AKA The Strengthener: This means targeted micronutrient support that fixes your plant deficiencies fast.
See visible results in days.Trusted by hobbyists and pros across every grow system.
Corrects calcium, magnesium, and iron deficiencies
Designed for coco coir and RO water environments
Compatible with all grow mediums (soil, hydroponic systems, coco)
Includes Chelated Iron for maximum uptake
$11.99
Deficiencies show up fast — this stops them faster.
Think of it as the gardener’s fix-it formula. CalMag & Iron helps you correct the root cause of yellowing leaves, weak stems, and blossom-end rot before it affects your yield.
“I’ll never grow without it again.”
For all grow mediums: Safe for use in coco coir, hydroponic systems, soil, and containers
Safe for edibles: No banned PGRs or hidden additives. Garden-safe and clean.
Tested by gardeners: Thousands of 5-star reviews and trusted results at home.
Maximum absorption: Chelated iron ensures nutrient uptake across pH ranges.
Corrects core deficiencies: Calcium, magnesium, and iron in one optimized formula.
Faster recovery: Visible improvement in color and leaf strength within 3–7 days.
For all grow mediums: Safe for use in coco coir, hydroponic systems, soil, and containers
Safe for edibles: No banned PGRs or hidden additives. Garden-safe and clean.
Tested by gardeners: Thousands of 5-star reviews and trusted results at home.
Maximum absorption: Chelated iron ensures nutrient uptake across pH ranges.
Corrects core deficiencies: Calcium, magnesium, and iron in one optimized formula.
Faster recovery: Visible improvement in color and leaf strength within 3–7 days.
CalMag & Iron: FAQs for gardeners using coco, hydroponic systems, and soil.
Can I use this to treat blossom-end rot in tomatoes?
Blossom-end rot is typically caused by a calcium deficiency, especially in fast-growing crops like tomatoes and peppers. CalMag & Iron delivers bioavailable calcium along with magnesium and iron to correct the issue quickly.
Should I use it as a soil treatment or a foliar spray?
You can apply it either way. As a soil drench, it improves root-zone nutrient uptake. As a foliar spray, it offers faster correction of visible leaf symptoms. For stressed plants, many growers do both.
Why is this necessary with coco coir or reverse osmosis water?
Coco coir tends to bind calcium and magnesium, making them unavailable to plants. RO water strips out all minerals, including essential micronutrients. CalMag & Iron makes sure your plants still get the elements they need.
Is it safe for vegetables, herbs, and fruit trees?
Humboldts Secret Cal Mag & Iron is perfectly safe for your veg, herbs, and growing fruit trees. The formula contains no harsh chemicals or banned substances. It’s safe for all edible and ornamental plants when used as directed.
Will this work with the rest of my nutrient system?
CalMag & Iron was formulated to work seamlessly with Humboldts Secret Base A & B, Golden Tree, and most other nutrient lines. Always dilute before mixing with other products.
Unlock the fix your plants can’t live without.
Get the calcium, magnesium, and iron support your plants need — without complicated dosing or risky side effects.
