I recently taught a class for the Sustainable Farming Association, titled Homestead Gardening and Seed Starting for Beginners. It was a great group of people who attended with excellent questions that took us beyond class time. My first Taiga blog post is answering one of those questions for these homesteaders and home gardeners.
Blossom-end rot is a common problem for fruiting garden plants such as tomatoes, peppers, eggplants, melons, and squash; occurring when tissue of the blossom end (a.k.a. the “bottom”) of the fruit breaks down and rots, reducing fruit quality and potentially plant production.
Most often it is the result of a lack of calcium in the plant that may be due to low calcium levels in the soil or soil that is over and under watered. Wide fluctuations in soil moisture reduces the plant’s ability to take up calcium, and other nutrients, from the soil. When the demand for calcium exceeds the supply, the fruit break down, and blossom-end rot occurs.
In addition to watering issues, calcium deficiency during fruit formation may be caused by:
- Too much nitrogen-heavy fertilizer
- Damage to plant’s roots, which are shallow for all these
- High salt levels in the soil
- Improper soil pH
Some blossom-end rot is to be expected in the first fruits of the season, particularly tomatoes, as the plant is usually under stress during the initial fruit set. It happens more often to plants grown in containers, as the soil is more susceptible to fluctuations in moisture. In other words, the plants dry out too much, and their fruit is affected.
Blossom end rot cannot be reversed once a fruit is affected. The guide below will stop the rot affecting other developing fruit.
- Water consistently and evenly; do not overwater, if you forgot. If it’s rainy, ensure plants have good drainage and not waterlogged. Plants need about 1 inch of water (about 0.6 gallons) per square foot per week.
- When growing in containers, check soil moisture often on hot, sunny days. You may find plants need watering more often on these days. Also, it will reduce plant stress to be in the shade during the hottest hours of the afternoon. As long as the plant receives 8-10 hours of sunlight, a little shade for container plants keeps soil temps from getting too hot.
- Use mulch to retain soil moisture. Straw (2-3”deep) is excellent, so are leaves (2-3” deep) and dried grass clippings (1” deep). I do this for my container plants, as well.
- Have your soil tested periodically to determine if there is sufficient calcium in the soil. If using new soil (delivered or bagged), most likely will have enough calcium for the first season. Over time in-ground and raised beds may have low calcium levels.
- At planting (place at the bottom of the hole) and at first blossom (surface sprinkle), an organic source of calcium such as bonemeal, crushed oyster shells or crushed eggshells (my favorite!) and lime. Go light, you can add more, if needed.
- Check the soil pH each spring, particularly if you use lime as a calcium source. A pH of about 6.5 (slightly acidic) is ideal for most vegetables, as it allows for the best nutrient uptake.
Because blossom-end rot is caused by a calcium deficiency, you might be tempted to just fertilize your plants more. However, in most cases, there is already sufficient calcium in the soil; the plants just cannot absorb it. Over fertilization can be harmful with having too much nitrogen, magnesium, and potassium in the soil worsening blossom-end rot. If you are going to fertilize, follow these guidelines:
- Consider using a fertilizer that is formulated to contain more calcium.
- Use a product that contains nitrate nitrogen instead of ammonium nitrogen (as the latter may contribute to more blossom-end rot).
- Don’t over-fertilize during early fruiting, when blossom-end rot is more likely to occur.
- Avoid cultivating or digging near the roots of plants, as root damage can affect their ability to absorb water and nutrients.
- It is helpful to stake plants, like tomatoes, at planting or while young, for minimum root disturbance.
Final take-away.
- Blossom-end rot is common and can be easily remedied.
- Consistent watering and leaving roots undisturbed is a preventative.
- Lightly fertilize and observe your plants; less is more and you can add as plants respond.
- Egg shells, bonemeal, oyster shells are all super calcium supplements that won’t affect soil pH. Keep your egg shells from cooking to mash up and use in the garden.
Most importantly, you got this! Gardening is a practice. Act, observe, respond. If the plant doesn’t completely recover, it’s okay. It’s happened to me too.
Blessings for a bountiful garden,
Caroline
Cold Climate Growing, Think Taiga
Let's CULTIVATE THE NORTH together!
