Fertiliser
Cal-Mag for Plants | pH-Neutral Calcium & Magnesium Feed
Adds calcium and magnesium for firm growth and fewer deficiencies.
from £10.49
How Amino Chelated Calcium compares
Full guide and scienceAmino acid chelated calcium powder
- Calcium held by plant-derived amino acids; 8% nitrogen comes with it
- Dissolves fully at 2.5–3.5 g per litre with no sediment
- Solution pH 4–6, so soil pH is left alone
- No chloride, no nitrate
- Works as a spray, a drench or a fertigation feed from the same tub
Calcium chloride, garden lime or gypsum
- Calcium chloride is a cheap foliar source but brings chloride with every gram of calcium
- Garden lime raises soil pH, which is the last thing an ericaceous bed wants
- Gypsum is a good soil calcium source but is a suspension, not a solution, and is not a spray product
- All three feed the soil, which is only useful if the roots can then move the calcium fast enough
Customer highlight
Great stuff
I bought this and used it recently as I needed to get some more calcium into the soil during mid -late flower, this is mostly water soluble which means that the plant should absorb it relatively quickly.
Editorial highlight from marketplace and store reviews — separate from the full review list below.
Made by Growers · Backed by Science
Amino acid chelated calcium: a water soluble calcium feed for spray and drench
10% Chelated Calcium 8% Amino Nitrogen 100% Water Soluble Soy-chelated Spray, Drench or Fertigate Handcrafted in Stockport
Cal-Mino is amino acid chelated calcium: 10% calcium bonded to amino acids from soy protein, sold as a fine powder that dissolves completely in water. Calcium only travels one way in a plant, up the xylem with the water stream, and it cannot be moved from an old leaf to a swelling fruit. A soluble calcium that can be sprayed onto young fruit, drenched around roots or run through a drip line gives you a way to put calcium where the plant is struggling to get it. It carries 8% nitrogen from the amino acids, no chloride, no nitrate, and it does not shift soil pH.
It is a spray-dried powder that dissolves without sediment, and you are not paying postage on a bottle of water. Use it on tomatoes, peppers, courgettes and aubergines through fruiting, on lettuce and brassicas for tip burn, and on apples and soft fruit. It is vegan (soy-chelated mineral calcium). The amino acid base is made by enzyme digestion of non-GMO soybeans, and the calcium comes from calcium carbonate.
10%Calcium (Ca)
8%Nitrogen (N)
100%Water soluble
pH 4–6In solution
What chelated calcium is used for in the garden
- Blossom end rot on tomatoes, peppers, courgettes and aubergines — sprayed directly onto young fruit, weekly, as part of a routine that starts with even watering
- Tip burn in lettuce and brassicas — fast-growing inner leaves are the last stop on the calcium line, so growers spray the heart rather than rely on the roots
- Apples and soft fruit — calcium sprays on developing fruit are routine practice in commercial orchards
- A calcium drench that does not lime the soil — the solution runs slightly acidic, so blueberries, rhododendrons and other acid-loving plants can have calcium without a pH rise
- Feeding through drip lines and fertigation — dissolves with no residue, so it will not block emitters or leave a crust
- Compost teas — the amino acids and peptides feed the brew while the calcium stays in solution
Why a chelated powder rather than calcium chloride or lime?
Amino acid chelated calcium powder
- Calcium held by plant-derived amino acids; 8% nitrogen comes with it
- Dissolves fully at 2.5–3.5 g per litre with no sediment
- Solution pH 4–6, so soil pH is left alone
- No chloride, no nitrate
- Works as a spray, a drench or a fertigation feed from the same tub
Calcium chloride, garden lime or gypsum
- Calcium chloride is a cheap foliar source but brings chloride with every gram of calcium
- Garden lime raises soil pH, which is the last thing an ericaceous bed wants
- Gypsum is a good soil calcium source but is a suspension, not a solution, and is not a spray product
- All three feed the soil, which is only useful if the roots can then move the calcium fast enough
Handcrafted in Stockport
Every Dr Forest product is made in small batches at our workshop in Stockport, Greater Manchester. Cal-Mino is one of our single-ingredient soluble feeds, alongside seaweed powder and fulvic acid. If your tomatoes have black-bottomed fruit, read what causes blossom end rot, and how I stopped it before you buy anything. Made by Growers. Backed by Science.
The Science
The science of calcium delivery: what a foliar calcium spray can and cannot do
Calcium moves one way
Most plant nutrients can be recycled. Nitrogen, potassium and magnesium are pulled out of old leaves and sent to new growth when supply runs short. Calcium is different. It travels up the xylem in the transpiration stream and, once it has been laid down in a cell wall or a vacuole, it stays put. The phloem carries almost none of it (Hocking et al., 2016). So a tomato fruit, which transpires little, competes badly with leaves for calcium even when the soil has plenty. The plant is not short of calcium; the fruit is.
That is why the disorders linked to calcium all show up in tissue that grows fast and transpires slowly: the blossom end of a tomato, the inner leaves of a lettuce, the flesh of an apple in store. Ho and White (2005) put it as a supply-and-demand problem at the level of the individual cell: blossom end rot starts when the calcium demand of a rapidly expanding cell outruns what the xylem can deliver to it. Anything that slows the water stream, such as erratic watering, high humidity or salty compost, tips the balance.
What is in the tub
| Analysis | Value | Form |
|---|---|---|
| Calcium (Ca) | 10% | Amino acid chelate, from calcium carbonate |
| Nitrogen (N) | 8% | Amino acids and short peptides |
| Amino acid source | Soy protein | Enzyme digestion of non-GMO soybeans |
| Solubility | 100% | Spray-dried powder, no residue |
| Solution pH | 4–6 | Slightly acidic; does not lime the soil |
An amino acid chelate is a metal ion held by the carboxyl and amino groups of amino acids, so the calcium is carried as part of a small organic molecule rather than as a bare Ca²⁺ ion with a chloride or nitrate partner (Souri and Hatamian, 2019). Enzyme digestion, rather than acid treatment, keeps the amino acids in their natural L-form. The nitrogen is entirely organic and comes along for free.
Water the plant evenly first. Then spray the fruit, not the leaves. Calcium on a leaf mostly stays in that leaf.
Mechanisms of action
01
Foliar uptake is real, but the leaf keeps what it takes
Fernández and Eichert (2009), in a review of foliar fertilisation in Critical Reviews in Plant Sciences, describe the cuticle as a waxy, water-repelling barrier that lets ions and polar molecules through slowly and unpredictably, and note that responses to foliar sprays are often variable because the penetration mechanisms are still poorly understood. Humidity matters: droplets that dry fast stop delivering. Whatever calcium does get into a leaf is then phloem-immobile, so it will not travel on to the fruit. The practical conclusion is to spray the tissue you want the calcium in, in cool, humid conditions.
02
Spray the fruit, and treat it as insurance rather than a fix
Ho and White (2005) recommend spraying calcium directly onto young fruit for blossom end rot, while acknowledging that horticultural approaches are not completely effective. Kabir and Díaz-Pérez (2025), reviewing the calcium route in the plant, note that because calcium barely moves in the phloem, foliar calcium may not improve fruit calcium status at all. A 2023 Latvian greenhouse trial of five commercial preparations, one of them a complexed calcium, sprayed weekly onto young fruit found none raised fruit calcium or cut the share of affected fruit (Karlsons et al., 2023). The honest reading is that the evidence for foliar calcium against blossom end rot is thin and mixed. Even watering is the intervention with the strongest support; the spray is what you add on top.
03
Blossom end rot may be a stress disorder that calcium deficiency follows, not causes
Saure (2014), in Scientia Horticulturae, reviewed the literature and concluded that calcium deficiency is a result of blossom end rot rather than its cause: soluble calcium in fruit only drops after the symptoms appear, and the real trigger is abiotic stress (drought, salinity, heat, high light, ammonium feeding) driving oxidative damage and cell death. He still notes that spraying calcium salts onto the fruit may help reduce incidence. It is a useful corrective. If your plants are stressed, no calcium product will out-argue that.
04
Calcium builds the cell wall
White and Broadley (2003), in their Annals of Botany review, describe calcium as required for structural roles in the cell wall and membranes, and as the messenger that coordinates the plant's response to stress. It cross-links pectin in the middle lamella, the layer that glues cells together. Tissue that formed without enough calcium is soft and leaky, which is why a calcium-short fruit collapses from the inside, and why calcium sprays on developing fruit are routine practice in commercial growing (Hocking et al., 2016).
05
The amino acids do their own work below ground
Protein hydrolysates, the family this product's amino acid base belongs to, are studied as biostimulants in their own right. Colla et al. (2017), in Frontiers in Plant Science, report that foliar and root applications improve uptake and use efficiency of macro- and micronutrients, that peptides and amino acids complex nutrients and keep them available, that root dry weight, length and surface area rose by 35%, 24% and 26% in treated plants versus controls in one trial, and that soil microbial activity increases. Used as a drench, Cal-Mino is a calcium feed that also feeds the soil. Our guide to amino acid biostimulants covers which types are worth buying.
Scientific references
- Hocking, B., Tyerman, S.D., Burton, R.A. and Gilliham, M. (2016). Fruit calcium: transport and physiology. Frontiers in Plant Science, 7, 569.
- Ho, L.C. and White, P.J. (2005). A cellular hypothesis for the induction of blossom-end rot in tomato fruit. Annals of Botany, 95(4), 571–581.
- Fernández, V. and Eichert, T. (2009). Uptake of hydrophilic solutes through plant leaves: current state of knowledge and perspectives of foliar fertilization. Critical Reviews in Plant Sciences, 28(1–2), 36–68.
- Kabir, M.Y. and Díaz-Pérez, J.C. (2025). Calcium route in the plant and blossom-end rot incidence. Horticulturae, 11(7), 807.
- Karlsons, A., Osvalde, A., Cekstere, G. and Āboliņa, L. (2023). Effects of Ca sprays on fruit Ca content and yield of tomato variety susceptible to blossom-end rot. Plants, 12(8), 1640.
- Saure, M.C. (2014). Why calcium deficiency is not the cause of blossom-end rot in tomato and pepper fruit: a reappraisal. Scientia Horticulturae, 174, 151–154.
- White, P.J. and Broadley, M.R. (2003). Calcium in plants. Annals of Botany, 92(4), 487–511.
- Colla, G., Hoagland, L., Ruzzi, M., Cardarelli, M., Bonini, P., Canaguier, R. and Rouphael, Y. (2017). Biostimulant action of protein hydrolysates: unraveling their effects on plant physiology and microbiome. Frontiers in Plant Science, 8, 2202.
- Souri, M.K. and Hatamian, M. (2019). Aminochelates in plant nutrition: a review. Journal of Plant Nutrition, 42(1), 67–78.
How to Use
How to use amino chelated calcium: application rates and guide
100% water-soluble — dissolves completely
Cal-Mino is a fine, spray-dried powder that dissolves fully in water with no sediment or residue. Apply as a foliar spray, root drench, through fertigation or drip systems, or added to compost teas. No straining required. Use fresh solution within 24 hours. Half a level teaspoon is approximately 2.5 g.
Key timing for blossom end rot prevention
Blossom end rot is set during early fruit development. Once the black patch appears, that fruit cannot be saved. Prevention is everything. Begin foliar calcium sprays when the first flowers open and continue weekly throughout fruiting. Consistent watering is equally important, because calcium transport depends on steady transpiration. Irregular watering is the single biggest trigger for blossom end rot, even in calcium-rich soil.
Application rates
Foliar spray — blossom end rot prevention
Dissolve in water and spray developing fruit and surrounding foliage in early morning or late evening. Target the fruit trusses directly: calcium needs to reach the fruit tissue, not just the upper leaves. Begin at first flower and continue throughout the fruiting period. This is the primary application for preventing blossom end rot in tomatoes, peppers, courgettes and aubergines.
Foliar spray — general calcium supplementation
Spray both leaf surfaces. Particularly useful for lettuce (tip burn prevention), brassicas, apples and soft fruit. Spray the tissue you want the calcium in; what lands on a leaf largely stays there.
Root drench — soil and container application
Dissolve and apply to the root zone. Suitable for all container and bed-grown crops. The amino acid chelation helps keep calcium in solution in the soil, and the peptide base feeds soil biology.
Solution feeding and fertigation
Fully soluble with no residue, so it is safe for drip lines and recirculating feed systems. Add to the feed solution after mixing main nutrients. Perform a jar test before first use to confirm compatibility with your existing nutrient solution.
Compost tea additive
The amino acids and peptides feed microbial activity in the tea while the chelated calcium stays in solution.
Rates at a glance
| Situation | Rate | Frequency |
|---|---|---|
| Foliar spray, blossom end rot prevention | 2.5–3.5 g per litre | Weekly from first fruit set until harvest |
| Foliar spray, general calcium | 2.5–3.5 g per litre | Every 7–14 days in the growing season |
| Root drench, soil and containers | 2.5–3.5 g per litre | Every 2–4 weeks in the growing season |
| Solution feeding and fertigation | 2.5–3.5 g per litre | As part of the regular feed cycle |
| Compost tea | 2.5 g per litre of tea | Add during the brew cycle |
Step-by-step preparation
- Measure the powder. Half a level teaspoon is approximately 2.5 g. For a standard 10-litre watering can, measure 25–35 g (5–7 level teaspoons).
- Dissolve in water and stir. Sprinkle powder onto the water surface and stir until fully dissolved. Dissolves quickly with no sediment.
- Apply immediately or within 24 hours. For foliar sprays, use a fine mist sprayer targeting fruit, growing tips and both leaf surfaces. For root drenches, apply evenly around the root zone.
- Time foliar sprays correctly. Spray in early morning or late evening, not in full sun. Cool, still conditions maximise absorption time before the solution dries.
- Store dry powder sealed. Keep in a cool, dry place. The powder is hygroscopic and will absorb moisture if left open.
Works well combined with…
Use alongside Liquid Micronutrients for a combined calcium and trace element foliar programme. Combine with Seaweed Powder for biostimulant activity; the alginates help the spray wet the leaf. For soil-applied calcium alongside potassium and magnesium, use Yorkshire Polyhalite as the slow-release base and Cal-Mino as the fast-acting foliar top-up.
Storage
Keep the tub sealed, cool and dry. The powder draws moisture from the air and will cake if left open. Mixed solution should be used within 24 hours. Keep out of reach of children and pets, as with any concentrated feed.
Questions & Answers
Frequently asked questions about chelated calcium
It is calcium bonded to amino acids from soy protein, dried to a powder that dissolves completely in water. It gives you a soluble calcium for plants that can be sprayed onto fruit and leaves, drenched around roots or run through a drip line, with 8% organic nitrogen alongside and no chloride, nitrate or lime. It is used for blossom end rot, tip burn and general calcium feeding.
No. Once the black patch appears, that fruit is finished; the cells have already collapsed. Calcium sprays are for the fruit that has not set yet. Start when the first flowers open, spray the young fruit weekly, and sort your watering, because uneven watering is the biggest single trigger. The research on foliar calcium for blossom end rot is mixed, which is why we say even watering first, spray second.
Most garden soils already hold enough calcium. The problem is usually transport: calcium moves up the xylem with water and cannot be sent from leaves to fruit. If watering is erratic or the plant is growing fast, the fruit runs short even in calcium-rich soil. Lime also raises pH, and gypsum is a soil amendment rather than a spray. A soluble chelate lets you put calcium directly onto the tissue that needs it.
Calcium chloride is the cheap, standard foliar calcium. The difference is what comes with the calcium. Calcium chloride delivers chloride; this delivers 8% amino acid nitrogen and nothing else. The solution is mildly acidic rather than salty, and the amino acids are a food source for soil life when you drench. We do not claim it is absorbed several times better than a salt; that number appears in a lot of marketing and we could not find it in the literature.
It is made with organic ingredients: amino acids from enzyme digestion of non-GMO soybeans, and calcium from calcium carbonate. There are no synthetic chelating agents such as EDTA. It is vegan (soy-chelated mineral calcium). We do not hold an organic certification, so we do not describe it as certified.
No. The solution sits at pH 4–6, slightly acidic, so it does not raise soil pH the way lime does. That makes it a usable calcium source for blueberries, azaleas, rhododendrons and other acid-loving plants.
For blossom end rot, spray weekly from first flower set through to the end of harvest, at 2.5–3.5 g per litre. Aim at the trusses and the young fruit, not just the canopy. Spray in early morning or late evening when it is cool and still, so the droplets stay wet long enough to be taken up.
It is compatible with most water-soluble feeds, seaweed extracts and fulvic acid, and pairs well with our liquid micronutrients for a combined calcium and trace element spray. Avoid mixing with concentrated phosphate solutions, because calcium and phosphate can form an insoluble precipitate. Do a jar test before tank-mixing with anything new.
It is a soy-derived amino acid and calcium powder with no synthetic chelating agent, used at 2.5–3.5 g per litre. Treat it as you would any concentrated feed: store it sealed and out of reach, and keep the dry powder away from children and pets. Once diluted and applied, there is nothing in it that is a concern for bees or garden wildlife.
Sealed, cool and dry. The powder is hygroscopic, so an open tub in a damp shed will cake. Caked powder still dissolves, it is just harder to measure. Mixed solution should be used within 24 hours.
Calcium in lime, gypsum or shell meal is a soil mineral. It works slowly in the soil and can't be sprayed onto a plant. Chelated calcium is held by another molecule, here amino acids from soy protein, so it dissolves completely in water and stays in solution. That means you can spray it onto the fruit and leaves that are short of calcium, rather than relying on the roots to move it there.
Dissolve 2.5–3.5 g per litre of water (half a level teaspoon is about 2.5 g) and use it the same day. As a spray, mist the young fruit, growing tips and both sides of the leaves in early morning or late evening, weekly from first fruit set for blossom end rot or every 7–14 days for general feeding. As a root drench, water it around the root zone every 2–4 weeks in the growing season. It also goes through drip lines and into compost tea at the same rate.
Spray it straight onto the tissue that needs it. Calcium moves up the plant with water and can't be passed from leaves to fruit, so a soil dressing can take weeks to show and may never reach a fast-swelling fruit. A soluble calcium sprayed on young fruit and growing tips gets there directly. Do it in cool, still conditions so the droplets stay wet long enough to soak in, and sort out uneven watering at the same time.
Tomatoes, peppers, courgettes and aubergines through fruiting, where it helps prevent blossom end rot on fruit that hasn't set yet. Lettuce and brassicas, where fast-growing inner leaves get tip burn. Apples and soft fruit, where calcium sprays on developing fruit are routine in commercial orchards. Because the solution is slightly acidic, it's also a calcium source for blueberries, rhododendrons and azaleas that won't lime the soil.
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