URBAN CEA: Part 3

Motherly Love:
Starting and Maintaining
Stock Plants They say the apple doesn’t fall far from the tree. While this phrase might not be applicable in all areas, it certainly holds true in the realm of plant production. Superior results in production plants stem from the environmental influences added to the genetic potential of the plant. Growers have control of the environment, while plant breeders hold the key to the genetics. Starting with the best genetics possible for your individual needs is the most important decision a grower can make. Ensuring that the genetic potential of the plant can be reached to the fullest starts with the mother plant; sometimes also known as the “donor” plant.
Asexual plant propagation, or growing with “cuttings” and “clones,” ensures that all of the genetic profiles of the individual plants in the garden are identical. If all the plants are grown in the same environment, all the plants should grow at the same rate, finish at the same time, and exhibit all of the characteristics of the mother plant. For all the genes to be identical they all have to originate from the same mother plant (from the same seed). Over the course of months or years that same mother plant may produce other mother plants, which in turn may produce hundreds or even thousands of cuttings annually — all with exactly the same genetic makeup and all with the same potential, given the same environment and cropping schedule.
Growers who intend to cultivate successive crops or to grow as propagators for other gardens should consider creating a separate area for starting and maintaining stock plants, to ensure healthier and more consistent crops in their flowering areas. For the grower, knowing the exact history of the plants’ origins is helpful in determining what to apply and when, because any deficiencies, infections, etc. are known by the grower. Cuttings or seedlings acquired from outside sources can be very consistent and may produce excellent results; however, the history of the plants is unknown.
A small-scale (2 x 4 x 8-ft., or 60 x 120 x 240-cm) prefabricated growing enclosure fits the bill for servicing an urban CEA (controlled environment agriculture) setup as described in the first two instalments of this series. The initial setup was based around a water-cooled HID-lit CEA growing environment housed in a 4 x 4 x 8-ft. pre-fabricated growing enclosure. CEA gardens are often described as “closed-loop” gardens, where there is no direct intake or exhaust; the grower creates the ideal environment. The setup discussed was located in a city dwelling, where space was limited and the gardener is often required to cohabitate with their endeavours and neighbours more closely.
The new smaller-scale prefabricated enclosure has all the same features as the bigger version, but scaled down for the relatively smaller space required for maintaining mothers, cuttings, and seedlings. It also helps to conserve space. Theoretically, using two sealed enclosed growing environments, the grower can operate both a vegetative and flowering chambers simultaneously in the same lung room (the lung room as described in previous instalments and articles). This eliminates the need to have two separate rooms; all growing endeavours can be housed in the same room, a plus in space-limited urban settings. The grower must ensure that light is not leaking into the flowering chamber during the internal dark cycle. If total darkness is not maintained for lights-off periods in flowering chambers, problems arise and flowering is diminished.
Conveniently, the 2 x 4 x 8-ft. (60 x 120 x 240-cm) chamber was chosen to include an integrated racking/benching system. This allows for mother or larger vegetative plants to be grown on the upper tier of the enclosure, where there is more vertical height, while seedlings and cuttings can be started or maintained on the bottom of the chamber, where less vertical space is required. As with any totally enclosed growing environment, issues regarding heat from lamps must be managed to maintain optimal growing temperatures, a critical parameter in any successful growing environment. It is worth noting for the micro-gardener that the 2 x 4x 8-ft. split-level chamber may also be modified to support a vegetative chamber on the bottom and a flowering chamber on top.
The range of high-output full-spectrum fluorescent lighting available to today’s indoor gardeners is fantastic. Considerably high light levels can be supplied to relatively shorter plants using plug-and-play T-5 high output fluorescent lights and fixtures. The T-5 lamps are also available in a variety of spectral outputs. Different light wavelengths will have different influences on plant growth. A 4-ft (120-cm) six-lamp fixture is ideal for the top portion of the chamber. It produces very bright light in proximity to the lamp and produces a very even light footprint under the fixture. Note that towards the ends of the fixture the intensity is not as high or even. Overall, the fixture produces more than 30,000 lumens and the lamps can be kept within a few inches of the plants. This equates to an initial lumen rating of nearly 4000 lumens per square foot (936 cm2). Very bright sunlight is about 5000 lumens per square foot. The lamps run relatively cool, but some heat is dissipated by the fixture and requires venting away from the chamber into the lung room or adjoining area. For taller specimens and flowering chambers, HID lamps are preferred because they can deliver higher lighting intensities at greater distances from the lighting source.
The lower portion of the chamber can be lit with a similar lighting fixture, but with greater distances maintained between the lamps and the cuttings and seedlings. One great feature on some innovative fixtures is that you can flip switches and shut off a portion of the lamps (four lamps on, two off, or vice versa) to reduce light intensities and/or heat output. Simply raising or lowering lamps will also decrease or increase the amount of light reaching the plants — fewer lamps “on” often means less heat. While the fixtures run relatively cool, it is very important that there is a space left between the bottom of the top tier supporting larger or mother plants and the lighting fixture(s) in the chamber below. The space between the two should be well ventilated to prevent overheating the root zone in the plants supported above the fixture.
Naturally, the enclosure will be outfitted with a vent fan plugged into an atmospheric controller. At a minimum, temperature and humidity should be evacuated once they exceed the set-point(s) on the controller(s) in the growing chamber. Note that in the CEA system described in this series, the exhaust or intake fans are not connected to the outdoors. For higher outputs where larger numbers of cuttings are required frequently, or for faster vegetative growth, the vent fan may also be integrated into a carbon dioxide enrichment system so that CO2 levels are supplemented in the individual chamber(s). Infrared monitors such as featured in the first instalment of this article are ideal for these purposes. Bottled CO2 is the preferred source for urban CEA setups. To run both a vegetative and flowering chamber consecutively in the same room, you may either enrich the CO2 levels in the lung room to a happy medium, such as 1000 ppm, or outfit each chamber with separate CO2 monitoring and enrichment systems. Also, the temperature in the lung room will need to be maintained near 65–70ºF (~18–21ºC). In cooler months this may be done passively, whereas during summer months an AC unit will likely be required to keep the temperatures in the lung room down. When running both a flowering and vegetative chamber in the same room, each chamber will require its own temperature and humidity control units to operate the intake and exhaust fan drawing and discharging air from within the lung room, where they are housed. Air in the lung room is also de-humidified (with a de-humidifier and/or AC) and purified (carbon filters, HEPA filters).
The highly reflective walls of the prefabricated growing enclosures are very easy to clean. Cleanliness is absolutely essential in maintaining a propagation area. Young plants and rooting cuttings are more susceptible to pathogens, and damage from insects or diseases tends to be more severe in young plants.
The following is a theoretical step-by-step guideline in selecting and maintaining a mother plant for successive crops utilizing the smaller 2 x 4-ft (60 x 120-cm) vegetative propagation chamber (upper and lower tiers) in conjunction with the larger, 4 x 4-ft. flowering chamber in the sealed lung environment.

Step 1. Germinate seeds from a reputable source.
Take the time to research the variety you want to grow. Does it have all the characteristics you are looking for? Does the strain suit your growing methods, timeline, and environment? Do not germinate seeds in paper towels, etc. Start seeds directly in your growing medium of choice using plugs, cubes, cells, etc. in a propagation tray with dome. Bury seeds to a depth of about twice their size. Ensure that there is good contact between the seed and the germinating medium. Before planting, pre-treat the growing medium with one-quarter-strength base nutrients (about 450 ppm). Additions to the soak, such as beneficial microbial inoculants, are ideal. They will inoculate the seeds that grow to mature plants with beneficial fungi and bacteria such as mychorhizae, trichoderma, bacillus, rhizobium, etc. If a seed has a very healthy start, including inoculations with beneficial fungi and bacteria, it will grow leaps and bounds over plants that didn’t while being more resistant to diseases. Once most of the seeds have sprouted and surfaced above the growing medium, remove the humidity dome so that they do not stretch and become leggy. Apply very gentle light and air movement to tender young seedlings so as not to dry them out or place too much stress on the young plants. Seedlings will not require any additional fertilizer until they have developed their first set(s) of true leaves. The cotyledon (small seed leaves which first emerge) will nourish the plant until true leaves develop.
Avoid keeping seedlings too wet, as they are more susceptible to stem rot. Products containing silicate can be applied to strengthen plant cells against pathogens. Use gentle fluorescent lighting high in the blue spectrum, with an 18 to 24 hour “on” period. Gradually increase fluorescent light intensity as plants begin to develop. Maintain very gentle but constant airflow over seedlings; they are fragile but will strengthen with air movement.

Step 2. Transplant seedlings into containers, cubes, etc.
Gently transplant seedlings that have gained a few sets of true leaves into larger cubes, net baskets, or other containers. Be very careful not to damage the root system. It is advisable to pre-treat the seedling with a vitamin solution before transplant, to reduce the stresses the tender plants may encounter during transplant. Solutions containing a full spectrum array of vitamins such as B-1, B-2 (riboflavin), B-3 (niacin), and B-7 (biotin) have been demonstrated to be highly beneficial for reducing stresses and improving growth rates in young seedlings. Organic B-vitamin solutions are also available and have shown to be effective. After transplant, water again with a vitamin solution, mild vegetative nutrient, and beneficial root growth inoculants. Good-quality root inoculants will quickly build larger and healthier root masses with more fine hairs for greater absorption of water and nutrients. The plants will also benefit from the naturally occurring growth promoters exuded by the beneficial microbes.

Step 3. Label all the plants started from seed.
Once plants have grown to a desired size, you will need to propagate some cuttings from each of the plants (at least three per plant) and be sure to label them accurately (corresponding to the donor plant). It is advisable to retain the donor plants in the vegetative chamber while propagating labelled cuttings for rooting, vegetative growth, and then flowering. Alternatively, the donor plants can be flowered as long as the labelled cuttings removed are maintained in a vegetative state until the donor plants have finished flowering.

Step 4. Select your mother plants.
Once you have seen different plants started from the same batch of seeds grow and flower, you will have an idea of which phenotype (physical expression of genes) will suit your needs and garden best. Often there are subtle characteristics you select for that only become evident after harvest, processing, and, finally, tasting or otherwise enjoying. At harvest be sure to separate the material harvested from each individual plant. On this basis, you will be able to make the best selection of mother plant (including yield, if that is a criteria). Once you have decided you may dispose of or cull the plants that didn’t make the grade from your garden, and keep your chosen phenotype (still in the vegetative chamber). This would be either the original seed plant you labelled, created, and flowered cuttings from, or the cuttings you labelled, rooted, and kept in a vegetative state of growth that came from the seed plants you flowered. Once your ideal donor plant is selected you may create more mother plants by taking cuttings from your selection or just retain the one mother plant and use it for donor material for all of your successive gardens.
Following the method outlined above, you will have an ideal variety available whenever required. Typically, in a 2 x 4 x 8-ft. (60 x 120 x 240-cm) vegetative chamber with split levels the gardener will maintain two to four mother plants on the upper tier, which has more vertical height, and propagate cuttings on the lower tier. Once the cuttings are rooted they can be transplanted into larger containers, cubes, etc. (if applicable) and grown for several weeks in the lower chamber. To conserve vertical height in the lower chamber, T-5 HO fluorescent lamps with 5000+ K ratings will keep the plants growing with tighter internodal spacing; this means more sets of leaves and branches for every foot (30 cm) of vertical growth. Once the mother plants are well established,a 2 x 4 x 8-ft. growth chamber constructed as described can produce near 100 cuttings per week, depending on the variety of plant.
For very high output in your mother plants, you can foliar spray specialty formulations that will greatly increase shoot production. There are also nutrient programs available specifically formulated and designed to give you the most shoot growth in short periods of time for mother/donor plants while contributing to healthier cuttings. When harvesting many cuttings frequently from donor plants it is imperative to keep them in an extremely healthy and vigorous state of vegetative growth to maximize shoot production. Fulvic acid, B-vitamins, and carbohydrates should, therefore, be incorporated into your feeding program for maintaining your stock plants. Also, stock plants that receive periodic inoculations of beneficial fungi and bacteria will tend to produce donor material that roots quicker, is more resistant to stresses, and promotes more bountiful yields in plants flowered from that original donor material. The possibilities and cropping schedules that are available to the urban CEA grower operating both vegetative and flowering chambers simultaneously are limitless. The grower may operate a perpetual harvest schedule, grow sea-of-green style, vegetate for longer periods to produce heavy yielding but fewer plants, etc. Whatever you choose to grow, it should thrive if you spend the additional time, expense, and thought on perfecting your urban CEA growing environment.
Still more to come in this series, so stay tuned.…

Erik Biksa first appeared in Maximum Yield in December 1999, and in 2000 the first “Ask Erik” column was printed. Erik has contributed dozens of in-depth articles to Maximum Yield since. The “Ask Erik” column has assisted many gardeners by providing answers to a wide range of growing questions.
Erik resides in Vancouver, British Columbia (Canada). He has acted as an independent representative for several hydroponic industry leaders and visited industry members and gardeners alike throughout North America.At present, Erik hopes to further cultivate his growing network by becoming more familiar with overseas indoor gardening markets in Europe.