The Rules of Growing

An Amazing Grow Room Built Inside of a Cave: Birds Botanicals

An amazing grow room built inside of a cave: Birds Botanicals

Most of us live a technology-packed, fast-paced life with push notifications influencing our behavior as we walk down the street, and our pockets constantly buzzing, dinging, and ringing as we sync our ever-busier schedules from phone to tablet to desktop. It is no surprise that we have lost touch with Mother Nature. Whatever the excuse for our lack of connection with the earth, the fact remains that sometimes what we need most is our hands in the dirt as a reminder that all of our scientific innovations and accomplishments still pale in comparison to the magic of a seed sprouting and growing into the very food that sustains our bodies. Gardening is for everyone. It is a reconnection with nature, a time where we can think in peace, pound our frustrations into the soil, and all the while regain a Zen state of being. No matter your schedule or living situation there is a type of garden that will fit your life!

Traditional Gardening:

The Backyard Garden – Simple and easy. Find a sunny spot in your yard and dig away. Any size plot will do, just stick your shovel in the ground and start turning the soil. Add plants or seeds and you have a garden!

The Raised Bed GardenFor the DIYer or those of us that have less than ideal soil, simply buy or build a raised bed, fill it with soil, and start your seeds.

The Square Foot GardenFor the space challenged, the urban gardener, or the balcony bound, a container or a few 3-5 gallon pots of soil along with a little planning and some organic seeds, and you are on your way to food self-sufficiency.

Urban / Modern Gardening:

 The Closet Garden – For anyone with a closet to spare. Protect the floor, reflect the light  (more on that in a minute), add a grow light, soil, and some seeds, and you can be a year round farmer.

A Great Example of a Grow Room: See Why Below...

A great example of a grow room

 The Grow Tent GardenThe simplest and fastest way to have a garden that meets your needs, as well as the needs of your plants. A perfect fit for every space (they come in lots of sizes), with all of the forethought already built in, it will make your garden a lush cornucopia in no time.

The Vivarium – This terrarium-style garden can be designed to meet the needs of more exotic plants, but for you “Type A” control freaks out there this might be what you are looking for. These little gardens are designed to be tiny working ecosystems behind glass. Attractive and compact, it is a perfect fit for your high rise apartment overlooking the concrete jungle, adding a bit of nature back to your brick bastion. Check out Orchid Karma for an exciting look at Vivariums.

A Vivarium is Like a Living Painting in Your Home

A Vivarium is like a living painting in your home

The “Out of the Box” Garden:

The Trailer Garden – Although not every gardener’s cup of tea, this type of garden is proving to be perfect for dooms day preppers and businessmen alike. It’s essentially a re-purposed  shipping container transformed into a cash cow or an end of the world Eden. Check out our friends at Podponics in Georgia for a more in-depth exploration of this contemporary take on farming.

A Shipping Container Makes a Great Garden...

An impressive garden built inside of a shipping container

The Cave Garden – I admit this one is a bit of a stretch as most of us do not have a vacant cave in our real estate portfolio, but this is really cool. What can you do when your mine shuts down, and you are left with a maze of tunnels winding inside the earth? Well if you are smart you may turn it into an underground farm. Check out Bird’s Botanicals to see how this gardener made an environment without sunlight into a horticultural oasis.

The Rooftop Garden – With a strong movement towards locally grown produce and a desire to reduce carbon footprint, many gardeners have transformed urban rooftops into productive and profitable farms.


So what do these different gardens have in common? Basic needs. All plants require that five basic needs be met: Light, Air, Water, Fertilizer, and Substrate. Let’s examine how these needs are met by growers using the the various gardening methods above.

A Rose Grower Has Chosen To Use High Pressure Sodium Light to Grow Their Roses Indoors

A rose grower has chosen to use high pressure sodium light to grow his roses indoors.


Light provides the input of energy for the chemical process of photosynthesis that turns carbon dioxide and water into sugar and oxygen. Outdoor gardeners simply utilize the sun as their light source; after all it is free and effective on all but the cloudiest of days. Indoor growers like the closet gardener may employ a variety of light sources to provide energy to their gardens including fluorescent, HID, LED, and plasma lights. All mentioned will work for providing the energy necessary for photosynthesis, but some might be better suited to your needs. Talk to the associate at your garden specialty or local hydroponic store to find the best light for you.


Air is a category that encompasses several factors including carbon dioxide, temperature, and humidity. All of these are critical to plant growth and are all important to account for in any type of garden.

Carbon dioxide naturally occurs in the air we breathe (and ironically by the air we exhale), but the 400+ parts per million (PPM) in the air may not be sufficient if there is not enough air exchange or air movement in the garden. Outdoor gardeners have it pretty easy in that the natural movement of air ensures they always have enough CO2.

Indoor growers who have constructed rooms and grow tent gardeners must actively work to ensure their plants receive adequate CO2. For a grower just starting out a grow tent can be a good option. The grow tent manufacturers built in all of the same universal and necessary features of a grow room, affording a novice grower a well designed grow space without the years of experience necessary to design a grow room on their own.

A Well Designed Grow Room: Grow Tents offer all of the Same Features with Less Work

A well-designed grow room: grow tents offer all of the same features with less work.

One of the best things about grow tents are that the manufacturers, knowing that CO2 is necessary, have designed ventilation holes for both the intake and exhaust of air. Exhausting the air with an inline fan creates negative pressure inside the tent, and allows for the passive (or active if a second fan is also used) flow of fresh CO2 rich air from outside via the intake flaps. A gardener can also choose to supercharge their indoor garden by utilizing either bottled CO2 or a COgenerator to increase the available amount of CO2 in the room to 1500 PPM, but we’ll touch more on methods of adding CO2 to grow rooms in another blog post.

Achieving the Proper Temperature Inside The Cave Garden Took 6 Months: Now it is Perfectly Controlled With Just the Heat From the Lights & a Network of Fans

Achieving the proper temperature inside the cave garden took 6 months. Now it is perfectly controlled with just the heat from the lights and a network of fans.

Temperature requirements vary with the plant, and although most plants can survive for a short time outside of their ideal temperature range, longer exposure to extreme temperatures will slow growth and possibly kill them. Some orchids for example, like the Phalaenopsis (2nd most grown potted plant in the world) prefer a minimum of 65°F but prolonged exposure to temperatures below 50°F will cause severe damage or even death. That is why I must tip my hat to the ingenuity of David Bird, the cave gardener. He knew the ambient temperature of the cave in the mid 50s combined with HID lights would increase the temperature by 15+ degrees providing ideal temperatures for his tropical plants. Cooling is accomplished with fans pulling colder air from unheated areas deeper inside of the cave, while simultaneously exhausting the warm grow room air.

Humidity is sometimes overlooked by gardeners, but a necessary factor to be aware of and mitigate. Plants will grow in a wide range of humidity but some are more finicky than others. Humidity being too high can result in an environment that is overly hospitable to mold and bacterial infection, while low levels of humidity can stress a plant as it tries to replace moisture constantly lost to transpiration. The vivarium gardener must keep a watchful eye on their humidity as the small volume of air in the garden allows for rapid swings in humidity with slight increases in temperature. Often both a humidifier (to raise the humidity) and an exhaust fan (to lower humidity) are built into the design of a vivarium.


Water is necessary for all life, and one that all of our gardeners must supply. Fresh water can be provided from any number of sources including streams, reservoirs, ponds, aquifers, and wells. One of the simplest and best sources of water is rainwater. Using a simple rain water collection system and a rain barrel allows our rooftop gardener or square foot gardener to provide fresh water to their garden. When it comes to water, the question isn’t just its source, but how to use it. For plants growing in either soil or soilless mix, the best advice comes from a sage old orchid grower who said, “You can never water too much, only too often.” What he meant by that is if you water a little bit every day the growing medium will stay wet and the roots will rot. Conversely if you water a 1 gallon pot with 20 gallons of water the growing medium will be fully saturated but as long as you wait until the growing medium dries out appropriately your plant will not suffer. In fact heavy watering will help prevent fertilizer build-up in your growing media.

This Roof Top Herb Garden Relies on Rain Water for Irrigation

This rooftop herb garden relies on rainwater for irrigation


There are 16 elements that plants must have, although some would place that number in the twenties. There are many brands and formulations of fertilizer to choose from, and none of them are “the best.” That is because different plants, growing mediums, and growing environments all necessitate different fertilizer choices. So what do our square foot and back yard gardeners do? Many make their own fertilizer using grass clippings, leaves, and organic kitchen waste, by tossing it into the compost bin. It takes just a few months for free, supercharged, rich compost for their gardens that feeds the plants an organic diet rich in minerals and nutrients, while improving the quality of their soil.

Square Foot Raised Bed Garden

In a square foot garden, using rich organic compost helps improve the soil


The growing medium can have a significant impact on the success of any garden by determining several factors: moisture, pH, drainage, fertilizer retention (CEC), and oxygen content in the root-zone. There are many growing mediums to choose from: soil, soilless, LECA stone, diatomite, perlite, vermiculite, coconut, redwood fiber, sawdust, recycled glass (Growstone), volcanic rock, gravel, rockwool, and even air. Each of the growing mediums listed above (and by no means is it an exhaustive list) have attributes and differences that will make them more or less effective in a particular application. However, sometimes you just do not have many options, like the two inventive youths from Swaziland who took the limited materials they has access to (sawdust and chicken manure) and used them as the media for a hydroponic science experiment, winning $50,000 and the Scientific American’s inaugural Science in Action award.

Regardless of the type of gardener you are, the style of gardening you practice, or the crops you grow, the five basic needs of plants will always need to be addressed. The better you are at meeting the fundamental needs of your plants, the greater amount of attention you can devote to the details which differentiate a good gardener from a great one. With so many gardeners and innovative methods of farming coming into practice, remember the basics of growing remain the same.


Is there a Light at the End of the Tunnel? A Look at LED Technology in Horticulture

LED Side by Side Trial With Lumi Grow ES330

Side by Side Trial – Lumi Grow ES330 LED vs. 270 Watt HPS (on left)

We have all seen the plethora of advertisements in the magazines about LED grow lights.  When LEDs first hit the horticulture market they were little more than Light-Brite™ toys with expensive price tags and big promises. They claimed that each watt of LED lighting was equivalent to more than 10 watts of HID lighting, on top of which they asserted LEDs would produce no heat, have better penetration of light through the canopy, and that they would revolutionize the growing industry.  Unfortunately, the early LEDs were unable to deliver on most of their promises.

LED stands for Light Emitting Diode.  Unlike traditional light sources with delicate filaments, electrodes, or pressurized gas filled lamps (i.e. HIDs), LEDs are solid state electronics, and as such are more robust and longer lasting (Bourget, 2008).  Solid state by its most simple definition means “made without any moving parts.”  A flash memory card is solid state device, where as a typical hard drive is not.  By not incorporating moving parts into the design, solid state electronics are less likely to break, wear out, or malfunction. This added level of reliability is one of the biggest benefits of LEDs.  Current LEDs are rated for as many as 70,000 hours of operation before they reach the point where replacement is advisable.  Although they will still be working at that point, at 70,000 hours of operation they will have reached a 30% diminishment in luminous output making it cost effective to replace them.  Seventy-thousand hours means that a grower using LEDs will not change the diodes for almost 16 straight years, running 12 hours per day, every day.

LEDs have not always had the longevity and reliability they are able to deliver today.  The history LEDs being used in horticultural applications started in the late 1980’s with crude arrays of red only (660 nanometer) LEDs.  Early experimentation with LEDs in horticulture was driven by their potential for use in growing food for space travel.  In the late 1990s the crops research group at the Kennedy Space Center conducted several studies on the yield and physiological response of several crops to LED lighting.  LEDs became even more promising with two critical advances in LED technology; the advent of blue LEDs, and high output diodes.  For a full timeline of LED lighting in horticulture please see the timeline below (HortScience Vol.43(7) Dec. 2008)

Horticulture LEd Lighting Timeline

Horticulture LEd Lighting Timeline

The advances in LED technology keep on coming; each decade LED prices have fallen by a factor of 10, while their performance has grown by a factor of 20 (a phenomenon known as Haitz’ Law).  So it seems the future of LEDs is getting brighter! In the next blog we will look at the different applications of using LEDs for growing plants and see if they are close to delivering on their original promise of revolutionizing the horticultural world.

Lumens are for Humans but PAR is for Plants!

Prism Splitting Light

Prism Splitting Light

It blew my ten-year-old mind when my “all knowing” grandmother told me that the Blue Jay we were watching was in fact not blue. She explained that light is composed of many colors, and it is the colors that are reflected, not absorbed that our eyes perceive as the color of an object. This is a necessary reminder that what is perceived might not be what it appears to be. For decades the indoor gardening community has used Lumens as the standard increment for the measurement of light. Lumens were unfortunately a poor choice, here’s why.

Diagram of How a Prism Works

Diagram of How a Prism Works
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Lumens are essentially a measure of brightness based on human perception. Precisely, a lumen is equal to the light emitted by one candle falling on one square foot of surface located one foot away. This however presumes a human as the perceiver of the light. Plants “perceive” light differently; from a plant’s perspective, light that is useful for photosynthesis is not necessarily bright. Light, or more specifically, visible light is made up of wavelengths of energy on the electromagnetic spectrum ranging from 380-770 nm (nanometers). Plants utilize wavelengths from 400-700nm for photosynthesis. Brightness does not accurately describe if the light will be more or less useful to a plant.

Light can be characterized in other ways when discussing its benefit to plants. Color temperature is often referred to in the horticultural industry on lamp boxes to describe the color of the light emitted by the lamp. Does 4,000K grow a plant better than 7,500K? Color temperature is listed in Kelvin (K), which is a measurement of temperature. The temperature of what you might ask? It is a description of the relative whiteness of a piece of tungsten steel when heated to that particular temperature in degrees Kelvin. This accurately characterizes the color of the light as we perceive it, but color temperature again fails to address how effective a particular light source will be at providing the energy necessary to drive photosynthesis.

Don’t get frustrated by this inadequate information. There is in fact a measurement that precisely describes how effective a particular light will be for growing plants; PAR (Photosynthetic Active Radiation). PAR spectrum accounts only for light or more precisely photons emitted between 400-700nm. Scientists have concluded that it requires about 9 photons to bind one CO2 molecule in photosynthesis [6CO2 + 6H2O (+ light energy) C6H12O6 + 6O2]. Even though blue photons have more energy it has also been found that there is little difference between the effectiveness of red versus blue photons at driving photosynthesis as long as the photons are within the 400-700nm range. This leads to a direct correlation between the number of photons produced in the PAR spectrum by a given light, and the photosynthetic potential of that light.

Photons are emitted by light sources in very large numbers so we do not talk about billions or quadrillions of photons, instead we refer to them using the multiplier moles (which stand for 6.0221415 x 1023) To make the numbers even more accessible, the number of moles is often divided by 1 million resulting in micro-moles (μmol). Light sources emit photons continuously over time so the number of micro-moles is more accurately described as μmol/per unit of time (most commonly seconds).

When trying to quantify how effective a light source is beyond the total output of μmol/per second, you must consider one last piece of information… the size or area of your garden. Inevitably some of the photons produced will not reach your garden. So the most accurate representation of a light source’s ability to drive photosynthesis will take into account the area being lit and how many photons reach that given area per second; usually a square meters. That representation which actually summates the effectiveness of a light source for photosynthesis is written as μmol/m2/s. This descriptor is actually referred to as Photosynthetic Photon Flux Density or PPFD for short.

So in light of all of the information above, let’s remember that lumens are not a useful descriptor of a light’s ability to drive photosynthesis. I think I will sit back with a drink, and digest all of the information about PAR & PPFD while I watch the not blue Blue Jay outside my window.