. Sodium hydroxide is a register Salt and vinegar are also commonly seen
herbicide which helps to control tree as a cheap and abundant herbicide in
roots in sewage system which in turn households. As commercial vinegar
will kill the plant. Preparation of soap contains about 5% acidity, the acid
through a process called saponification, present there affects the weed growth.
where fatty acid reacts with sodium The acetic acid, found in vinegar, is not

8. absorbed into root systems, hence Next for the group of clove oil and citrus
vinegar will eliminate surface growth, oil, they are both known as essential oil.
but perennial plants (plants that live for For clove oil, it contains eugenol which
more than two years) will reshoot. Note is a type of biocide. It is also a type of
though, that commercial vinegar does phenol which is found in citrus oil too.
not exceed 5% acidity whereas vinegars Therefore, the similar substance is
sold as herbicides have at least 10% phenol.
acidity.
The disadvantage of having vinegar as Clove oil kills weed by desiccating the
herbicide is that vinegar can indirectly plant shoot, also from a research it states
kill the plants that are desirable. It is also that since it does not move into perennial
not a hundred percent control over the weeds, none of the substances will
weeds. directly kill the root system. Another
source says that due to the presence of
One of the reasons why salt is used as an eugenol it will kill weeds by disrupting
herbicide is due to the fact that the cells cell membranes and thus causing content
of plants contain a certain amount of like electrolyte to leak out resulting in
water and other dissolved substances. the cell death.
When surrounded by water that contains As for the citrus oil, in most organic
a larger amount of salt, there is a general based herbicide there will be a certain
rule, called osmosis, which water will try concentration of citrus oil being added to
to move through the plasma membrane it. An example is the combination of
to make the concentration of dissolved vinegar and citrus oil. As this product
substances equal. Hence, if there is a tends to be foliar spray which kills most
higher concentration of salt outside the broad leaf weed on contact and many
cell, water from the cell is lost to its other well established weeds that may
surroundings through osmosis. This need a stronger formula like the
same theory applies to how salt can be combination of vinegar and citrus oil.
substituted as an herbicide.
Lastly, it is the group of walnut.
Another reason can be due to A black walnut produce a substance
dehydration. Salt, applied to the ground called juglone (5 hydroxy-1, 4-
around the weed will soak in and the salt napthoquinone). Juglone kills and
will interact with the roots. Water will be reduces plant growth like those found
drawn out to equalize the osmotic under the tree canopies. Juglone is also a
pressure, and the plants will die of toxin, which exerts its effect by
dehydration. inhibiting certain enzymes needed for
metabolic function. In a research article,
However, the disadvantage is that it can it says that plants growing near the black
remain in the soil as run-offs and affect walnut tree exhibits systems such as
distant plant. It also affects the growth of foliar yellowing, wilting and eventually
desirable plant other than the weeds that death. Juglone is present in all parts of
should be eliminated. Salt also defeats the plant.
the purpose of developing a healthy soil.
The experiment for the walnut
generally did not succeed was probably

9. due to the fact that the walnut used was for our experiment, it resulted in
baked. But in researches it is the black substituting baked walnuts as the
walnut and not baked walnut. Being herbicide instead.
unsure of the species of walnuts used
and due to unavailability of the species
Plants Sensitive to Juglone Plants Tolerant of Juglone
Vegetables: cabbage, eggplant, pepper, potato, Vegetables: lima beans; snap beans; beets;
tomato corn; onions; parsnips
Fruits: apple, blackberry, blueberry Fruits: cherry; black raspberry
Landscape plants: black alder (Alnus); azalea; Landscape plants: red cedar; crabapple*;
basswood; white birches; Hopa crabapple*; elm; winged euonymus; forsythia;
hackberry; Amur honeysuckle; Japanese larch; hawthorn; hemlock; hickories; black
lespedeza; lilac; saucer magnolia; silver maple; locust; most maples; oaks; autumn olive;
mountain laurel; loblolly pine; red pine; scotch pachysandra; pawpaw; persimmon; wild
pine; white pine; potentilla; privet; rhododendron; rose; sycamore; most viburnums; Virginia
Norway spruce creeper
Flowers & herbaceous plants: bluebells;
Kentucky bluegrass; daffodil; daylily;
Flowers & herbaceous plants: autumn crocus
ferns; fescue; iris; Jack-in-the-pulpit;
(Colchichum); peony
liriope; narcissus; phlox; poison ivy;
Shasta daisy; trillium
Field crops: white clover; red top grass;
Field crops: alfalfa; crimson clover; tobacco
orchard grass; soybean; timothy; wheat
Table 2 Water is crucial to all lives, including the
plant. If there is not enough entry of
The third experiment was water in a plant, the plant could not get
counted as a failure because no results of the nutrients it needs to survive. Water
the weeds growth can be extracted and helps a plant by transporting important
all weeds have died. It is believed that nutrients through the plant. Nutrients are
the lack of water was the essential cause drawn from the soil and used by the
for the plant to die because all the plants plant. Without enough water in the cells,
that are used for this experiment, even the plants wilt, so water helps a plant
the plant used as a control had died. stand. Water carries the dissolved sugar
Another reason why lack of water was and other nutrients through the plant. So
regarded as the essential reason for the without the proper balance of water, the
plants is due to the fact that the fourth plant not only is malnourished, but it is
experiment, which was carried out after also physically weak and cannot support
the third experiment was a success when its own weight.
the plants were watered, even though the
other variables from the third experiment Photosynthesis is the process by which
was left unchanged to the fourth green plants, in the presence of
experiment. chlorophyll and light energy,
manufacture carbohydrates (glucose)
from carbon dioxide and water. While

10. carbon dioxide is considered essential the half boiled egg thus creating another
for this process, water is also counted as problem, to clean up the fungi. The
critical raw materials that are needed for vinegar changed the pH of the soil thus
photosynthesis. Without photosynthesis, killing the weed, but it may also affect
plants will die. surrounding wanted plants. The soap
effectiveness as an herbicide is not as
Hence, from the third experiment, we good as clove oil. Thus, the conclusion
can conclude that other than the different that has been arrived is that clove oil,
agents (vinegar, salt solution, distilled among all the other tested household
water, etc.) that are used to test the best item is the best herbicide. This has to be
herbicide; water is also an important further research and proven to confirm
agent that affects the growth of the the results.
plants. Particularly for this experiment,
lack of water is believed to be the main Acknowledgements
cause for the plants to die and water is
proved to be an important agent in order We are thankful to Mdm Mok for
for the plants to survive. helping us in the experiment. We are
also grateful to Mr.Kelvin Chee and
While bleach, half boiled egg, Ms.Jasmine Goh in helping us in this
clove oil, citrus oil, salt solution and report and relevant matters in the
toothpaste can all kill weeds, the item experiment.
that is concluded as the best herbicide is
the clove oil. Several factors had been
taken into consideration, such as cost,
eco-friendliness and the speed which the
plant is killed. Clove oil is mass
manufactured; also, it can be easily
bought from most shops. While salt can
also be an effective herbicide, the time
taken for salt to kill the plant is much
longer than clove oil’s. In comparison to
clove oil, the time taken for toothpaste to
kill the weed is much longer. Citrus oil
may be another option as the best
herbicide but due to the cost, and also, it
will attracts ants and other pest and thus
worsen the situation of the numbers of
unwanted pest present. Bleach is also
another very effective herbicide, but as it
is harmful human being and also it will
harm the environment and affect other
plants or crops by increasing the pH
value of the soil, and thus creating an
undesirable environment for any plant
germination. Half boiled egg also can act
as herbicides, but fungus will grow on

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