Cal-Mag Extreme Liquid 1 Gallon Fertilizer - Corrects Secondary

Our review of Cal-Mag Extreme Liquid 1 Gallon finds it best suited for gardeners who already manage primary N-P-K feeding but need a reliable secondary nutrient and trace element boost. The bottom line: this formula is designed to correct subtle but growth-limiting deficiencies in calcium, magnesium, iron and sulfur using natural chelates, and it proved effective when mixed with regular feeds or applied as a foliar spray. For growers who want an easy-to-use supplement to prevent blossom end rot and support flower quality, this product delivers clear, practical benefits.

Key Features

• High secondary nutrient content: Provides a concentrated source of calcium and magnesium to target deficiencies that limit growth even when N-P-K is adequate.
• Trace element blend: Includes iron and other micro-nutrients to support chlorophyll production and overall plant vigor.
• Natural chelates: Uses chelating agents that help nutrients remain available and be transported into plant tissue for efficient uptake.
• Flexible application: Can be mixed with normal fertilizers or water, and applied to soil, growing medium, or used as a foliar spray.
• Easy dosing: Simple mixing ratio of 1 teaspoon per gallon and safe to apply up to twice weekly for routine maintenance.
• Corrects blossom end rot: Customers report measurable improvement in blossom end rot issues when used as directed.

Who It's For

This product is aimed at hobby and serious gardeners who already monitor macronutrients but struggle with secondary nutrient or micro-nutrient deficiencies, such as blossom end rot or poor flower development. It is useful for container gardeners, raised bed growers, and small-scale indoor setups who want a single supplement to address multiple secondary and trace elements.

Growers who do not track fertilizer schedules or who need a complete primary fertilizer should look elsewhere, since Cal-Mag Extreme is a targeted supplement with an N-P-K of 2-0-0 and is intended to be mixed with routine feeds rather than replace them.

Pros & Cons

Pros

• Concentrated formula corrects calcium and magnesium shortages without changing primary fertilizer plans.
• Trace elements and natural chelates improve nutrient availability and uptake across different plant types.
• Simple, repeatable dosing and versatile application methods make it easy to add to weekly feeding routines.
• Customers note good value for money and consistent longevity of the product in use.

Cons

• Some users reported a concern with dissolved quality, suggesting careful mixing and stirring before each use are necessary.
• Not a full N-P-K fertilizer, so it must be combined with a primary nutrient program for balanced feeding.

Specifications

Product name	Cal-Mag Extreme Liquid 1 Gallon
Primary brand	GS Plant Foods
N-P-K	2-0-0
Key nutrients	Calcium, Magnesium, Iron, Sulfur and trace elements
Application	Soil, growing medium, or foliar spray
Mixing rate	1 teaspoon per gallon; up to twice weekly

Our Verdict

Cal-Mag Extreme is a focused, high-concentration supplement that works best for gardeners addressing specific secondary nutrient and micro-nutrient gaps. It pairs well with a separate N-P-K program, is easy to use, and represents good value for those seeking to prevent blossom end rot and improve flower quality without overhauling their feeding schedule.

Frequently Asked Questions

Can this be used as a foliar spray?
Yes. The formula is suitable for foliar application as well as soil drench when mixed at the recommended rate and stirred before use.

How often should it be applied?
Mix 1 teaspoon per gallon and apply up to two times a week as a supplement to regular fertilizer routines.

Will it replace my regular fertilizer?
No. With an N-P-K of 2-0-0 it is a secondary and micro-nutrient supplement and should be combined with a primary nutrient program for balanced feeding.