NOTE: I thought I would make a post about cannabis deficiencies to serve as a guide to help myself as a new grower and others alike… I use these notes a lot. Most of these are from Ed Rosenthal’s book Marijuana Garden Saver which I highly recommend. Edit: still adding a few things
Feel free to add any information!
(Ca)
CALCIUM (Ca)
How common is it?
Calcium deficiency is rare outdoors except in sandy and very
acidic soils. The deficiency is occasionally found in planting mixes
and is more common in hydroponics. Ca deficiency sometimes
occurs in soilless growing mediums that have not been
supplemented with lime, which is composed mostly of calcium.
Rainwater, river runoff, distilled water and reverse osmosis water,
as well as some tap water, lack significant amounts of dissolved Ca.
This often leads to Ca deficiency unless the water is supplemented.
Some fertilizers are too low in Ca to create an adequate supply.
Symptoms
Ca is semi-mobile so symptoms show up first in newer growth that
fails to properly form and turns brown. Young shoots crinkle and
turn yellow or purple. In severe cases they twist before they die.
Large necrotic (dead) blotches of tan, dried tissue appear mostly on
new growth but also on other plant parts along leaf edges. Necrosis
appears along the lateral leaf margins. Problems migrate to the
older growth, which browns and dies. Stems and branches are weak, lack flexibility and crack easily.
The root system does not develop properly, leading to bacterial
problems that cause root disease and die-off. The roots discolor to a
sickly brown.
Role in plant nutrition
Ca strengthens plant cell walls and therefore stems, stalks and
branches, and it aids in root growth—mostly the newer root hairs. It
travels slowly and tends to concentrate in roots and older growth.
Ca also enhances the uptake of K.
MAGNESIUM (Mg)
How common is it?
Magnesium (Mg) deficiency is common in all mediums and hydro. It
is not common outdoors.
Symptoms
Mg deficiency starts in the older leaves. The veins remain green
while the rest of the leaf turns yellow, exhibiting chlorosis. The
leaves eventually curl up and then die. The edges of affected leaves
feel dry and crispy. As the deficiency continues it moves from the
middle to upper leaves. Eventually the growing shoots change from
a pale green to white. The deficiency is quite apparent in the upper
leaves. At the same time, the stems and petioles turn purple.
Role in plant nutrition
Mg helps support healthy veins and maintains leaf production and
structure. It’s required for chlorophyll production and enzyme
breakdowns.
MOLYBDENUM (Mo)
How common is it?
Mo deficiency is very rare but is more likely to occur in color-
changing strains in cold temperatures.
Symptoms
Mo is immobile so deficiencies appear first on new growth while
older leaves remain healthy looking. The middle and lower leaves
turn yellow. The leaf veins stay green. As the deficiency progresses
toward the shoots the new leaves become distorted or twisted. Mo
deficiency causes leaves to turn pale green, along with retarded or
strange-looking leaf growth. Older chlorotic leaves experience rolled
margins, stunted growth and red tips that move inward toward the
middle of the leaves.
Sometimes Mo deficiency is misdiagnosed as N deficiency.
However, N affects the bottom leaves first. Mo affects leaves in the
middle of the plant first and then moves up to the newer growth.
Excessive Mo in cannabis looks like Fe or Cu deficiency.
Role in plant nutrition
Mo is contained in enzymes that help plants convert nitrates to
ammonia, which is required for protein production.
NITROGEN (N)
How common is it?
N deficiency is the most commonly occurring nutrient deficiency in
cannabis.
Symptoms
N is a mobile nutrient so deficiency symptoms appear in lower
leaves while new growth remains healthy. The leaves yellow and die
as the N translocates to support new growth. Eventually the
deficiency travels up the plant until only the new growth is green,
leaving the lowest leaves to yellow and wither. Lower leaves die
from the leaf tips inward.
Other symptoms include smaller leaves, slow growth and a sparse
profile. The stems and petioles turn a red/purple tinge.
Too much N causes a lush dark green growth that is more
susceptible to insects and disease. The stalks become brittle and
break from lack of flexibility.
Role in plant nutrition
N is directly responsible for the production of chlorophyll and
amino acids, and it is essential to photosynthesis. It is an essential
element of tissue; without it, growth quickly stops.
Without high amounts of N, especially during the vegetative growth
stage, the plant’s yield is greatly reduced. Water uptake slows from
lower photosynthesis due to lower production of chlorophyll. N
issues happen throughout the entire growth cycle. Plants should
never experience N deficiency during vegetative growth. However,
overfertilizing with N causes problems too.
Tapering off the use of nitrogen towards flowering promotes
flowering rather than vegetative growth. However, a small amount
of N is always necessary in order for the plant to manufacture amino
acids, which use N as an ingredient. This supports flower growth
and utilization of P and K. Some “Bloom Boosters” have N-P-K ratios
of “0-50-30.” While high numbers sound impressive, using this
fertilizer too early causes the flowers to be smaller than they could
have been. If there is not enough residual N available, the plants are
not getting the most out of the fertilizer.
In the middle to the end of the flowering stage, plants frequently
show a N deficiency. They’re using the nutrients that were stored in
the leaves and dropping their oldest, bottom fan leaves. To prevent
the deficiency from getting extreme, you can supplement nitrogen
from a fast-acting source at a small or controlled rate, especially if
the fertilizer flowering formula lacks N.
PHOSPHORUS §
How common is it?
Because cannabis nutrient recipes use very high phosphorus levels,
phosphorus deficiency is highly unlikely.
Symptoms
P is mobile so it moves from older leaves to new growth when there
is a deficiency, so symptoms appear first on older leaves. First the
leaves turn dark green and become weak. Then they develop dull
blue or purple hues. The edges of the leaves turn tan/brown and
curl downward as the deficiency works its way inward. The lower
leaves turn yellow and die. This purpling can also be seen on stems
and branches exposed to cool/cold temperatures. The stems and petioles turn purple or red. Some strains, however,
normally possess red or purple stems and petioles, so these traits are
not a surefire sign of phosphorus deficiency. Plants exposed to cold
conditions outside or frequent indoor temperature drops over 15°F
can also exhibit these symptoms. Adverse cold conditions seem to
adversely affect P uptake or availability
Plants use high amounts of P during flowering. Without abundant
supplies, yields suffer.
§
Role in plant nutrition
P aids in root and stem growth, influences the vigor of the plant and
helps seedlings germinate. P is extremely important in the
reproductive stages and flowering.
(K)
POTASSIUM (K)
How common is it?
K deficiency is highly uncommon when using commercial premixed
nutrients and water-soluble nutrients.
Outdoors, light sandy and organic soils without much clay may be
deficient in K because it is water soluble and can leach from the soil
with heavy rains.
Symptoms
K is a mobile nutrient so it can be moved from older leaves to new
growth. K deficiency shows up first on older leaves while new leaves
remain healthy.
Plants suffering from minor deficiencies look vigorous, even taller
than the rest of the population, but the tips and edges of their
bottom leaves die or turn tan/brown and develop necrotic spots.
As the deficiency gets more severe the leaves develop chlorotic
spots. Mottled patches of red and yellow appear between the veins,
which remain green, accompanied by red stems and petioles. More
severe deficiencies result in slower growth, especially when plants
are in the vegetative stage. Severe K shortages cause leaves to grow
smaller than usual.
Larger fan leaves have some dead patches, or necrosis, on their
margins. These leaves eventually turn brown and die off.
Role in plant nutrition
K is necessary for all activities having to do with water
transportation, as well as all stages of growth; it’s especially
important in the development of buds. K aids in creating sturdy and
thick
stems, disease resistance, water respiration and photosynthesis.
K, along with P, accelerates plant growth when added during
Flowering. Vegetative plants need K levels about equal to N levels.
However, Flowering plants react to high levels of K by ramping up
metabolism and growth. Successful Flowering levels of K are up to
four times those of N.
SULFUR (S)
How common is it?
S deficiency is rare. You are not likely to encounter it.
Symptoms
The first signs of S deficiency are yellowing, young leaves. Leaf
growth is slow; leaves become brittle and narrower than usual and
are small and mutated. Buds die off at the tops of flowering plants.
Overall growth is stunted. Some S deficiencies may show orange and
red tints rather than yellowing. In severe cases the veins of the
growing shoots turn yellow with dead areas at the base of the leaf where the blades join. The stems become hard and thin and may be
woody. They increase in length but not in diameter.
Role in plant nutrition
S is essential during vegetative growth and plays an important role
in root growth, chlorophyll supply and plant proteins.
IRON (Fe)
How common is it?
Fe deficiency occasionally occurs outdoors, in planting mediums and
in hydro.
Symptoms
Fe deficiency starts in new leaves, which lack chlorophyll and may
have necrotic spots. This causes them to turn bright yellow except
for the veins, which remain green. New leaves start to experience
chlorotic molting, first near the base of the leaflets, so the middle of
the leaf appears to have a brown mark. The veins remain dark
green. Fe deficiency affects the new growth but not the lower
leaves.
Role in plant nutrition
Fe is necessary for enzymes to function and acts as a catalyst for the
synthesis of chlorophyll. Young actively growing tissues need Fe to
function. Older leaves also require a small supply.
ZINC (Zn)
How common is it?
Zn deficiency occurs occasionally. It often occurs combined with Fe
and Mn deficiencies.
Symptoms
Zinc deficiency is identifiable by radically twisted leaf blades on
new growth, chlorosis and yellowing between the veins of older
leaves. Interveinal yellowing is often accompanied by overall
paleness. During the flowering stage, buds may contort, twist and
turn hard. When the deficiency first appears, the spotting can
resemble that of Fe or Mn deficiency, but it affects new growth.
Zn excess is very rare but produces wilting and even death in
extreme cases.
Role in plant nutrition
Zn aids in plant size and maturity, as well as in the production of
leaves, stalks, stems and branches. Zn is an essential component in
many enzymes and in the growth hormone auxin. Low auxin levels
cause stunted leaves and shoots. Zinc is also important in the
formation and activity of chlorophyll. Plants with high levels of zinc
can tolerate longer droughts.
BORON (B)
How common is it?
Boron (B) deficiency is rare. It occurs very occasionally in some
western and sandy soils. In planting mixes it can be washed out by
overwatering. B is very soluble at pH levels to 6. As the pH rises it
becomes less soluble and is mostly precipitated at pH 7.
Symptoms
The first sign of a B deficiency is the browning or graying of the
growing tips followed by their death. Soon after, the lateral shoots
start to grow but then die. Shoots appear sunburned, twisted and in
a bright green color. The leaves develop small, brown necrotic dead
spots that look like strawberry seeds and are surrounded by an area
of dying tissue between leaf veins. B deficiency resembles a Ca
deficiency but can be differentiated by the small size of the necrotic
areas. Stems and petioles (leaf stems) are brittle and show signs of
hollowness. Roots become stunted and the smaller secondary roots become
short and swollen as the root tips die. The roots are vulnerable to
fungal and bacterial attacks that rot the root hairs and cause
discoloration.
Role in plant nutrition
B is important in the processes of maturation, pollen germination
and seed production. It also aids in cell division, protein formation,
healthy leaf color and plant structure formation. Proper amounts
keep stems, stalks and branches strong and help plant cells maintain
rigidity. B helps Ca remain soluble.
(Cu)
COPPER (Cu)
How common is it?
Cu deFIciency is rare
Symptoms
Cu deficiency first appears in young leaves that exhibit necrosis and
coppery, bluish or gray with metallic sheen coloring at the tips and
margins. The young leaves turn yellow between the veins.
Other symptoms include limp leaves that turn under at the edges
and eventually die and wilting of the whole plant. New growth has
difficulty opening, flowers do not mature or open in males and the
stigmas don’t grow properly.
Copper toxicity is rare but fatal. As the plant approaches death, its
leaves yellow from its inability to use Iron (Fe). The roots are
abnormally sized, then start to decay.
Role in plant nutrition
Cu is essential to healthy plant production, reproduction and
maturity, and assists in carbohydrate metabolism and oxygen
reduction.
SILICON (Si)
How common is it?
Si is not an essential element to plants but it probably helps plants
resist stresses. A lack of it does not cause any metabolic dysfunction
and is likely totally undetectable.
Symptoms
There is no such thing as a Si deficiency. Plants grow well without
it. However, when it is present there is some absorption. It seems to
strengthen leaves, stems and perhaps roots. It also seems to make
the plant less susceptible to fungal and bacterial diseases and insect
infestation. The plant may also increase photosynthetic activity and
increase overall yield.
Role in plant nutrition
Si helps the plant overcome different stresses that occur and helps to
protect the plant from pests and diseases. It aids in growth,
development, yield and disease resistance. It is used to strengthen
stem and branch structure. Abundant amounts of Si may result in
stronger stems and greater resistance to water stress. It helps plants
resist pests by making the tissue tougher to pierce.
Note: Zn, Fe and Mn get locked out when the pH is too high.
These deficiencies often occur together.
