Marijuana bloom phase is your payoff phase.
Using tips in this article, you’ll see fatter, stickier, tastier, stonier buds, and more of them!
Flush Your Cannabis Root Zone At Start of Marijuana Bloom Phase
On the same day you switch your grow lights to 12 hours on, 12 hours off, flush your root zone using only Flawless Finish and reverse osmosis water for a 24-hour period.
Give your root zone a day or two to dry out so you don’t waterlog your root zone and destroy your roots by drowning them.
Note: The tactic of allowing the root zone to dry out doesn’t apply to growers using aeroponics, deep water culture, NFT, or other pure hydroponics systems.
It only applies to growers using rockwool, coco coir, soil, soilless mix, or other root zone substrate that holds substantial amounts of water for long periods of time.
Beware of Plant Stretch
Depending on the strain you grow and whether or not you did topping or other plant modification, a plant that starts marijuana bloom phase two feet high could end up 4-5 feet high at harvest time.
I use only HPS (high pressure sodium) grow lights during the first 2-3 weeks of marijuana bloom phase, especially if I’m growing Sativa genetics.
HPS light wavelengths are better for keeping plants short when compared to metal halide (MH) wavelengths, and they help trigger more budding sites and earlier budding.
One brand of LED grow lights is engineered to reduce plant stretch and create denser, heavier buds.
Read about that here.
Measure grow room height to make sure the finished height of your marijuana bloom phase plants leaves at least two feet between the top of your plants and the bottom of your grow light reflectors.
If you’re using double-ended bulbs, you might need even more than two feet.
Please read this great article that has several techniques for reducing plant stretch.
Do the “Hot Hand” Test to Avoid Canopy Burn
High Intensity Discharge (HID) metal halide and high pressure sodium lighting, along with LED grow lights, are what you need for full-size photoperiod marijuana plants.
But they’re hot and can burn your plants.
The way to know if your plant canopy is too close to your grow lights is by holding your hand palms up directly under your grow bulbs at the same height as your topmost buds…
If your hand feels anything more than barely warm from the light radiation hitting it, the canopy is getting too much light intensity.
Remember that your buds do best when they grow in a constant light breeze at 74F, unless you’re running no more than 1100-1200 ppm ambient C02 in your grow room, in which case, you can go as high as 84F.
But temperature measurement isn’t the only thing to consider: if your palm feels like it’s being burned by the grow light at the same distance your buds are at, you’re harming your plants and buds, and need to raise your grow lights.
Use Hydroponics Nutrients Made Only for Marijuana
I’ve used all the major brands of hydroponics nutrients and supplements.
Most of them caused problems. Only one was made for marijuana and tested on marijuana by its manufacturer.
Now my preferred very early marijuana bloom phase formula is Connoisseur pH Perfect base nutrients, Bud Ignitor, Nirvana (quarter strength), Voodoo Juice, Tarantula, and Piranha, Bud Candy (quarter strength), B-52 (quarter strength).
Note that this hydroponics nutrients line-up is only for the first couple of weeks after you put your plants into 12-12.
Later on in this article, I give you a different recipe for later marijuana bloom phase sub-phases.
Also, realize that although marijuana growers commonly say marijuana has one bloom phase, it actually has four distinct flowering sub-phases.
As soon as your 24-hour initial flush is completed and you’ve allowed your cannabis root zone to dry out, start the early flowering feed program.
Your plants will create budding sites earlier, and give you more budding sites.
Change Your Hydroponics Nutrients & Lighting Recipe After Buds Have Set
About 2-3 weeks after you switch to 12-12, when your buds have set and you have clearly visible early flowers (a nice bush of white hairs on each), dial Bud Ignitor down to quarter strength and start using Big Bud at ¾ strength.
Continue using Nirvana (half strength). Use Rhino Skin (half strength). Use B-52 (quarter strength). Use Bud Candy (quarter strength). Use Bud Factor X (quarter strength). Use Voodoo Juice, full strength.
Continue using Connoisseur pH perfect hydroponics base nutrients at manufacturer’s recommendations.
Watch your parts per million (ppm) and your leaf tips to make sure you’re not overfeeding. If most leaf tips are brown/burning, you’re overfeeding and need to remediate.
Feed only RO water for one cycle, then starting with ongoing waterings, reduce your parts per million by about 10-20 ppm.
At the same time, add metal halide. LED, and/or Hortilux high-ultraviolet PowerVeg T-5 lighting to your grow op.
Some growers stagger a 1000-watt HPS with a 600-watt Hortilux Blue.
In marijuana bloom phase, you always want the ratio of HPS to non-HPS lighting to favor HPS.
Use this marijuana bloom phase lighting and feed program until your buds are just reaching or have reached peak bloom.
For most marijuana strains, this will be around week 3-6.
Peak Marijuana Bloom Phase Lighting & Feeding
When your buds are fat and covered in clear resin glands with white hairs, and still adding size and cannabinoids, your plants are in peak bloom.
Here’s a recipe that’s put rockhard, massive colas on my plants. Your flowers are visibly larger and aromatically sweeter when you use a recipe like this.
Discontinue Bud Ignitor and B-52.
Increase Rhino Skin, Big Bud, Bud Candy, and Nirvana to full strength. Continue Connoisseur pH Perfect full strength. Continue Voodoo Juice, half strength. Continue Bud Factor X, half strength. Start using SensiZym, full strength.
In peak bloom, go 50-50 HPS and MH, or 50-50 HPS and PowerVeg.
At all times, ensure that your plants are getting the right amount of light intensity.
Calculating the right amount of light intensity is somewhat complicated if you use a combination of HID and non-HID, such as using HPS, MH, and the PowerVeg T-5.
Remember that a 1000-watt MH or HPS will only give you good light penetration and intensity for a 4 x 4 or 5 x 5 area, maybe a little larger area if you have a light mover.
So if you have marijuana bloom phase plants that spill out to make a 6 x 6 growing area, you’d add a couple of T-5s or LEDs onto the edges (darker parts) to even out the lighting.
Because many LED units, and the Hortilux PowerVeg and AgroMax Pure UV T-5 bulbs pump lots of ultraviolet light that increases cannabinoid production and resin glands, park your plants directly under those lights at the proper distance from time to time during marijuana bloom phase.
Rotate your marijuana bloom phase plants so they get full light coverage and penetration.
Or install a light mover.
Note: What I mean by “rotate” is: rotate their pots or buckets if possible, and rotate them around the grow room so they occupy different positions in the grow room during marijuana bloom phase.
Late Bloom Flushing, Feeding, Lighting, Conditions
When just a few resin glands are starting to go cloudy and/or collapse, your marijuana bloom phase is heading into late bloom.
Watch your resin glands like a hawk, because a crop can mature overnight sometimes, with late boom turning into “oh no, all my resin glands collapsed.”
For most strains except for pure Indica or Indica-dominant, which finishes earlier, late bloom will be around weeks 6-9.
When you see just the beginning of resin gland die-off, in most strains, you still have 1-3 weeks of blooming left.
During this time, if you handle your marijuana bloom phase as follows, you’ll add a lot of bud weight and cannabinoids:
Do a half-day mini-flush using only reverse osmosis water.
Then experiment with induced drought by not watering for 1-3 days until your plants are just about to wilt.
Moderate drought stress used once or twice during peak and late marijuana bloom phase often creates higher-potency buds.
After the drought stress, initiate a feed program of only Connoisseur pH Perfect ¾ strength, Overdrive (2/4 strength), Bud Candy (3/4 strength), Rhino Skin (half strength), Nirvana (3/4 strength), Voodoo Juice (half strength), SensiZym (full strength).
If large leaves are totally yellowed and wrinkled, remove them, especially near the top of the canopy so they’re blocking light penetration.
Make sure that throughout bloom phase you’ve continued to raise your lights to prevent bud burn.
Make sure you’ve continued to keep a gentle breeze blowing on your plants at all times.
Keep your hydroponics nutrients water at 68F at all times.
Final Flushing Before Harvest
Five to seven days before harvest, discontinue all nutrients.
Apply Flawless Finish and reverse osmosis water to purge pollutants from your crops.
Monitor resin glands with magnifying glass. When more than 20-25% of them are cloudy or fallen, it’s time to harvest.
The article you just read gives you a time-tested formula guaranteed to grow massive, sticky buds for newbie and professional growers in large and small gardens.