A Beginner’s Guide to Seed Saving: Being Self-Sufficient and Saving Money Doing It!

The basics of seed saving involve selecting suitable plants from which to save seed, harvesting the seeds at the right time, and storing them properly.

Seed saving does not take a huge amount of time nor financial commitment.  In fact, it can translate into monetary savings or even profit if you get more involved in the hobby. I now have a sophisticated breeding program trying to make new and better hybrids never before seen or tasted, but that level of commitment is not necessary for the home gardener who merely wants to be self-sufficient.

I have fond memories of being child and accompanying my mother to the farm stand each spring to choose the seeds we would grow in our garden that year. As much as I enjoyed that experience, I thought it was ridiculous that every spring my mother would pay good money for vegetable seeds which were produced in every piece of produce we grew that summer. This was the beginning of my obsession with seed saving.

Vegetable Seeds Ready for Harvesting!

Vegetable Seeds Ready for Harvesting!

Which Plants to Start With?

As with most things there is no universal rule that encompasses the correct procedure of how to save seeds.  Some seeds require that the plants have been alive for several growing seasons in order to produce viable seed, while others plants require special steps to be taken in order to harvest viable seed. Tomatoes, peppers, beans and peas are good choices for the beginner to start with. These plants have flowers that are self-pollinating and seeds that require little or no special treatment before storage.

Dioecious plants with separate male and female flowers, like cucumbers and corn, may cross-pollinate. So it is difficult to keep the seed strain pure. For example, a strand of sweet corn can be pollinated by dent corn (feed corn) from a nearby farm on a breezy day. The flavor of the sweet corn crop would not be good, and any crop grown from these seeds will not have the true sweet corn flavor.

Plants of the family Cucurbitaceae such as cucumbers, melons, squash, pumpkins, and gourds can all be cross-pollinated by insects. While the harvest of fruit this year will not be affected, seeds from the inadvertent cross pollination will grow into vines with fruit unlike that of the parent plant; often inferior in flavor, size, or texture.

When saving seed, chose open-pollinated varieties rather than hybrids. Open-pollination is when pollination occurs by insects, birds, wind, humans, or other natural mechanisms. Open-pollinated plants are more genetically diverse. If open-pollinated varieties self-pollinate or are cross-pollinated by other plants of the same variety, the seed produced will grow into plants that are very similar to the parent plant. They will also bear similar fruit and set seed that will produce similar plants.

Hybrid plants are the product of a cross between two different varieties or cultivars. Remember that hybrids are a combination of the genetics of both parents. As such, the offspring will exhibit a mixture of traits from both parents. This means that some plants may exhibit all of the worst traits of both parent, while others will have the best of all possible combinations of the parental genetics. If selecting an outstanding hybrid look for plants that exhibit hybrid vigor, disease resistance, and are outstanding producers.

Hybrid plants, such as ‘Big Boy’, ‘Beefmaster’ and ‘Early Girl’ tomatoes will produce viable seed. Plants grown from that seed however, will not be just like the hybrid parents. Instead, they will be a completely new combination of traits of the plants that were initially crossed. It’s impossible to predict just how an individual seedling plant will perform or what qualities the fruits produced will have.

Some tomato varieties are not hybrids. Instead they are open-pollinated types such as ‘Hillbilly’, Yellow Pear’ and ‘Brandywine‘. Seed produced by these varieties will grow into plants very similar to the parent plants, with nearly identical fruit. Likewise, ‘Cayenne Long Slim’, ‘California Wonder’ and Hungarian Yellow Wax’ peppers; ’Sugar Snap’, ‘Little Marvel’ and ‘Tom Thumb’ peas; and ‘Kentucky Wonder‘, ‘Bronco Bush’ and ‘Provider‘ beans are all open-pollinated varieties that will produce close to true from seed.

Once you have planted an open-pollinated crop, select the plants from which you want to save seed. Choose only the most vigorous plants with the best-tasting fruit as parents for the next year’s crop. Do not save seed from weak plants.

Harvesting Seeds

Saving tomato seeds can be done with little trouble. Simply allow the fruit to ripen fully, scoop out the seed and gelatinous interior and place the mixture in a glass jar with some water. Place the glass jar in a sunny window or on a protected area of a back porch. Stir the mixture gently daily. A white mold will start to cover the top of the mixture and then, after five to seven days, the seed will start to sink to the bottom of the bowl. Pour off the liquid and mold and rinse off the seeds. Place them on a dry paper towel and let them dry out for a few days. Once the seeds are completely dry, they are ready to be stored.

Saving pepper seeds is even easier. Leave some peppers on the plant until they are completely ripe and start to wrinkle a bit. Remove the pepper(s) from the plant and cut them open. Harvest the seeds and spread them out on a paper towel. Allow them to dry, Once dry, they are ready to be stored.

Peas and beans are also easy to store. Save pea and bean seeds by allowing the pods to ripen on the plants until they are dry and starting to turn brown, the seeds will make a rattling noise inside if shaken at this point. This may be as long as four or five weeks after you would normally harvest the peas or beans to eat. Remove the pods from the plants and spread them out to dry indoors. They should dry at least another two weeks before removing the seeds.

Storing Seeds

Store seeds in tightly-sealed Tupperware or glass container. You can store different kinds of seeds, each in individual paper envelopes. I prefer to use the Kraft #1 coin collecting envelopes. Keep seeds dry and cool. A temperature between 32°F and 41°F is ideal, so your refrigerator is often a good place to store seeds.

A small amount of silica-gel desiccant added to each container will absorb moisture from the air and help keep the seeds dry. Silica gel packets and bulk silica used for drying flowers can be found at craft supply stores.

Be sure to label your saved seed envelopes with their name, variety, and the date collected. It’s too easy to forget the details by the following spring. Now you can have a whole lot of seeds to choose from for next years garden at a fraction of the price. Happy gardening!


Stanhopea Wardii Orchid

This beautiful Stanhopea Wardii ‘Edwin Boyett’ AM/AOS orchid was grown by one of the Atlantis crew members and is currently at our Atlanta location.

Stanhopea Wardii Orchid

This species of orchid is natively found growing on rocks and trees in Nicaragua, El Salvador, Costa Rica, Panama, Columbia, Venezuela, and northern Brazil. It typically grows in humid environments and in elevation ranging from 2,600 – 5,300 feet (800 – 1,600 meters), making it one of the most wide ranging orchids in geography. This species of Stanhopea orchids is also considered one of the easier species to grow.

The flowers only last two to three days and have a lemon/citrus (sometimes even a honey-like) scent. Stop by to see this beautiful flower while it is still in bloom!

The Great Norcross Pumpkin

Organic Pumpkin

Henry & Joe grew this amazing pumpkin at our Norcross location. Not an easy task, but well worth the work! It was started indoors under a 1000 watt HPS light and fed Canna Coco nutrients. Once it started to get much bigger, they moved it into a 100 gallon Viagrow cloth pot to grow outside. Since then, it has been fed Jamaican bat guano and worm castings.

Now we want YOU to guess the final weight when it is harvested this week!

Comment on this post with your best guess. The person with the closest guess will win their choice of one of the following prizes:

Complete propagation kit
Beer brewing kit
Fertilizer regiment (quart size) from General Hydroponics
Fertilizer regiment (quart size) from Canna Nutrients
Fertilizer regiment (quart size) from Botanicare

The winner will be announced Monday, August 4th. Don’t wait! Send us your guess early!

Atlantis Hydroponics Pumpkin

Organic Pumpkin

You can also submit your guess by commenting on our Facebook page or by tweeting @atlantishydroponics with #NorcrossPumpkin and your guess.

** To win one of the prizes, you must be located within the lower 48 states.

Hydroponic System Record Chart

Hydroponic System Record Chart
Nutrient management and environmental changes can be a great opportunity to discover optimal plant growth. Whether you are a beginner or professional gardener, this hydroponics chart allows you to easily record even the smallest variables of your indoor garden without being too complicated.

Why should you record changes to your garden? By keeping track of what changes you made (lower/higher temperature, added/decreased nutrients, etc) and when those changes were made, you are able to see the impact those variables made to your garden. Use the chart over and over each week to keep track of your entire crop. Save each harvest record and compare over time. The possibilities are endless and so are the benefits of recording changes to your hydroponic system.

Click to open a printable version of the Hydroponic System Record Chart

Even a Perfect Design Can’t Overcome the Laws of Physics: Dealing With Heat in Grow Rooms – Part 4

Physics can manipulate fire but cannot separate heat from fire; they are inexorably linked.

Physics can manipulate fire but cannot eliminate heat.

The laws of physics, as we understand them at this time, do not allow for negotiation or manipulation, which means heat cannot be destroyed. The fact is that our grow room equipment makes lots of heat and, even if we utilize the best equipment and grow room designs, we still can only remove a fraction of that heat before it enters our grow rooms. This still leaves us with tremendous amounts of heat to deal with. Our only option being to remove the heat from our rooms. This is where a heat exchanger comes in.

Heat exchangers are devices used to remove heat from one location and transfer it somewhere else. Air conditioners are a perfect example, but heat exchangers also include water chillers and evaporative coolers.

The most common heat exchangers used in grow rooms are air conditioners. Air conditioners have a couple of basic components. These components manage refrigerant and move air in two directions: indoors and outside. See the image below for an illustration of the components.


  • Evaporator - Receives the liquid refrigerant
  • Condenser - Facilitates heat transfer
  • Expansion valve - regulates refrigerant flow into the evaporator
  • Compressor - A pump that pressurizes refrigerant

The cold side of an air conditioner contains the evaporator and a fan that blows air over the chilled coils and into the room. The hot side of an air conditioner is made up of the compressor, condenser, and another fan to vent hot air coming off the compressed refrigerant. In between the two sets of coils, there is an expansion valve. It regulates the amount of compressed liquid refrigerant moving into the evaporator. Once in the evaporator, the refrigerant experiences a pressure drop, expands, and changes back into a gas. The compressor is actually a large electric pump that pressurizes the gaseous refrigerant as part of the process of turning it back into a liquid.

Most gardeners will use one of the following 3 types of air conditioners:  window units, split component units, and ductless air conditioners. Window air conditioners have all the above mentioned components mounted into a relatively small metal box that installs into a window opening. The hot air vents from the back of the unit, while the condenser coils and fan cool and re-circulate indoor air. The biggest drawback of window units is that they remove air from a grow room – making a sealed grow room or the use of CO2 nearly impossible.

Larger air conditioners with split component work a little differently: they utilize a control thermostat (preferably located in the grow room) to monitor and set the desired temperatures. The compressor and condenser (the hot side of the unit) is mounted in a separate all-weather housing outdoors. The cold side of the air conditioner, consisting of the expansion valve and the cold coil, is generally placed into an air handler. The air handler blows air over the coil and distributes the cool air throughout the grow room(s) using a series of ducts. This type of air conditioner can also make a sealed grow room or the use of CO2 problematic if the return air vent is located in the grow room.

Mini Split AC Diagram

Mini Split AC Diagram – photo courtesy of www.kingersons.com

Ductless air conditioners separate the components similarly to the larger split air conditioners but as their name implies they do not utilize any duct. The internal unit (the air handler) is mounted to the grow room wall with only a small hole needed to connect the refrigeration and low level electrical lines to the outside unit (the condenser), which can be located anywhere from 15 to 50 feet away (depending on the line set used). In addition to the refrigeration lines, which allow refrigerant to move between the two units, there is also condensation line that removes the accumulated condensation from the air handler.  One of the most significant benefits of the ductless units is that they do not transfer any air between the internal and external components allowing a grower to construct a truly sealed room.

Quick Tip: When sizing an air conditioner, factor in the room size. A 500 square foot room requires 12,000 BTU of cooling just to maintain comfortable living conditions. Your air conditioner will need to be able to handle that plus the heat created by your grow room equipment.

When choosing an air conditioner knowing how they work is useful, but their level of efficiency should play into your deliberative process too.  Air conditioners are rated in BTU or British Thermal Units; the higher the BTU, the more cooling capacity a unit will have.  Efficiency however does not correlate to size; the efficiency of an air conditioner is rated by its energy efficiency rating (EER). The EER rating is calculated by dividing a unit’s BTU by its wattage. The higher the EER the more electrically efficient it will be.  EER is generally calculated using a 95°F outside temp and an inside temp of 80°F and 50% relative humidity; making the EER a more realistic measurement of energy efficiency in warmer climates.

Another efficiency rating seen on air conditioners is SEER or seasonal energy efficiency ratio. The seasonal energy efficiency ratio (SEER) is similar to EER but instead of being evaluated at a single operating condition, it represents the expected overall performance for a typical year’s weather in a given location. The SEER is calculated with the same indoor temperature, but over a range of outside temperatures from 65°F to 104°F. This difference provides a better picture of how a unit will perform over the course of a season.

*Quick Tip: The higher an air conditioner’s EER & SEER, the less electricity it will consume. This equates to lower electrical bills!

Water chillers are another type of heat exchanger, which removes heat from water not air. Many people use water chillers in grow rooms to maintain hydroponic reservoirs at the ideal temperature of 68°F, but thanks to the ingenuity of companies like Hydro Innovations we also have the option of using water chillers to keep rooms cool with water cooled reflectors, water cooled CO2 generators, and radiator style airhandlers. All of these pieces of equipment circulate cold water through a radiator made of very thin and highly conductive metal with lots of surface area to absorb the heat. As heat passes over the radiator surface, the cold water absorbs the heat and becomes hot water. The hot water is then sent back into the water chiller to be cooled and the process starts over.

According to Hydro Innovations, water cooling can be up to 50% more efficient than using air conditioners. A water cooled CO2generator is able to remove as much as 86% of the heat created by the combustion reaction (burning of natural gas or propane) that creates CO2. An inline fan hooked up to a 6” Hydro Innovations Ice Box (a radiator style heat exchanger) can provide as much as 4500 BTU of cooling and the 8″ version up to 6500 BTU of cooling. The heat removed from water by a water chiller can not be destroyed. It is merely moved or transferred elsewhere. This means you can not place a water chiller in your grow room or you will remove heat from the water only to heat up the air!

*Quick Tip: If a water cooled CO2 generator is not an option for you and your grow room temperatures are too high in the summer because of heat created by your traditional CO2  generator, consider switching to a CO2 tank and regulator and wait to use your CO2 generator until the colder months of the year.

An evaporative cooler is more commonly found in greenhouses not indoor grow rooms.  Evaporative coolers provide a low cost, energy efficient method of cooling. When water evaporates it absorbs heat (BTUs) which result in a cooling effect in the surrounding vicinity. One type of evaporative cooling system uses misters to spray small micron water droplets (mist) into the air. These water droplets quickly vaporize resulting in a drop in the surrounding temperature. The reason this type of cooling is not utilized for indoor growing is because along with the temperature drop comes a sharp rise in humidity. Even more challenging is the fact that the higher the humidity goes, the less effective this type of cooling becomes.

The second type of evaporative cooler is known as a aspen cooler or swamp cooler. This style of cooler drips water across thick 4-6” treated cardboard pads that cover an air intake; large exhaust fans at the opposing end of the room or building pull large volumes of hot air from outside across the wet cardboard pads. As the hot air moves across the wet cardboard, water evaporates and provides a localized cooling effect. This type of cooler also adds humidity to the air and is similarly not suited for indoor cultivation unless someone is in a very arid region, and even then it would be very unlikely to keep a grow room at ideal temperatures.

Remember that sometimes hard problems have simple solutions. Adding a silicon fertilizer can increase the heat tolerance of your plants. Silicon is actively transported into the plant similarly to macro nutrients like potassium. From there it moves up the xylem and is distributed out to the growing shoots. There, the silicon forms larger polymer chains (polymerization) which allows plants to deposit silicon in the form of solid amorphous, hydrated silica which is then incorporated into the plant’s cell walls, thereby armoring the plant’s cells and allowing them better control over their rate of transpiration. This affords the plant improved internal temperature regulation.

So if you already have 99 problems, make sure that HEAT ain’t one!

Better Grow Room Equipment Builds Better Grow Rooms: Dealing With Heat in Grow Rooms – Part 3

Water Cooled 12,000 Watt Grow Room

Water Cooled 12,000 Watt Grow Room

When building a grow room, functionality needs to be your primary concern. That means choosing the right equipment for the job is all that matters. Maybe you are the kind of person who likes flashy sports cars, but you go for the sleek exterior with the small engine when money runs short. Not me, I could care less about aesthetics. It is function over form every time.

One of the most common pieces of equipment used to help reduce heat in a grow room is the air cooled reflector. The job of a reflector, air cooled or otherwise, is to focus the light emitted from the lamp; thereby maximizing the light available to drive photosynthesis. Air cooled reflectors reduce heat in a grow room by running a stream of air (usually from a centrifugal fan) through the reflector via an air intake and exhaust vent. By passing the briskly moving air stream over the lamp, much of the heat created from the bulb can be exhausted before it can radiate into the grow room. An additional benefit is that if air is pulled from an adjacent room and passed through the sealed light(s) and then exhausted out, not only is heat removed but CO2 is not – making this a great option for closed environment grow rooms.

Air Cooled Cylinder

Air Cooled Cylinder

Air cooled reflectors are available in three styles:

  • air cooled cylinders
  • truncated prism reflectors with horizontally mounted lamps
  • truncated prism with dual internal chambers

The air cooled cylinder is the simplest design. Air is passed through a solid 6” or 8” glass cylinder in one end and exhausts out the other. Inside of the cylinder is often a small reflector to focus the light towards the plants. This design leads to efficient air cooling, but the tiny reflector does a poor job maximizing light intensity and coverage area. If the reflector is removed and the air cooled cylinder is mounted vertically (instead of horizontally) it can be an ideal choice for 360 degree vertical gardens. Air cooled cylinders are also excellent choices for small confined garden spaces (like those built inside of furniture or tiny closets) and lower wattage bulbs.

Truncated Prism Reflector With  Horizontally Mounted Lamp

Truncated Prism Reflector With Horizontally Mounted Lamp

The next and most common style of air cooled reflector is the truncated prism with a horizontally mounted lamp. This style of reflector first appeared in the early 1990’s with 4” vents, but now is more commonly seen with 6”, 8”, or even 10” vents. The larger the vent size the greater the potential airflow. If using more than 4 lights in a row connected together (in series) then increase your vent size from 6” to 8” or 10”.

Truncated Prism With Dual Internal Chambers

Truncated Prism With Dual Internal Chambers


The last style of air cooled reflector is the truncated prism with dual internal chambers. The bottom chamber is sealed in reflective aluminum and houses either a vertically or horizontally mounted lamp. The top chamber is located between the steel housing and the aluminum insert. This air gap allows the heat from the lamp to radiate through the aluminum and be carried away with the air stream. The benefit of this style of reflector is that it allows the lamp to operate at an ideal temperature; thereby producing its optimal spectral output.

This reflector design overcomes a flaw present in other styles of air cooled reflectors – HID bulbs are designed to run hot (as high as 750° Fahrenheit). When a bulb is exposed to a brisk moving cool air stream, the bulb never reaches its ideal operating temperature. This prevents the bulb from producing its intended spectral output and intensity. Operating a lamp below its ideal temperature can reduce PAR output by 7-10%. Another argument against the use of air cooled reflectors is that the tempered glass used inside air cooled reflectors diffuses the light as it passes trough it, which reduces light transmission by 6-8%.

If we accept both of the above arguments, we are talking about losing a maximum of 18% of the light created. When you hang a reflector over the plant canopy, a non air-cooled reflector has to be hung higher than an air-cooled reflector to prevent the heat created by the lamp from burning the plants. Now consider the inverse square law, which states that the intensity of light is inversely proportional to the square of the distance from the source of that light. This means that if we compare an air cooled reflector hung at 12″ above the canopy and a non air cooled reflector hung at 24” above the canopy, the air cooled reflector will provide significantly more usable light to the plants – even with the 18% reduction due to glass and lamp operating temperature.

An illustration of the Inverse Square Law

Being an additional foot from the lamp reduces the overall intensity of light by over 75% per square foot – making the 18% loss from air cooling, incorrect temperature, and glass trivial when compared to the intensity gained by moving the light source closer to the plants.

Including air cooled reflectors in your grow room design will allow much improved heat control, but you can take air cooling a step or two further preventing even more heat from entering your grow room with the use of insulated duct and insulated reflector covers. After heat from a lamp is picked up by the air stream, it is normally moved out of the room via thin aluminum duct. If you want the most efficient and coolest grow room then spring for a higher end duct that has several layers of insulation wrapped around the aluminum duct work. This insulation will prevent heat from radiating into your grow room as the hot air is evacuated.

The other item that prevents heat from radiating into the grow room is a reflector cover. A reflector cover is a flame retardant fabric insulation custom fit to enclose a reflector. Reflectors are made of metal and the longer a bulb burns inside of that reflector the hotter the metal housing gets, which radiates that heat into your grow room. A reflector that is being actively air cooled can still have a surface temperature of 102° Fahrenheit, but when you install a reflector cover the surface temperature can drop to below 70° Fahrenheit. This prevents a lot of heat from ever entering your grow room.

Do Your Plants Have A Nutrient Deficiency?

Have you noticed discoloration or spotting on your plants? Any signs of plant distortion? It may not be an insect or disease – you could have a nutrient deficiency.

Not all issues in your garden are a result of insects or plant diseases, even though the signs may appear similar on the surface. Nutrient deficiencies in plants can also manifest in discoloration, damage, and distortion. Furthermore, these problems are not only caused when a plant lacks nutrients. A plant can also show signs of damage if it is given too much of a nutrient. Balance and attention to detail are important.

Plants require a mix of nutrients to remain healthy. Those nutrients and the amounts of each may differ depending on the type of plant you grow, but all plants take in nutrients through their roots by water. If you think you may have issues related to nutrients, begin by making sure you have plenty of pH balanced water. If the water or soil is too alkaline of acidic, your plant may have problems absorbing the nutrients regardless of what you are trying to feed.

After checking your water and soil, it is time to start looking at what you are (or are not) feeding your plants. To help check what issues you may be facing, Canna has put together a helpful Deficiency Guide that lists some common symptoms and possible causes.

Deficiency Guide Canna

Canna has also made their latest version of CannaTalk available for download. If you would like to check it out, a copy is available for download here: http://www.cannatalk.com/downloads/files/24_CannaTalk.pdf

Hops Growing In Our Organic Garden

Our hops bine is looking healthy at 20 feet tall (and still growing!) and is just beginning to show signs of flowering!

Kent Hops Bine

The heat of summer is not stopping our organic garden from thriving! This Kent Golding hop bine is being grown in a keg tub filled with all natural Ocean Forest Potting Soil and is fed a steady diet of compost tea and Botanicare Pure. This variety of hops is scented with a touch of lavender and citrus and is sure to make a savory ale. Great hops for warm weather brewing!

Want to Save Money in Your Grow Room? Put Down Those LEDs & Grab Double Ended HPS Lights!

How can you save money on your grow room? It may be time to reconsider the grow lights you use.

Double Ended HPS Lamps are the Most Efficient Lighting Technology Available!

Double Ended HPS Lamps are the Most Efficient Lighting Technology Available!

The Copernican revolution was as seismic a shift in paradigms as there ever has been in all of scientific theory. Recently there has been a similar shake-up, granted not quite as earth shattering as the movement away from the Ptolemaic model, but it has turned the agricultural world on its ear. A study conducted by scientists at Utah State University compared the efficiency of 6 HID lights, 10 LEDs, 3 ceramic metal halides, a fluorescent induction light as well as a standard T8 fluorescent light. The results were illuminating!

The agricultural community has long been looking for more efficient ways to produce artificial sunlight. Whether it is in a greenhouse for supplemental light or in a research facility as a primary light source, there has been nothing that could efficiently produce light to drive photosynthesis. Fluorescent lighting quickly gave way to HIDs but their high power consumption and tremendous heat output made them an undesirable option. People reexamined Nikola Tesla’s work and produced efficient electrodeless induction lights but they were not the answer. Light emitting diodes, after much improvement over their original designs, have been proclaimed the answer to our artificial lighting dilemma. In fact, a recent study estimated the LED market for plant applications will be $3.6 billion by 2020, a nine-fold increase from 2013. However, their price and coverage ability has been a huge barrier to their much hyped & heralded victory.

There are some LED companies making unsubstantiated claims like “photons emitted from their LEDs are two to four times more “effective” than photons from the sun.” There is no evidence to support this. Recent studies suggest that photons within the photosynthetic wavelengths of 400 to 700 nm are essentially equally capable of driving photosynthesis, and therefore plant growth. Erik Runkle, a professor at Michigan State University says that “light intensity has a much larger effect on plant growth than light spectrum, and this is especially true when electrical lighting supplements sunlight, such as in greenhouse applications.”

Most recently a new type of HID lamp known as a double ended (DE) HPS has captured the growing community’s attention. Information released just weeks ago by Jacob Nelson and Bruce Bugbee placed DE technology at the front of this ever evolving technological race to efficiently mimic sunlight. The study compared 22 different lights in their efficiency to drive photosynthesis. The lights tested included lights already in use by many indoor growers like: the Gavita Pro 1000w Complete Double Ended, the Lumigrow Pro 325, the IGrow 400w Induction Light, the Cycloptics Ceramic Metal Halide, standard T8 fluorescent lights as well as mogul based 1000 & 400 watt magnetic ballast light systems by Sunlight Supply.

The study compared fixtures based on “photon efficiency” which describes the photons that are produced useful to a plant. The measure of efficiency used in the experiment was micromoles of photosynthetic photons (µmol) per joule (J) of electricity. The higher the value, the more efficient the fixture. The findings show that the new DE technology produces the same 1.7 µmol/J as the best LEDs but the five year cost of ownership and operation is 2.3 times higher for the LED fixtures. Simply put, DE HPS lamps will produce just as many useable photons as LEDs at a fraction of the price. For more information about the actual results of the study see Figure 1 below.

Figure 1. Photon efficiency and cost per mole of photons, assuming all photons (180°) are captured by plants.

This data begs the question “if currently LEDS and DE HPS lamps are tied for their level of efficiency, and the main factors for choosing one over the other is a unit’s initial cost plus its cost of operation over time then what will happen when LED technology inevitably falls in price?” Based on Haitz’s law which states that every 10 years the price of LEDs decrease by a factor of 10, while their efficiency increases by a factor of 20; that means that it is only a matter of time before the efficiency of LEDs overtake DE technology. Problem is that new technology comes at a premium price, and it will be several years before the improved efficiency of LEDs can chip away at the 5 year cost of operation differential which currently stands at 2.3 times that of DE lighting options.

Other findings from the Nelson/Bugbee study concluded that there are currently applications where LED fixtures may be a better choice compared to DE HPS fixtures. That is because a DE HPS fixture emits light in a 360 degree pattern or when combined with a luminaire (reflector) in a 180 degree pattern. LEDs produce a focused beam of energy; that means that depending on the arrangement of plants and aisles a focused photon source will reduce wasted photons and allow for a more efficient lighting.

In order to maximize production one must have a full plant canopy. That is because we need the canopy to be able to absorb the light emitted from the lamp; this is known as canopy photon capture. As the plant growth area under a fixture gets smaller, wasted radiation often increases. Figure 2 illustrates the concept of canopy photon capture efficiency.


Figure 2.

Figure 2.

For greenhouse applications selection of supplemental lighting should be made based on the cost to deliver photons to the plant canopy. This takes into account 2 factors: 1) the fundamental fixture efficiency, measured as micromoles of photosynthetic photons per joule of energy input, and 2) the canopy photosynthetic (400–700 nm) photon flux (PPF) capture efficiency, which is the fraction of photons transferred to the plant leaves. With technology advancing almost as fast as papers can be published it will not be long before we will see a truly efficient artificial light source to drive photosynthesis.  If you would like help maxamizing your indoor garden design and layout come into any of our Atlantis Hydroponics locations. We are always glad to help!



If you would like to read the original Nelson & Bugbee journal article it can be found here.

Note: All data and charts, graphs etc provided in this article are part of the Nelson & Bugbee study: Economic Analysis of Greenhouse Lighting: Light Emitting Diodes vs. High Intensity Discharge Fixtures, Published: June 06, 2014DOI: 10.1371/journal.pone.0099010 is Copyright: © 2014 Nelson, Bugbee.

This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Data Availability: The authors confirm that all data underlying the findings are fully available without restriction. All data are included within the manuscript.

Dealing With Heat in Grow Rooms – Room Design & Construction Considerations

A well designed grow room capable of handling heat effectively is a must, especially when considering all of the heat created by our equipment. Much like real estate, the first consideration when designing a grow room should be… location, location, location!

Grow Room Construction

Photo Courtesy of freedigitalphotos.net

As an example, a basement will naturally be cooler and better insulated than an attic. A room without windows might mean it will be necessary to cut holes in the ceiling or wall(s) for ventilation. If you are not comfortable with this type of construction then a grow tent may be the perfect option!

When designing a grow room consider your access to electricity: check your panel, plan where your electricity will come from, and consider how much electricity you need versus how much is available. Safety is tantamount. It is not worth burning your house down for an extra 400 watts. Does the room have air conditioning? Where is the thermostat located? You don’t want the whole house to be 60°F so your garden can be 78°F, that would be both expensive and inefficient.

Once you have assessed your options and chosen a room to grow, there are still a few things to keep in mind before beginning to cut holes willy-nilly with your sawzall. First, are you going to build a closed growing environment? Or a room with intake and exhaust? A closed room (based on Closed Environment Agriculture or CEA) will necessitate a larger air conditioner and also a CO2 source, which could make your initial expense greater. However, a closed room can be dialed-in more precisely. On the other hand, a ventilated room can be less expensive to construct, but will require cutting more ventilation holes.

A standard suggestion when venting a grow room is to provide a minimum of 1 complete air exchange every 5 minutes. This is a minimum and (depending on the heat load, location, and size of the room) it may be recommended that 100% of the air be exchanged as often as once each minute. To determine how big an exhaust fan you need, divide the cubic footage by the number of minutes you want all of the air exchanged. To determine cubic footage:

  • Calculate the total square footage by multiplying the length of your room by the width of your room.
  • Then multiply the total square footage by the height of the room to find the total cubic volume.
    – For example a 10 ft wide by 14 ft long room with 8 ft ceilings has a total volume of 1,120 cubic feet of air
    10ft x 14ft = 140sq ft
    140sq ft x 8ft = 1120 cubic ft

To figure out how big an exhaust fan you need, divide the cubic footage by the number of minutes that you want all of the air exchanged. For this example lets say 5 minutes: So 1,120 cubic ft / 5 minutes = 224.

That means your exhaust fan will need to provide a minimum of 224 CFM (cubic feet per minute). Remember that that 224 CFM is with no resistance. Adding a length of duct will increase the size of the fan needed! A 25’ length of flexible ducting will decrease air flow by about 7% and each bend will further reduce air flow by an additional 1-4%.

QUICK TIP: Make your runs of duct as straight and short as possible to maximize air flow and minimize resistance.

Now that you have calculated the size of your exhaust fan(s) you can cut the holes for your ventilation. Remember that you want to vent hot air out and that heat rises, so exhaust holes should be cut high & conversely intake holes should be cut low. Intake air can be passively brought in by the negative pressure created by your exhaust fan(s) or actively with a fan with less CFM than your exhaust fan; this will maintain negative pressure (a desirable trait in vented rooms). Try to place the exhaust and intake openings on opposite sides of the room to create cross ventilation. Two quick tips of sage advice: measure twice and cut once & be aware of where your electrical lines and plumbing are BEFORE you cut into a wall or you may be in for a very WET SHOCK!

A well insulated room can keep hot air out and cold air in. When you build out your grow room, line the interior walls with extruded polystyrene foam (XPS) insulation board (commonly called pink or blue foam board). XPS has an R factor of 4.5 to 5 per inch of thickness. R-factor is the capacity of an insulating material to resist heat flow. The higher the R-value, the greater the insulating power. Another lesser used but very useful type of insulation is a radiant barrier. Radiant barrier insulation is a reflective insulation designed to reflect heat, not absorb it. It is applied to the exterior of the walls to prevent heat from the house from entering the grow room.

Another type of room design is called a high air exchange room. No CO2 enrichment, no air conditioning, just LOTS of air movement. By exchanging the air in the room faster than the heat can be added you can essentially maintain the temperature of your grow room at the temperature of your intake air. For this type of grow room design you need to exhaust 100% of the air in your room at least every minute. Fans use less electricity than air conditioners so this can save you LOTS of money on your electric bill.  Please remember that a high air flow grow room will only work for those growing in areas with a moderate climate. 

One last note on room design – when picking your grow area make sure you can place the ballasts outside of the grow room. Ballasts are the second greatest heat producing piece of grow room equipment and putting them in the grow room due to lack of planning is a cardinal sin. If you currently have your ballasts in your room, this is an easy problem to overcome. If you are not lucky enough to have external space for your ballasts then consider making a vented ballast chamber. Place your ballasts in 12” diameter section of hard metal duct and blow air across them using an inline fan which exhausts out of the grow room. This will remove the heat from the ballasts before it can enter your grow room.

Check out part I of this article!