Specs are compiled from manufacturer listings and verified buyer reviews and can change over time — please confirm the key details on the product page before buying.
If you’ve ever watched a tomato swell on the vine only to find a black, leathery patch on its bottom, you know the heartbreak of blossom end rot. That sunken spot isn’t a disease — it is a clear cry from your plant saying it needs more calcium, fast. A good calcium nitrate fertilizer delivers that calcium in a form roots and leaves can actually use, turning weak, spotty fruit back into the bumper crop you were hoping for.
I’m Rikta — the founder and writer behind Lawn Gear Lab. This guide is built by comparing the manufacturers’ published specifications and the patterns across verified customer reviews, so you get each pick’s real strengths and trade-offs instead of marketing spin.
Whether you are tending hydroponic greens in a basement or a row of tomatoes in the backyard, the best calcium nitrate fertilizer is the one that dissolves cleanly, delivers consistent results, and fits your specific feeding style without leaving oily residue or clumpy sediment in your tank.
Our Picks at a Glance
How To Choose The Best Calcium Nitrate Fertilizer
Calcium nitrate is not a one-size-fits-all bag. The right choice depends on how you grow — whether you mix a solution for a drip system, foliar spray, or simply side-dress your soil beds.
Greenhouse Grade vs. Agricultural Grade
The single biggest mistake buyers make is grabbing a low-grade agricultural calcium nitrate that leaves an oily film on the water surface. That residue can clog irrigation emitters and coat plant roots. Look for “greenhouse grade” or “solution grade” on the label — it signals high purity and complete solubility.
Solubility and Particle Size
Fine, uniform granules (around 1-3mm) dissolve faster and more completely than chunky, uneven pellets. For hydroponic systems, quick dissolution matters because any undissolved sediment can settle in the reservoir or block the pump intake. A fertilizer that dissolves without clumping means less hassle and fewer pH swings.
Bag Size and Your Garden’s Appetite
It is easy to underestimate how much calcium nitrate a full growing season consumes. A small 2.2-pound bag might be plenty for a few containers or a single hydroponic run, but a backyard vegetable patch or a multi-tower garden will go through it fast. Buying a larger bag upfront saves money and ensures you never run out in the middle of fruit development.
Two-Part vs. Standalone
Many professional fertilizer programs use a two-part system: one bag of 5-12-26 (Part A) and one bag of 15-0-0 calcium nitrate (Part B). The two never mix in concentrated form — they combine only in the final tank. If you are serious about hydroponic nutrition, a two-part system gives you precise control that a standalone bag cannot match.
Quick Comparison
| Model | Best For | Form | Weight | Calcium Content | Amazon |
|---|---|---|---|---|---|
| Jack’s Nutrients 15-0-0★ Best Overall | Hydroponic precision | Powder | 2.2 lb | 19% | Amazon |
| Cz Garden CaNO3 15.5-0-0Garden Value | Soil & rot prevention | Granules | 5 lb | 19% | Amazon |
| Greenway Biotech Solution Grade | Fine hydroponic mixing | Liquid/powder | 5 lb | 19% | Amazon |
| Go Garden 900 Gram | Foliar spray small jobs | Granules | ~2 lb | N/A | Amazon |
| Mega Crop 2 Part B | Large-scale crops | Granules | 21.8 lb | 19% | Amazon |
| Jack’s Dual Pack A+B | Complete two-part system | Powder | 4.4 lb total | 19% | Amazon |
| ENVY Solution Grade 3-Pack | Heavy tomato feeding | Granules | 9 lb | 19% | Amazon |
In‑Depth Reviews
1. Jack’s Nutrients 15-0-0 Part B Calcium Nitrate, 2.2lbs
Our pick — over 4.5★ from 600+ verified ratings; the strongest balance of quality and price.
The crowd-favorite powder that hydroponic growers stick with for years.
This is the benchmark. Jack’s 15-0-0 Part B is a water-soluble powder designed to work alongside Jack’s 5-12-26 Part A in a continuous liquid feed program. The mixing rate is simple: 8.6 ounces per 100 gallons of water to hit 100 PPM of nitrogen. The result you get from that precision is vigorous, consistent growth that growers describe as class-leading — one owner who has used it for years says he has never been disappointed.
The 15-0-0 analysis provides a very soluble source of calcium, which buyers confirm with real results. The review pages are full of reports about “amazing quality veggies and fruit” and one gardener noted it helps with tomato end rot. At 2.2 pounds, the bag is compact but potent — a little goes a long way because the powder dissolves cleanly and mixes with multiple gallons of liquid fertilizer.
It is note this is strictly Part B, so you will need a separate micronutrient source (like Jack’s Part A) for a complete feed. That is by design — it gives you full control over the formula. The thing buyers praise most is the overall quality, with effectiveness a very close second. The unanimous sentiment is that this fertilizer just works, batch after batch.
Jack’s reliable calcium
- Clean mixing powder — dissolves with no sediment, so your lines stay clear
- Proven results in hydroponic gardens for years of consistent use
- Very cost-effective compared to bottled competitors
small bag size
- Requires a matching Part A for a complete nutrient profile
- Only 2.2 pounds — small-scale growers love it, but big gardens will need multiple bags
consistent results: you are running a hydroponic system and want a proven, clean-dissolving calcium nitrate that integrates into a two-part feeding schedule.
limited quantity: you want a standalone fertilizer for soil side-dressing and prefer granules over powder.
2. Calcium Nitrate 15.5-0-0 Fertilizer – Made in USA – 5LB Greenhouse Grade
The 5-pound resealable pouch that saved tomato plants from blossom end rot.
This Cz Garden Supply fertilizer is greenhouse grade, meaning it is high purity and 100% water soluble — no oily skim on the surface. With 19% calcium and 15.5% nitrogen, it gives plants exactly what they need for green leafy growth and hardy cell walls. The granule form dissolves nicely in water, which buyers confirm across the board.
The most-discussed outcome by far is blossom end rot prevention. Buyers report it “really prevented blossom end rot of my zucchini and tomato plants” after years of struggling with the issue. One gardener revived a dying Granny Smith apple tree after noticing leaves falling off — the first dose showed great improvement. The bag itself is heavy-duty and resealable, so you can pour the granules you need and store the rest without moisture getting in.
At 5 pounds, this weighs 5 pounds compared to the Jack’s bag at 2.2 pounds. If you are growing in soil or using drip irrigation, the larger volume and lower price point per ounce make this the better value. Effectiveness and blossom end rot reduction are the top two aspects buyers bring up — and the feedback is overwhelmingly positive.
USA-made quality
- Resealable bag keeps granules dry between uses in humid conditions
- Proven rot prevention — tomato and zucchini growers see results within a season
- Greenhouse grade means no oily residue left on roots or equipment
heavier bag
- A few buyers find it slightly expensive for a granule fertilizer compared to raw sources
- Granules need a little more stirring to fully dissolve than a fine powder
large gardens: the backyard vegetable gardener who wants a generous, resealable bag of greenhouse-grade calcium nitrate to prevent blossom end rot in tomatoes, zucchini, and peppers.
bulky storage: you need a fine powder for precise hydroponic dosing — the granules work but require a minute of stirring.
3. Greenway Biotech, Inc. Calcium Nitrate Solution Grade 15.5-0-0
The solution-grade powder that mixes clean and stays consistent batch after batch.
Greenway Biotech markets this as “solution grade,” which is a step above standard greenhouse grade. The particles are small, uniform white spheres (under 1-3mm) that dissolve quickly without clumping. Buyers notice the difference immediately compared to cheaper brands with larger, tan-colored spheres. One owner put it plainly: “although this is more expensive than some others brand I’ve tried, I will always buy choose this over the cheaper brand” because it mixes “very clean and works great.”
With 15.5% nitrogen and 19% calcium, it is formulated to prevent tip burn in lettuce, rust spot in potatoes, and stem rot in broccoli. Several growers use it as a foliar spray for weak seedlings and report that it strengthens stems and straightens plants within days. The feedback on solubility and purity is excellent — 12 buyers specifically mention solubility as a standout trait.
The bag is 5 pounds, which puts it in the same weight class as the Cz Garden product but at a higher price tier. What you are paying for is the smaller, more consistent particle size and the guarantee that it will mix clear without leaving residue. A good tip from the review pages: use cold tap water to avoid nutrient precipitation when mixing with other elements.
solution grade purity: small, uniform spheres dissolve quicker and cleaner than chunky granules — a real advantage in automated drip systems.
premium price: the price premium is noticeable; budget-focused growers may prefer a larger granule bag and accept a few extra seconds of stirring.
dissolves fast: you run a hydroponic setup and want the cleanest, most consistent dissolution without any risk of clogging your lines.
budget buy: you fertilize by sprinkling granules on soil — the fine powder is overkill for that application.
4. Go Garden Calcium Nitrate Fertilizer for Plants (100% Water Soluble) – 900 Gram
A small 900-gram bag that’s easy to store and ideal for foliar spraying.
Go Garden’s calcium nitrate comes in a dense granular form that dissolves quickly and completely in water. The mixing instructions are straightforward: 4-6 grams per liter of water for foliar spray, or 4-6 kg per acre for drip application. This is the smallest bag on the list by weight, making it a good entry-level option for someone who just wants to try calcium nitrate without committing to a five-pound supply.
Buyers use it for hydroponic solution prep and report it is easily soluble with good results. One noted that after application, “plants were so much better, could see new buds.” The label also mentions it is free from chloride, sodium, and other harmful elements, which matters for sensitive plants. However, the feedback is more mixed here than on the higher-rated picks — a few found it “not as expected” and the overall consensus is less enthusiastic.
The unit count is 950 grams, which is roughly 2.1 pounds. That is comparable to the Jack’s bag in size, but at a higher price per ounce. If you are working with a small container garden or want to test calcium nitrate before buying bulk, this fills that niche.
starter-friendly pack: the 900-gram size is perfect for hobbyists who want to experiment with calcium nitrate without a big investment.
small trial size: the price per gram is higher than larger bags, and a handful of buyers felt the quality didn’t meet their expectations.
first timers: the casual gardener who needs a small quantity for foliar spraying a few tomato plants or a modest hydroponic run.
serious growers: you want a proven, crowd-trusted brand with thousands of positive reviews — the other picks have stronger track records.
5. Calcium Nitrate 15.5-0-0 Mega Crop 2 Part B Hydroponic Soil Fertilizer
The enormous 21.8-pound sack for serious growers who feed at scale.
Greenleaf Nutrients’ Mega Crop Part B is the heavyweight on this list — 21.8 pounds of granulated calcium nitrate with 19% calcium and 15.5% nitrogen. It is designed to work in a 1:1 mixing ratio with the corresponding Part A (5-12-26) for a complete nutrient program. This is not a bag for the weekend gardener; it is for someone running multiple reservoirs, a large greenhouse, or a commercial vegetable patch.
The review feedback focuses heavily on plant vigor. Growers using coco coir report seeing plants “now thriving and growing with vigor.” It comes recommended by a professional tomato grower who supplies restaurants — a strong real-world endorsement. The granules are highly soluble and customizable for any crop type, including concentrated fertilizer injector setups.
At this volume, the price per ounce drops significantly compared to smaller bags. The 21.8-pound sack contains 348.8 ounces of fertilizer, dwarfing the 35.2 ounces in the standard Jack’s bag (a tenfold difference in quantity). If you are feeding a large operation, the savings add up fast. Just be prepared to store a sizable bag — it weighs 21.8 pounds compared to a 5-pound bag and takes up real shelf space.
hydroponic ready: a massive supply of greenhouse-grade calcium nitrate at a much lower cost per ounce than any smaller bag.
specific use: requires a separate Part A purchase to be a complete feed, and the bag is too large for small spaces.
soilless setups: you are feeding more than a few dozen plants and want the lowest cost per feeding on this list.
general soil: you only have a small raised bed or a few pots — this bag would last years and may clump before you finish it.
6. Jack’s Classic Nutrients Calcium Nitrate Fertilizer 15-0-0 (Part A and B Dual Pack, 4.4 Pounds Total)
The complete two-part package that eliminates guesswork from your feeding schedule.
This is the same trusted Jack’s formula, but now you get both halves in one purchase: a 2.2-pound bag of Part A (5-12-26) and a 2.2-pound bag of Part B (15-0-0). That is 4.4 pounds total of water-soluble powder designed to work together. Part A drives strong roots and leaf growth, while Part B provides calcium uptake and strong leaf development. The mixing ratio is a straightforward 1:256 dilution.
The crowd rating here is exceptional — the highest on the list — and buyers consistently call it the best nutrient mix on the market. One grower described it as “doing great” after switching from bottled nutrients and noted it takes “a third of the amount to feed my plants.” Several users specifically mention its effectiveness for cannabis cultivation, with one citing a world-class grower who recommends it for the most demanding harvests.
The value proposition is clear: buying the dual pack costs less than purchasing Part A and Part B separately, and the powdered concentrate goes much further than liquid fertilizers. The only real requirement is to keep the powder in a dry place, as it is hygroscopic and will clump if exposed to humidity.
classic nutrient brand
- Complete A+B system — no need to source a second product separately
- Extremely concentrated — owners mention needing a third of the amount compared to bottled nutrients
- Backed by professional growers, including cannabis cup winners, for the quality of the harvest
higher cost
- Higher upfront cost than a standalone calcium nitrate bag
- Powder must be stored in a sealed, dry container to prevent moisture clumping
trusted formula: you want a turnkey two-part hydroponic system with the highest owner satisfaction on the list and a proven track record.
cost sensitive: you already have a complete micronutrient source and only need a calcium nitrate refill.
7. ENVY Solution Grade Calcium Nitrate (15-0-0) Prevents Blossom End-Rot (3.0 lb x 3)
Three resealable pouches of greenhouse-grade calcium that keep your hydro system clean.
ENVY markets their calcium nitrate as “solution grade,” meaning it uses higher-grade ingredients than standard greenhouse fertilizers to ensure complete solubility and no oily residue. Each pouch contains 3 pounds, and you get three pouches for a total of 9 pounds. The set comes with a measuring scoop, which buyers appreciate for easy dosing. At 19% calcium and 15.5% nitrogen, the nutrient profile matches the other top-tier picks.
Blossom end rot prevention is the headline use-case, and the reviews back it up. Growers report that using this product on their tomatoes led to “very little blossom rot” and a better yield. One gardener dissolved two scoops in warm water to treat a calcium deficiency in a hydroponic setup and saw “strong leaves, better roots, thicker stems” within weeks. The resealable pouches are a thoughtful touch — you can open one pouch at a time without exposing the other 6 pounds to air.
The most common point of feedback is that solubility is mixed — most owners say it dissolves fine, but a few have struggled with it. The manufacturer recommends dissolving in slightly warm water first if you are adding it to a nutrient tank. Compared to the Jack’s powder, this requires more active stirring, but the convenience of three separate pouches and the included scoop make it a strong option for heavy tomato feeders.
blossom end rot fix: three separate pouches mean you can keep the bulk of your supply sealed and fresh — no need to scoop from one giant bag for a year.
single purpose: a small number of buyers found the granules less soluble than expected; warming the water helps, but it is an extra step.
tomato plants: you grow a lot of tomatoes or peppers and want a bulk supply that stays fresh in separate sealed pouches.
multi-purpose: you need a super-fine powder that dissolves instantly with zero effort — the granules here need a bit of patience.
Understanding the Specs of Calcium Nitrate Fertilizer
NPK Ratio (15.5-0-0)
The first number is the nitrogen percentage, and for calcium nitrate it is always 15.5%. The second and third numbers are zero because this product contains almost no phosphorus or potassium. That 15.5% nitrogen is all nitrate-nitrogen, which plants can absorb immediately through their roots or leaves — no waiting for soil bacteria to break it down. The zero phosphorus and zero potassium mean you must pair it with other fertilizers (usually a 5-12-26 base) for a complete feed.
19% Calcium
Calcium is the real star here. It strengthens cell walls, which makes fruit firmer, less prone to cracking, and more resistant to blossom end rot. The 19% calcium content is the highest concentration you can get from a water-soluble fertilizer. Plants absorb calcium slowly and only through actively growing root tips, so a consistent supply throughout the fruiting stage is critical. Once blossom end rot appears, the damage is already done — the calcium prevents it on new fruit, not on existing spots.
Water Solubility and Greenhouse Grade
“Greenhouse grade” means the fertilizer has been purified to dissolve completely in water without leaving sediment or an oily film. Lower-grade agricultural calcium nitrate often contains impurities that leave a visible skim on the water surface. That skim can coat irrigation tubing and plant roots, reducing water uptake. Greenhouse grade is more expensive but necessary for any system with drip emitters, sprayers, or hydroponic pumps — even tiny clogs will ruin a feeding schedule.
Particle Size and Mixing
Calcium nitrate comes as either a fine powder (like Jack’s) or small granules (like Cz Garden and ENVY). Powders dissolve fastest but can be dusty to handle. Granules are less messy and store better in resealable pouches but need a minute of stirring in warm water to fully dissolve. If you are using a concentrate injector system, fine powder is preferred because it passes through the injector without clogging. For hand-watering or foliar sprays, granules work perfectly well.
FAQ
Can calcium nitrate fix blossom end rot that already appeared on my tomatoes?
Is calcium nitrate safe for all plants?
Can I mix calcium nitrate with other fertilizers in the same tank?
What is the difference between greenhouse grade and agricultural grade calcium nitrate?
How often should I apply calcium nitrate to my tomato plants?
Can I use calcium nitrate as a foliar spray?
How should I store calcium nitrate to keep it from clumping?
Can I use calcium nitrate for hydroponic lettuce to prevent tip burn?
Why does calcium nitrate have a 15.5-0-0 label instead of a calcium percentage?
Will calcium nitrate lower or raise my soil pH?
Final Thoughts: The Verdict
For most growers, the best calcium nitrate fertilizer is the Jack’s Nutrients 15-0-0 Part B because it combines the cleanest dissolution with a proven track record from thousands of hydroponic and soil growers — it is the bag people keep repurchasing year after year. If you want a complete two-part system that removes all mixing guesswork, grab the Jack’s Dual Pack A+B. And for the backyard tomato grower who needs a generous supply at a friendly price, the Cz Garden 5-pound bag is the one to reach for.
How We Picked
We do not accept paid placement. Every pick is matched to a real buyer and a real use-case; we do not hands-on test units.
Sources & Methodology
Specifications: manufacturer listings and product documentation. Review insights: verified customer reviews, as of July 2026. Pricing: not shown on this page (it changes often); check the current price via the retailer link.
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