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Medical Cannabis

The Vegetative Phase

You wanted some green... now you've got it.
By Updated:No Comments9 Mins Read
(Image from cannabisgrowing.blog)

This middle growth phase is the longest, you’ll be here for months. For the most part you just need to monitor nutrients and pH over time, as well as the correct amount of light.  Use of a scrog net and low-stress training are things you’ll read about / see on YouTube, so I’ll mention that here as well.

The purpose of this phase is to grow the best leaf and stalk foundation for the bloom phase, at which time the tips get quite heavy.

Potential Hydrogen – pH

(this definitive chart from growdiaries.com)

pH is the first and foremost consideration you’ll need to keep in mind until the very day you cut the stalk to harvest your plant.

If you’re growing hydroponically and are using perlite, you need to target a pH of 5.5, no more, no less. This is because since perlite is alkaline the water will be 5.6-6.0 as soon as it hits the medium!

The thing about pH is that it defines the plant’s ability to uptake nutrients. As you can see from the image above, some elements can’t be brought into the root system unless the pH is correct, so even if they’re in the water, they’re useless.
 
Further, there is a real thing called “nute lock” – more on that in a minute.

Nutrients (“Nutes”)

There is nothing less than a metric fuck-ton to learn about nutrients, especially when it comes to hydroponics. This is because soils can be more forgiving, but with hydroponics you’re in control of an IV drip that your green patient needs to survive and it needs to be monitored very closely.
 
I used General Hydroponics solutions, specifically:

These three are the core of what you’ll need for the next five months.

  • FloraGrow, best for this vegetative phase
  • FloraMicro, which contains necessary micronutrients
  • FloraBloom, which  you’ll use almost exclusively in the Bloom phase

iI also needed CalMag and ArmorSI would have been a good idea:

  1. Blue Blood is notoriously hard to grow and showed signs of magnesium deficiency pretty early.
  2. The plants showed signs of silicon deficiency as well, but the FloraMicro kept that in check. If I did it again, I’ll get a bottle of ArmorSi.
  3. If you’re splicing, you actually don’t need RapidStart – just use a bit of honey on the stem.
  4. KoolBloom might have helped as the BlueBlood flowering phase couldn’t get enough potassium.
  5. You will want small bottles of phUP and pHDown to help you control pH. They’re concentrates, so a) do not touch, and b) use sparingly. Use as little as you can because it’ll add to the water sodium content

As you can see there are very many products available, most you won’t need but some you definitely will.

Nutrient Order

I thought for months that “Nute Lock” and application order was garbage “bro science” but it turns out these bro’s know what they’re talking about.  There are two causes of nute lock:

  • Incorrect pH, which will prevent nutrient uptake, or allow too much of one, which prevents the plant from wanting/taking the other.
  • Incorrect order, causing a chemical reaction that causes heavier contents to precipitate out.

You absolutely must watch Coco for Cannabis’ Youtube video, “How to Mix Nutrients For Cannabis”, which I didn’t think was necessary and is in fact crucial. His video lists the nutrient order and makes two crucial distinctions:

  • Naturally the first is concentration, you don’t want to just dump whole bottles in your solution, nor put in a drop for 15 gallons, right?
  • Ratio of one to the other, as you might want 3 parts one, and 1 and 1 part of the other for a total of five. Another way of putting this is that the plant, like people, likes candy: put in too much candy and it won’t want its meat and potatoes.

In order for your plants to be green and happy, you must master concentration and ratio.  After that is subtleties, such as adding the right quantity of nutrient in the right order to the total solution and monitoring over time since the plant will uptake different materials on different weeks.  You have to do this for all media types, not just hydroponic, so if you want green, you need to master these.

Water Quality

There’s junk in your water, straight up.  Even if you pull it straight from a mountain stream there will be bacteria and sediment.  Whether you are growing in soil or hydroponically you have to control your water.

Aside from hydrogen and oxygen, there are three elements to monitor for water quality:

  • pH is first, then
  • Particulate or hardness, and lastly
  • Sodium (salt) content

If your pH is off, you’ll have to adjust it right out of the chute, increasing your sodium levels.

If your water is hard then you’ll start at a disadvantage since any addition of elements will increase the density of the water. Put another way, if it’s out of the tap at 600 parts (debris) per million and you add nutrients, you could end up at 1000ppm and this vegetative phase needs 800ppm max. If you’re at 50ppm out of the tap though, you’ll be able to add 400ppm of nutrients and have room to spare.

Adding pHUP or PHDown as well as nutrient solution increases the sodium content of the water, which while good for general conductivity is bad for the plant since, like any other nutrient, sodium kills.

Light

Turns out, weed loves light.  It’s hard to give it too much, but the key thing to consider is that light absorption for photosynthesis also requires carbon dioxide!  Unless you’re feeding CO2 into your grow tent, your plant will never actually apply more than 1,000 watts.
 
Further, some indoor lamps are particular about the spectrum – you need a grow lamp that is wide spectrum and will serve your needs for both vegetative and bloom phases.

Chart from percysgrowroom.com

Rather than use their hand method, I highly suggest you use the Photone app for Android, which precisely measures the light output, no guessing games.

drcannabis.io is the site I got this infographic from – A broad spectrum inside light is the way to go, otherwise you’ll have to switch  modes when your plant moves into flower, which is like a monkey letting go of one vine before clinging to the next!

A broad spectrum inside light is the way to go, otherwise you’ll have to switch  modes when your plant moves into flower, which is like a monkey letting go of one vine before clinging to the next!  Broad spectrum means no switches to flip.

I chose the Vipar Spectra 2023 version P2000, purchased via Amazon. I had to purchase two of them for three plants, but if one was only growing one or two then one unit would have been sufficient. Increasing intensity (it turns out) is not a replacement for “light canopy”.

I like them for a number of reasons, including energy efficiency and that you can chain them together: adjust one and you control them all. They hang easily and are easy to adjust.

Low-Stress Training

Your research will produce a great deal of information when it comes to “low stress training”, but all you’re after is making your plant grow not just up, but out.

See the image at right?  Provided by growweedeasy.com, you can see that the plant will always grow towards the light, but if you gently bend a branch out, it’ll grow out… then up. It’s clear that the plant pictured will receive more light evenly because there’s room between the branches.

weedseedshop.com provided this next image, which shows clearly how you can use string to gently hold branches in position.  Gently pull on the string until you meet genuine resistance and then tie it there. Over time, you can remove the string and the plant will maintain its shape.

My grow photo at bottom shows my limbs growing apart, and this is how I accomplished that – early in the grow, I tied strings to those young branches and gently attached them to the 5 gallon container with small binder clips.

Scrog Netting

A scrog net is an elastic grid-shaped net that you want your plant to grow into.  I thought it was a useless add-on, but consider genetically engineered chickens: their bodies are too heavy for their legs, and they often break just from standing up! Modern cannabis plants aren’t that different, they get top-heavy fast and are in fact genetically engineered to do just that.
 
If you don’t use a scrog net then you can expect your plant to flop over, get broken branches and crush your yield since broken limbs don’t uptake nutrients. The more you use low stress training and grow the plant OUT as well as up, the more a scrog net is important because the stalks are bent and gravity will pull those heavy blooms down.
 
I recommend installing scrog netting when the flower phase starts, since if you put it in too early you’ll have a BITCH of a time cutting down the plant without scraping off the trichomes you’re trying to preserve.  You need to support the top, not the middle of the plant. Gently feed the tops into the net as it grows until the new growth stays in its little square.
 
Image provided by growerscrognets.com .

Plant Size

While photoperiod plants are the biggest, autoflowers can get quite large.  Three plants took an entire bathtub and its stall.  If the plant meets resistance in the roots and flowers too early then it’ll be only waist-height, but if you do everything right it can be pretty huge.

Something to note is that by the time your bloom phase STARTS, your plant size will almost double again!

After a couple months, the autoflower plants will indicate a transition into the bloom / flower phase.

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