Winter production poses many growing obstacles, including low light, cool temperatures and poor ventilation.
When plants are started under these conditions, whether from cuttings, seedlings or transplant plugs, growth is slowed and the need for fertilizer diminishes. These conditions must be taken into consideration when fertilizing every watering. During this time in the production cycle, monitoring the EC of your irrigation water can be the most important management tool since fertilizers contribute to the EC of your growing medium. In addition, uptake by the plants is reduced and the drying of soil is slowed, allowing salts to build up quickly in the media. This results in stunting or injury of young plants. The best way to avoid such damage is by using low fertilizer rates to maintain low EC levels.
Growth under low light and cool temperatures should be done at an EC level between 0.25-0.30. This can be achieved by fertilizing with Plantex® Cal Mag Royal 13-2-13 or Plantex® Cal Mag +P at 25 ppm. Both of these products have low ammonia and lower phosphorous, conditions which are critical during early plant development. Once plants are established and growing conditions improve, rates should be increased to 50 ppm, providing EC levels between 0.90-1.90. As plants develop, continue to increase fertilization rates to meet nutritional needs.