Blossom end rot is a perennial problem for gardeners. We’ll show you both preventative and immediate techniques to minimize this all-too-common disease.
The Wild Galapagos Tomato (Solanum cheesmaniae), is very popular for its production and adaptability to extreme environments from hot to cold.
Blossom end rot affects mainly tomatoes and peppers, but can affect other fruiting crops such as eggplant, watermelon and summer squash. This is a perennial problem, meaning that as a gardener, you will deal with this yearly in your garden. There are two approaches to working with blossom end rot – prevention and reaction, or a primary and secondary solution. Unfortunately, most gardeners only realize they have a problem when the fruit are showing black spots on the end. This is the acute phase – once there are problems – and immediate action is needed to prevent further damage to fruit that is just beginning to set.
We will look at the underlying causes of blossom end rot, along with what happens and what can be done about it in the prevention as well as the acute phase.
As mentioned, blossom end rot will affect more than just tomatoes and peppers, but we will focus mainly on those as this is what most gardeners’ experience. Just tuck the other varieties into the back of your mind, and you’ll have a jump start if you see it strike them. In reality, the prevention will most likely have a beneficial effect for everything as you will be creating an environment that won’t support the cause of the problem!
Blossom end rot is caused by a lack of enough available calcium in the fruit at the blossom end. What most often alerts us is a black spot or patch at the blossom end of the tomato or chile, opposite of the stem. This black spot is a secondary issue caused by a fungus attacking the weakened fruit. Contrary to what many think, we aren’t aiming for the eradication of the fungus and resulting black patch, but fixing and preventing the cause of the problem. Correcting the underlying issues that lead to the weakened fruit will automatically prevent the fungus from being able to attack.
Let’s start with the problem and work backwards, to better understand what is needed for both an acute fix and a preventative approach for blossom end rot. Calcium is a very important part of the growth process for plants and the proper development of high quality, tasty fruit as it contributes to healthy cell wall growth, insect resistance and helps to regulate many cell processes. Calcium is non-mobile in the plant once it is imported, meaning the plant can’t move it from one part of itself into the fruit, or from one part of the fruit to another. Thus, the tomato or chile plant needs a continuous supply of calcium as it grows, flowers and produce fruit all through the season.
Blossom end rot usually occurs early in the season with the first or second flush of fruit. It happens just when the plant is at maximum growth and is putting on the first fruit, with a second set of flowers on the way. It is in high gear and needs all of its nutrients available to be healthy, resist pests and disease, as well as grow lots of delicious tomatoes and peppers. The key to preventing blossom end rot is to supply a sufficient, steady amount of calcium to the plant so it can be transported into the fruit continuously. Problem solved!
Not so fast, just how can we make sure that the plant has a steady supply of calcium?
Early Blossom End Rot
Here is where we branch off into the two approaches – the primary and the secondary. The primary, preventative approach is to have enough calcium in the soil that feeds the roots and is transported to the fruit throughout the growing season. That calcium in the soil must be ‘available’ meaning that the roots can actually absorb it and transport it where it is needed. Available means that it isn’t tied up by another mineral or a pH level that won’t ‘let go’ of it. There is more to the story than just adding a calcium amendment to the garden bed!
A very good example of this is where we live in central AZ, there is a decent amount of calcium in the soil that plates out on faucets and glassware as a calcium deposit. Conventional wisdom says not to worry about calcium because it is everywhere. That’s true, but the challenge we have is the pH of the soil is fairly alkaline at 8+ on the pH scale, so the calcium is ‘tied up’, or not available to the plants. This is proven by the weed populations we typically see that only grow in calcium deficient soils.
So what can be done? A comprehensive soil test is one of the best, first steps to take. This is much more than the simple NPK type of test done by university extension offices or the do-it-yourself test kits bought at the local garden center. A complete soil analysis is one that is collected and sent off to a recognized, professional lab that sends back a report on every mineral found along with recommendations on what direction to go and what nutrients to add in what form. They will usually cost from $25 to $75 range, depending on what analysis and information you need. There are several of these labs in the US; the two that we’ve worked with and are familiar with are Crop Services International and Texas Plant and Soil Lab. From this, you will have a very good indication of where to go next.
Fall is a great time to get your soil tested and amended in preparation for next spring’s season for a few reasons – the soil testing labs are generally not as busy, so results are quicker; and soil amendments will need some time to become integrated and available into the soil nutrients, so fall gives you the needed time, and it is easily incorporated into the traditional fall garden cleanup and prep.
Calcium is closely tied with magnesium, and this will be indicated on the soil analysis. More acidic soils, such as those generally found in the eastern states, will benefit from lime or calcium carbonate, while the more alkaline soils in the western states will need gypsum or calcium sulfate. Lime tends to raise the pH, while gypsum tends to lower it.
Water plays an often overlooked, but equally important, role in the blossom end rot saga. Inconsistent levels and rates of water will greatly vary the amount of calcium and other nutrients available to the plant, increasing the chance of diseases attacking the fruit like blossom end rot. This is one of the reasons we talk a lot about a drip system on a timer – it really helps even out the moisture levels in the soil and greatly reduces the stress on the entire garden, with the happy result of lowered amounts of nutrient and stress related problems. Of course, the weather can also play havoc with all of our carefully laid plans, as heavy and sudden rainfall can cause blossom end rot and splitting of tomatoes, along with a noticeable ‘wash-out’ of flavor and taste.
This is where the acute or secondary approach is needed. Calcium carbonate tablets, or anti-acid tablets (Tums or the equivalent) work great when a couple of them are inserted at the base of a tomato or chile plant, where they will dissolve and make the calcium available to the plant in just a few hours, saving this flush of fruit if done right after the rains, or the next set if done when blossom end rot is first noticed.
Another approach is to feed calcium directly to the roots through the drip system as a liquid fertilizer, usually with calcium chloride or calcium nitrate. This approach works very well in offsetting one of the most overlooked causes of blossom end rot – great weather. That’s right – excellent weather with moderate temperatures and lots of sunshine put the plants into overdrive, and their rapid growth can often simply outstrip the amount of available calcium in the soil, even if you have been proactive last fall. The calcium just cannot be taken up out of the soil fast enough, so feeding through the drip system can be a big bonus during these times. The secondary approach will always be needed, even if you’ve done your homework and amended the soil the previous fall.
Calcium isn’t absorbed very well by the leaves of a plant, especially older leaves. The roots are much better at absorption, plus they can transport the calcium faster than through a foliar approach. For these reasons, stay away from trying a foliar spray to supply calcium to your tomatoes.
Blossom end rot won’t ever quite go away, because of the reasons you’ve seen here. With some knowledge and practice, you can easily create a much better environment in the soil that supports the plants much more fully and then use the supplemental approach to keeping the calcium levels high enough to minimize blossom end rot and keep more of your hard work for your dining table instead of as scraps for the chickens or compost pile!
We love it when we hear from customers about their gardening/growing projects. One of our tomato varieties, the Wild Galapagos Tomato (Solanum cheesmaniae), is very popular for its production and adaptability to extreme environments. One of our customers has been doing research in Italy on the salt tolerance of the Wild Galapagos tomato as well as other salt tolerant plants. The goal is to develop an aquaponics system that uses salt water instead of freshwater to grow food where there is no fresh water available. Many parts of the world have limited access to fresh water, but ample access to salt water so if salt water could be used to grow food there would be much less hunger!
Here’s some photos of Eddie’s research projects:
Growing Wild Galapagos tomato plants under controlled agronomic techniques, about 8-10 times more salinity than usually tolerated by such plants. Plants grew well.
Saline aquaponics. Tomato trials under saline condition – working towards a fully marine fish aquaponics system.
Saline aquaponics. Testing beets on fish water under medium salinity.
Another interesting project is our customer Harry in Anchorage, AK who spent the winter growing the Wild Galapagos Tomato inside under grow lights. Harry wrote to us saying; “I have started a project that I know will be difficult. I am trying to raise a few Solanum cheesmaniae, an outdoor tropical plant, indoors in Alaska in the dead of winter.” He goes on to state “The system is based on multiple artificial lights, with wires and artificial props, and even some duct tape as needed.” Ingenuity is what we love about our customer’s imagination!
After an email exchange, he elaborated a bit,
“I use an array of “daylight” fluorescent lights, mounted on a framework made of do-it-yourself shelving material from the hardware store. I can’t let the plants sprawl, so I have to make them grow upward, using a system of strings and wires. As a result, plants that grow from pots less than a foot off the floor are already touching the 8-foot ceiling, and they aren’t stopping! If I had unlimited space, I could be growing hundreds of plants now, because each tomato (those that I have saved seeds from) has over 20, and often over 50, seeds. I have given away a potted second-generation plant, and have 8 others growing — one with flowers, and one, now about 7 feet tall, with both flowers and green fruit.
Although I ordered two seed packets from you last October, I used only 10 seeds from one (and got 5 plants, all still living and bearing), and sent some seeds to a friend in CA. One of my colleagues (at work) planted the remainder of the packet, and has 15 plants growing in limited space in his house at a chilly 2500-foot elevation outside of Anchorage.”
He finishes by saying, “The appeal these plants have, to myself and others, is the intensity of the tomato flavor. The flavor grows in your mouth and lasts at least 2 minutes if you don’t eat anything else.”
Here is a photo essay of his project:
Our customers in Texas report that the Wild Galapagos tomato is the only tomato that keeps producing throughout the heat of the summer! With a daily high of 110°F for over 40 days, the Wild Galapagos was the only tomato to keep going, giving about 2 pints of tomatoes every other day from 2 plants. On the other end of the scale, our customers from the northern tip of Idaho and southern British Columbia and Alberta, Canada say that this is the first tomato to flower and set fruit and is also the last at the end of the season!
This is a very versatile tomato along with its cousin Sara’s Galapagos. The Wild Galapagos Tomato is one of two indigenous varieties of tomatoes on the Galapagos Islands, and is the only edible one. This is why it’s scientific name is completely different than any other tomato! Sara’s Galapagos is a domesticated variety that was brought back by Sara and Amy Goldman on one of their tomato expeditions, is adapted to the island’s climate and does well in harsher environments.
A few things to remember about them, they can take anywhere from 4 to 45 days to germinate based on recent reports. Under germination testing these two varieties have taken longer than “regular” tomatoes to germinate under controlled conditions. Sara’s produces red fruit and the Wild produces a golden yellow-orange fruit. So, get creative and feel to experiment with any of our varieties that we offer – you will be amazed what might happen!
Blossom End Rot – What To Do
Blossom end rot is a perennial problem for gardeners. We’ll show you both preventative and immediate techniques to minimize this all-too-common disease.
Wild Galapagos Tomato
The Wild Galapagos Tomato (Solanum cheesmaniae), is very popular for its production and adaptability to extreme environments from hot to cold.