Botanicare Cal-Mag Plus 2-0-0 | 3.2% Ca, 1.2% Mg, 0.1% Fe

What the Guaranteed Analysis on Botanicare Cal-Mag Plus Actually Says

Cal-Mag Plus is a liquid supplement, not a base feed, and the label is short enough to read in one go. Botanicare guarantee 2.0% nitrogen, 3.2% calcium, 1.2% magnesium and 0.1% iron, plus what they describe as a proprietary blend of select trace minerals. The working rate is 1 tsp, or 5 mL, per gallon of water, used with every watering as needed. For a foliar pass the rate climbs to 10 to 15 mL per gallon. Mix it in, then set pH between 6.2 and 7.0 before the solution goes anywhere near a root zone. Shake the jug first, because the calcium settles. Botanicare name three situations it is built for: reverse osmosis water, coco coir and other low-calcium media. Those three share one problem, which is that the water or the medium arrives with no calcium buffer of its own. Iron at 0.1% is the quiet part of the formula and it is why new growth stops going pale.

Where a Calcium Magnesium Supplement Earns Its Place in the Feed

Coco is the obvious case, since the fibre holds onto calcium and magnesium and hands the plant back less than you put in. Reverse osmosis water is the other one, because it strips the hardness out along with everything else. Run it with every feed in coco and the pale new leaves and the rusty-looking spotting between veins stop showing up. In soil it is a correction rather than a routine, and over-applying it there will lock out potassium instead of helping. The foliar rate exists for a reason, which is that a tissue deficiency shows up faster through the leaf than through the root. Keep foliar passes to the vegetative stretch and early flower, since nobody wants residue on finished buds. It mixes with any nutrient programme, Botanicare's own or anyone else's, and it goes in before the base nutrients rather than after. That sequence matters more than it sounds, because concentrated calcium meeting concentrated phosphate in a small volume of water will precipitate out as sludge. If your tap water already reads high in hardness, you may need none of this at all. A low cost hardness test will tell you that before a bottle does.

Key Features

• Guaranteed analysis: 2.0% N, 3.2% calcium, 1.2% magnesium and 0.1% iron.
• Working rate: One teaspoon, or 5 mL, per gallon with every watering as needed.
• Foliar rate: Ten to fifteen millilitres per gallon for a tissue-level correction.
• pH window: Mix first, then set the solution between 6.2 and 7.0.
• Built for: Reverse osmosis water, coco coir and other low-calcium media.
• Programme compatible: Runs alongside any base nutrient line, not just Botanicare's own.
• Mixing sequence: Goes in ahead of the base nutrients so phosphate cannot precipitate it.
• Five sizes: From a quart for one tent up to a drum for a fertigation room.

Technical Specifications