IciBif igiFfr n

and flow io/j/cs am be the length of a greenhouse. Long tables take a long time to flood and require a huge reservoir of nutrient solution.

Marijuana Fertilizer Schedule
Big beautiful buds grow super dense on tables.

THIRTEEN

Smoke is immediately sucked out of the room when using this Mine fan. The fan demonstration took place at the 2000 CannaBusiness trade show in Germany.

At least one good circulation fan and an extraction fan are necessary in grow rooms. The extraction fan in this grow room Is attached to a carbon filter.

Carbon Filters For Cannabis

Monitor temperature and humidity regularly. The 06T (33°C) 34 percent relative humidity conditions make plants use more water and less fertilizer. Adjust irrigation schedule to meet needs, life. Tor example, the level of CO, in the air over a field of rapidly growing cannabis could be only a third of normal on a very still day. Wind blows in fresh CO^-rich air. Rain washes air and plants of dust and pollutants. The outdoor environment is often harsh and unpredictable, but there is always fresh air. Indoor gardens must be meticulously controlled to replicate the outdoor atmosphere.

Carbon dioxide and oxygen provide basic building blocks for plant life. Oxygen is used for respiration-burning carbohydrates and other foods to provide energy. Carbon dioxide must be present during photosynthesis. Without CO, a plant will die. Carbon dioxide combines light energy with water to produce sugars. These sugars fuel the growth and metabolism of the plant. With reduced levels of CO,, growth slows to a crawl. Except during darkness, a plant releases more oxygen than is used and uses much more carbon dioxide than it releases.

Roots use air, too. Oxygen must be present along with water and nutrients for the roots to be able to absorb nutrients. Compacted, water-saturated soil leaves roots little or no air, and nutrient uptake stalls.

Air Movement

Air ventilation and circulation are essential to a healthy indoor harvest. Indoors, fresh air is one of the most overlooked factors contributing to a

Smoke is immediately sucked out of the room when using this Mine fan. The fan demonstration took place at the 2000 CannaBusiness trade show in Germany.

At least one good circulation fan and an extraction fan are necessary in grow rooms. The extraction fan in this grow room Is attached to a carbon filter.

Introduction

Fresh air is essential in all gardens. Indoors, it could be the difference between success and failure. Outdoor air is abundant and packed with carbon dioxide (CO,) necessary for plant

Monitor temperature and humidity regularly. The 06T (33°C) 34 percent relative humidity conditions make plants use more water and less fertilizer. Adjust irrigation schedule to meet needs,

Water Vapor

Circulation

Plants use al! CO.

around the leaf within a few minutes. When no new COj-rich air replaces the used CO,-depleted air, a dead air zone forms around the leaf. This stifles stomata and virtually stops growth. If it is not actively moved, the air around leaves stratifies. Warm air stays near the ceiling, and cool air settles near the floor. Air circulation breaks up these air masses, mixing them together. Avoid these would-be problems by

Water Vapor

Water Vapor ygen

Microscopic stomata located on leaf undersides must remain clean and un-stifled by humidity to promote rapid growth.

healthy garden and a bountiful harvest. Fresh air is the least expensive essential component required to produce a bumper crop. Experienced growers understand the importance of fresh air and take the time to set up an adequate ventilation system. Three factors affect air movement: stomata, ventilation, and circulation.

Stomata

Stomata are microscopic pores on leaf undersides that are similar to an animal's nostrils. Animals regulate the amount of oxygen inhaled and carbon dioxide and other elements exhaled through the nostrils via the lungs. In cannabis, oxygen and carbon dioxide flows are regulated by the stomata. The larger the plant, the more stomata it has to take in carbon dioxide and release oxygen. The greater the volume of plants, the more fresh CO,-rich air they will need to grow quickly. Dirty, clogged stomata do not work properly and restrict airflow. Stomata are easily clogged by dirt from polluted air and sprays that leave filmy residues. Keep foliage clean. To avoid clogging stomata, spray foliage with tepid water a day or two after spraying with pesticides, fungicides or nutrient solution.

This photo of a half-opened stomata, the mouth-like opening on leaf underside, was magnified 2500 times.

opening a door or window and/or installing an oscillating circulation fan. Air circulation also helps prevent harmful pest and fungus attacks. Omnipresent mold spores do not land and grow as readily when air is stirred by a fan. Insects and spider mites find it difficult to live in an environment that is constantly bombarded by air currents.

Air Circulation Marijuana

This garden has several circulation fans to move air between dense, resinous buds.

Place circulation fans far enough away from plants to prevent too much airflow on any one portion of the garden.

Here Is an example of a heavy-duty extractor fan from a Dutch grow room.

Hot air flows upward naturally. Always design grow rooms and greenhouses to take advantage of this principle.

Marijuana Fan Leaves

Floor-mounted oscillating fans stir the air in this CO, aroand leaves is used quickly and must he room 24 hours a day. replaced every few minutes.

MARIJUANA HORTICULTURE The indoor/Out

Floor-mounted oscillating fans stir the air in this CO, aroand leaves is used quickly and must he room 24 hours a day. replaced every few minutes.

Place circulation fans far enough away from plants to prevent too much airflow on any one portion of the garden.

Here Is an example of a heavy-duty extractor fan from a Dutch grow room.

This garden has several circulation fans to move air between dense, resinous buds.

Hot air flows upward naturally. Always design grow rooms and greenhouses to take advantage of this principle.

Hot Roof Weed Grow

This blower is at the end of intake air ducting. The main fan is at the other end.

Avoid long, unnecessary ducting such as shown above. Keep ducting as short as possible.

Roof fans and vents make grow roam ventilation easy and inconspicuous.

A booster fan in the gray box pushes intake air down the duct to the bottom of the garden.

Avoid long, unnecessary ducting such as shown above. Keep ducting as short as possible.

Ballasts are kept in the box which contains the extra heat. Separate ducting carries out the hot air.

This blower is at the end of intake air ducting. The main fan is at the other end.

Roof fans and vents make grow roam ventilation easy and inconspicuous.

Squirrel Cage Duct

Squirrel cage blower moves a lot of air, but it is noisy! This blower has been necked down to force more air through the ducting,

For indoor rooms, in-line fans arc one of growers' favorites. These fans arc quiet and efficiently move large volumes of air.

Squirrel cage blower moves a lot of air, but it is noisy! This blower has been necked down to force more air through the ducting, es, stomata function properly, and growth rebounds. A vent fan that extracts air from the grow room is the perfect solution to remove this humid, stale air. Fresh air flows in through an intake vent or with the help of an Intake fan.

Ventilation is as important as water, light, heat, and fertilizer In many cases, fresh air is even more important. Greenhouses use large ventilation fans. Grow rooms are very similar to greenhouses and should follow their example. Most grow rooms have an easy-to-use opening, such as a window in which to mount a fan, but security or room location may render it unusable. If no vent opening is available, one will have to be created.

All grow rooms require ventilation. This system could be as simple as an open door or window that supplies and circulates fresh air throughout the room, but open doors and windows can be inconvenient and problematic. Most growers

This fan is suspended by bungee cords to shunt noisy vibrations. Always keep your fans well lubricated so they run smoothly and quietly.

Ventilation

Fresh air is easy to obtain and inexpensive to maintain-it is as simple as hooking up and placing the proper-sized exhaust fan in the most efficient location. An intake vent may be necessary to create a flow of fresh air in the room.

A 10-foot square (0.92 m2) garden will use from 10 to 50 gallons (38 to 190L) or more of water every week. Plants transpire (similar to evaporation) most of this water into the air. Every day and night, rapidly growing plants transpire more moisture into the air. If this moisture is left in the grow room, humidity increases to 100 percent, which stifles stomata and causes growth to screech to a halt. It also opens the door for pest and disease attacks. Replace moist air with fresh, dry air, and transpiration increas

For indoor rooms, in-line fans arc one of growers' favorites. These fans arc quiet and efficiently move large volumes of air.

Straight with no bond is the most efficient

Thirty degree curve cuts up to 20 percent of air transmission.

Forty-five degree curve cuts up to 40 percent o( air

Ninety degree curve cats up (a GO percent of air

transmission.

transmission.

329

Straight with no bond is the most efficient

Thirty degree curve cuts up to 20 percent of air transmission.

elcct to install a vent fan. Some growers need to install an entire ventilation system including ductwork and several fans.

A vent fan pulls air out of a room four times more efficiently than a fan is able to push it out. Vent fans are rated by the amount of air, measured in cubic feet per minute (CFM) or (square meters per hour [m'/h]) they can move. The fan should be able to replace the air volume (length x width x height = total volume in cubic feet) of the grow room in less than 5 minutes. Once evacuated, new air is immediately drawn in through an intake vent or with the help of an intake fan. (Covering the intake vent with fine mesh silkscreen will help exclude pests.) An intake fan might be necessary to bring an adequate volume of fresh air into the room quickly. Some rooms have so many little cracks for air to drift in that they do not need an intake vent.

Do not set up a circulation fan in the room and expect it to vent the area by pushing air out a distant vent. The circulation fan must be very large to adequately increase air pressure and push enough air out a vent to create an exchange of air. A vent fan, on the other hand, is able to change the pressure and exchange the air quickly and efficiently.

Squirrel cage blowers are efficient at moving air but are very loud. Blowers with a balanced, well-oiled wheel run most quietly. Felt or rubber grommets below each foot of the fan will reduce noise caused by vibrations. Run motor at a low RPM to lessen noise.

In-line fans are designed to fit into a duct pipe. The propellers are mounted to increase the airflow quickly, effortlessly, and as quietly as possible. In-line fans are available in quiet, high-quality models that run smoothly.

Propeller or muffin fans with large fan blades expel air through a large opening, and are most efficient and quiet when operated at low RPM. A slow-moving propeller fan on the ceiling of a grow room will quietly and efficiently move the air.

Hot air rises. Adept growers locate air exit vents in the hottest peak of the room for passive, silent air venting. The larger the diameter of the exhaust ducts, the more air that can travel

To control the air temperature, hang the thermostat near the canopy of the garden.

Intake air ducting has holes covered with duct tape. Air flow is directed by removing pieces of tape.

Fresh Air Intake For Grow Room

Fresh air in this room is piped in directly where plants need it.

Most often, the vent fan is attached to ducting that directs air out of the grow room. Flexible ducting is easier to use than rigid ducting. To install, run the duct the shortest possible distance, and keep curves to a minimum. When turned at more than 30°, much of the air that enters a duct will not exit the other end. Keep the ducting straight and short.

Intake Air

Many rooms have enough fresh air coining in via cracks and holes. But other grow rooms are tightly sealed and require fresh air to be ushered in with the help of an intake fan. An intake fan is the same as an exhaust fan, except it blows fresh air into the room. The ratio of 1 to A (100 CFM [mJ/h] incoming and 400 CFM [mVhJ outgoing) should give the room a little negative pressure. Delivering fresh air to plants ensures they will have adequate CO, to continue rapid growth. One of the best ways to deliver air directly to plants is to pipe it in via flexible ducting. Ingenious growers cut holes in the intake ducting to direct air where it is needed. The air is dispersed evenly throughout the room.

Always make sure fresh air is neither too hot nor too cold. For example, one friend that lives in a hot, arid climate brings cool fresh air in from under the house, where the air is a few degrees cooler than ambient air.

Security

When installing a vent fan, security concerns dictate that no light or odor escape from the exterior vent while allowing ample air release. This can be accomplished in several ways. Baffle or turn the light around a corner to subdue brilliance. Many chimneys in British Columbia, Canada, shoot light out like a spotlight against the low cloud cover. You can walk down city streets where half the chimneys in the neighborhood are beacons of bright light A 4-inch (10.16 cm) flexible dryer hose will subdue light in smaller grow rooms. Larger 8, 10, and 12-inch (20, 25, 30 cm) heat duct pipe is ideal for moving larger volumes of air.

To control the air temperature, hang the thermostat near the canopy of the garden.

through them. By installing a big, slow-moving vent fan in this vent, hot stale air is quietly and efficiently evacuated, A fan running at 50 RPM is quieter than one running at 200 RPM. Smart growers install 12-inch ducting and inline fans.

Intake air ducting has holes covered with duct tape. Air flow is directed by removing pieces of tape.

Fresh air in this room is piped in directly where plants need it.

Place one end of the duct outdoors. It should be high enough, preferably over 12 feet, so the odor disperses above most people's heads. One of the best vents is the chimney. The outlet may be camouflaged by using a dryer hose wall outlet attached to a vent fan. The vent fan is then placed near the ceiling so it vents hot, humid air. Check for light and air leaks. Set up the fan and go outdoors after dark to inspect for light leaks. See below; "Setting Up the Vent Fan" and "Odor,"

Greenhouse fans are equipped with louvers (flaps or baffles) to prevent backdrafts. During cold and hot weather, undesirable backdrafts could alter the climate in the room and usher in a menagerie of pests and diseases. Installing a vent fan with louvers eliminates backdrafts, but may present a security risk if it attracts the attention of the wrong crowd.

Temperature

An accurate thermometer is essential to measure temperature in ail grow rooms. Mercury or liquid thermometers are typically more accurate than spring or dial types, but ecologically unsound. An inexpensive thermometer will collect basic information, but the ideal thermometer is a day-night or maximum/minimum type that measures how low the temperature drops at night and how high it reaches during the day. The maximum and minimum temperatures in a grow room are important for the reasons explained below.

A thermometer that Thermometer Hygrometer measures in Fahrenheit and Celsius will come in very handy.

Under normal conditions, the ideal temperature range for indoor growth is 72-76°F (22-24°C). At night, the temperature can drop 5-10°F (2-5°C) with little noticeable effect on growth rate. The temperature should not drop more than 15°F (8°C), or excessive humidity and mold might become problems. Daytime temperatures above 85°F (29°C) or below 60°F (15°C) will slow growth. Maintaining the prop-

Day/Night

67'-rnfflri9"

Knowing Celsius and Fahrenheit equivalents makes grow room calculations more precise.

Check the temperature and humidity in several places in the grow room. Lights really heat a room!
This combination thermometer/hygrometer is fairly accurate and easy to mount.

Fill barrels with water and let the sun heat them several days. Water stays warm all night to heat the greenhouse!

This simple humidistat/them iostat controller is just one of many different time/controllers found at mMigreenair.com. It is very easy to use and foolproof.

er, constant temperature in the grow room promotes strong, even, healthy growth. Make sure plants are not too close to a heat source, like a ballast or heat vent, or they may dry out, maybe even get heat scorch. Cold Intake air will also Stunt plant growth.

Cannabis regulates its oxygen uptake in relation to the ambient air temperature rather than the amount of available oxygen. Plants use a lot of oxygen; in fact, a plant cell uses as much oxygen as a human cell. The air must contain at least 20 percent oxygen for plants to thrive. Leaves are not able to make oxygen at night, but roots still need oxygen to grow. A plant's respiration rate approximately doubles every 20°l"

(10°C). Root respiration increases as the roots warm up, which is why fresh air is important both day and night.

Temperatures above 85°F (29°C) are not recommended even when using CO, enrichment. Under the proper conditions, which are very demanding to maintain, higher temperatures step up metabolic activity and speed growth. The warmer it is, the more water the air is able to hold. This moist air often restrains plant functions and decelerates growth rather than speeding it. Other complications and problems result from excess humidity and moisture condensation when the temperature drops at night.

Heat buildup during warm weather can catch growers off guard and cause serious problems. Ideal grow rooms are located underground, in a basement, taking advantage of the insulating qualities of Mother Earth. With the added heat of the HID and hot, humid weather outdoors, a room can heat up rapidly. More than a few American growers have lost their crops to heat stroke during the Fourth of July weekend, since it is the first big holiday of the summer, and everybody in the city wants to get away to enjoy it. There are always some gardeners that forget or are too paranoid to maintain good ventilation in the grow room while on vacation. Temperatures can easily climb to 100"F (38DC) or more in grow rooms that are poorly insulated and vented. The hotter it is, the more ventilation and water that are necessary.

The cold of winter is the other temperature extreme. Montreal, Quebec, Canada, growers will remember the year of the big ice storm. Electricity went out all over the city and surrounding areas. Water pipes froze, and heating systems failed. Residents were driven from their homes until electricity was restored some days later. Many growers returned to find their beautiful gardens wilted, stricken with the deepest, most disgusting green only a freeze can bring. Broken water pipes, ice everywhere! It is difficult to combat such acts of God, but if possible, always keep the grow room above 40°F (5°C) and definitely above freezing, 32°F (0°C). If the temperature dips below this mark, the freeze will rupture plant cells, and foliage will die back or, at best, grow slowly. Growth slows when the temperature dips below 50"F (10°C). Stressing plants with cold weather conditions is not recommended; it may yield a proportionately higher TI-IC content, but will reduce plants' overall productivity.

A thermostat measures the temperature, then controls it by turning on or off a device that regulates heating or cooling, keeping the temperature within a predetermined range. A thermostat can be attached to an electric or combustion heater. In fact, many homes are already setup with electric baseboard heat and a thermostat in each room.

A thermostat can be used to control cooling vent fans in all but the coldest grow rooms. When it gets too hot in a room, the thermostat turns on the vent fan, which evacuates the hot stale air, The vent fan remains on until the desired temperature is reached, then the thermostat turns off the fan. A thermostat-controlled vent fan offers adequate temperature and humidity control for many grow rooms. A refrigerated air conditioner can be installed if heat and humidity are a major problem. Just remember, air conditioners draw a lot of electricity. If excessive heat is a problem, but humidity is not a concern, use a swamp cooler. These evaporative coolers are inexpensive to operate and keep rooms cool in arid climates.

Common thermostats include single-stage and two-stage. The single-stage thermostat controls a device that keeps the temperature the same both day and night, A two-stage thermostat is more expensive but can be set to maintain different daytime and nighttime temperatures. This convenience can save money on heating, since room temperature can drop 5-10°F (2-5°C) at night with little effect on growth.

Many new grow room controllers have been developed in the last ten years. These controllers can operate and integrate every appliance in the grow room. More sophisticated controllers integrate the operation ol CO, equip-

7his air conditioner lowers grow room temperature and humidity, The hot radiator is outside, about 10 feet ( 3 m) ciway.

1 kc ".sa ■ - '

H

I i

\ \

■ ffl

i'\- 1

' 1 '

XH 'y. >»', ^ijtiimiMu imm

vrti

en r• \

A simple electric heater may be necessary to warm the room after lights go out.

A simple electric heater may be necessary to warm the room after lights go out.

ment, vent, and intake fans. Relatively inexpensive computerized controllers are also available for grow rooms. If temperature and humidity regulation are causing cultural problems in the grow room, consider purchasing a controller.

Un-insulated grow rooms or grow rooms that experience significant temperature fluctuations require special consideration and care. Before growing in such a location, make sure it is the only choice. If forced to use a sun-baked attic that cools at night, make sure maximum insulation is in place to help balance temperature instability. Enclose the room to control heating and cooling.

When CO, is enriched to 0.12-0.15 percent (1200-1500 ppm), a temperature of 85°F (29UC) promotes more rapid exchange of gases. Photosynthesis and chlorophyll synthesis are able to take place at a more rapid rate causing plants to grow faster. Remember, this higher temperature increases water, nutrient, and space consumption, so be prepared! Carbon dioxide-enriched plants still need ventilation to remove stale, humid air and promote plant health.

The temperature in the grow room tends to stay the same, top to bottom, when the air is circulated with an oscillating fan(s). In an enclosed grow room, HID lamps and ballasts keep the area warm. A remote ballast placed near the floor on a shelf or a stand also helps break up air stratification by radiating heat upward, Crow rooms in cool climates stay warm during the day when the outdoor temperature peaks, but often cool off too much at night when cold temperatures set in. To compensate, growers turn on the lamp at night to help heat the room, but leave it off during the day.

Sometimes it is too cold for the lamp and ballast to maintain satisfactory room temperatures. Grow rooms located in homes are usually equipped with a central heating and/or air conditioning vent. The vent is usually controlled by a central thermostat that regulates the temperature of the home. By adjusting the thermostat to 72°F (22°C) and opening the door to the grow room, it can stay a cozy 72°F (22°C). However, using so much power is expensive, and could cause a security quandary. Keeping the thermostat between 60 and 65°F (15-18aC), coupled with the heat from the HID system, should be enough to sustain 75°F (24°C) temperatures. Other supplemental heat sources such as inefficient incandescent lightbulbs and electric heaters are expensive and draw extra electricity, but they provide instant heat that is easy to regulate. Propane and natural gas heaters increase temperatures and burn oxygen from the air, creating CO, and water vapor as by-products. This dual advantage makes using a CO . generator economical and practical.

Kerosene heaters also work to generate heat and CO,. Look for a heater that burns its fuel efficiently and completely with no tell-tale odor of the fuel in the room. Do not use old kerosene heaters or fuel-oil heaters if they burn fuel inefficiently. A blue flame is burning all the fuel cleanly. A red flame indicates only part of the fuel is being burned. I'm not a big fan of kerosene heaters and do not recommend using them. The room must be vented regularly to avoid buildup of toxic carbon monoxide, also a by-product of combustion.

Diesel oil is a common source of indoor heat. Many furnaces use this dirty, polluting fuel. Wood heat is not the cleanest either, but works well as a heat source. A vent fan is extremely important to exhaust polluted air and draw fresh air into a room heated by an oil furnace or woodstove.

Insect populations and fungi are also affected by temperature. In general, the cooler it is, the slower the insects and fungi reproduce and develop. Temperature control is effectively integrated into many insect and fungus control programs. Check recommendations in Chapter 14, "Pests, Fungi and Diseases."

Humidity

Humidity is relative; that is, air holds different quantities of water at different temperatures. Relative humidity is the ratio between the amount of moisture in the air and the greatest amount of moisture the air could hold at the same temperature. In other words, the hotter it is, the more moisture air can hold; the cooler it is, the less moisture air can hold. When the temperature in a grow room drops, the humidity climbs, and moisture condenses. For example, an 800 cubic foot (10 x 10 x 8 feet) (21.5 nv) grow room will hold about 14 ounces (414 ml) of water when the tempera-

A maximum/minimum digital hygrometer registers the high and low humidity as well as current humidity.

Marijuana Low Humidity

Clonei ture is 70°F (2 PC) and relative humidity is at 100 percent. When the temperature is increased to 100T (38^0, the same room will hold 56 ounces (1.65 L) of moisture at 100 percent relative humidity, That is four times more moisture! Where does this water go when the temperature drops? It condenses, onto the surface of plants and grow-room walls, just as dew condenses outdoors.

Relative humidity increases when the temperature drops at night. The greater the temperature variation, the greater the relative humidity variation will be. Supplemental heat or extra ventilation is often necessary at night if temperatures fluctuate more than 15°F (8°C).

Seedlings and vegetative plants grow best when the relative humidity is from 65 to 70 percent. Flowering plants grow best in a relative humidity range from 55 to 60 percent. The lower humidity discourages diseases and pests. As with temperature, consistent humidity promotes healthy, even growth. Relative humidity level affects the transpiration rate of the stomata. When humidity is high, water evaporates slowly. The stomata close, transpiration slows, and so does plant growth. Water evaporates quickly into drier air causing stomata to open, increasing transpiration, fluid flow, and growth. Transpiration in arid conditions will be rapid only if there is enough water available for roots to draw in. If water is inadequate, stomata will close to protect the plant from dehydration, causing growth to slow.

When the relative humidity climbs beyond 70 percent, the pressure outside the leaf is too high and inside too low. This causes the stomata to close, which slows growth. For example, a 40-inch (1 m) tall plant can easily transpire a gallon (4 L) per day when the humidity is below 50 percent. However, the same plant will transpire about a half-pint (0.5 L) on a cool humid day.

A 10 x 10 x 8 foot (800 cubic feet) (21.5 nr) grow room can hold:

4 oz (118 ml) of water at 32°F (0°C). 7 oz (207 mi) of water at 50°F (10°C). 14 oz (414 ml) of water at 70°F (21°C). 18 oz (532 ml) of water at 80°F (26°C). 28 oz (828 m!) of water at 90°F (32'C). 56 oz ( 1.65 L) of water at 100°F (38°C).

The moisture holding capacity of air doubles with every 20"F (I0°C) increase in temperature.

A maximum/minimum digital hygrometer registers the high and low humidity as well as current humidity.

Humidity

Clonei riowi-jiiiii

Vegetative

This is the best relative humidity range (or clones, as well as vegetative and flowering plants.

B4u Pictures Flowers
JJ.

Air conditioners cooi and dehumidify grow rooms. Growers must weigh the benefits against the extra electricity they use.

Growing Soilless

Growing Soilless

This is an easy-to-follow, step-by-step guide to growing organic, healthy vegetable, herbs and house plants without soil. Clearly illustrated with black and white line drawings, the book covers every aspect of home hydroponic gardening.

Get My Free Ebook


Responses

  • marko
    What stifles stomata?
    6 years ago

Post a comment