Blossom End Rot of Tomatoes

By Carol Quish for UConn Extension


blossom end rot on tomato
Photo: Ohio Extension

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 that sinks in, always on the bottom of the fruit.

Blossom end rot can also occur on peppers.

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, and 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 reduce 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 that 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.

Late Blight Now in CT

Article and update by Joan Allen for UConn Extension.

Late_Blight by JATomato and potato growers and gardeners: Protect your crops NOW from late blight infection. The disease has been reported in Litchfield County, Connecticut on July 18, 2015. With moist weather conditions the pathogen, Phytophthora infestans, will sporulate prolifically and spread rapidly on wind currents. Fungicide products can be applied preventively to protect plants. Active ingredients to look for include chlorothalonil, maneb, mancozeb, and copper formulations. Organic growers can use copper formulations. Symptoms of late blight include large brown leaf lesions, dark brown stem lesions, and brown, bumpy and firm lesions on fruits. During humid or wet weather, white sporulation will be visible within the lesions. Infected plant parts or plants should be removed and disposed of. Bag and place in the trash or bury about a foot deep. More information and photos are available in the fact sheet at this website.

10 Tips for the June Gardener

green tomato
Photo: Diane Hirsch, UConn Extension
  1. Control and reduce aphid numbers on vegetables, roses, perennial flowers, shrubs and trees with a hard spray from your garden hose or two applications of insecticidal soap.
  2. Plant seeds of bush beans every three weeks for a continuous harvest.
  3. Heavy rains encourage slug problems. Check for slugs during rainy periods and hand pick the pests.
  4. Watch for and control blackspot and powdery mildew on rose foliage.
  5. Keep mower blades sharp and set your mower height at 2-3 inches. Remove no more than one-third of the total height per mowing and mulch to return the nitrogen to the soil.
  6. For the sweetest pea harvest, pick regularly before pods become over-mature and peas become starchy.
  7. Stake or cage tomatoes and spray them if necessary to prevent disease problems. Call the UConn Home & Garden Education Center (877) 486-6271 if you suspect tomato disease problems.
  8. To minimize diseases, water with overhead irrigation early enough in the day to allow the foliage to dry before nightfall. Use soaker hoses instead if possible.
  9. White grub preventative control should be applied prior to egg hatch and a target date of June 15th is recommended although it can be done up to July 15th.
  10. Check apple, cherry and other fruit trees for nests of tent caterpillars. Blast low-lying nests with water to destroy them, or knock them to the ground and destroy them. A spray of Btwill kill emerging caterpillars but is not toxic to beneficial insects, birds, or humans.

Canning Tomatoes: There is a Right Way

By Diane Wright Hirsch, MPH, RD

UConn Extension Educator – Food Safety


Canning tomatoesIn the recent past, the tomato crop has not been so great, but thankfully, this year looks like a winner. The tomato plants in my garden are pulling the stakes over; they are so laden with fruit. Next year, it will be back to cages, I think!


An abundant harvest may mean that you want to can some of your tomatoes this year. If you are new to the task (or maybe even more importantly, if you are a long time tomato canner), it is essential that you learn the safest techniques for canning. Over the thirty plus years that I have been canning, recommendations for the safe home canning of tomatoes have evolved.  Here is what you should NOT be doing anymore:

  • Canning tomatoes without processing them in a water bath or pressure canner
  • Processing tomatoes without adding lemon juice to each jar as added “safety insurance”
  • Processing quarts of tomatoes in a water bath canner for 30 minutes


So, what are the safety concerns related to home preservation of tomatoes? They include the possibility of spoilage and even botulism poisoning. “But aren’t tomatoes acidic?” you might ask. “Doesn’t that mean that you do not have to worry about botulism?”


Well, the answer is yes and no. It depends on the tomatoes. The pH of tomato varieties can range from an acidic low of 3.8 to a much less acidic pH of 4.7. The story goes that as the consumer has demanded a less acidic tomato, hybrids have been developed that taste less acidic—but some argue that this is due to more sugar in the tomato, not less acid. Would that mean that older heirloom varieties are likely to be more acidic? Not necessarily.


A study by Heflebower and Washburn at Utah State in 2010 looked at hybrid varieties, open pollinated and heirloom varieties. The results indicated that the average pH was 3.92 for the hybrids they tested, 4.03 for open pollinated and 4.16 for the heirloom. Of course all of these are below the 4.6 borderline. The authors still recommend the addition of acid to ensure that the final product remains below 4.6. In a bulletin from the North Dakota Extension Service regarding the use of lemon juice in canned tomatoes and salsa (Garden-Robinson, Houge, & Smith, 2004), the pH of 15 different tomato varieties were tested. The pH readings were taken from the pure tomato pulp prior to canning and again after lemon juice was added and the tomatoes were made into salsa. In this particular study, all of the raw tomatoes tested had a pH from 4.8 to 5.2 prior to canning.


In your home garden, a number of factors can influence the pH of even the more acidic tomatoes:  these include soil, vine health, ripeness.


When using a water bath canner we caution home canners to be mindful of the pH of the food you are canning. As a general rule of thumb, if the pH is 4.6 or higher, the food is considered to be “low acid” and should be canned in a pressure canner.  If the pH of a tomato product is below 4.6, there is the chance that if clostridium botulinum is present when processed in a water bath canner, that the bacteria will develop the spore form during the heating process, protecting it from destruction. Once the tomatoes are stored at room temperature, the spore can germinate and allow the production of toxin by the bacteria. This generally happens at room temperatures when the environment is moist, low in acid and free of oxygen. A pressure canner can reach temperatures well above the boiling point of water achieved in a boiling water bath canner. These temperatures (240 degrees F) will destroy botulism spores.


So rather than risk the chance of botulism at worst or spoilage, a less ominous outcome, but still one that results in the waste of food and a lot of hard work, why not just learn to can tomatoes using tested, safe methods? The go-to source for up to date information on canning tomatoes is the National Center for Home Food Preservation ( You will find directions for canning tomatoes and tomato products in a water bath canner and a pressure canner. For any tomato products, be sure to add a tablespoon of lemon juice or ¼ teaspoon of citric acid to pints and two tablespoons of lemon juice or ½ teaspoon of citric acid to quart jars.


Some folks are nervous about using the pressure canner. New pressure canners are easy to use and have many built in safety features. And using one makes sense for canning tomatoes. If you want to can tomatoes using no added water, you will need to process quarts in a water bath canner for 85 minutes. If you have lots of tomatoes, that’s a lot of minutes! And a lot of electricity or gas is used in the process. The same tomatoes will only take 25 minutes in a pressure canner at 11 pounds of pressure. It just makes sense to consider the pressure canner in this case.


In addition, if you want to make tomato products that contain significant amounts of low-acid ingredients such as meat, garlic, onions, peppers, or mushrooms, the pressure canner is essential for producing a safe product. All of these low-acid ingredients will surely bring the pH of your sauce or other tomato mixture well above 4.6 even if you start with acidic tomatoes.


The National Center also has tested recipes for canning some tomato products that have a lesser amount of low-acid ingredients. There are recipes for salsa, a tomato-vegetable juice, ketchup, and barbecue sauce. For each of these products, vinegar or lemon juice are important ingredients, adding the acidity needed to safely can in a water bath canner. Never add any additional ingredients or an extra pepper or two as this will likely make these products unsafe to can in the water bath canner.


For more information on home food preservation, contact the UConn Home and Garden Education Center at or 1-877-486-6271.

10 Tips for the August Gardener

1.      Fertilize container plantings.

2.      Pick summer squash and zucchini every day or two to keep the plants in production.

3.      Pick up and destroy any fallen summer fruits/vegetables to reduce pests and disease for next year.

4.      Continue to stake tomatoes and allow them to ripen on the plants for the best flavor. The exception is cherry tomatoes, which are prone to splitting. Pick any ripe or almost ripe tomatoes before a rain.

5.      Renovate strawberry beds in late August.

6.      Make note of where vegetables are planted in the garden so that crops can be rotated next year.

7.      Do not add weeds with mature seed heads to the compost pile.

8.      Water fruiting shrubs such as hollies and firethorn to ensure that berries mature and don’t drop.

9.      Check hanging plants and containers daily. The wind and sun can dry them out.

10.  Reseed the lawn in late August. Be sure to keep the seed moist until germination.

For more information please visit the UConn Home and Garden Education Center or UConn Extension.

Photo: Jude Boucher for UConn Extension

Fall Scenes

UConn Extension’s Jude Boucher, who specializes in Integrated Pest Management in Vegetable Crops took these pictures. The pumpkins are a Hijinks variety that are a past winner in the All-America Seed Trials. The tomatoes are packaged and ready for sale at Bishop’s Orchards in Guilford.

Sakata Seed America Bishop tomatoes

We also had a chance to enjoy some fall foliage around Tolland County. It was a spectacular year for leaves.

foliage7 foliage5

foliage3 foliage