This is the sixth article in a series where I present some selected tricks and advanced growing techniques. My name is Franco, and I work at Green House Seed Company, in Amsterdam, since the year 2000. Over the last 10 years I have learned from Arjan countless tricks and advanced techniques, and I developed a few of my own as well. And now it’s time to share some of this knowledge with growers worldwide. If we share the knowledge, everybody wins.
Last month I explained some of the best tricks for controlling and optimizing the medium pH. This month, I give you...
Franco’s tricks on growing large outdoor plants
In this time of the year most outdoor growers already planted their seeds or cuttings, and the plants are already boosting in full vegetative growth. More and more growers these days have the possibility of growing large outdoor plants in containers or in open soil. As a passionate outdoor grower, I always enjoyed growing large plants because it is one of the most challenging and most rewarding ways of making cannabis.
Growing large plants requires a good preparation, careful choice of the location, and a keen eye to prevent problems rather than fix them after they happened. To begin, it is always good to start plants in small containers, and re-pot them as they grow bigger. Starting the seedlings, or cuttings, in 3-5 liters containers, one can re-pot them to 20 liter containers when they have formed a beginning of root-ball, and then again into very large containers, or in open soil. This process of allowing the root-ball to begin to form and then re-pot allows the root system to grow to its full potential very rapidly. The root system boosts after having formed a semi root ball and more lateral root-shots are formed. The depth of the final large container of choice will influence the shape of the plant as well: large, short containers will produce shorter, bushier plants, as the tap-root cannot extend and forms root-ball. On the contrary, if the container is tall the plants will grow taller, as the main tap root goes down deeper.
When the plants are 50-60 cm tall it is time to clear the bottom branches close to the soil, and allow 20-30 cm of clean stem from the level of the earth, to avoid contact between leaves and the soil. This prevents animals from crawling onto the plants, especially leaf-eaters, and avoids rotten leaf-material at the bottom of the plants. In some cases it is also good to remove some leaf material (especially with extra-dense indica genetics).
When the plants have to grow very large, it is essential to boost feeding intake from an early stage, and to allow enough N to be absorbed. For this purpose mineral feedings work best, but also organic compost can perform miracles when properly prepared. The pH of the watering solution should be kept at optimal levels for growth in soil (5.7-6.0) until needed, and P, Mg and Ca intake should be boosted to form strong stems to support the large flower clusters.
The structure of the plants depends on the genetics and the container, but in order to grow very large plants that can support the flowers it is almost always necessary to prune and to give some form of support to the branches. The plants are ready to be pruned at an early age, as long as they have 3-4 internodes, but in order to grow large plants it is best to wait and top them at 6 or more internodes. Topping the main growth will produce lateral development and make the whole plant structure sturdier. The same can be done to each branch if it tends to grow too long and become to weak to support the flowers. Any pruning can be done until the metabolism is still in vegetative growth starts changing into flowering mode. The plants should not be pruned after the flowering has started because this would reduce the number of flower clusters and reduce the total production. Furthermore, pruning plants already in flowering can shock them and produce hermaphroditic traits.
The drainage of the container is essential to guarantee good flushing of the salts that will eventually buildup in case of mineral feeding. Drainage allows also a good flow of air to the root system, promoting a healthy growth. If the plants go in open soil, it is very important to dig a deep hole (over 1 meter) and deposit some drainage-material at the bottom.
When plants grow very large, it is sometimes useful to cage them in a net-cage, to create a sort of external frame where the branches lean on. Other effective ways to support plants are bamboo sticks, or ropes. Whatever the system, the purpose is to support the branches and, at the same time, to allow access to the plant for feeding and pest control.
Working with large plants can produce monster-size harvests (up to several kg per plant) so it is always good to plan the logistics of the harvest well in advance (cutting, transport, drying space, manicuring crew). The most important thing to remember is that quality should never be spoiled by quantity.
Franco – Green House Seed Co.
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