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Cannabis Plant Growth and Anatomy 101

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Cannabis Plant Growth and Anatomy 101


Part A


Plant growth is primarily based on two conditions: Genetics and environmental conditions. I havent taken either into account whilst writing this, and this another extremely in depth topic in itself. The growth rate of certain varieties can vary within and particular geographical race and genetic makeup of the strain, the growth curves are always characteristic of the varieties. Plant development is dependant upon temperature and the availability of nutrients and water.This guide is not a step by step grow guide, it is merely a reference for information on the Cannabis plant anatomy. I hope it helps and educates others, and if there is anything you would like to add, please feel free to mention it!


Generally with most Cannabis plants you end the vegetative period by altering the light cycle. The vegetative cycle can be divided into different phases:

The Germination Phase: This involves the germination of the seed and lasts until the firat pair of true leaves on the germinating plant reach the size of the cotyledons and are capable of photosynthesis.

The 'Slow Growth" stage: Is started from the initial appearance of the first set of true leaves, and lasts approximately until the growth of the fifth set of leaves.

The 'Rapid Growth" stage: Which lasts from the start of the Slow Growth stage up until the formation of flowers.

The Period between the growth of flower buds in the leaf axis and the time when the first flowers open, after which growth gradually slows.

Flowering: Extends from the time when the anthers on the first male flowers open and release their pollen to the time when the flowers in the upper third of the inflorescence open and their pollen is released.

The growth of the achene: Lasts from the initial swelling of the seed embryo to the maturation of the first seeds.


Under adequate conditions, roots begin to form after 24-48 hours after planting the seed. After this the cotyledons will appear, from which the hypocotyl develops. The next process is the growth of the epicotyl. Concertedly the primary pair of first leaves will develop. Growing oppositely oriented, sets of pairs of leaves continue to grow along the epicotyl and then eventually after the cotyledons nutrients are expended, the cotyledons dry out and the plant starts to live autonomously. It is very important that a grower does NOT remove the cotyledons whilst the plant is growing, as this is a very valuable nutrient resource for the seedling, and may result in problems with the growth of it. After approximately two weeks (Strain and environmentally dependant) the stem segments become longer and the first axial limb buds will begin to form and branch out.


Now, you might notice that the leaves are starting to differ from eachother in the size, and the amount of individual 'fingers' or pinnations, also known as leaflets. The number of leaflets are determined by three antecedent factors. Variety and genetics of the strain, age of the plant and the position on the stem. In the vegetative phase the leaves will grow decussate, their position changing later to an alternate node positioning. Each leaf is supported to the main stem via petioles, which above these petioles grow the axial limb buds. Odd shaped leaves are common on some plants, and develop from fused leaflets, from a dual-leaf formation, or from chlorophyll defects, resulting in leaflets with teratogenic formations.




Male flowers

The male flowers develop in pairs at the petiole nodes (intersections) of the inflorescence. The male flower consists of a simple calyx (floral sheath) with five petals that are yellowish-green. The petals surround five stamens that consist of anethers (pollen sacs) suspended on thin filaments. The anthers have an elongated prism shape prior to maturation and turn light-yellow following maturation. The open male flowers appear star-shaped when viewed from above. The number of male flowers primarily depends on spacing of the plants. Fiber help plants having fewer branches that are thinner and longer have relatively few male flowers because inflorescences develop only on the tip of the plant. One secondary branch of a widely spaced male plant has considerably more flowers than another in a dense crop. Cannabis is a crop-pollinated, wind-pollinated plant. The pollen is dry and floury, and forms dense clouds during the flowering period. These pollen clouds can reach an altitude of 30 meters and travel as far as 10km.


Female flowers

The secondary branches of the female inflorescece are very short, bearing tightly clustered female flowers. Therefore the female inflorescence is dense and club-shaped after pollination and during harvesting. The female flower consists of a green, single leaf calyx that surrounds the 'hidden' ovary, which has one seed. Only the two thin pistils protrude from lateral slits. They bear dual-forked stigmas that are initially white but later become a red colour. The end of the flowering period sees the glandular hairs on the pistils and the surrounding calyx ecrete sticky resin.


Epicotyl - The stem of a seedling or embryo located between the cotyledons and the first true leaves. http://dictionary.reference.com/search?q=epicotyl


Cotyledon - A leaf of the embryo of a seed plant, which upon germination either remains in the seed or emerges, enlarges, and becomes green. Also called seed leaf. - http://dictionary.reference.com/search?q=cotyledon


Hypocotyl - The part of the axis of a plant embryo or seedling plant that is below the cotyledons. http://dictionary.reference.com/search?q=hypocotyl


The attached images are properties of their rightful owners and I've asked permission to use them from most of them.


Edited by Nath
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I hope this helps out, If there is anything anyone would like to add or correct me on, once again, please feel free to let me know. After I do a bit more research on b asic plant nutrient requirements and insufficiencies I post up Part B lol




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hi, I was jsut wondering if the female plant MUGHT be polinated to create bbuds... and if yes, what do I do with femenize seeds....???

thank you for the info helps lots


There are alot of methods for creating feminized seeds.. but STS seems to be the best.. I have no clue about feminized seeds, here's a post by Wild Rover:



How To Reverse Sex Using Silver Thiosulfate Solution

The following is a safe, inexpensive, and successful method for reversing the sex of female cannabis plants. Individual plant responses may vary based upon strain, but I can verify that this process is fully effective in stimulating profuse staminate flower production.


This process can be used to:


A: create new feminized seeds from solitary prize mothers that you currently have

B: create interesting feminized-seed hybrids from different prize strains that you currently have

C: create feminized seeds for optimum outdoor use

D: accelerate the "interview" phase of cultivation, in searching for interesting new clone-mothers

E: reduce total plant numbers- great for medical users with severe plant number restrictions

F: increase variety, by helping to create stable feminized seedlines to be used as an alternative to clones


At the bottom of this post are some specific details about the chemicals used, their safety, their cost, and where to get them.


It is important to educate yourself about cannabis breeding theory and technique prior to using a method like this one. Here is a link to Robert Clarke's "Marijuana Botany", which is a very good reference.


"Marijuana Botany" by Robert Connell Clarke

(unfortunately missing the appendices)



It is also important to use basic safety precautions when mixing and handling these chemicals, so read the safety data links provided. The risk is similar to mixing and handling chemical fertilizers, and similar handling procedures are sufficient.


Remember: nothing will ever replace good genetics, and some of your bounty should always go back towards the professional cannabis breeders out there... the ones who have worked for many generations to come up with their true-breeding F1 masterpieces. Support professional breeders by buying their seeds. Also, order from Heaven's Stairway. Not that they need a plug from me, but they are very professional and provide very fast service worldwide.


Preparation of STS:


First, a stock solution is made. It consists of two parts (A and :D that are initially mixed separately, then blended together. Part A is ALWAYS mixed into part B while stirring rapidly. Use distilled water; tap water may cause precipitates to form.


Wear gloves while mixing and using these chemicals, and mix and use in a properly ventilated area. A mask will prevent the breathing of any dust, which is caustic. STS is colorless and odorless, and poses minimal health risks if used as described here. (See material safety data sheet links below). Note that silver nitrate and STS can cause brown stains upon drying, so spray over newspaper and avoid spilling.


Part A: .5 gram silver nitrate stirred into 500ml distilled water

Part B: 2.5 grams sodium thiosulfate (anhydrous) stirred into 500ml distilled water


The silver nitrate dissolves within 15 seconds. The sodium thiosulfate takes 30-45 seconds to dissolve.


The silver nitrate solution (A) is then mixed into the sodium thiosulfate solution (:wub: while stirring rapidly. The resulting blend is stock silver thiosulfate solution (STS).


This stock solution is then diluted at a ratio of 1:9 to make a working solution. For example, 100ml of stock STS is added to 900ml of distilled water. This is then sprayed on select female plants.


Both the stock STS and the working solution should be refrigerated after use, as well as the powdered chemicals, to avoid activity loss. Excess working solution can be safely poured down the drain after use (with ample running water) with negligible environmental impact. It's pretty cheap.


Each liter of stock STS will make ten 1-liter batches of working solution of STS. With the minimum amount of base chemicals ordered from Photographer's Formulary (see link below), this means that each 1-liter bottle of working solution STS costs less than 9 cents, and can treat 15-20 mid-sized plants. That's 200 1-liter batches of STS for $18. Note that the distilled water costs far more than the chemicals.




The STS working solution is sprayed on select female plants until runoff. Do the spraying over newspaper in a separate area from the flower room. You probably won't smell anything, but ventilate anyway. You now have what I call a "F>M plant"; a female plant that will produce male flowers.


After the F>M plant dries move it into 12/12 immediately. This is usually done three to four weeks prior to the date that the target (to be pollinated) plants will be ready to pollinate. Response times may vary slightly depending upon the strain. More specific times can be determined by trial with your own individual strains. In my trials it took 26 days for the first pollen. 30-35 days seems optimum for planning purposes.


So, assuming that a target plant needs 3-4 weeks to produce fully mature seeds, a strain that takes 8 weeks to mature should be moved into flower at about the same time as the female>male plant. A target plant that finishes flowering in 6 weeks needs to be moved into flower later (10 days or so) so that it doesn't finish before the seeds can fully mature.


A seeded individual branch can be left to mature on a plant for a bit longer, while harvesting the other seedless buds if they finish first. Just leave enough leaves on for the plant for it to stay healthy.




Within days I noticed a yellowing of the leaves on the F>M plants. This effect persisted for two weeks or so; after this they became green again, except for a few of the larger fans. The plants otherwise seemed healthy. No burning was observed. Growth stopped dead for the first ten days, and then resumed slowly. No stretch was ever seen. After two weeks the F>M plants were obviously forming male flower clusters. Not just a few clusters of balls, but complete male flower tops. One plant still formed some pistillate flowers, but overall it was predominantly male.


It is strange indeed to see an old girlfriend that you know like the back of your hand go through a sex change. I'll admit that things were awkward between us at first.


When the F>M plants look like they may soon open and release pollen, ( 3-1/2 to 4 weeks) move them from the main flower room into another unventilated room or closet with lighting on a 12/12 timer. Don't worry too much about watts per square foot; it will only be temporary.


When the pollen flies, move your target plants into the closet and pollinate.


A more controlled approach is to isolate the F>M plants in a third remote closet (no light is necessary in this one, as they are releasing pollen now and are nearly finished anyway). In this remote other closet the pollen is very carefully collected in a plastic produce bag or newspaper sleeve and then brought back to the lighted closet, where the target plants are now located. If this is done, be careful to not mix pollen types by letting the F>Ms dust each other. Avoid movement, or use yet another closet.


Take special care to not let pollen gather on the outside of this bag- a static charge is sometimes present. Drop small open clusters of blooms inside and then close the bag at the mouth and shake. Important: next, step outside and slowly release the excess air from the bag, collapsing it completely, so that pollen doesn't get released accidently. Point downwind; don't let it get on your hands or clothes.


This collapsed pollinated bag is now very carefully slipped over only one branch and is then tied off tightly at the mouth around the branch stem with a twist tie or tape, sealing the pollen inside. Let the bag inflate slightly with air again before sealing it off, so the branch can breathe. This technique keeps the entire plant from seeding. Agitate the bag a bit after tying it off to distribute the pollen. Don't forget to label the branch so you know which seeds are which. Other branches on this same plant can be hit with different pollen sources.


If no lighted closet is available, the plant can be moved back into the main room, but- be very careful: pollen is sneaky. After 4-5 days, the bag is gently removed and the plant completes it's flowering cycle.


Yet another method has worked well for me. I position the target plants in a non-ventilated lighted closet, and then I collect pollen on a piece of mirror or glass. This is then carefully applied to the pistils of one pre-labeled branch by using a very fine watercolor paintbrush. Care is taken to not agitate the branch or the pollen. No sneezing. The plant needs to be in place first; moving it after pollination can shake pollen free and blow this technique.


Regardless of technique, at completion you will have feminized seeds. Let them dry for 2-4 weeks.


About the chemicals:


Silver nitrate is a white crystalline light-sensitive chemical that is commonly used in photography. It is also used in babies' eyes at birth to prevent blindness. It can cause mild skin irritation, and it stains brown. Avoid breathing. I didn't notice any smell or fumes, but ventilation is recommended. Be sure to wash the spray bottle well before you use it elsewhere; better yet: devote a bottle to STS use. A half gram is a surprisingly small amount; it would fit inside a gel capsule.


Here are links to some safety data. A Google search will bring up more information if needed.


Silver Nitrate info:




For a realistic hazard level comparison, here is a link for the safety and handling data for Ammonium Nitrate, or common fertilizer:



Sodium thiosulfate is also a white crystalline chemical commonly used in photography; it is used in photographic fixers. Same general cautions apply, minus the staining. This formula uses the anhydrous type. Non-hazardous.


Sodium Thiosulfate info:






Where to get the chemicals:




silver nitrate: 10 grams: $10



sodium thiosulfate (anhydrous): 100 grams: $3.95



Postage runs around $4. Fast service. Can be shipped to Canada.


Have fun experimenting with this technique. Use it responsibly. There are a few good threads here at CW that go into the pros and cons of transsexual agents and feminized seeds. Read them. And most importantly, use STS with quality F1 strains developed by professional breeders for the most consistent results.


A huge thanks to Fet from Spice Brothers Seeds for his help and advice in using this technique. I simply brought together available information from previous posts and tried my own recipe. I'm thrilled to share the results. Future tests will be done to adjust the formula so the molar ratios of the chemicals are correct, as specified by Gobgoober (thanks, Gob) but the formula posted here is completely effective.

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hi, I was jsut wondering if the female plant MUGHT be polinated to create bbuds... and if yes, what do I do with femenize seeds....???

thank you for the info helps lots


no mate, you dont want your buds to get pollinated at all, remove all plants with male flowers cos they will fuck your crop...


your feminized seeds are a good way to have no (hopefully) male flowers in your crop... and pull pull pure sinse seedless buds...


to create bud, female plants need 12 hrs minimum of darkness per day.. indoors can set it with a timer, outdoors gotta wait for nature to do it...

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