August is supposed to be the month of non-stop tomatoes. Occasionally things go awry to interrupt those carefully laid spring visions of bountiful harvests, sauce making, and endless tomato sandwiches. Blossom end rot can appear to put an end to the crop production by damaging the ripening and developing fruits. We are seeing and receiving calls in a  higher number than more recent years from backyard gardeners complaining about black rotten spots on the bottom of their tomatoes. The spots start as a thickened, leathery spot which sinks in, always on the bottom of the fruit.

Blossom end rot on tomato,

Blossom end rot on tomato,

Blossom end rot can also occur on peppers.

Blossom end rot on peppers, photo taken by client

Blossom end rot on peppers, photo taken by client

Blossom end rot is a physiological condition due to lack of calcium. Calcium is needed by plants for  proper growth in all functions of cell making, but is most important for cell walls. Without enough calcium either in the soil, or if delivery of uptake of dissolved calcium in soil water is interrupted, cell division stops in the fruit. Tomatoes are especially sensitive to a lack of calcium.

Interruptions in uptake of calcium can happen by repeated cycles of soil drying out, receiving water, then drying out again. Times of drought and hot, humid weather make the problem worse. Plants lose water through their leaves through a process called transpiration, similar to the way we sweat. They then pull up water through their roots. If there is not enough soil moisture, plants wilt. This break is water delivery also limits calcium delivery. Tomato, and to a lesser degree pepper fruits, respond by developing rot on the bottom, the end where the blossom was before the fruit started growing.

High humidity and multiple cloudy days reduces transpiration, thereby reducing water uptake. This leaves plants not able to bring up new calcium rich water to the site making new cells of the fruit. Another interruption of delivery of calcium resulting in blossom end rot. This means that even if you have enough calcium in the soil and you water the soil regularly, the plants still may not be able to move enough calcium to where it is needed to produce a fruit.

Have a soil test done to make sure soil has enough calcium and that pH levels are around 6.5 so nutrients are most readily available. Water regularly so plants receive 1 to 2 inches of water per week for optimum growth. Feel the soil around the root zone to make sure water is soaking in and reaching the roots. Humidity and cloud cover are not obstacles we can help the plant with, so monitor the fruit for rot spots and remove. There are calcium foliar sprays which claim to deliver calcium to be absorbed by the leaves for use by the plant. This won’t help after the rot has already developed, but may help deter future spots on still developing tomatoes.

-Carol Quish




Most of the year at the UConn Soil Nutrient Analysis Lab ( the soils and plant problems we get asked about are fairly routine. Summer stresses, however, seem to bring on more intriguing inquiries. Two that we have dealt with in the past two weeks are blossom end rot on peppers and a likely case of copper toxicity on melons.

According to our UConn Vegetable Extension Specialist, Jude Boucher, many growers are experiencing blossom end rot in tomatoes, peppers and squash and black heart in celery. These are physiological conditions due to lack of calcium. Most of us know that people require calcium for strong bones and healthy teeth. Plants also have calcium requirements that must be met for good growth and establishment. It is needed for the proper growth and functioning of shoot and root tips, and is an integral part of cell walls. As your tomatoes and peppers grow in size, more cells with more cell walls are needed!

Plants take up the calcium they need through their roots. Nutrients like calcium, potassium and others are dissolved in the water that is in the soil. When a plant loses moisture on a hot day through the process of transpiration, the roots take up water to replace that loss and keep the plant turgid. The soil water contains nutrients the plants need. Anything that restricts the plant roots’ ability to take up water also reduces the amount of nutrients a plant receives.

The most common disorder in vegetables caused by calcium deficiency is blossom end rot. This physiological disorder usually has two causes. Either there is not enough calcium in the soil or there is not enough water in the soil for the calcium to be able to move into the plant. This year because of the high humidity, cause number three comes into play. Plants are not transpiring that much because of the high humidity. Since little water is being lost through the leaves, little water (containing calcium and other nutrients as well) is being absorbed by the roots. So even if your soil is loaded with calcium, and your garden is irrigated, plants may not able to transport enough calcium from the soil water into their internal structures. Other common calcium deficiency disorders that we are seeing or have heard about are black heart in celery, internal tip burn in cabbage, and cavity spot in carrots.

Blossom end rot first appears as a small, water-soaked spot at the blossom end of tomato, cucumber, squash or melon fruits. As the spot enlarges, the fruit tissue shrinks and becomes dry and leathery.

Pepper sample -photo taken by client

If blossom end rot is noticed, first take a soil sample and send it to a soil testing laboratory to determine the soil pH and calcium levels. Next, evaluate your watering techniques. Often this disorder occurs when succulent, vigorously growing plants are subjected to drought conditions. There isn’t much one can do to lower the humidity and increase plant transpiration rates except hope for a bout of dry weather. To thwart blossom end rot, some gardeners are purchasing blossom set sprays containing calcium to apply to their plants foliage. Others are fertilizing and spraying the plant’s foliage with calcium chloride, as directed on the package or making up a calcium solution by mixing gypsum or limestone with water and letting it sit over night. After 24 hours or so, it can be used to drench the plants and soil. Another option is to search out water soluble fertilizers that contain calcium and can also be used as a foliar spray and apply them to the plant’s leaves.

 As many more gardeners and growers are turning to least toxic, non-synthetic means of disease and insect control, copper-based sprays for diseases are becoming quite popular. One client had sprayed his melon crop with a copper-based fungicide and shortly thereafter noticed the edges of the leaves of some of both melons and cucumbers to be turning yellow and brown and dying. The copper spray did seem to affect some varieties more than others. Leaf tissue samples of both healthy and affected leaves were sent into the lab for analysis.  

Melon leaves exhibiting possible copper toxicity

After again speaking to our UConn Vegetable Extension Specialist, he concurred that copper toxicity would be a good call as he has seen some cucurbit cultivars or varieties to be extremely sensitive to copper applications while others are not affected at all. Plant tissue analysis showed greater levels of copper on affected plants than on unaffected leaves. I did find it curious though that the amount of calcium in the infected leaves was 2 to 3 times what would normally be expected and can’t help wonder if this high level was affecting the amount of other elements available to the plant and if that could explain some more of the visual symptoms. This really brings up the importance of using any pesticide – whether natural/organic or synthetic – as directed on the package, and also of not applying anything to plants if the temperature is greater than 85 degreed F which we New Englanders have seen a lot of lately. Some varieties or hybrids seem more susceptible than others so, if using copper, make a note of any plant injury.

Last Friday. while driving onto the UConn Depot Campus to get to the lab, I noticed this little thing in the road. It was quite small and really wasn’t the shape of a rock or leaf so I slowed way down to see it. A baby bird! I scooped it up and examined it thinking maybe it was hit by a car but it seemed okay. After looking around for a few minutes for mother bird or a nest, I was not able to find either and thought I would bring him/her to work with me and then to our local wildlife sanctuary this weekend. When I got the baby bird inside, it became apparent that this was a fledging with pretty good flying capacity and I made the decision to put him/her back where I found it (in a field on the side of the road, not on the road!) and let Mother Nature take her course. It appears to be a cedar waxwing. I did search for the baby bird after work and no luck. Hopefully, this little guy/gal was reunited with mom who will continue to feed and show him/her the ways of the world. Good luck little one.

Fledging Cedar Waxwing, I think!

“Fly like an eagle, into the future’ Steve Miller Band