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Blossom end rot can be fixed with proper watering, not more nutrients

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Q uestion: I am sending you pictures of my tomatoes. They have some kind of disease, but the plant itself looks healthy. The plants were in a pot on my covered deck, so I watered them regularly and used Miracle-Gro for tomatoes. Can you tell me where I went wrong so I can correct my methods for next year?

Answer: Your tomatoes are showing classic signs of blossom end rot. The black, sunken cankers on the bottoms of the fruits are typical of this ailment. Thankfully, it’s easy to prevent. But first, it’s important to understand why your tomatoes developed it in the first place.

Blossom end rot is the result of a calcium deficiency within the growing fruit. If the plants cannot acquire enough calcium during fruit development, the base of the tomato will become discolored and mushy. However, the problem is usually not remedied by adding more calcium to the soil, as some people may think, but rather by making sure the plant is properly watered. Let me explain.

Unlike some other nutrients, calcium is acquired by a plant primarily through a process called “mass flow.” This means the nutrient can come into the plant only via the water absorbed by the roots. If there isn’t enough water coming into the plant, it can’t access enough calcium, even if there’s plenty of it in the soil, and the plant begins to show signs of a calcium deficiency.

Here in Western Pennsylvania, our soils typically have ample calcium, so soil calcium deficiencies are unusual in a garden setting. The calcium is in the soil; your plants just can’t access it unless they have ample and consistent water. The same goes for plants grown in pots, especially if they’re grown in a commercial potting soil with added fertilizer or potting soil mixed with compost. The calcium is there; your plants just aren’t getting it.

Because you mentioned that your pots were grown on a covered deck, they probably did not have regular access to rainwater, and the water you were adding via hose-end irrigation was not enough.

A few tips for next year that will help prevent blossom end rot:

1. Make sure each tomato plant is growing in a pot that holds a minimum of five gallons of potting soil. The bigger the pot, the bigger the root system and the healthier the plant. Each container also should have a drainage hole in the bottom.

2. Proper watering is not adding a little water to the pot every day. Proper watering is using a hose to thoroughly saturate the soil every two to four days. I add five or six gallons of water, at minimum, to each of my potted tomatoes every few days throughout the summer. This is very important, especially if your tomatoes are growing somewhere where rainwater can’t reach them. As long as the pot has a drainage hole and it isn’t sitting in a saucer of water, it’s nearly impossible to overwater them. Deeper, less-frequent irrigation is always better than adding a little bit of water every day.

3. As I mentioned earlier, if you planted your potted tomatoes in a commercial potting mix with fertilizer already included, there was ample calcium present. Miracle-Gro tomato fertilizer supplies nitrogen, phosphorous and potassium, but it does not contain calcium. I suggest you mix your potting soil next year half-and-half with compost (either purchased in bags or from your own pile). It has a blend of macro- and micronutrients and supports good tomato growth. Plus, it increases the water-holding capacity of the potting soil. Another option would be to mix a half-cup of organic-based, granular fertilizer into the potting soil-compost blend at the start of the season. Espoma’s Tomato-tone or Gardener’s Supply Co.’s Organic Tomato Fertilizer are two good choices.

Horticulturist Jessica Walliser co-hosts “The Organic Gardeners” at 7 a.m. Sundays on KDKA Radio with Doug Oster. She is the author of several gardening books, including “Attracting Beneficial Bugs to Your Garden: A Natural Approach to Pest Control” and “Good Bug, Bad Bug.” Her website is

Send your gardening or landscaping questions to [email protected] or The Good Earth, 503 Martindale St., Third Floor, D.L. Clark Building, Pittsburgh, PA 15212.

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Question: I am sending you pictures of my tomatoes. They have some kind of disease, but the plant itself looks healthy. The plants were in a pot on my covered deck, so I watered them regularly and used Miracle-Gro for tomatoes. Can you tell me where I went wrong so

Foliar Feeding With Calcium: How To Make Your Own Calcium Fertilizer

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.

Why Use Homemade Calcium Rich Foliar Spray?

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.

Homemade Calcium Rich Foliar Spray

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.

Foliar Feeding with Calcium Rich Eggshells

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.

Foliar Feeding with Calcium Rich Seaweed

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.

How to Make Your Own Calcium Fertilizer Out of Chamomile

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.

Other Methods for Making Calcium Spray for Plants

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.

Foliar feeding with calcium may make the difference between a bumper crop of fruit/veggies to blossom end rot or bitter produce. Learn more about making and using a calcium foliar spray in this article.