by Ed Rosenthal
To make a change there has to be an advantage for at least one species. We have always respected marijuana as a fall flowering and ripening crop. However, it turns out that our interests and the plant’s natural proclivities have diverged.
John Lydon published his Ph.D thesis in which he reported on experiments he performed on marijuana. They showed that the amount of THC that a high quality marijuana plant produces goes up in a direct ratio to the amount of UVB light that the plant receives.
The relevance of this information to this discussion is that when the angle of the sun to the earth is most perpendicular, on June 22, the first day of summer, is when that hemisphere receives the most UVB light, which is past the far end of the visible spectrum, on the blue-violet side. As the angle of the Earth and sun becomes more oblique, Earth receives a higher proportion of light from the red spectrum and less blue and UV. By September or October, when sinsemilla normally ripens, not only is the light far less intense, but the amount of UVB being delivered is a small fraction of the amount that is received on June 22nd.
UVB LIGHT CHART
The amount of UVB light a plant receives affects THC and terpene production. Plants growing under higher UV levels are more potent.
The amount of UV light that an area receives is determined by the latitude, season, climate, and weather. Light reaches the equator most directly, and is the most intense. As the latitude increases light reaches Earth at a more oblique angle so it becomes less intense.
Throughout the Northern Hemisphere, which includes North America and Europe, UV light is at its lowest levels in December and January. After these months, the levels start rising. The further from the equator, the longer it takes to peak, the shorter the peak period and weaker the light.
For instance, in San Francisco (latitude 37.75), UVB reaches it peak with a UVB index between 9-11 around May 15. It stays there until around August 15. By September 1 it drops down to 8 and by October down to 6.
If you can ripen plants during the peak UV period the plants will be at their most potent. As the season wears on and the UVB levels decline the marijuana does not attain the same potency.
Using this information, no matter where you live, even in the far north you can grow potent plants using light deprivation, so that plants ripen at the peak period rather than late in the season. This chart can help you determine planting strategy.
In Alaska (latitude 61.22), UV peaks around May 20 and starts declining at the beginning of September. At its peak, it stays within 5 and 6 on the UV index, and stays below 2 on the index between September 15 and April 1. At the other extreme, Hawaii’s UV peaks and stays at between 10 and 12 on the index between March 1 and October 1. At its lowest point in December it is at level 6, a higher level than Alaska at its peak. More UV index information is available online at: http://www.weather.gov/view/national.php?prodtype=ultraviolet
Marijuana buds that are ripening under the intense sun of early summer grow bigger, denser and are more potent than when they ripen under the waning sun and variable weather of the fall.
To induce flowering in plants they should be placed under 12 hours of darkness each day. Darkening curtains are placed over the garden, There are many ways to accomplish this. They range from moving the plants to and from a dark place daily, to covering the garden using an opaque plastic sheet over tunnels, to automated blackout gardens.
UVB light has health consequences to humans. It is a known carcinogen and leads to cataracts. Always shut UVB lights off before you start working in your garden. Outdoors, protect yourself from the sun’s UVB rays by covering your body and applying sunscreen. Protect you head and face by wearing an extra wide brimmed hat.
To force plants to flower you must be punctual and watch the daily changes in dawn-dusk times to make sure that the plants are getting enough darkness. You can also use an automatic system to regulate the curtains.
There are two ways to approach restricting light: darken in the morning or at night. Morning darkening is the preferred method. The shade material is placed over the garden each morning before dawn. The plants need to be shaded counting forward 12 hours from dusk. If dusk is at 9:00 pm and dawn is 6:00 am, curtains should cover the garden before dawn, around 5:30 am They should be removed at 9 a.m. after receiving 12 hours of no light.
The other method is to install the curtains in the evening. Count back 12 hours from dawn, which occurred at 6 am in the above example. The curtains are placed over the garden at 6 am Then at 9 pm, after dusk ends and night begins, the curtains are removed so that any condensed moisture can evaporate into the night air.
To force the plants to flower during the summer they need to receive the critical dark period each day. Covering the plants with a blackout cloth each day so they receive 12 hours of darkness pushes the plants into flowering mode.
In late stages, mold prevention measures should be taken because moisture levels often build up when the plants are covered. Spray the plants with Serenade® biological fungicide, Ed Rosenthal's Zero Tolerance® herbal fungicide, potassium bicarbonate, diluted milk or other organic fungicides to prevent fungal attacks.
The advantage of placing the curtain over the garden early in the morning rather than before or after dusk is that the plants transpire and dew settles after dusk. The plants stay wet under the tarp. When the tarp is spread in the morning there is less moisture to deal with. The further from the plants that the coverings are placed the less of an effect condensation has on the garden.
The very best outdoor marijuana is grown using this technique. The reasons are more intense light, more UVB light and better weather conditions with less chance of cool weather that slows growth and development.
UVB LIGHT FACTS
Ultraviolet B (UVB) light is a spectrum of light that is invisible to us but is visible to insects and some other organisms. On humans it causes suntan and sunburn and is implicated in the formation of eye cataracts. Tanning bulbs emit UVB light.
UVB light also affects marijuana potency. The potency of high quality marijuana increases in direct ratio to the amount of UVB light it receives. This is very significant. In California, where medical dispensaries operate in an unrestricted market, many dispensaries reject fall-harvested outdoor material as inferior. They have found it lacks the potency of indoor crops and is a harsh smoke. However, marijuana grown outdoors that was forced to ripen August 10th was accepted—because it had the high potency and lacked the harshness of indoor crops. Harshness is probably a result of cool nights.
Indoors, under fluorescent and High Pressure Sodium (HPS) lamps, gardens receive little UVB light. Metal Halides (MH) without glass reflectors emit a bit more. However, there are ways of supplying your garden with UVB light. Tanning lamps work, that is, lamps that tan people, because of the UVB light they emit. Using tanning lamps increases the THC content of the crop. Reptiles and lizards require the UVB spectrum to stay healthy, so 10% of the output of “reptile fluorescent” lights is UVB. Tanning lamps are available on the Internet. Use between 5-10% of your total wattage to these lamps. For a 1,000 watt garden use 100 watts of special lighting.
"Everyone smiles as you drift past the flowers, That grow so incredibly high."
Lyrics: John Lennon and Paul McCartney “Lucy in the Sky with Diamonds”
Adding UVB light to your garden enhances your marijuana naturally, without “special formulas” and chemicals.
A green CFL can be used in a flowering garden without upsetting the flowering cycle.
This light has green LEDs installed; clipped to a hat it creates a hands-free green light.
GREEN LIGHT AT NIGHT
Plants evolved for hundreds of millions of years and never encountered a separation of light spectrums or unusual lighting regimes. When they received light it came from the sun in a mixture of spectrums from which they could pick and choose. With the advent of gas and then electric lighting, plants encountered unusual regimens and splintered spectrums.
Plants measure
day length using the red and far-red light spectrums. While they use other spectrums, they are not sensitive to most of them as far as flowering is concerned.
They use less green light than other spectrums, and reflect much of it while absorbing most other spectrums. Plants’ insensitivity to green light can be used to a gardener’s advantage. Turning a light on in the middle of the dark cycle disturbs the plants’ flowering paradigm. HPS, fluorescent and MH lamps all emit red light. Green fluorescent and LED lights contain no red light and will not disturb the dark period. You can go in the garden under adequate light to work, as long as it is green.
PART IV QUICK POINTS: LET'S GET GROWING!
VEGETATIVE GROWTH
As soon as the roots have adjusted to the new environment, it is time to increase the light and nutrients. Firm, turgid leaves and new growth are indications that the plant is ready for rapid growth. The plants should be kept on a high nitrogen (N) fertilizer regimen until they are put into flowering.
When marijuana is supplied during the vegetative stage with ample amounts of all its requirements, including nutrients, it grows very quickly. If the soil or planting mix cannot meet the plants’ nutrient needs, they require fertilization.
Leaves have stomata that serve the same purpose as human pores: they open and close as needed to regulate the absorption of CO2, water and nutrients.
Plants that are foliarly fed grow faster. Foliar feeding is especially helpful when plants are suffering from a deficiency; because the needed nutrients get directly to the plant parts that need it, the leaves.
Some pruning techniques increase yield in a given area. In addition pruned plants usually occupy more space than plants left unpruned, so yield per plant may increase substantially with pruning. Pruning, bending, and supercropping can be used to increase yield, control shape and direction of plant growth.
Things to Know
•It is important to prune the lower leaves of the plant to provide airflow under the canopy and to create cuttings for cloning. This also maximizes yield by forcing the plant’s growth energy to the top limbs where they receive the most light.
•Contrary to myth, most fan leaves should not be removed during the vegetative stage. They are sugar factories that turn light into chemical energy. They are used to power metabolism and build tissue by combining them with nitrogen and phosphorous to make amino acids and proteins.
FLOWERING
Marijuana is a short-day plant. As the days get shorter, the plant determines when it is time to flower based on the number of hours of uninterrupted darkness it receives. The natural life cycle of the marijuana plant, a fall-flowering annual, is to germinate in the spring, grow vigorous vegetative growth through midsummer, then flower and produce seed in the fall. You can manipulate the natural cycle and increase production by altering the light regime, even outdoors.
As long as the plant is exposed to red light in the 680 nanometer range, phytochrome, the hormone responsible for flowering, remains inactive. When the plant is in a period of extended darkness, the hormone gradually changes to the active form over a period of two hours. When the flowering hormone levels remain high for a critical period of time over several days, plants change their growth from vegetative and initiate flowering.
The number of hours of darkness plants need in order to initiate flowering differs by variety. To force flowering, lights must be turned on and off with consistent regularity, and the darkness must be uninterrupted. A consistent, uninterrupted dark period is key to good results for marijuana and other long-night flowering plants.
In order for the female flowers to ripen without creating seeds, they must remain unpollinated (unfertilized). Because cannabis is dioecious, male and female flowers appear on separate plants. Male flower buds look like bulbs growing from thin stems, with a curved protrusion at the bulb’s end that comes to a blunt point. Female flowers have no petals, but they are identifiable because of their pistils. Some plants that are primarily female can become hermaphrodites and grow male flowers in addition to female ones.
It is clear when the flowers have approached maturity and have begun ripening; capitate trichomes, the tiny stalk-like resin glands that fill with THC, terpenes and other cannabinoids start to grow on the leaves surrounding the flowers. The flower areas will become totally covered with resin glands. The trichomes become more prominent and stand more erect. As the resin accumulates in the cap, the flowers’ odor becomes more intense and reaches a peak at the same time the trichomes begin to fluoresce in the light.
Since marijuana grows and flowers based on the number of hours of light and darkness, manipulating its light cycle can convince a flowering plant to return to vegetative growth.
Things to Know
•The active state of the flowering hormone phytochrome is called Pr. The inactive state is Pfr.
•Some plants that are primarily female can become hermaphrodites and grow male flowers in addition to female ones. This may occur for several reasons including genetics, stress or other drastic environmental changes.
•All marijuana varieties respond to a longer dark period by hastening ripening. Shortening the light regimen down to 10 hours of light and 14 of darkness forces plants to ripen faster.
•When the caps of the trichomes, which fill with resin as the plant ripens, turn from clear to either amber or cloudy white, the buds are ready to be harvested.
HARVESTING
When the bud is ripe, it’s time to harvest. As you would expect, there is more than one way to harvest the plant. The methods fall into two main categories: harvesting the entire plant or harvesting individual buds as they ripen.
The advantage of harvesting individual buds as they ripen is that it gives the lower buds and buds hidden inside the canopy the chance to fully mature. This usually occurs within 10 days. There is a significant difference in potency and quality between unripe and ripe buds, so the extra time and labor that multiple harvesting sessions or daily bud inspections entail are well worth the effort, even for large harvests.
PICK NO BUD BEFORE ITS TIME
Some buds ripen before others since the upper canopy captures most of the light. Indoors, if there are only one or two stationary lights, a high proportion of the plant parts near the tops are in continuous shadow. Buds and leaves beneath the top canopy are also in shadow. Fewer portions of the plant are in shadow when light movers or multiple sources of light are used. However, there are still buds in the understory (the area below the canopy top) that are not ripe and need additional time.
Outdoors, buds may be hidden by fan leaves or other plant parts. Even if the plant was pruned and tied, parts may be in shadow some of the time. The variety is a factor in how the plants mature. Some plants ripen top first, others ripen bottom up, and usually buds closest to the outer edge ripen first.
Waiting the extra time and picking no bud before it is ripe assures you the finest harvest.
Another advantage of partial harvests, particularly for large crops, is that there is more time to process the material. A large harvest cut over two weeks is a lot easier to process than one that is cut all at once.
MANICURING
Manicuring is the process of removing the leaves that are growing around the buds. The best time to manicure is when the plants are freshly picked. Fresh, “wet” vegetation is turgid while it is being clipped so it is easy to handle. Just as important, the trichomes that hold THC and the terpenes are pliable rather than brittle, and are more likely to stay attached to the plant.
When dry, many of the glands snap off when the bud is handled. Growers sometimes manicure a bit while the plants are still standing. The plants are in a convenient position to remove fan leaves and other vegetation so there is less damage to the bud. Use this technique only a few days before harvest.
The plant is cut using large clippers.
Close-up of cutting.
The plants are placed in a pile that will be moved to the processing area within minutes.
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sp; Once you’ve harvested, use plenty of light when manicuring so you can see clearly exactly what you are doing. Overhead lights as well as directional desk lamps get the light where it is needed. Work over a smooth surface so the clippings and loose trichomes can be easily collected. Some manicurists work over a screen made from silk, nylon, or steel wire stretched tightly on a frame. A screen with a mesh count of about 100 strands per square inch allows any glands broken off while manicuring to drop through for later collection, while keeping the plant material on the screen. The loose trichomes, called kief, contain cannabinoids but little vegetation, so they are much more concentrated and potent by volume than the buds. Once they are collected, they can be smoked, vaporized, or added to edibles.
There are many ways to manicure, and gardeners use all kinds of scissors. What’s important is that the scissor blades are long and thin enough to get to the petiole, the leaf stem. Spring-loaded trimmers are probably the most popular. They reopen after they have been squeezed shut, so the operator doesn’t expend muscle pulling the blades apart. They also offer better control.
The procedure for manicuring freshly harvested plants begins with clipping the branches from the stem. You can then manicure the leaves while the bud remains on the branch or pick the buds from the branches.
Next, remove the large sun (fan) leaves from around the buds. This material is known as leaf. Some manicurists find it easier and faster to remove some of the vegetation by hand before switching to scissors. Fan leaves often snap off when they are pulled down.