Peters Excel 15-5-15 Cal-Mag Special with Black Iron
Best professional-grade fertilizer for container plants grown in soft water.
Peters Excel 15-5-15 Cal-Mag Special is a premium water-soluble fertilizer designed for continuous, balanced nutrition, especially in soft water systems. It addresses common deficiencies in calcium and magnesium, promoting healthy, compact growth with its high nitrate and low phosphate formulation. Ideal for peat-based cultures like potted plants and container nursery stock, it delivers a complete nutrient profile, including essential micronutrients and three forms of chelated iron, notably black iron (Iron HBED). This 100% water-soluble powder ensures rapid nutrient absorption for effective liquid feeding programs.
$51.11
Owner Satisfaction
4.7
/ 5
Category Rank
50
/ 4425
#50 in Fertilizers
Price vs Category Average
-17%
Below average
Fertilizer Grade
15515
/ --
Who it's for
- Commercial growers seeking an all-in-one nutrient solution
- Gardeners managing hard water or high-pH growing environments
- Professionals using automated irrigation and fertigation systems
Who should skip it
- Beginners lacking the tools to monitor electrical conductivity levels
- Botanists requiring specialized ratios for flowering or rooting stages
- Hobbyists operating on a strict, budget-conscious gardening plan
Performance breakdown
Nutrient Solubility
Dissolves completely without leaving residue in irrigation or drench systems.
Micronutrient Availability
Advanced chelation ensures iron and trace elements remain accessible to roots.
Growth Regulation
High nitrate ratio effectively prevents leggy growth in containerized plants.
Soft Water Compatibility
Specifically engineered to balance calcium and magnesium in low-mineral water.
Feeding Consistency
Formulated for reliable, continuous nutrient delivery in professional nursery settings.
Purity Standards
Clean, ballast-free composition minimizes salt buildup in peat-based growing media.
Key Specs
Fertilizer Grade
15-5-15
Total Nitrogen (N)
15%
Available Phosphate (P2O5)
5%
Soluble Potash (K2O)
15%
Calcium (Ca)
5.0%
Magnesium (Mg)
2.0%
Iron (Fe)
0.08%
Package Weight
25 lb
Features
- Supplies missing calcium and magnesium in soft water.
- High nitrate, low phosphate for compact growth.
- Includes black iron for superior delivery.
- 100% water soluble for continuous feeding.
- Pure formulation, free from ballast substances.
- Elevated trace elements for robust growth.
- Exclusive M-77 chelating formula.
- Complete nutrition in one bag.
What customers say
Customers consistently praise the exceptional quality and reliability of Peters Excel. Users report significant improvements in plant vigor and color, attributing the success directly to the balanced Cal Mag and Black Iron formulation. The product is highly valued for its consistent performance, making it a dependable choice for managing specific nutrient deficiencies. While the initial cost is higher than standard fertilizers, the visible results and ease of application justify the investment, confirming its status as a professional grade solution.
Know before you buy
Soft water often lacks sufficient calcium and magnesium, which are essential for plant structure and photosynthesis. This formula is specifically balanced to supplement these missing minerals, preventing common deficiencies that occur when using soft water for irrigation.
Black iron, or Iron HBED, is a highly stable form of chelated iron. It remains available to plants across a wider range of pH levels compared to standard iron sources, ensuring your plants can absorb it effectively even in challenging soil conditions.
Yes, it is designed for peat-based cultures like potted plants and container nursery stock. Its high nitrate and low phosphate ratio promotes compact, healthy growth, making it an excellent choice for a wide variety of indoor and outdoor container plants.
This product is formulated for continuous feeding programs. Because it is 100% water-soluble and free from ballast substances, it can be used regularly during your normal watering routine to provide a steady supply of nutrients.
No, this is a synthetic, water-soluble fertilizer. It is engineered for precision and rapid nutrient uptake, which is typical for professional-grade liquid feeding programs.
Because it is a pure, 100% water-soluble powder free from ballast substances, it dissolves completely in water. This minimizes the risk of clogging irrigation lines or leaving residue on your plants' foliage.
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