Calcium for Plants

In spring and summer, apply once weekly at 2 tsp per gallon, using a watering can or a hose-end sprayer on the 2 tsp setting. In fall and winter, cut back to every 2-4 weeks. Use it alongside your regular fertilizer, not instead of it, since it supplies calcium and trace minerals but no N-P-K. For crops prone to blossom-end rot, start early in the season rather than waiting for symptoms to appear.

At 1 tsp per quart, the 8 oz bottle makes about 48 watering cans of feed. For a typical shelf of 10–15 plants fed every 1–2 weeks in season, that's several months of feeding — and the 32 oz bottle four times that.

It can help, but it's often not the whole answer. Blossom-end rot is usually caused by inconsistent watering that blocks the plant from moving calcium into the fruit, even when there's plenty of calcium in the soil. So the first and most important fix is steady, deep watering plus mulch to keep soil moisture even. Adding calcium helps when the soil is genuinely short, but if watering swings between dry and soaked, supplementing calcium alone frequently won't stop the rot.

Because calcium doesn't move within the plant, deficiency shows in the newest growth: distorted, curled, or dying growing tips, brown papery edges on young leaves, and blossom-end rot on the fruit of tomatoes, peppers, and squash. Older leaves usually look fine. If instead the oldest leaves are yellowing or scorching, that points to nitrogen or potassium, not calcium. Matching the symptom to the right nutrient saves you treating the wrong problem.

Yes — the label supports leaf misting at 2 tsp per gallon. Foliar application can help calcium reach growing tips and developing fruit more directly, which is useful since calcium moves poorly through the plant. Spray in the cooler morning or evening to avoid leaf burn, and coat the new growth and young fruit. That said, foliar calcium is a supplement to good soil moisture and root feeding, not a substitute for the consistent watering that prevents most calcium problems.

New growth and fruit that develop after you start treating will benefit, but existing blossom-end rot or damaged tips won't reverse — those parts are already affected. With consistent watering plus calcium, you'd expect later fruit on the same plants to come in clean over the following weeks. The clearest results come from starting early and pairing calcium with even soil moisture, rather than reacting once damage has appeared.