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Cultivation

Greenhouses Made In USA

By Sama’a Djomehri

As the medicinal and recreational use of Cannabis is legalized in more and more U.S. states, its cultivation in greenhouses is emerging as the most ideal and suggested way of production. This is because it includes the best of the two worlds: it collects sunlight, while keeping the cultivation space in a controlled climate and free from infections.

There are many different greenhouse designs and technologies that have been created due to the different climate found in the U.S. states. As the production of high-content THC medicinal cannabis in Greece is allowed only in greenhouses, we can use the experience and knowledge of these growers to design greenhouses adapted to the conditions of our climate, which will maintain an ideal environment for the plant and thus produce a high quality medicine.

The most fundamental difference in the designs of greenhouses is the seasonal cultivation facilities, to enhance the natural growth cycle of the plant without the use of complementary lamps, or those of the annual crop using artificial light.

Seasonal greenhouses:

This kind of greenhouse is dominant in California due to its abundant sunshine and warm and dry climate. California is the largest cannabis producer in the U.S.. Plastic made of soft polyurethane has better permeability and light diffusion agents than glass or polycarbonate polymer, which is why it is preferred as a greenhouse cover. The seeds are usually planted in early March, in a greenhouse with a heat dissipation system adjustable by a temperature sensor that keeps the levels around 30°C. If clones are used, they start from the inside. Because they have been cut off from the main plant, they have a sensitive photoperiod and may enter the flowering prematurely if they do not accept a sufficient period of exposure to light. It is safe to place most varieties of strands in a greenhouse without supporting lighting only after March 22, the summer equinox. To be sure, most growers in the U.S. remove clones from supportive lighting after April 1.

A warm and humid environment is created inside the greenhouse. This is ideal for young, leafy plants, which do not require bright lighting in relation to the subsequent stages. Fresh air circulation is also important during the day to avoid destructive mold and other plant diseases. Ventilations to remove old air from the inside are often used. A simple technologically and low-cost solution is simply to have automatic ventilation windows that will open during the day and close at night.

Some seasonal greenhouse growers operate only a number of plants, starting in March and harvesting at the beginning of October. These plants are becoming huge! Many greenhouses in California produced plants with a height of up to 5 meters. There are many creative methods of pruning, climbing, tying and supporting the branches for the ideal use of the space inside the greenhouse as effectively as possible, in order to prevent the tops of the plants from touching the roof. Growers who choose this technique usually have a smaller number of plants, but each plant can reach 6 kg in maturation.

Other seasonal greenhouse growers are targeting 2-3 harvests per season. this involves applying a technique called Deprivation of Light. The seeds or clones that start in early March, are placed in another greenhouse in early April. This greenhouse is equipped with blackout curtains, which when closed prevent any external light. The curtains are placed in a system with pulleys and cables, they work automatically or manually, and the sunlight that the plants receive is limited to 12 hours a day. This activates the early flowering of the plant. Without the deprivation of light, plants naturally bloom only in the first week of August. Plants subjected to light deprivation are ready to be harvested after 8 weeks in a technically submitted system of 12-hour light exposure.

In the meantime, the producer has started a new set of seeds or clones in the greenhouse-nursery. When the first batch of plants is harvested in early June, the new set of plants is placed in the light deprivation greenhouse, and the cycle begins again. The second harvest is ready around the beginning of August, and the grower may choose to have a third batch ready to place in the greenhouse at that time. Because this third batch is placed at the time when the days get shorter and the flowering is naturally activated, the blackout curtains are not needed. The plants will begin to bloom on their own, and will be ready in early October, that is, their normal season.

Annual Crop :

In areas of the U.S. that have less sunshine and cold, humid weather, seasonal greenhouses cannot give high yield and drug quality. To produce the same amount and quality of medicine, growers in these places choose the annual crop in climate-controlled, insulated spaces. The vegetation and flowering cycles of plants must be artificially modified for annual cultivation. This also requires complementary lighting systems that lengthen the day to keep plants in the germination stage as well as a light deprivation system to activate flowering when needed. Using these methods it is possible to have 5-6 harvests per year, depending on the size that the grower desires for each plant.

In mountainous areas such as Colorado, with low sunshine and a lot of snow and wind in winter, the greenhouses used are made of glass or polycarbonate polymer instead of soft plastic. They can be dug into the ground on the north side, using the earth as insulation, or incorporate a compact insulating northern wall. This helps maintain heat, especially since temperatures can drop below the freezing point very often. Heating systems, such as air heaters, radiators and transporting hot air from floor to ceiling, can all be used to maintain appropriate temperatures during the cold months.

During the warm months, cooling systems must be integrated. Atomizing cooling techniques are ideal for dry climates such as in Colorado, California and southwestern U.S. Including cooling panels and fans, high-pressure fog creation systems, combined with powerful ventilations that provide continuous ventilation. However, cooling systems that are not based on water pumps are also used. This is an ideal solution for areas such as South Carolina or Michigan, which have excessive humidity during the summer period. At the flowering stage, hemp needs a humidity height of about 60% or lower to avoid mold formation or rotting.

The need for low levels of humidity during flowering, brought to the fore the dehumidification systems so that the annual cultivation in a greenhouse is possible. This is very important for cold, humid climates as well as for those that have hot and humid weather. Many greenhouses in high-rainfall areas such as Oregon, Washington, Michigan, Maine and the southeastern part of the U.S., incorporate the winter and summer dehumidification systems. In areas like Colorado and California this is only done during the winter.

Greece is also a country with many different micro-climates. By studying the climate-like techniques used in the U.S., Greek medicinal cannabis growers can apply these techniques as a guide for designing greenhouse facilities ideally adapted to different regions, creating high-yielding plants with good structure and high pharmaceutical capabilities.

The Green Greeks Magazine

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