Garden Calcium: Best Ways To Counter Calcium Deficiency

Does your garden need calcium? When many consider nurturing plants to secure large reaping, the primary NPK (nitrogen:phosphorus:potassium) supplements usually cross your mind. However, calcium is also an essential mineral in gardening and is among the secondary macronutrients in soil.

Calcium is responsible for the high strength of plant cell walls, and vital for cell division, cell membrane permeability, and nitrogen utilization.

It’s not just required to build strong cell walls to maintain the plant’s firmness, but it also helps transport other essential minerals. Without a sufficient and even decent amount of it, all the NPK in the plant won’t function. Although not needed in the portions of NPK, calcium is vital for plant growth, makes plants less exposed to pests and diseases, and prevents one of the most undesirable garden concerns – blossom end rot.

Correct quantities of calcium in the soil will result in a healthy soil structure. Calcium may neutralize the alkalinity and acidity in the soil. When you add calcium to the ground, it appears you’re providing your garden with vitamin medication. Roots absorb calcium from the soil solution and transport it to the shoot via the xylem.

If you’ve never added calcium to your plant, this article will walk you through the different ways of adding calcium and how much you need for a wealthy, flourishing garden.

Common Signs Of Calcium Deficiency In Plants

Plants with low calcium levels have stunted growth or dead root tips, deformed young leaves and shoot tips due to weak cell wall development, inhibited bud growth, leaves with burnt-looking edges called tip burn, curled leaves, and yellowing of leaves (chlorosis).

Blossom-end rot observed in tomatoes, peppers, and squashes, black heart in celery, and internal tip burn in cabbages are the best illustration of necrosis or death of plant tissue caused by calcium deficiency.
A soil supplement can provide the missing nutrient if plants exhibit calcium deficiency symptoms. But sometimes, low calcium levels in the soil aren’t the culprit for the plants’ deficiency signs. Your potting soil could have adequate calcium, though it isn’t accessible to the plants. A soil test can tell whether your soil would enjoy the added calcium and which supplementation is best.

Generally, the soil finds it easy to supply the needed calcium for most garden plants, but some are more susceptible to calcium deficiency. Here are some of them:

  • Apple Trees
  • Broccoli
  • Brussels Sprouts
  • Cabbage
  • Cantaloupe
  • Carrots
  • Cauliflower
  • Celery
  • Cherry
  • Conifer Trees
  • Cotton
  • Grapes
  • Legumes
  • Lemons
  • Limes
  • Lettuce
  • Peaches
  • Peanuts
  • Pears
  • Peppers
  • Potatoes
  • Tobacco
  • Tomatoes
  • Watermelons
Identifying the calcium-loving plants will help a lot during the soil preparation process when cultivating such plants.

How To Add Calcium To Garden Soil

a man in camouflage holding a bucket of water.
When attempting to add more calcium to your soil, you should add the correct amount. Too much calcium can be more harmful than helpful, and too little will be unproductive.

There are various methods to add calcium to garden soil, depending on the condition of the soil.

Soil Additive

Lime (Calcium Carbonate)

Lime is made from crushed limestone and comes in powder form. It can be obtained in most garden and farm stores. The quickest way to add calcium to soil is by applying lime (calcium carbonate) to the soil during autumn.

Adding lime into the soil in autumn provides it several months to dissolve before spring. Dig the lime into the soil to a depth of about 6 inches, and water the soil later to the same depth.

Considering it increases your soil PH level to alkaline levels, which is unhealthy for most plants, you’ll need to ensure that you don’t apply too much. You can purchase an at-home soil test kit or ask your local cooperative extension office for a soil test to know its pH level.

If your soil pH is too low, adding lime helps grow most vegetable crops by raising alkalinity. Generally, it must take about 2 tablespoons of dolomitic lime per square foot to recalibrate your soil 1 pH point. And you must bring it within the ideal range, 6.5 to 7.5.

Dolomite lime also holds magnesium carbonate, which raises pH in low-magnesium soils. Opt for another calcium product if a soil test indicates that magnesium levels are already elevated.

Gypsum (Calcium sulfate)

Gypsum is another reliable, fast-acting calcium source for your soil. It is a naturally occurring mineral that contains 20 to 23% calcium and 15 to 18% sulphur.

Gypsum is a more suitable option for adding calcium to soils with a pH of 6.5 to 6.7. Unlike lime, gypsum will not increase the soil pH, so you can apply it without stressing pH imbalance. It can encourage better root growth of crops, specifically in acid soils, even without a significant pH shift.
Calcium sulfate is most promising in soils where excess sodium is present. It removes sodium by the interaction between the sulphate ions and sodium. And that’s precisely what you need if you live in a coastal area with high salt content.

If you think your garden will benefit from gypsum, add about 2 lbs for every 10 square feet of garden space. Make sure that you spread the gypsum evenly over the soil of your backyard. You can then water the soil so that it is easier for the soil to absorb it.

Bone Meal

Organic gardeners love bone meals. It’s made from finely ground-up bones of animals, and because bones contain calcium, this is a rich source. It is also composed of phosphorus and nitrogen, making it an ideal fertilizer. Bone meal works slowly, increasing calcium levels gradually, and it will take more than an entire growing season before reaching its maximum potential.

The good thing about bone meal is that it is ideal for all varieties of plants, from vegetable plants to flowering plants, bulbs, and root crops.

Use one tablespoon of bone meal fertilizer for every two square feet of soil. Sprinkle and rake the bone meal into your garden soil so there are no chunks or unmixed fertilizer. Think of adding a tiny amount of bone meal fertilizer within a planting hole before planting.

Wood Ashes (Calcium Carbonate)

Hardwood ashes are supreme soil amendments. Wood ashes contain nutrients that can be valuable for plant growth, like boron, potassium, and phosphorus, but they don’t have nitrogen.

Not all wood ash fertilizers are the same. Don’t use ashes from softwoods, coal, charcoal briquettes, or those faux logs. These ashes can be discarded because they are ineffective in the garden. Oak is a typically burned wood and an excellent candidate for plant use.

Please consider that wood ash will also increase the pH of your soil.

The use of wood ash is typically capped to a maximum of 15 to 20 pounds per 1000 square feet yearly. Apply it in the winter before planting or as a side dressing around actively growing plants. Make sure it doesn’t touch the stem or leaves as it will burn the plant.


Crushed Oyster Shell (Calcium Carbonate)

An excellent amendment can be produced by pulverizing oyster shells. This delivers calcium carbonate in the aragonite form, perfect for changing soil pH because of its relatively higher solubility than the calcite form. A crushed oyster shell can be utilized as a substitute liming material to correct the soil’s chemical and microbial properties, and help maintain a healthy pH.

However, it is less concentrated and works more slowly than lime, lowering the risk of overfilling your soil.

The best time of year to add oyster shell mulch is in the late spring or early summer when the soil has warmed up. Approximately four to six pounds per 100 square feet is standard when used for garden plants. And when applied as a mulch, layers roughly 2″ thick are recommended.


Eggshells are another great option. You can add eggshells to your compost, increasing the calcium in your pile. Although they decompose at a slow pace to be compelling as a fertilizer, they are still a good addition as an organic matter. However, you would require plenty of ground eggshells to affect plants significantly.

Dry them first, then grind them with a food processor or coffee grinder. The finer the shell powder is, the better the soil can absorb its calcium. After they are ground into powder, you can mix them into the water and pour the mixture into your compost pile.

Some gardeners plant eggshells and tomato seedlings simultaneously to add calcium to the soil and prevent blossom end rot.

Collodial Phosphate – Calcium Oxide

Colloidal phosphate is typically called soft rock or rock phosphate, and though it’s a good source of calcium, it doesn’t have as much calcium as other alternatives on the list. It won’t raise the soil pH as well, unlike lime or other soil amendments.

It is also a slow-release fertilizer, slower than lime or gypsum. And because the nutrients get available slowly, it is not the best option if you want to correct a nutrient deficiency quickly.

To apply soft rock phosphate, add it into your soil before planting, or spread it in the planting hole for transplants and when planting trees. You must not use this in alkaline soil. Applying 5 lbs per 100 square feet in calcium/phosphorus-deficient soil is recommended.

How To Add Calcium Via Foliar Applications

a hand holding a spray bottle with calcium solution over a garden.
You can add calcium via a spray containing calcium chloride, calcium acetate, or calcium nitrate. Foliar sprays are an ideal option and something that experts strongly recommend having within reach always.

They are calcium fertilizers that are made to be sprayed directly onto the leaves of the plants. You know that roots draw in nutrients, but leaves can also bring in nutrients. Foliar sprays are excellent alternatives since you’re offering the nutrients where your plant specifically wants them and won’t impact the soil’s pH.

It is commonly used as a treatment for potted plant problems, particularly for seedlings and transplants, and for curing blossom-end rot, bitter pit, and cork spot. You can mix four tablespoons of the fertilizer in a gallon of water and then spray it on the plant.

To use calcium fertilizers as a disease preventative, or correct calcium deficiency and add nitrogen, use one tablespoon of calcium fertilizer for each gallon of water. Lightly spray it on a cloudy day or sundown when the temperature is less hot and plants have been watered adequately.

Alternatively, you may mix Epsom salt with water or boil chamomile tea, then spray it on your foliage of plants. Or mix some seaweed into the soil between the rows of your plants and water thoroughly.

Calcium Nitrate Fertilizer

Calcium nitrate is generally the best fertilizer or foliar additive to nurture plants. It is a water-soluble chemical solution that supplies plants with additional calcium and nitrogen, making them more bountiful while defending against some prevalent plant diseases, such as blossom-end rot and stunted growth.

Wrap Up

Calcium is a critical secondary nutrient that your garden soil and plants crave. Having sufficient calcium in your plants’ soil may result in a healthier root system. It also helps plants to grow at a steadier pace.

The most reliable way to determine the contents of your soil is to perform a professional soil test. You can likewise conduct a DIY soil test with a kit; however, professional soil testing will deliver the most precise results.

And if your plants are exhibiting symptoms of a calcium deficiency, you must add calcium to the soil. Luckily, there are methods on how you can add just the right amount to your plants.

Consider carefully how you can get enough calcium into your mix so your garden can produce tremendous yields, securing a bountiful growing season.

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