Color changes in mixed fertilizer are cosmetic

Univ. of Mass. extension floriculture specialist Paul Lopes reports some growers are seeing color changes when they mix Jack’s Professional fertilizers manufactured by J.R. Peters Inc. The company said the color changes are strictly cosmetic and don’t affect the physical properties of the bag or the fertilizer inside.
The company said the color of Jack’s fertilizer can range from a blue/green to grey when mixing due to the chelated iron in the formulation. Discoloration can also occur when the fertilizer is stored in high heat due to the plastic bags. The company routinely receives calls regarding the color particularly for its petunia fertilizer products. Various grades of chelated iron is used in its products which accounts for the grey color when mixing.
Color changes in the product packaging, which is referred to as pinking, yellowing, discoloring and gas fading, describe color changes in polyethylene. The color changes are generally associated with the over-oxidation of the phenolic antioxidant that is added to the resin to protect and stabilize the bags during processing and use. This over-oxidation can make the bags appear various shades of yellow to red.