By Damian Solomon
By mid-November, most northern vegetable greenhouse growers are finishing off their crops. It’s getting dark and too cold to grow a winter crop of veggies. At least, this is the way it was done in the past. However, due to the increased innovation and advances in greenhouse technology, some growers are pushing the limits to see what’s possible.
In growing regions like Leamington, Ontario — known as the “Tomato Capital of Canada” — where traditionally, the season ended before winter started, some growers are using the latest in technology to grow through the winter months. The limitations to crop growth in the period is mainly due to the cold temperatures and low light levels in the northern areas. In order for it to be successful, only the most modern greenhouses can achieve this. There are a handful of operations that now have learned to grow through the winter, and they all share several key principles.
– Dutch-style glass greenhouse: Using glass as the glazing material ensures high light transmittance and durability of the structure.
– High-pressure sodium grow lights: Due to the low light in the winter months, supplemental lighting must be used in the greenhouse. Depending on the crop’s light requirements, the lights are used to increase the day length, sometimes up to 18 hours. These grow lights are specifically designed to offer the same spectrum as the sun, which ensures maximum crop growth.
– Industrial-sized heating system: Northern climates can experience extreme cold temperatures, and their greenhouses need large heating systems to be able to supply enough heat when needed. These large water boilers use natural gas as the fuel to heat water, that later flows into the greenhouse via heating tubes/rails to heat the growing environment. A side benefit to this is that the CO2 produced in the combustion of the natural gas can now be used to enrich the growing environment.
– Energy screens and curtains: When the temperatures outside drop and the heating system is at full capacity, the use of energy screens can add great efficiency and lower heating costs. A screen that is designed to trap heat inside the greenhouse is placed above the crop (just under the vent windows). This traps in the heat from the heating system and keeps the inside climate warm and toasty. Some operations even feature a double-layered screen system. These systems are all automated and can be set to operate under different parameters.
– Fully integrated computer control system: As these operations are high technology and rely on automation, there is a need for a computer system that can control every aspect of the growing operation. These systems can control everything from irrigation, heating, cooling, humidity, air flow, supplemental lighting and energy screens — all from one screen.
Winter growing can definitely be achieved, however, it’s more important to have the correct technology in place to ensure a greater chance for success.
Damian Solomon has been involved in the greenhouse vegetable industry for more than 14 years.