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Role of Calcium in Plant Culture

Along with magnesium and sulfur, calcium is one of the three secondary nutrients. Like primary nutrients (nitrogen, phosphorus and potassium), those elements are essential for healthy plant growth. However, they are needed in lesser amounts. 

Function of Calcium

Calcium, in the form of calcium pectate, is responsible for holding together the cell walls of plants. When calcium is deficient, new tissue such as root tips, young leaves, and shoot tips often exhibit distorted growth from improper cell wall formation. Calcium is also used in activating certain enzymes and to send signals that coordinate certain cellular activities.

Calcium Deficiency

Calcium is not mobile within the plant. So the plant relies on the process of transpiration in which the plant roots take up the soil solution (which contains the needed calcium), transports it to new growth where the calcium is used and the excess water vapor escapes out through holes in the leaves called stomata. Anything that slows transpiration, such as high humidity or cold temperatures, can induce calcium deficiency even if the calcium levels are normal in the growing medium. Parts of the plant that transpire little water, i.e. young leaves and fruit, will display calcium deficiencies first. Blossom end rot of tomatoes is a classic case of calcium deficiency. Calcium deficiency can arise if levels in the fertilizer solution are less than 40-60 ppm and/or potassium, magnesium, or sodium levels are too high.

Calcium deficiency causing leaf edge necrosis in poinsettias by PRO-MIX Greenhouse Growing.

Calcium deficiency causing leaf edge necrosis in poinsettias.


Calcium deficiency causing bract edge burn by PRO-MIX Greenhouse Growing.

Calcium deficiency causing bract edge burn.


Calcium deficiency causing blossom end rot of tomatoes by PRO-MIX Greenhouse Growing.

Calcium deficiency causing blossom end rot of tomatoes.

Calcium Toxicity

Calcium toxicity rarely occurs. High levels of calcium can compete with magnesium and potassium uptake, causing their deficiencies.

Calcium Source - Fertilizer

Not all fertilizers contain calcium, such as those with a significant percentage of phosphorus, so it is important to read the label. Some fertilizers list the percentage of calcium and magnesium in the fertilizer analysis, i.e. 15-7-14-3Ca-1Mg. Those that are identified as a “Cal-Mag” such as 15-5-15, 17-5-17, etc., will contain calcium. If you are not certain that a fertilizer contains calcium, check the percentage list of ingredients in the fertilizer.

Most calcium-containing fertilizers are formulated with calcium nitrate. Keep in mind that calcium nitrate is potentially basic, meaning it will cause the pH of the growing medium to rise unless acid is injected or potentially acidic fertilizers are used in rotation.


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Calcium Source - Water

All water sources supply some calcium. As a general rule, water coming from deep wells or most non-coastal regions of North America has sufficient calcium for normal crop growth, while water from a shallow well, coastal region, rain, lake, river or pond generally has insufficient calcium levels. Regardless, it is best to have your water tested to verify if your water is supplying sufficient calcium. If the calcium level in your water is 40-60 ppm or more, then there is little need to use a fertilizer that provides calcium.

If it is less, then talk with your Premier Tech Grower Services representative and together a customized fertilization program can be developed to fit your specific needs.

BLOE          PEEJ              LAWL

Ed Bloodnick
Horticulture Director
US-South East

JoAnn Peery
Horticulture Specialist
US-Central, Canada-Central

Lance Lawson
Horticulture Specialist
US-West, Canada-West


Troy Buechel
Horticulture Specialist
US-North East

Susan Parent
Horticulture Specialist
Canada-East, US-New England

Jose Chen Lopez
Horticulture Specialist
Mexico, Latin & South America

PRO-MIX® is a registered trademark of PREMIER HORTICULTURE Ltd.

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