Marijuana bloom phase is payoff time for your entire season, and today we’re sharing bloom phase hacks that increase harvest weight, potency, grow op efficiency, and your cannabis-using pleasure.

The first hack has to do with how you transition your plants from grow phase to bloom phase. Many growers do sudden shifts in lighting and nutrients during this transition, and this causes plant stress that leads to problems with growth rate, vigor, flowering, and potency.

Growers of photoperiod cannabis plants often abruptly shift their light cycle from 18 hours to 12 hours per day when their plants are ready for bloom phase.

This shocks plants, and can lead to hermies, slow growth and other problems.

A better method is to first set a target start date for the 12-hour bloom phase light cycle. Then, beginning a week or two before target date, reduce your lights-on hours by 30-45 minutes per day until you get to 12 hours on, 12 hours off.

Many growers add to the shock of abruptly going from 18 to 12 hours in one day by changing their grow lights to bloom spectrum on that same day.

Growers using HID bulbs switch from metal halide to high pressure sodium bulbs abruptly, and this causes plant stress.

HID growers are better off using the full-spectrum (and ridiculously overpriced) Hortilux Blue in grow phase and the first 2-3 weeks of bloom phase.

The Hortilux Blue spectrum reduces bloom phase stretch, leading to shorter internodes and more bud weight per branch.

Indeed, when we’ve used HID grow lights, our most productive bloom phase array has been to use Hortilux Blue for the first two weeks of bloom, and then use 800 watts of Hortilux Blue for every 600 watts of Hortilux Super-HPS to create a varied array of intense full-spectrum output with the Blue being slightly dominant.

Growers using LED grow lights with customizable controllers have a much easier time of transitioning their plants and maintaining optimal spectral output.

Controllers allow you to dial in recipes for pre-flowering transition and then gradually ease the spectrum into a full-on bloom phase approach after the plants have been in bloom for three weeks or more.

Of all the grow light companies offering customizable spectrum control, we find the California Lightworks controller to be the most reliable, versatile and easy to use.

The company offers recipes for ratios and amounts of green, red, and blue output, timed to the phase of growth your plants are in. Their recipes include different spectra for pre-flowering, peak bloom, and late bloom.

Also, their controller has advanced software features. For example, you can duplicate dawn and sunset, so your cannabis plants get a more natural light experience.

What surprises many growers is that the recommended LED light recipe is more blue at the beginning of bloom phase and at the end, with the high-red recipe operational only during the middle marijuana bloom phase weeks.

If you’re growing autoflowering marijuana, your plants get 18 hours of light from start to finish and don’t need a daily 12 hour period of darkness to trigger flowering. A week or two after autoflowering plants start pre-flowering, you transition to a bloom phase spectrum for 18 hours per day, and then finish with a slightly-blue dominant spectrum for the last two weeks before harvest.

Tailoring your wavelengths creates shorter internodes, relieves plant stress, increases bud weight, and stokes cannabinoid and terp production.

Marijuana Bloom Phase Nutrients Hacks

The grow-to-bloom transitional period is a time when many growers make big mistakes with their feed program by shifting lights to bloom phase 12 on/12 off and immediately starting to use bloom phase nutrients.

A better method is to choose a bloom phase start date target, and have the last 1-2 feedings before bloom phase starts be a 50-50 combination of grow phase and bloom phase base nutrients.

After bloom phase starts, the first watering should be a reverse osmosis flush that includes only a beneficial microbes root zone product. We’ve tested all the beneficial microbes products and the best one by far is called Root, made by RX Green.

For added bloom phase plant health and increased bud weight and potency, follow the Root feed chart to use Root nearly all the way through bloom phase. During peak bloom phase, use a dose of Root as a flush to cleanse the root zone of nutrients build-up.

You may have heard of a bloom phase hack involving adding sugars into the root zone. Most hydroponics companies sell a sugary product for marijuana bloom phase plants.

We’ve found that blackstrap unsulphured molasses works better and is far less expensive. Just add a quarter teaspoon per gallon of nutrients water for one watering at the beginning of peak bloom and another dose three weeks before harvest.

Molasses contains iron and magnesium along with sugars. It feeds beneficial microbes in the root zone; its iron and magnesium are useful nutrients elements, especially during marijuana bloom phase.

Speaking of nutrients, fertilizer companies constantly hype “bloom booster” products heavy in phosphorus and potassium that are alleged to create faster bloom phase onset, more budding sites, and a faster bloom phase.

We’ve never seen evidence these products actually work; some contain plant growth regulators and other substances that may harm plants and people.

These early bloom phase products pollute the root zone with too much phosphorus and potassium, especially if you use other P-K bloom boosters later on. This often leads to nutrients lockout and other problems.

If you’re in a big hurry to get bloom phase going, reduce your lights-on to eleven and a half hours instead of twelve during the first two weeks of bloom phase.

If you’re growing pure or near-pure Sativa, sometimes you have to do that to force your plants into flowering.

After the third week in bloom phase when your plants are definitely fully triggered into flowering, gradually increase the lights-on time a few minutes per day until you’re at 12 hours.

Another marijuana bloom phase hack is to ensure that your lights-off grow room temperature during bloom phase is at least 3-5 degrees below lights-on temperature.

Some strain families such as Kush and Afghani that come from places with very cold nighttime temperatures do much better with this regimen, and it’s generally useful for all types of cannabis except equatorial Sativa strains.

Incremental Marijuana Harvesting

One of the most important bloom phase hacks is called incremental marijuana harvesting.

Most growers wait until resin glands are going cloudy and many are falling apart, and/or the breeder’s recommended bloom phase duration, and then harvest all at once.

Incremental harvesting gives you more versatility than that. To do it, first set a target date for harvesting as the upward end of the breeder’s duration estimate.

For example, I often grow an amazing, beautiful, lemony autoflowering strain called Auto Cinderella Jack, made by Dutch Passion. The breeder says the strain needs 8-9 weeks from seed to harvest; I’ve found it’s more like 12-14 weeks.

On one occasion, I was forced me to harvest almost three weeks earlier than I normally would for this strain, when its resin glands were still firmly erect, bulbous, and crystal clear.

Most growers correctly wait until a percentage of resin glands are cloudy, amber, and/or falling apart before harvesting, but I didn’t have that option.

I feared that early harvesting would cost me maximal harvest weight and potency. However, the high from that early harvest was like psychedelic caffeine, almost all THC, with little or no CBD, CBN, and other compounds that tend to limit THC’s effects.

The high was wonderfully energizing, great for exercise, and much less sedating than the high from Cinderella Jack buds I’d harvested later in bloom phase.

The next time I grew Cinderella Jack, I harvested some buds three weeks before the long-duration harvest date, two weeks before, one week before, on the target date, and one week after the target date.

Each set of buds had its own taste, scent and high. The earliest harvested were the most stimulating and caffeine-ish, and that harvest timing is now the timing I use with Cinderella Jack.

The last-harvested buds produced a small amount of euphoric head high, but had an overwhelming body high perfect for getting rid of pain, insomnia and similar complaints. It was almost like cannabis Quaalude.

Sampling buds in an intelligent, aware way reveals how incremental marijuana harvesting uncovers the ripening and production of cannabinoids and terpenoids during bloom phase.

Instead of looking at the breeder’s seed catalogue, seeing that the strain is listed as ready for harvest after 56 days in bloom phase, for example, and harvesting at 56 days, harvest earlier and/or later than that recommendation, sampling the buds to see which high suits you best.

When I grow highly-sedating Kush and Indica strains for customers, I personally dislike the heavy, sedating high of those strains.

So I harvest buds for myself about two weeks early and get a more stimulating high, while allowing most buds to continue ripening to create the knockout Kush and Indica punch my customers crave.

This works in the other direction too. I’ve grown Sativa strains, sampled them at the recommended harvest time, and found them so stimulating that they made me anxious, paranoid, or sleepless.

By allowing these zingy Sativa buds to ripen past ideal harvest time, some THC degrades to CBN, and more CBD develops, creating a less-jarring, more chill high.

Doing incremental harvesting, you find the effects you love the most, and that set of buds is used to determine bloom phase duration the next time you grow that strain under the same conditions.

Incremental harvesting doesn’t significantly decrease your total harvest weight or total resin gland weight. Indeed, incremental harvesting of top buds may actually increase total harvest weight because it allows lower buds to grow bigger than they normally would, in part due to increased light penetration.

One thing we discovered by accident while growing autoflowering cannabis in the same room with photoperiod marijuana is that some autoflowering strains produce nearly as heavy a harvest with only 12 hours of light per day in bloom phase, instead of the 18-20 that autoflowering breeders recommend.

Not only does Cinderella Jack and other autoflowering strains produce large harvests after an 18 hour grow phase light regimen and a 12-hour bloom phase light cycle, the high was very different from usual, very strong, different even than incremental harvesting effects.

However, be aware that that some autoflowering strains perform poorly if you fail to give them 18-20 hours of intense light from seedling all the way to harvest.

When we tested Dutch Passion’s Auto Glueberry OG with only 12 hours of light per day in bloom phase, the plant never fully matured, yields and resin percentages were too low.

We gave subsequent crops of the same strain 18 hours of light start to finish from then on, and they produced massive stacks of gooey buds that are as potent as top photoperiod strains.

Some Marijuana Bloom Phase Hacks Work…Some Don’t

More and more growers are hearing about far red and ultraviolet wavelengths for cannabis. We’ll be having a blockbuster insider report about that soon, but right now we’re affirming that studies show ultraviolet light properly applied just before lights off during the last three weeks of bloom phase.

Problem is, there are many theories about how long to expose your plants to ultraviolet light each dose, and there are many different types of ultraviolet hardware being marketed to marijuana growers.

Most of that hardware is defective. The Cleanlight handheld professional UV wand is the one we recommend.

Some LED grow light companies include ultraviolet and far red in their generic spectral output, even though the science indicates that this might do more harm than good. Ultraviolet radiation, for example, can cause cellular damage that severely harms plants.

When we ask these grow light companies for original, third-party verified science showing how their UV and far red affect marijuana plants, and for detailed instructions on using ultraviolet and far red, they don’t do it.

It would be great if a grow light company made an affordable, customizable LED grow light that allows you to switch far red and ultraviolet wavelengths on and off.

We’ve had our best success using a handheld ultraviolet wand that you can read about here. You expose your plants to a few seconds of this light every day starting 3-4 weeks before harvest, just before lights go off.

Not only does the wand’s ultraviolet shock the plants into producing more resins, its UV also kills gray mold (botrytis cinerea) and powdery mildew.

And of course, never forget the traditional bloom phase hack of adding carbon dioxide (C02) to your grow room air to create ambient levels of 800-1100 parts per million during lights-on phase.

Added C02 stimulates photosynthesis and plant metabolism to give you bigger, more resinous buds faster. It also allows you to run your room a little hotter than usual.

We conclude this article with a warning: you hear a lot of people talking about marijuana bloom phase hacks such as plunging their plants into total darkness for the last two days before harvest, interrupting the night cycle with far red or other wavelengths, using so-called bud hardeners and bud sweeteners, withholding water, and other tactics.

We’ve tried these bizarre tactics…and they all suck. None of them are backed by legit, third-party scientific research done on cannabis plants.

In fact, one traditional, popular bloom phase hack called “flushing,” (feeding your plants only reverse osmosis water and perhaps a flushing formula for the last 7-10 days of bloom phase), has been proven to be harmful.

All that hydroponics flushing does is starve your plants of necessary nutrients at a time when continued nutrients feeding will stoke more bud weight and resin development.

The claim that unflushed hydroponics buds are polluted and taste bad compared to flushed buds or “organic” buds is a myth.

The marijuana bloom phase hacks we’ve just given you have been tested in numerous grow ops with a variety of cannabis strains. Experiment with them while paying close attention to your plants, as every grow room and strain is different.

If your marijuana bloom phase plants respond like ours do, these hacks will give you faster growth, bigger yields, and more potent buds.