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🌿 Unlock your garden’s secret weapon for vibrant growth and bountiful blooms!
Humboldts Secret CalMag & Iron is a 32-ounce concentrated liquid fertilizer delivering essential calcium, magnesium, and chelated iron. Designed for versatile use in soil, coco coir, hydroponics, and RO water, it prevents nutrient deficiencies, supports strong stems, vibrant leaves, and abundant flowering. Trusted by over 2,000 users with a 4.6-star rating, this fast-acting formula ensures maximum nutrient absorption and rapid plant recovery, making it a must-have for professional and home growers aiming for healthy, productive gardens.



















| ASIN | B01GB23TEY |
| Best Sellers Rank | #12,195 in Patio, Lawn & Garden ( See Top 100 in Patio, Lawn & Garden ) #419 in Garden Fertilizers |
| Brand | Humboldts Secret |
| Brand Name | Humboldts Secret |
| Coverage | Medium |
| Customer Reviews | 4.6 out of 5 stars 2,054 Reviews |
| Item Form | Liquid |
| Liquid Volume | 32 Fluid Ounces |
| Manufacturer | Humboldts Secret |
| Mixing Ratio | 1-2ml:1000ml for vegetative growth and 2-5ml:1000ml for flowering |
| Model Number | 15195521384514 |
| Number of Items | 1 |
| Number of Packs | 1 |
| Part Number | TUEEQE-09 |
| Specific Uses For Product | Hydroponic |
| Target Species | Plants |
| UPC | 648260730390 |
| Unit Count | 32 Fluid Ounces |
C**S
Helps azaleas for chlorosis if your water is hard or alkaline .
Excellent source of trace elements as well as iron. My azaleas responded really nicely. Chlorosis disappeared in a few days and the leaves turned to deep green. I also used a bit of Epsom salts (MgSO4).
J**N
Great for my hydroponic garden
Great for my hydroponics!
J**7
This stuff WORKS!!
This stuff is great! My pepper plants were turning yellow and had blossom end rot so they were getting a lottlw rotten hole before they were even ready to pick. I read online that several ppl recommended this for that problem. It was like a miracle, I used it twice and my plants turned green again and the peppers started growing perfectly! I kept using them as recommended and got so many beautiful peppers from my plant all summer! Life saver! Plus it is so concentrated, you only use about a cap full with a gallon of water so it will last FOREVER!
D**A
That calcium is very important when growing tomatoes.
I got what I ordered which is good now to see how this works.
J**N
Good product
Good product
K**O
Quickly shows improvement to my house plants. Good company
Had some confusing instructions but their customer service got back to me quickly and cleared confusion. The jug arrived with no leak, has no order and my house plants are happy to get the dose of this fertilizer, especially my old lemon tree which goes out in summer and come in for winter. I notice when plants are healthy not many bugs appear. as it takes very little per gallon of water, it's a good value for the price.
E**E
Works well
My tomatoes are doing much better. No ugly black spots on the bottom.
M**Y
Bad delivery experience
I’m sure works great I just ordered their entire line of products, but unfortunately a good amount was spilled by the time it was delivered. I don’t know if it just doesn’t get sealed right or if these guys are driving the Superman. This stuff is expensive for it to be delivered with a good amount gone! I initially had just base a and base b with the sweet and sticky additive, then my plants started looking a little sick so I’m glad the calmag is here. Will still give 3 stars just to give the benefit of a doubt and will update soon
Trustpilot
3 weeks ago
1 month ago