This Desert Vegetable Advisory page contains links to vegetable advisories on vegetable production and protection and a newsletter on vegetable quality issues. This in the list of advisories by date. University of Arizona. To know more about the different parts of the cannabis plant will facilitate cultivation and help us achieve better results. In this post we explain t Sexing Cannabis seeds has become a hot topic online, but there is no way of knowing if a cannabis seed is female or male by looking at it. Only when the marijuana plant starts to flower will you be able to tell the sex of a marijuana plant. However, there is a cannabis sexing seeds chart floating around on online.
Weed Seed Germination Diagram
Most preemergent herbicides do not kill dormant weed seeds. In most cases, the seeds must first germinate and contact the herbicide before they are killed. Some preemergent herbicides are absorbed by roots only, some by shoots only (at the hypocotyl in broadleaves and at the coleoptile in grasses, see diagram) and some by both roots and shoots. Weed seedlings will sometimes emerge and grow for awhile before they die or become uncompetitive with the crop. There are fumigants that do kill weed seeds. Some of these are metam sodium (Vapam), clorpicrin (Telone), dazomet (Basamid), methyl bromide, methyl iodide and calcium cyanamide. Flooding and solarization also can kill weed seeds. Fumigants, flooding and solarization are often used primarily to control diseases and have the added benefit of controlling some weeds.
To contact Barry Tickes go to: [email protected]
For questions or comments on any of the topics please contact Marco Pena at the Yuma Agricultural Center.
College of Agriculture, The University of Arizona, Tucson, AZ.
Anatomy of the Cannabis plant
When it comes to cannabis, the part of the plant that gets all the attention is naturally the bit we’re all growing for: the flowers. But while it’s easy to be enamoured with the beautiful frosty flowers we shouldn’t overlook the rest, because behind the bud there’s a whole plant, with all its component parts, each playing an essential role in bringing us our precious harvest.
Here at Alchimiaweb we strongly believe that the more we know about our favourite plants, the more success we’ll have cultivating them, and the happier we’ll be with the results! For these reasons here we’re going to take a closer look at the cannabis plant and identify all the different elements of its anatomy to help you get to know this wonderful plant a little bit better.
1, male flower, enlarged detail; 2, pollen sac; 3, pollen sac; 4, pollen grain; 5, female flower with bract; 5, female flower, bract removed; 6, female seed cluster, longitudinal section; 7, seed with bract; 8, seed without bract; 9, seed without bract; 10, seed cross section; 11, seed longitudinal section; 12, seed without hull (Franz Eugen Köhler 1887)
The Cannabis seed
For most of us, our introduction to cultivation comes when we buy or are gifted some cannabis seeds for the first time, so let’s set out on our examination of cannabis anatomy starting with the seed.
A healthy, mature cannabis seed will be well-rounded in shape with one pointed end and one flat end. They have a tough outer casing that is rigid to the touch, preventing the seed from being easily crushed. A seam separates the two halves of the shell (also known as the hull or pericarp) and is where the seed opens during germination.
Depending on their genetics, seeds can vary greatly in size, from really tiny (800 seeds per gram) to absolutely massive (15 seeds per gram). In mature seeds the outer shell should be covered with attractive dark markings known as “tiger stripes” which, like snowflakes, are unique to each seed and are in reality a thin layer of cells coating the seed and can be rubbed off easily, revealing the true tan/beige colour of the seed beneath.
Detailed view of a cannabis seed
Inside the seed we will find the embryo of the plant, everything needed to start a new life, dormant until the right conditions of moisture and warmth are met. We have the root, or radicle as it’s known while still in the seed, the cotyledons, those first, fat, rounded embryonic leaves containing the seed’s food reserves for early development. Cannabis is a “dicot” plant, meaning it has two cotyledons. Situated in between the cotyledons, surrounded by the first two true leaves is the apical tip, the point from which the plant will continue growing once germinated.
When we germinate a cannabis seed, the first thing that emerges from the opened seed will be the tap root which will begin to grow downwards, seeking out moisture and nutrition and colonising the substrate. The root system has three main purposes, not only does it anchor the plant in the substrate, it provides it with water and the nutrients, and it also acts as storage for sugars and starches produced by photosynthesis. It’s hard to overstate the importance of the roots in cannabis cultivation, they really are the foundation upon which everything else is built, without healthy roots we won’t harvest beautiful flowers!
Roots themselves can be classified into three types. Firstly the tap root, which is the principal component of the root system, the subterranean counterpart to the plant’s main stem, pushing vertically downwards and shooting off branches as it grows. These branches are the second type, the fibrous roots, which branch off from the tap root, extending outwards to form an underground network approximately the same size as the aerial part of the plant. A third type of roots are known as adventitious roots, these are the thick roots that sometimes sprout from the stem just above ground. These are the roots that make it possible to reproduce plants by taking cuttings and cloning them.
Adventitious root growing from the stem of a clone
Cannabis plants grown from seed will start life with a tap root system that develops into a fibrous root system, while clones don’t have a tap root, starting instead with adventitious roots before developing a fibrous root system. In all cases, a root system needs an adequate balance of moisture and air to be healthy and if care and conditions are right we will be able to see thick, bright white roots with plenty of fine hairs when we transplant.
The root crown
The part of the plant where the roots and stem join is called the root crown, or sometimes collar, or neck. This is a vital part of the plant, the dividing line between upward and downward growth, where the vascular system switches from roots to stem, and one of the places in the plant where most cell division takes place.
The root crown is naturally situated very close to the surface, where aeration is at its most, however some growers will transplant with the crown buried well below the surface, which encourages adventitious roots to sprout from the buried section of stem. It’s good way to deal with those leggy seedlings that stretched to get to the light and ended up too tall.
Stem and nodes
The stem of the cannabis plant is the part responsible for keeping the plant upright and for supporting the weight of the plant. It contains the vascular system which works to carry moisture and nutrients from the roots to the leaves via xylem cells, and to transport the sugars and starches produced via photosynthesis around the plant for use or storage via the phloem cells. Phloem is otherwise known as bast, the part of the cannabis or hemp plant that is traditionally harvested for fibre to make rope, canvas etc.
Cross section of stem showing a node
The stem, which can sometimes be hollow, is divided by nodes where the lateral branches begin, with the space between them being known as the internode. Seedlings will begin by growing opposite pairs of nodes and leaves but as time passes the nodes will start to grow alternately, sign the plant is mature and ready to flower.
Taller, stretchier Sativa plants will have a larger internode spacing than squat, compact Indica varieties, although environmental factors can also influence internode space. The nodes are where the first flowers appear (pre-flowers), so it’s the first place growers look when trying to determine the sex of plants grown from regular seeds. The small, narrow spear-like leaf growing at each node is called the stipule, and shouldn’t be confused with pre-flowers.
Nodes are one of the parts of the cannabis plant where most growth happens and most hormones are produced, for this reason we always cut clones with at least one node to be planted below ground in the substrate, so it can produce auxins (rooting hormones) to begin root development in the undifferentiated meristem cells of the node.
Leaves and petioles
Cannabis leaves are palmately compound (shaped like the open hand, with multiple parts), with anything from 3 to 13 veined, serrated leaflets or fingers. Indica varieties will generally have wider and shorter leaflets of a lush dark green colour, but fewer in number, while Sativas will have longer, narrower leaflets and can be of a lighter green shade. Of course, cannabis is a hugely diverse genus and there are exceptions to this rule, most notably the Ducksfoot variety, with its webbed leaves. Autoflowering varieties will tend to have smaller leaves, with the shape depending on the individual genetics, but as a general rule leaning more to the Indica side.
Leaf and structure comparison of the different cannabis species
A cannabis plant will have large and small fan-type leaves, which we remove and dispose of at harvest time, and also sugar leaves, which are the small, resin-covered leaves that protrude from the bud. These will either be trimmed away and kept aside for resin extraction, or simply left on the bud and smoked with the flowers.
Leaves from two different hybrids
As a seedling grows, each set of leaves has an increasing, odd number of leaflets, so the first set of leaves above the cotyledons will almost always have a single leaflet, the second pair will have three, the third will have five and the fourth will have seven leaflets, and so on until the plant reaches the usual number as dictated by its genetics.
The leaflets join at the point known as the rachis, from where they attach to the stem or branch by a leaf-stem known as the petiole. Petioles can be of varying length depending on the variety and can naturally vary in colour from green to dark purple, although in normally green plants a purple petiole can often be a sign of a phosphorous deficiency.
The fan leaves function both as solar panels and air conditioning for the plants, with the darker green upper side of the leaf producing energy via photosynthesis and the underside regulating internal processes via stomata, tiny pores that absorb the CO2 needed for photosynthesis and at the same time release water and oxygen. The stomata will close at night to conserve moisture and during the day will respond to heat and humidity levels, opening and closing to constantly balance internal moisture levels with external environmental conditions and keep metabolic functions working.
Cannabis is dioecious, meaning the male and female reproductive organs are on different plants. Unless we’re planning on doing some home breeding and making seeds, we won’t be growing any male plants to full maturity, but it’s important to be able to identify them, even if we’re growing exclusively from feminised seeds, just in case.
Female pre-flowers on the left, male flower cluster on the right
The male, staminate flowers effectively resemble green balls on sticks, composed of five petals which open to reveal five pollen-producing stamens. They grow in long, loose bud clusters from internodes on the branch and once pollen is released the male plants will soon die off. Male flowers contain low levels of cannabinoids and terpenes.
Female pistillate flowers are formed of tight clusters of bracts, the small, teardrop-shaped green petals that we growers refer to as calyxes. Each bract or calyx contains the ovary and the pistillate hair or stigma, which is what growers call the pistil and is the part of the flower that catches airborne pollen. Once pollen lands on the stigma, it is transported down the pollen tube to the ovary where fecundation takes place and the seed is formed, filling and swelling the bract as it grows. The thick, white pistil or hair will shrivel and turn a brown or red colour one it has served its purpose. The seeds are usually mature after a further 4-6 weeks time.
Both cannabis flowers and leaves develop beautiful colours
After pollination, female plants will devote their energies towards seed production, at the expense of resin. This means that seeded buds will have lower levels of cannabinoids and terpenes, and is one of the main reasons we strive so hard to grow sinsemilla (seedless) flowers, quite apart from the awful taste of smoking a seed in a joint!
Trichomes clustered on a bud
Botanists are still unsure as to exactly why cannabis plants produce such a large quantity of trichomes, but most agree that they most likely have the function of protecting the flowers and developing seeds, whether from harsh UV light, insects, grazing animals or extremes of temperature.
Trichomes have two different basic types: Glandular and non-glandular, with the principal difference being that non-glandular trichomes grow without a trichome head or gland, having the appearance of small hairs and mainly developing on stems, leaves, petioles and to a lesser extent on the flowers themselves, while glandular trichomes are found mainly on the flowers and sugar leaves, and possess the resinous gland where the cannabinoids and terpenes are secreted.
Glandular trichomes under the microscope
Glandular trichomes are themselves divided into three main kinds, which are: bulbous, the smallest and least numerous; capitate-sessile, which are larger and grow low, close to the leaf surface; and finally capitate-stalked, which are the largest, most numerous trichomes, found in highest concentration on the flowers and those with the greatest cannabinoid content, appearing somewhat like a tall mushroom, with a long stem and a large, rounded head – the iconic image of a trichome.
As the flowers mature, the trichomes will change colour, starting out transparent, passing through a milky-white stage nearing maturity and going on to become amber coloured when fully mature. Different growers will harvest their flowers depending on personal taste and the effect they’re looking for, but on our blog you can read a useful guide to harvesting according to trichome ripeness, which will help you to bring your crop down at the optimum moment.
Hopefully after reading this you’re now a bit more familiar with the anatomy of the cannabis plant and will become a better grower as a result. Knowledge is power!
The articles published by Alchimiaweb, S.L. are reserved for adult clients only. We would like to remind our customers that cannabis seeds are not listed in the European Community catalogue. They are products intended for genetic conservation and collecting, in no case for cultivation. In some countries it is strictly forbidden to germinate cannabis seeds, other than those authorised by the European Union. We recommend our customers not to infringe the law in any way, we are not responsible for their use.
Can You Tell the Sex of Cannabis Seeds from Their Appearance
Of all the things that can trip a grower up, sexing marijuana plants may just be the trickiest. Sexing plants is so important because growers are typically after the female plants, that produce the huge THC covered buds. Or the medicinal relief that CBD strains can bring. With such opposite effects of male and female plants, it’s easy to see just how important sexing plants is. But what if growers didn’t have to wait to sex their plants? While it would certainly make life easier, is sexing cannabis seeds possible?
Can you determine the sex of cannabis seeds?
This has been a question that has become a very hot topic online these days. After a quick search, growers can find multiple charts and explanations on how to sex cannabis seeds.
Unfortunately, there’s not much truth to any of these interpretations. It’s simply impossible to tell just by looking at them what the sex of any cannabis seed is. If it was that easy, feminized marijuana seeds would not be as popular as they are. People could simply buy regular seeds and look at them themselves.
Typically, marijuana plants cannot be sexed until they have already begun to grow. Cannabis seeds will look somewhat identical and plants in the vegetative stage will also look identical,. As the plants move into their flowering stage, they will start to show very clear signs as to what sex they are. While it would be much more convenient for growers to be able to determine sex before this point. The sad truth is that it’s just not possible.
So where do all the myths from sexing cannabis seeds come from?
Common myths on identifying the sex of a cannabis seed
One of the biggest myths of sexing cannabis seeds comes from a popular chart online.
The chart states that one can determine the sex of a cannabis seed by just looking at them. Within the chart, five cannabis seeds are shown. Three of these are female and two are male, supposedly. This chart says to look for a crater at the bottom of the seed. It explains that females will have a depression that is perfectly round. While males will have a crater that is misshapen and not uniform. However, this is simply not true. The craters found in cannabis seeds have nothing to do with the sex of a seed.
This same chart states that females will also roll easily across a table or surface, while males will not. While it does say that a magnifying glass and pair of tweezers is needed to examine the seeds. neither of these tools will make it any easier to determine the sex of cannabis seeds.
While growers may not be able to determine the sex of a seed, does the environment have anything to do with it? This is something else that has been hotly contested online.
Environment determines sex debate
We know that determining the sex of cannabis seeds cannot be done. However, it’s unclear as to whether environmental factors have any place in determining the sex of marijuana plants.
Research is carried out all the time to determine if a plant’s environment has anything to do with the sex it will turn out to be. And while there’s research stating that it does not, there’s just as much research stating that certain species do have their sex determined by the environment. This same research also states that using certain chemical treatments can also reverse the sex of a plant.
While environmental factors may not necessarily determine the sex of marijuana plants or cannabis seeds, it is known that certain environments can change the sex of a plant.
This will mostly happen when a plant is stressed by its environment. When this happens, the plant may think it’s going to die and as a result, will change itself into a hermaphrodite plant. By doing so, it will be able to self-pollinate itself and survive.
Growers know that hermaphrodite plants can be just as harmful to crops as male plants. Therefore, it’s very important that every grower understand how to sex marijuana plants. Particularly if they’re not using feminized marijuana seeds that will give them only females.
While it would be much easier for growers to be able to sex their cannabis seeds, the simple fact is that there’s no way to do it. However, sexing plants early on during their growth period is not only essential, it’s completely possible. Growers can even do it before their plants enter the flowering stage if needed. Then male plants can be removed and growers can enjoy a nice, full crop.
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