Healthy Soil Produces Healthy Plants

By Michael Dean

One of the trends in the hydroponic marketplace is that growing technologies have become increasingly user friendly. There was a time not too long ago when hobby growers had to be ¼ grower, ¼ engineer, ¼ builder and ¼ electrician. Today small-scale growroom construction is simplified, or can be by-passed altogether with complete pre-assembled growing environments. For the commercial grower things have gotten a little easier, but most still prefer to do-it-themselves.
This trend of more user friendly technology coupled with an increase in the public’s knowledge of hydroponic technologies has gotten many urban dwellers to convert a little extra space into productive indoor gardens. You will need to find an out-of the way space you can use to construct or house your growing system. Some of the pre-fabricated growing chambers are stealthy enough to be incorporated into your living area without being terribly obtrusive.
Firstly, we will look at converting a spare closet, crawlspace or attic into your personal garden. For high-quality herbs, you will need about one square foot of linear floor space to produce about one ounce of dried herbs. Experienced growers can achieve 1-1/2 ounces per square foot or better, depending on the variety. A good size for a small personal garden might range from 2’ X 3’ to 3’ X 5’. After that, we’re talking about walk-in grow rooms because the average person only has a reach of about 36 to 40”. For efficient use of building materials and overall functionality 2’ X 4’ growing areas work well. If you don’t have a lot of vertical height there won’t be a sufficient volume of air to buffer temperatures, so climate control will have to be precise and constant. You will need to be able to completely enclose the space, providing a light and air-tight environment. You could be amazed at just how bright a ¼” light leak can be in a dark surrounding; like trying to keep the sun hostage in a broom closet. Black and white poly is inexpensive and relatively easy to wrap around a closet or crawlspace to close it in. Hold up a small square of cardboard where you staple to prevent the sheet of poly from ripping itself free of your staples. With doorways, cover the opening with a sheet of opaque poly and install a large zipper for an opening. This is the most simple and inexpensive way to address the challenge of constructing a light-tight space, although as far as construction materials go, it’s not especially durable.
To take it a step further you could line the growing area with 6 mil vapour barrier and install an insulative layer. I like the blue sheets of foam. A 1-1/2” thickness is nice to work with because you can create rigid panels with 2” X 2”’s. For maximum insulation and soundproofing you can use ½” thickness plywood. Use two sheets along with some wood lathing to sandwich a ½” of packed fine sand. These sand-filled panels are very heavy to handle and require a fair bit of support. However, you could crank the 1812 Overture in the growing area and be near deaf to it on the other side. Cover the sand-filled panels with a durable and reflective surface.
Providing adequate ventilation can be a challenge when converting extra living space into a growing area. Actually, it can be really quite easy if you don’t mind drilling six inch diameter holes in your wall and stepping over and ducking around labyrinths of ducting. It can make for some interesting conversations when you have company over. However, do not be discouraged because it is possible to eliminate or minimize your ducting requirements. To do this, you will need to enrich the growing environment with carbon dioxide via a tank and flow meter. You will also need an activated carbon filter so that the exhaust from smaller growing areas can be safely introduced into your living space. In winter months the extra heat and humidity can be quite welcome. The exhaust system may serve to function as: air exchange, heat reduction, and humidity reduction. Your thermostat(s) must control heating and cooling. If not using a dehumidifier, a dehumidifying thermostat will also be need to be wired in-line with the exhaust fan. A high degree of thermostatic accuracy is important to maintain constant temperatures as changes can occur quickly in growing environments with limited air volume. Look for a narrow differential (+/- rating) on the thermostat you use. Digital is preferred. If using H.I.D. lamps in small areas, air-cooled reflectors will be a must, and you may need to run ducting to draw air to the growing area.
Alternatively, you can illuminate the growing area with fluorescent lighting. The new generation of compact fluorescent lights help closet growers eliminate many of the problems associated with using H.I.D. lighting in small spaces. An inexpensive light meter was held up to the 90 watt version (high Kelvin) at a distance of about one inch, and came up with a reading of about 50, 000 lumens. At one foot from the bulb the light dropped considerably in intensity and read 5,000 lumens. With reflective walls close to the plants and using good quality light reflectors a grower could harvest a respectable crop using a “sea of green” application in an area of about 2’ X 2’ with the crop finishing at less than 12 to 16” high.
Standard 4’ fluorescent tubes are capable of producing high-quality plants provided that the area is blanketed by the tubes coupled with highly reflective surfaces enclosing the growing area. It can take a little bit of engineering to use a standard 4’ fixture while using 4’ building materials. The plants should be only about 12 to 16” tall at harvest if using fluorescent lighting due to the sharp decrease in intensity with distance traveled. Remember that if you blanket a small area with fluorescents and keep the distance to plants at a minimum, you will have good light intensity even if only 20% of the initial lumens produced are available for photosynthesis (although using more watts per lumen to do so). In all small growing environments it is critical to use the right strain. You are basically looking for “dwarf” varieties or plants that tend to maintain tight internodal spacing through a range of growing conditions. “Tiny Tim” tomato varieties produce harvestable fruit 45 days from transplant and can finish at less than 18” in height.
To help keep plants within an efficient size range you can try the following:

• Maintain narrow Day/Night temperature differentials as large swings in temperature can trigger stretching.
• Never let the temperature get higher than 85 degrees Fahrenheit with supplemental carbon dioxide or 75 degrees Fahrenheit using ambient carbon dioxide levels.
• Initiate the reproductive cycle as soon as a root system has become established. You may need to do a minor leaf pruning occasionally to improve air circulation and light penetration in the plant canopy.
• Good plant hygiene is a must when plants are growing in close quarters. Try to use materials that are durable and easy to keep clean.
• Keep a close eye on your nutrient strength around the roots, high ammonium levels can contribute to an increase in internodal spacing. In these types of situations it might be better to go a little under than over with nutrient concentrations. Use a nutrient that can be tailored to your particular growing situation and plant variety.
• Bend and tie down branches or entire plants as necessary to maximize light and reduce vertical height.
• Use lights higher in the blue spectrum of the photosynthetic response curve as this will help maintain tight internode spacing in certain varieties (often of more Northern origin-thanks Dave and Justin)

Now that we have scratched the surface of what’s involved in converting some extra space into a garden area, let’s look at some features found in manufactured growing systems or some concepts that you might like to incorporate into your own.
Carbon Dioxide is usually supplied via tank and flow meter. Most personal growing systems have limited air volume so the extra heat associated with fuel burning CO2 generators can pose a problem. However, they can be used provided that the hot carbon dioxide rich air passes through a cooling system before being introduced into the growing environment. Fossil fuel combustion also produces moisture (humidity) as a by-product of combustion. The flow of carbon dioxide from the tank into the distribution system is controlled by an air solenoid and digital timer. The grower must then adjust the flow meter so that the gas is released at the appropriate rate for the correct duration at timed intervals. A step-up is to use an infra-red CO2 sensor integrated with the climate control system (exhaust fan and thermostats). For most plants, supplemental carbon dioxide is only supplied during the light cycle. With all growing systems operated near living areas, you want to minimize the amount of noise and vibration. This is most easily done by using a high quality enclosed fan. It is better to have a fan with higher-output capabilities running on a slower speed than it is to have a medium to low output fan running at higher speed.
Separate timers are required to maintain different day lengths if you want to maintain a vegetative growth chamber and flowering chamber concurrently. This way you maintain a consistent supply. For short day plants, timers are usually set for 18 to 24 hours of day length per 24 hour cycle for vegetative growth and 12 hours of light per 24 hour cycle for reproductive growth (budding, flowering, fruiting, etc). If maintaining separate chambers you should try to have them be around the same size. This offers a lot more versatility with plant spacing, sizing, breeding, and experimentation. You can even attempt to create your own eco system by practicing aquaculture, which is a growing method that can help sustain live plants and raise fish for human consumption. Basically the fish waste feeds the plants and the plants clean the fish water.
If possible, the growing spaces themselves should be modular and relatively easy to move if necessary. The growing device should also be flexible in allowing you to switch and choose different growing methods. For instance, you should be able to run the area hydroponically with relative simplicity in ease of maintenance, refilling, cleaning, etc.
Accessibility is a must, preferably without disrupting growing cycles. You should also be able to grow in soil or soilless medium if you decide to try practice a few different methods. Planting density will also become very important when working with manufactured systems in a limited amount of space. You want to fit as much plant material in as little space as possible to maximize yields. There are some newer manufactured hydroponic systems that maximize light-use efficiency by completely surrounding the lights. In one such system the plants are suspended vertically facing a light column (similar to column culture of strawberries). In another, the plants rotate horizontally around a fixed light column (like a rotating drum). Always make sure that your planting density allows sufficient air volumes for healthy growth.
If you want to incorporate the growing device into a living area you will want to limit the amount of ducting required. As mentioned earlier, by reducing the cooling requirements (lighting), supplementing sealed environments with CO2, and using a safe air-purification system such as an activated carbon filter you can pretty much eliminate or minimize any additional ducting required.
The unit should also be light tight and aesthetically appealing if you intend to share living space with it. Raising any living thing takes a level of commitment, even if with high levels of automation and monitoring. Like many things in life, you will only get out of your grow space what you put into it. So be prepared for an initial investment, and with practice and patience you can be rewarded with a lifetime of bountiful harvests.