Foliar feeding with calcium (the application of calcium rich fertilizer to the plants leaves) may make the difference between a bumper crop of tomatoes to fruit with blossom end rot, or gorgeous Granny Smith apples to bitter ones. Let’s learn more about making and using a calcium foliar spray on plants.
Calcium foliar spray lends necessary calcium to the plant, preventing leaf necrosis, short brown roots, fungal issues, weak stems and stunted growth (damping off). Making calcium spray for plants will increase cell division, an important component, especially in those rapid growers such as tomatoes, sweet potatoes, and corn.
While it is true that acidic soils have a reduced amount of calcium compared to more alkaline soils, pH is not a true reflection of the necessity for foliar feeding with calcium but may be used as a general guideline.
While commercial calcium foliar sprays may be purchased, it may be less expensive and just as easy to make a homemade calcium rich foliar spray with ingredients already in the home or garden. If you are experiencing any of the plant symptoms above or have had your soil’s pH tested and it’s deficient in calcium, now is a good time to learn how to make your own calcium fertilizer.
Plants require a ratio of calcium and magnesium; when one goes up, the other goes down. Utilizing your compost, which is generally rich in calcium or can be amended with the addition of lime or eggshells, is one way to increase the calcium level in growing plants. Another way to accomplish this goal is by making calcium spray for plants with eggshells.
To make calcium spray for plants with eggshells, boil 20 eggs in a pan covered with 1 gallon (3.6 kg.) of water. Bring to a rolling boil, then remove from heat and allow to cool for 24 hours. Strain the water of shell fragments and store in an airtight container in a cool, dark place.
Another way to make homemade calcium rich foliar spray is by filling a gallon (3.6 kg.) jar with water and eggshells. Steep for one month, allowing the eggshells to dissolve and filter their essential nutrients into the liquid. To create your calcium foliar spray, mix 1 cup (454 gr.) of the resulting solution with 1 quart (907 gr.) of water and transfer to a spray bottle. This homemade calcium rich foliar spray is also rife with nitrogen and magnesium, phosphorus and collagen, which are all essential nutrients for healthy growth.
It’s not just for sushi anymore. Particularly rich in bromine and iodine, seaweed is also rich in nitrogen, iron, sodium and calcium! So, how to make your own calcium fertilizer out of seaweed?
Collect the seaweed (if legal to do so where you are) or buy at the garden store and rinse thoroughly. Chop up the seaweed and cover with 2 gallons (7 kg.) of water in a bucket. Cover loosely, ferment for a few weeks, and then strain. Dilute 2/3 cup (150 gr.) to one gallon of water to make a calcium foliar spray.
Chamomile contains sources of calcium, potash and sulfur, and as such is good for preventing damping off and many other fungal issues. Pour 2 cups (454 gr.) of boiling water over ¼ cup (57 gr.) chamomile blossoms (or you can use chamomile tea). Let steep until cool, strain and place in spray bottle. This foliar solution will keep for one week.
Great for any number of things, Epsom salts contain magnesium and sulfur, and where there’s magnesium there is certainly a correlation to calcium. The magnesium content aids the plant in utilizing other nutrients, such as calcium, more effectively. Plants, such as roses, tomatoes and peppers, which require higher amounts of magnesium, benefit the most from this spray. The general recipe for using Epsom salt as a calcium foliar spray is 2 tbsp. salts (29 mL.) to 1 gallon of water, but for the aforementioned, cut the Epsom salt to 1 tbsp (14.8 mL.) to 1 gallon (3.6 kg.) of water.
Antitranspirants can also be used in the amount of ½ tsp (2.4 mL.) to 8 ounces (227 gr.) of skim milk (or equal amount of prepared powdered milk) for foliar feeding with calcium. Antitranspirants can be purchased via a garden center and are usually made from natural oils such as those from pine trees. Be sure to flush the sprayer out with water when done.
And last but not least, I previously mentioned using one’s compost to enrich soils with nutrients. Compost tea can be made with one part of mature compost to two parts of water (this can be done with mulched weeds, herbs or pond weeds too). Let sit for about a week or two and then strain and dilute with water until it looks like a weak cup o’ tea. This makes a fine method of foliar feeding with calcium.
BEFORE USING ANY HOMEMADE MIX: It should be noted that anytime you use a home mix, you should always test it out on a small portion of the plant first to make sure that it will not harm the plant. Also, avoid using any bleach-based soaps or detergents on plants since this can be harmful to plants. In addition, it is important that a home mixture never be applied to any plant on a hot or brightly sunny day, as this will quickly lead to burning of the plant and its ultimate demise.
Believe it or not, calcium is as essential for plants as it is for humans. It is commonly found in nature and is second to being as common as oxygen. In the form of calcium carbonate, calcium can be extracted from something as common as eggshells when paired with vinegar. Natural and organic farmers, even gardeners, tend to create their own water soluble calcium at home. This is because all of the ingredients required are those you can find in most households, especially if you love eggs. So, how do you make water soluble calcium?
Here in the South (Georgia, USA) we experience long periods of high humidity, high temps, and very little wind. We call it sticky. It stays sticky down here, and with these conditions it’s all too easy to experience calcium deficiency. I’ve lost too many tomatoes this year to blossom end rot. At first I thought I hadn’t amended the soil well enough, or maybe it was the pH that was out of whack. After having the soil tested it was easy to see why I had been experiencing blossom end rot. Elemental levels were good 6.2 pH was perfect. There could be only one other possible cause. I was at the mercy of Mother Nature.
Since calcium is an immobile element within a plant, it meant that its dependence on the xylem’s pull of water up the plant, itself dictated by transpiration rate, would fall victim to our sticky southern days. If the days were sticky, that meant the plant’s transpiration rate was almost completely shut down. This was especially evident on the tips of the new shoot growth. They were yellow, soft, and stunted. I knew I had to correct this problem immediately, with a calcium foliar feed, if I had any hopes of saving my summer crop of tomatoes. And with the persistent high humidity, it meant I’d be doing this once a week for an extended period of time. So far I’ve only had to make three applications since first signs in early June. I picked a top tomato off this morning that had blossom end rot. It looks like another application is due. Side note, prevention is always best. I should have never stopped my applications unless I had seen toxicities.
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You may know that not all calciums are created equal. Typical fertilizer forms of calcium include calcium nitrate and to a lesser extent calcium chloride. When it comes to foliar applications we must be more precise with our choice of calcium. Fertilizer grade calcium nitrate can easily burn the bracts leaving you without a blossom to bloom. At least then you won’t have to worry about blossom end rot. You won’t have any blossoms to rot. In all seriousness though, there is but one truly safe way to apply calcium to the plant through the leaves. It is recommended that you use “reagent*” or “laboratory*” grade calcium chloride.
Calcium chloride is available in the dihydrate or anhydrous forms dihydrate is usually less expensive. Fertilizer grade calcium nitrate may contain impurities than will burn the leaves and bracts of the plant. However, horticultural grade calcium nitrate has also shown effective at correcting deficiencies without burning. There are several companies out there that you can most likely find at your local garden supply shop. Examples include: Cutting Edge Solutions Plant Amp, Monterey’s Foli-Cal, and Southern Ag’s Stop Blossom End Rot. I prefer Plant Amp from Cutting Edge Solutions due to it containing organic acids making it perfect as a foliar (foliar sprays need to be slightly acidic in order to more easily pass through the stomata). If you add Cutting Edge Mag Amp, a magnesium supplement, you won’t need a surfactant because it’s already in the mix. If not, make sure you use some sort of wetting agent, like soft dish soap at a rate of 2TBSP per gallon.
When applying a foliar spray it is important you test the spray on a small section of the lower portion of the plant, and if you have a variety of plants use one from each variety as a test. If there are no signs of burn within 3-4 days, it’s safe to proceed. With calcium chloride foliar sprays it’s important that you apply out of direct sunlight. If applied in direct sunlight, there will be severe leaf damage. You may even lose a growth tip to burn. Application in the early morning is safer especially when you have high humidity which can lead to Botrytis or Grey Mold when the application doesn’t dry completely before the sun sets. Apply once a week for 3 consecutive weeks upon first signs of deficiency. The problem may persist, but this is the best solution to slow it down. If you’re like me you’ve put way too much time, planning, and energy into producing the best crop possible to have it all taken from you by some extraneous variable like humidity.
Established Plants - Foliar Spray - Add 1 tsp per quart (liter) of water [1 tbs per gal] into sprayer. Mix well. Spray foliage focusing on underside of plant leaves. Repeat every 5-7 days for best results.
*Note Calcarb leaves a beneficial white residue of natural calcium. It may be rinsed off after 36 hrs, but left on will achieve best results*Calcarb is best applied alone, wait 36 hrs before applying other foliar nutrients.*Clean sprayer after every use.
• Fruiting & Flowering Plants - Foliar Spray - Add 2 tsp per quart (liter) of water. Mix well and add to sprayer. Spray focused "pop-shots" on the underside of outermost leaves. Calcarb need only be applied to 4-5 leaves. No need to saturate entirety of foliage. Avoid fruits and flowering bodies.