Marijuana is dioecious, being either male (pollen producing) or female
(ovule producing). Unseeded female marijuana flower buds
(sinsemilla, Spanish for “without seeds”) are more THC-potent than if
they were allowed to go to seed. Removing male plants as soon as
they are spotted, will ensure they do not pollinate females.
Occasionally a hermaphrodite (bisexual) plant with both male and female
flowers will occur.
Both male and female plants go through a pre-flowering stage.
Pre-flowers appear after the fourth or fifth week of vegetative growth
if you are growing from seed. Check the fourth or fifth node,
counting from the bottom of the plant. A node is where leaves and
branches grow. Pre-flowers can be found at upper end of the node
union. Small and difficult to see with the naked eye, pre-flowers
are best observed with a 6-10X magnifying glass.
The female pre-flower is the classic pear-shaped calyx with two white
hair-like pistils protruding out the top. However, all
pre-flowers do not grow pistils until well after pre-flower calyxes
have emerged. This is why you should wait until the pistils show
before you can determine sex. But wait, it gets more
complex. Some female pre-flowers never produce pistils!
When the female pre-flower does not produce pistils, such plants are
more difficult to distinguish from male pre-flowers. In this
case, hermaphrodite tendencies could surface and it is best to wait
until flowers actually form when flowering is induced by long 12-hour
nights and 12-hour days.
Plants will most certainly grow to be female plants that demonstrate
female pre-flowers providing they follow a normal growing season.
The second time a plant naturally distinguishes its sex is when days
grow short and nights long. Indoors, autumn is simulated with a
12-hour-long night and 12 hours of daylight. This light regimen
induces plants to flower. They will show visible signs of
flowering in one or two weeks. Plants grown hydroponically often
show signs of sex before soil-grown plants. You will see calyxes
and pistils growing from numerous nodes. This transformation from
vegetative to flowering growth takes longer outdoors because the nights
grow longer a few minutes each day. Flowering should be triggered
outdoors around the end of August through the mid September.
When plants start to flower, you can see other changes in growth
patterns, internal plant chemistry also changes. Stems elongate,
leaves grow progressively fewer blades, cannabinoid production slows at
first then accelerates; flower formation is rapid at first then
slows. Nutrient needs change as growth stages change.
Plants focus on flower production rather than vegetative growth.
Green chlorophyll production, requiring much nitrogen, slows.
Phosphorus uptake increases to promote floral formation. About
the time you see the first pistils form is when to change the
fertilizer from a high-nitrogen “grow” fertilizer to a
high-phosphorous-potassium “bloom” mix.
Male pre-flowers show about the same time and at the same place as
female pre-flowers, in the fourth to fifth week of vegetative
growth. There is a small spur just in front of the branch nodes
about the fourth or fifth set of nodes counting from the bottom.
Below this small spur will be the first sign of male sex. It will
look like a small node that is trying to develop pollen sacks.
The second time a male shows its sex is when flowering in the
autumn. It shows sex about a week before females. Once
flowering starts, males continue shedding yellowish, dust-like pollen
from bell-shaped pollen sacks (flowers), well into the females
flowering stage to ensure pollination. One centimeter-long and
pastel to yellowish green male flowers develop near the top of the
plant first and hang in clusters at the base of branches. After
2-6 weeks of the 12-hour photoperiod, fully formed floral sacks split
open shedding pollen.
Males are usually taller than females with stout stems, sporadic
branching and fewer leaves. Wind and gravity carry pollen from
taller males to fertilize receptive females. Relative to females,
male plants produce few flowers that contain less THC and overall lower
The last thing to remember, all males are not bad!
1.Small female calyx with two V-shaped white pistils at the branch node demonstrate pre-flowering.
2.Small pre-flowering calyx with two V-shaped white pistils are growing from the branch node.
3.Use one of the captions above.
4.Female “sinsemilla” flower top in full bloom with many white pistils.
5.Male pre-flowering is denoted by a small nub that grows behind a spur at the nodes.
6.These male pollen sacks are starting to develop during flowering.
7.Male flowers develop quickly. This male has been flowering about three weeks.
8.Male in full bloom.
9.Close up of male flower.
August is the last month you can still plant outdoors. Plants will be small and produce less.
Transplant clones and seedlings. Even though late in the year,
they will still flower. Remember they will need daily
watering. Remove lower leaves on stem and plant seedling
deep. New roots will grow on the stem.
Seedlings moved outdoors will need to be acclimated to the harsh
outdoor environment. Set them outside for several hours daily so
they “harden-off” for at least 5 days before leaving them outdoors for
Cover containers with a 2-centimetre layer of gravel or clay
pebbles. The rock mulch will retain moisture in the container and
keep the top layer of soil moist. Use organic mulch for plants in
Pests and diseases including vermin and deer are garden destroyers
now. Look for mollusk slime trails and evidence (poop) rabbits
and deer. Bait for slugs and snails. Build a fence or use
repellents for deer and rabbits.
Plants need lots of water this month. Stunting a plant now can
cost much yield. Big plants are using 5-10 liters of water per
Be sparing with fertilizers. Plants use more water and less
fertilizer in hot weather. It is easy to over-apply fertilizer
Shade containers so roots do not get too hot. How soil temperatures will cook roots.
Keep the temperature below 30 degrees. Hot weather will destroy
an indoor crop in just a few days. Keeping the room cool will
solve many problems before they occur.
Humidity over 70 percent will also cause many problems. Keep the
humidity around 50 percent and no higher than 60 percent for best
results. Add another vent fan if necessary. Keep fans on 24
hours a day!
Water as needed. If weather is hot and growing in small pots, you
could need to water as often as twice a day. Best to use a
fast-draining mix that can take heavy watering.
Decrease fertilizer concentration if not already decreased.
Plants use more water and less fertilizer in hot weather. It is
very easy to over-fertilize in hot weather.
Lower fertilizer dosage if leaves show signs of tip burn or are excessively green.
Flush plants with a mild fertilizer solution once this month. This will circumvent many problems.
Take clones for next crop so they are ready the day of harvest.
Spider mites, whiteflies, caterpillars and aphids can create real
problems now. Spray with pyrethrum or neem as needed.
Always spray leaf undersides because that’s where the pests live!
Odors are a real problem now. Check carbon filters for efficiency and keep running at top performance.
Harvest and clean the room thoroughly. Move in new clones.