tips & tricks
INCREASED RESISTANCE TO MOLDS,
FUNGI, AND BACTERIA
“ENRICHING A CLONING
AREA WITH CO 2 IS ONE OF
THE MOST EFFECTIVE AND
SAFEST WAYS A GROWER CAN
PREVENT PATHOGENS FROM
ATTACKING THE OTHERWISE
SUSCEPTIBLE CUTTINGS.”
REDUCED TRANSPIRATION
One of the main reasons why cuttings are kept in a
high-humidity environment is because, without a root
system, the cutting’s leaves become the main source of
water control and retention. Without a high-humidity
environment, the cuttings from some plant varieties would
transpire moisture to the point of wilting, and possibly
death, from lack of water. A high-humidity environment
reduces the cutting’s need for transpiration and protects
the cutting from losing too much moisture.
To better understand the relationship between transpira-
tion and CO 2 , we can look at an enriched CO 2 environment’s
impact on the plant’s stomata. Plants absorb CO 2 through
the open stomata on their leaves. Transpiration occurs when
the stomata are open as well. As mentioned, transpiration
leads to loss of water, which is another significant part of
the photosynthesis process. So, to conserve water, plants
will automatically regulate the amount of time the stomata
are open. When an indoor horticulturist enriches his or her
cloning environment with CO 2 , there is more CO 2 available
for absorption when the stomata are open. In other words,
the plant can absorb more CO 2 while trying to limit water
loss through transpiration. Some experiments have shown
that when provided with an increased amount of CO 2 , plants
will not open the stomata as wide, thus reducing the amount
of transpiration. This is a huge benefit for cuttings without
roots in the cloning stage. Any reduction in transpiration is
a large advantage for rootless clones. Overall, increased
CO 2 levels will increase the efficiency of a plant’s water use
which, for clones, can mean the difference between wilted
foliage and good structural integrity.
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grow cycle
It just so happens that the ideal environmental conditions
for cloning (warmer temperatures and increased humidity
levels) are also the conditions conducive to many patho-
gens. Powdery mildew, root rot, and grey mold are just a
few of the nasties that find the cloning area’s environment
perfect for setting up shop. Enriching a cloning area with
CO 2 is one of the most effective and safest ways a grower
can prevent pathogens from attacking the otherwise suscep-
tible cuttings. It is believed that CO 2 is an effective anti-
fungal due to its ability to alter intracellular pH levels.
In other words, an enriched CO 2 environment during the
cloning stage can actually alter the pH of the leaf’s surface,
making it impossible for particular fungi to become estab-
lished. A closer look at many of the products designed to
treat or prevent molds in the garden will reveal that most
of these products are effective because they alter the pH of
the leaf’s surface. When it comes to reducing pathogens in
the cloning area, prevention is key. Enriched CO 2 levels can
prevent problems before they occur and allow a grower to
increase his or her overall success rate.
METHODS FOR ADMINISTERING
CO 2 TO CLONES
There are a few different ways a grower can increase the
CO 2 level in the cloning area. CO 2 burners, compressed
CO 2 tanks, or mycelium bags can all be rigged to enrich
CO 2 levels during the cloning stage. However, too much of a
good thing can be bad. When using a CO 2 system designed
for a large area, a grower should be cautious to avoid the
CO 2 levels getting too concentrated. For clones, CO 2 levels
between 1,000-1,300 ppm should be the maximum. Levels
above this can be counterproductive as the available
oxygen gets displaced by CO 2 . The roots (or potential roots)
need some oxygen to develop and thrive. Growers who
choose to use CO 2 burners or compressed tanks with injec-
tor systems need to have a CO 2 monitor/controller so the CO 2
levels can be kept in check.
Perhaps the best solutions for administering CO 2 to clones
are the CO 2 pads specifically designed for cloning cham-
bers. These pads can be placed directly into a standard
propagation tray and dome and are activated by the humid-
ity within (or when the clones are misted with water). The
CO 2 pads are made from natural chemicals which, when
exposed to humidity, begin to release CO 2 . Since the pads
are made specifically for propagation trays and cloning,