Blossom End Rot in TomatoesMost gardeners have probably experienced blossom end rot, particularly in tomatoes. It is a frustrating disorder because it is physiological and not caused by a pathogen or insect that can be treated with a spray. Blossom end rot mostly affects tomatoes and peppers but can also be found in eggplants, watermelons, cucumbers, pumpkins, and squash. Blossom end rot affects the blossom side of the fruit, which is the side opposite the stem. The blossom end develops a water-soaked spot that turns blackened and leathery, then rots, making the fruit inedible. Particularly in peppers, it can be confused with sunscald because the rot can occur slightly to the side of the blossom end of the pepper, not always directly at the blossom end. Some tomato varieties are more susceptible to blossom end rot, particularly many paste types, and it can even occur internally with no visible blemishes outside. Other varieties are more resistant (see below). Blossom end rot frequently occurs early in the season and can later disappear with subsequent fruit set. What Causes Blossom End Rot?Many people believe if you add calcium to your soil when planting your tomatoes you will avoid blossom end rot. Although this idea is based on fact, it is not the whole story. Some add a calcium-rich fertilizer specifically designed for tomatoes, others add eggshells (which take too long to break down to be helpful, so compost them instead), or even Tums, which contain calcium carbonate. Although a localized calcium deficiency is the cause of blossom end rot, specifically, a lack of calcium in the fruit, it is rarely due to a lack of calcium in the soil. Most soils have plenty of calcium, get a soil test done to be sure, but it is not always available to be taken up by the plants. Unfortunately, many factors can prevent calcium uptake by the plant. Most commonly, alternating dry and wet soil conditions can prevent calcium uptake but also overly wet or dry soil for a long period, too high or too low pH, high concentrations of certain nutrients such as ammonia, magnesium, or potassium, soil that is too cold, too much salt in the soil, or damage to a plant’s roots, either from infection or mechanical disruption. Water-soluble calcium enters the plant via transpiration, the process by which plants lose water above ground, usually via the leaves, which causes moisture to be pulled, along with minerals and nutrients, such as calcium, from below ground. Calcium is most easily transported to the leaves, but any water that enters the fruit also brings along calcium and other nutrients. If most of the calcium enters the leaves, there is no way to later get it from the leaves to the fruit. Only water that moves from the ground directly to the fruit will bring calcium into the fruit. Therefore, overfertilizing, especially with ammonia-based fertilizers, will encourage leaf growth, and make the lack of calcium in the fruit even worse. Anything that also limits transpiration, such as too high or even too low humidity along with windy, hot weather makes less calcium enter the fruits. How Do You Control Blossom End Rot?The two easiest things to control are how much and how often you water and how much and what kind of fertilizer you use. You cannot control how much rain your garden receives but you can water regularly (I prefer drip irrigation or soaker hoses) during dry periods, at least 1 inch per week. Use nitrate-based fertilizers, not ammonia-based, or better yet, use compost which releases nutrients more slowly, and do not over-fertilize with potassium or magnesium. A soil test is helpful to know what you should and should not add. A soil test will also tell you if you need to alter the pH of your soil. A pH of 6.5-6.8 is ideal, significantly above or below that level can make it difficult for a plant to take up nutrients. Proper soil drainage will also help prevent waterlogged soil and prevent salt from building up in your soil. Also, avoid cultivating the soil close to the roots, instead, mulch to prevent weeds and foliar disease. Tomato Varieties That Resist Blossom End Rot Certain tomato varieties are more resistant to blossom end rot than other varieties. For example, pear/plum-type paste tomatoes are notorious for developing blossom end rot, I stopped growing the Roma variety specifically for this reason. Other varieties I found published that are particularly susceptible to blossom end rot include Big Boy, Castle King, Fantastic, Independence, Supersonic, Surprise, Whopper, and Wonder Boy (https://ipm.illinois.edu/diseases/series900/rpd906/). I have not grown any of these varieties, so I have no personal experience as to whether they are resistant or not. Varieties reported to be more resistant include Celebrity, Fresh Pak, Jet Star, Manapal, Mountain Pride, Pik Red, Sunny, and Winter. I grow Celebrity every year and have never had blossom end rot, not even in the summer of 2023 when we were in a drought or the summer of 2024 when it rained constantly. I have also grown Jet Star and do not recall blossom end rot being a problem. References and Resources
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 How to Overwinter Fall CropsEven in zone 4B in central Wisconsin, I have managed to get certain vegetables to overwinter. One important point is that there is a difference between overwintering vegetables and actively growing them. Temperature is not the only consideration for plants to grow. The total amount of sunlight is also a big concern. The “Persephone Period” sometimes called “Persephone Days” is the time period when days have 10 or fewer hours of daylight. Most plants need a minimum of 10 hours or more of sunlight for vegetative growth. During the “Persephone Period” plant growth slows or completely stops even if temperatures remain above freezing. For me, November 5th is the first day with less than 10 hours of sunlight and I will not go above 10 hours of daylight until February 5th. Most of this time it is too cold to grow anything anyway, but even if I had a heated greenhouse I could not grow much unless I also gave the plants supplemental light. You can check out this site to find your day lengths. So why bother overwintering vegetables if they are not going to grow much anyway? Basically, overwintering allows you to have fresh vegetables either in the middle of winter or earlier in spring than you otherwise would. Additionally, many root vegetables like parsnips and carrots taste better after a period of cold weather. I have been able to successfully overwinter spinach, kale, leeks, parsnips, and carrots, although the spinach and kale do look a little rough in the spring, but fresh growth usually starts as soon as the daylight increases and temperatures warm. One important point is that you want to harvest your vegetables fairly early in the spring or there is a risk of them going to seed. Once they start going to seed the root vegetables will be woody and the greens can get bitter. The two things I do to overwinter my vegetables are frost covers and mulching. I put layers of mulch, usually leaves, over my vegetables, I try for about a foot thick, but I have read if you go even deeper, 3 to 4 feet thick, you can dig root vegetables all winter long. We usually get too much snow to easily clear away the snow and leaves to dig so I generally just leave them there all winter and uncover in the spring. The second thing I use is frost covers. I started buying higher quality frost covers from A. M. Leonard or Johnny’s Selected Seeds which last longer than cheaper frost covers. Regardless, do plan to replace your frost covers occasionally as they get holes or tear. You can buy frost in various thicknesses which can give you a degree or two of protection up to 5-10 degrees. I also use frost covers in the fall to protect my crops from any early hard frosts. If you are still getting enough sunlight to grow crops you may not want frost covers too thick because these also block sunlight. Each frost cover description should give you the thickness, the degrees of protection and how much sunlight is blocked. So, it is a balance between enough frost protection and enough sunlight. For overwintering, I lay the frost covers over my mulched vegetables and weigh down the sides to keep cold air out and to keep them from blowing away. In the spring, once temperatures have warmed up enough, I pull away all the mulch but leave my frost covers over my vegetables to provide some protection. As soon as the ground thaws you can dig up your root vegetables. Greens and onions can be eaten as soon as they start to perk up, grow a little, and basically look edible. Also, as long as the ground is thawed make sure to water if needed. Vegetables should be well watered before covering them up, but you do not want standing water which could allow them to rot. Many plants die over the winter not from the cold but from drying out in the cold winter air and winds. Frost covers also help keep the cold wind from penetrating into your plants. The last consideration is what varieties of vegetables to choose. I have had good luck with Vates kale but I have had Red Russian kale die at 17°F. Blue Solaise leeks routinely overwinter for me although a few may rot. I have gotten Winter Giant Spinach to overwinter as well as Hollow Crown parsnips and any fall/winter carrot variety such as Oxheart, Kuroda, and Chantenay. Resources and References
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AuthorIn 2016, my family and I moved from the New York City area to small town Wisconsin. Our move, this website and blog (and our previous Etsy store) is the result of our desire over the past several years to simplify our lives, increase our quality of life, reconnect with nature, and enjoy a more self-sufficient life. I grew up as a country kid in central Pennsylvania working on my grandfather's fruit farm and as a corn "de-tassler" at a local seed farm. My background is in biology where my love of nature originated. I am a former research scientist and professor and have now transitioned to a part-time stay-at-home mom, self-employed tutor, and small business owner. Thank you for taking the time to check out my site. Archives
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