House & Garden CalMag
Best nutrient supplement for coco coir growers using reverse osmosis water.
House & Garden CalMag is a dry soluble fertilizer providing essential calcium and magnesium to promote vigorous plant growth. It serves as the primary nitrogen source in the 3-part House & Garden dry soluble system, ideal for pairing with Grow during vegetative stages and Bloom during flowering. This versatile supplement is highly recommended for use with reverse osmosis water and in coco coir growing media, ensuring optimal nutrient delivery for robust plant development. The 5 LB package offers a substantial supply for your gardening needs.
$57.34
Owner Satisfaction
4.7
/ 5
Category Rank
50
/ 4348
#50 in Fertilizers
Price vs Category Average
-7%
Below average
Form
Dry soluble
/ Dry soluble
Who it's for
- Gardeners needing an urgent fix for yellowing leaves
- Growers switching between soil and hydroponic systems
- Cultivators aiming for heavy yields and sturdy stems
Who should skip it
- Shoppers who rely on local big-box garden centers
- Budget-conscious hobbyists seeking affordable nutrient solutions
- Beginners who prefer a simple, forgiving feeding schedule
Performance breakdown
Nutrient Solubility
Dissolves rapidly in water without leaving behind stubborn sediment or residue.
Coco Coir Compatibility
Specifically engineered to bridge the nutrient gap in coco-based growing media.
RO Water Optimization
Perfectly balances mineral deficiencies common in reverse osmosis water systems.
System Integration
Seamlessly anchors the three-part dry soluble program for consistent feeding cycles.
Growth Efficacy
Delivers a potent nitrogen boost that visibly accelerates vegetative plant development.
Ease of Storage
Dry powder format ensures long-term stability compared to liquid nutrient alternatives.
Key Specs
Form
Dry soluble
Package Weight
5 LB
Primary Nutrients
Calcium and Magnesium
Compatibility
Reverse osmosis water and coco coir
Fertilizer Source
Mineral Based
Season of Application
Spring, Summer, Fall, Winter
Container Weight
5.0 pounds
Water Soluble
True
Features
- Promotes rapid plant growth with key nutrients.
- Primary nitrogen source for dry soluble program.
- Works with Grow and Bloom nutrients.
- Ideal for RO water systems.
- Beneficial for coco coir cultivation.
- Supplies essential calcium and magnesium.
- Supports healthy plant development.
What customers say
House & Garden CalMag earns consistent praise for its exceptional quality and reliable performance in correcting nutrient issues. Growers frequently observe that this supplement effectively boosts overall plant vigor and strengthens cell structure, particularly when utilizing reverse osmosis water or coco coir. While recognized as a premium choice, the predictable, high quality results strongly justify the investment. This makes CalMag a trusted and essential component for serious feeding programs focused on achieving superior outcomes.
Know before you buy
House & Garden CalMag is designed as the primary nitrogen source for the brand's dry soluble system. If you are using the H&G dry soluble program, it is essential for providing the necessary calcium and magnesium to balance your Grow and Bloom applications.
Yes, it is specifically formulated for use with RO water. Since RO water is stripped of minerals, this supplement effectively replenishes the calcium and magnesium levels your plants need to thrive.
Absolutely. Coco coir has a natural tendency to bind to calcium and magnesium, which can lead to deficiencies. Using this supplement helps ensure your plants receive these nutrients directly, preventing potential lockouts.
This product acts as the nitrogen foundation of the system. You pair it with the Grow formula during the vegetative stage and transition to the Bloom formula during the flowering stage to provide a complete, balanced nutrient profile.
This is a quick-release, water-soluble powder. It is designed to be immediately available to your plants, allowing for rapid uptake and efficient nutrient delivery.
Still have a question?
Ask Hayley anything about this product before you decide.