Seedling of Marijuana: Its Anatomy, Development, and Identification

marijuana seedling growth day by day

Your day-by-day and week-by week guide to marijuana seedling plants‘ progress from emergence to vegetative stage

In the present article we’ll be talking about the normal growth of marijuana seedlings. It will give beginner growers a pretty good idea of what to expect day by day and help them keep their cool and not react with panic whenever they suspect trouble. We understand that the seedling stage can be a nerve racking experience, right after the even more taxing time when you’re waiting for seeds to germinate. Those of you who already have their sprouts emerged can use this article to check whether or not they are doing okay. And if in doubt, consult our guide to seedling problems and how to solve them.

Cannabis Seedling from Day 1 and Onwards

So you’ve germinated your seeds between wet paper towels or using some other method and placed the sprout into a grow medium, like soil, or soil mix, or coco, or rockwool. It’s recommended to cover the sprout by the medium completely, so that its tap root has something to push off from when it’s trying to dig deeper. And when the tap root has established itself in the medium, it pushes the seedling out of the medium and its ‘helmet head’ breaks the surface.

If the medium is moist enough and coarse enough, the shell can peel off on its own. Otherwise, the seedling can be stuck in shell and needs your help (see the link above to remedy this and any other problem). Below the shell, there is a thin film covering the cotyledons. Sometimes, it sticks and doesn’t let the cotyledons open, even after the shell has been successfully removed.

weed seedlings day 1
This is day 1 for three OG Kush Auto seedlings. Only one of them has cast off its shell on its own.

 

pot seedlings no shell film
We have removed the shells from the seedlings on the right and in the center. The one in the center still retains the film though.

Sometimes, you will see the weed seedlings sprouting yellow. Don’t worry: it’s perfectly normal. The green color in plants is created by chlorophyll, a natural chemical that is created in the presence of light. And this process needs time. Give your yellow sprout a couple of hours under light, and it will start to turn green.

When the seedling sprouted, the pair of cotyledons will be ‘glued’ together – the way they used to be inside the seed, but soon they will move apart, and you will see the first tiny pair of true leaves tucked between them. Of course they will be whitish or yellow, too, at first.

On day 1, the cotyledons will be most probably pointing down, but on day 2 they will definitely straighten themselves (and so will the stem), and the first leaves with serrated edges will start to turn green and grow imperceptibly. These first leaves will have only one ‘finger’ each. The second pair – three fingers, the third – probably five.

The growth in the first week may seem painfully slow to you, but don’t you worry: the plants will pick up pace eventually, and right now a lot of progress is happening underground where the root system develops. The main root, called tap root, tries to reach as deep as it can. That’s why it’s recommended to use deep pots or tall party cups for seedlings. But secondary roots also actively grow at this stage which will be evident to you if you use rockwool or jiffy pellets: the root tips will grow through their sides.

Marijuana seedling height is controlled by the amount of light it receives. If everything is just right, the seedling is sturdy and not too tall: probably 2-3-4 inches the first several days, and hardly much taller when it is 1 week old or even 2 weeks old. The seedling’s main business at this time is root development and the growth of leaves, not the overall height. If you see that each successive pair of leaves eventually grows bigger than the previous one, your young plants develop beautifully. At day 10 the span of the second pair should be the same as the span of the first one.

It’s hard to point to the exact moment in time when a young plant stops being a seedling and begins its vegetative stage. You’ll see it happen when your cannabis starts to get noticeably bigger overnight. It may just grow higher, or rapidly develop side branches, or its leaves will get very large very fast. When you witness this sudden spurt in growth, congratulations: the vulnerable seedling stage is over and the plant has started vegging.

marijuana seedling day 1 og kush auto
On day 1, one out of three OG Kush Auto seedlings has yet to ‘unglue’ its cotyledons.

 

marijuana seedling day 1 yellow sprout cream caramel
This is Day 1 for Cream Caramel that managed to cast off the shell while emerging from the soil. It’s still yellow because it hasn’t yet been exposed to light.

 

marijuana seedling day 2 cream caramel purple stem
Cream Caramel seedling at day 2. The cotyledons and the first pair of true leaves are already green. The stem is brownish-purple, but it’s perfectly normal.

 

OG Kush Auto at day 3. The seedling is in the process of straightening up.

 

marijuana seedling day 4 six shooter fastbuds
This Six Shooter seedling is at day 4, and you can already see the second pair of true leaves.

 

marijuana seedling day 6 og kush auto
OG Kush Auto at day 6. A bit stretchy and bent as a result, but oherwise healthy.

 

marijuana seedling day 8 og kush auto
OG Kush Auto at day 8. Firts pair of leaves a bit wavy, probably due to overwatering at some point.

 

marijuana seedling day 10
On Day 10 or so, the spans of the first and second pair of true leaves should be the same. This Six Shooter is actually 13 days old which means that its growth has been too slow.

 

seedling next pair smaller
A very sick seedling. Besides yellow, dry, and brittle leaves (due to too aggressive LED light), you may also notice that the second pair of true leaves, though developed, is much smaller than the first one. This assymetry is a clear sign of major trouble.

 

marijuana seedling day 11 green crack fastbuds
Green Crack by Fastbuds at day 11 develops nicely. However, there is evidence of mild heat stress.

 

marijuana seedling 2 week old euforia
This 2 week old Auto Euforia seedling has leaves with 1, 3, 5, and even 7 ‘fingers’.

 

not a seedling anymore; vegetative stage begins
With noticeable side shoots at every node, this young cannabis plant shouldn’t be called a seedling anymore. Now it’s entering the vegetative stage and will develop rapidly.

The Color of Stem and Leaves in a Healthy Seedling

Generally, your seedling’s leaves should be medium green, not too light and not too dark. If the green color is too deep, it can mean that there’s too much nitrogen (N) either in the medium (soil mix), or in the plant food that you’re feeding your cannabis.

If the green color is just a bit too dark or too light, maybe it’s the genetics (see below). And when the leaves are turning purple or you see purple veins, purple stem, or even red stem, it also can be attributed to genetics. However, sometimes the cooler temps, especially at night or during the lights-off period, may lead to reddish hues in stem or purple leaves. White stem (usually with some greenish stem color) doesn’t mean there are any troubles.

The yellow coloration is a different story. Most often, it’s a sign of trouble, so don’t be complacent and resolve the issue a.s.a.p. The only exception is when you see yellow veins or yellow in the middle of leaves first thing in the morning when the growing parts of the seedling haven’t yet been exposed to light. Watch them for a couple of hours, and probably these new leaf parts will be filled by chlorophyll and turn the healthy shade of green.

marijuana seedling yellow in the middle
This picture was taken at lights on. The new tissue in the middle hasn’t been exposed to light yet, that’s why it’s yellow.

Another case of normal yellowing is when cotyledons die off at some moment. They are necessary in the first few days of a seedling’s life, before true leaves develop. Then they become redundant, get yellow and dry. This is inevitable and can be speeded up if the cotyledons are far from light or shaded by true leaves above them.

3-4 weeks old cotyledons yellow
This plant is probably 3 or 4 weeks old. The cotyledons have already served their purpose, and now it’s time for them to die.

Marijuana Seedling Identification: How Much Can You Really Tell?

Some people are very impatient to identify their strain already during the seedling stage. Maybe you’ve bought a mix of different seeds, and they are not marked in any way, so you can’t tell the difference between them. Or you’ve been gifted some seeds by a friend or decided to try some bag seeds. What can a seedling tell you about your future rewards, if any?

Well, not much. Basically, the only thing that you can tell with any confidence is whether your cannabis seedling is an indica or a sativa. Indica leaves (and it’s often apparent with the first set of true leaves) have darker green color compared to sativa leaves that are more light. Indica leaves are also shorter, broader, and ‘rounder’.

marijuana seedling indica
Judging by broad, round leaves, this seedling has dominating indica genes.

 

cannabis seedling sativa green poison early version
This Green Poison Early version has narrow, light green leaves that point to its sativa heritage.

As for the seedling gender, you can’t tell whether it’s male or female. Only when a young plant starts flowering, or, to put it more correctly, when it shows preflowers at the nodes, you can determine if they are female hairs or male fists. This seldom happens earlier than at 3 weeks (in the quickest of automatic strains). For photoperiod varieties, you can only wait until the vegetative growth really kicks in and the first preflowers appear. Alternatively, you can speed up this process by switching your light schedule to 12/12, which can be done even from day one. However, it will be a significant stress for your seedlings if they start flowering like this and then you decide to revert them back to veg with 18 hours of light and 6 hours of night.

male cannabis plant
This plant has clearly shown its sex. It’s a boy. Note that you wouldn’t see male or female flowers in a seedling; only in mature plants.

 

young plant male
A much younger cannabis plant has already shown male flowers.

 

male flowers at the nodes
Yet another plant (mature) showing male flowers at the nodes.

 

seedling female flowers
This young plant, probably 3 weeks old and not very healthy looking, shows the first white pistils (female hairs) on top. The yellow color in the middle probably means that the picture was taken at lights on.

There is one more thing that you can do to understand what you actually grow: you can slightly rub the leaves and smell them. The smell should be rich and pleasant for you. That’s what breeders do who germinate hundreds of seeds and want to decide early on which ones to keep and which to discard. And, of course, you should look for seedlings that are healthy and vigorous, not sickly and small.

Not much of identification guide, we know, but it is what it is.

So now you know enough about your little plants to stop worrying and enjoy the process of growing. And if you want to make sure that your sprouts receive all the proper L&C, check out our article describing the ideal conditions for your weed seedlings and how to take good care of them.

 

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