Blossom-end rot first appears as water- soaked spots on the blossom end, or bottom, of the tomato. The affected tissue breaks down rapidly and the area becomes sunken, dark brown or black, and leathery. This can happen at any time as the tomatoes mature, and most often on the first tomatoes of the season.
The fastest way to solve this problem is a calcium spray, like donttelltheginger said. I would suggest something like RotStop or FoliCal. The sprays work pretty quickly, so you might be able to save some of the younger tomatoes. I would also suggest adding a slow-release tomato fertilizer, with plenty of calcium.
Start by observing if there seems to be one or more flat spots in the surface. This is the first sign of mushiness, which is the start of degradation. Does part or all of the tomato feel really squishy? Not good. Are there places where the skin has cracked and beginning to weep fluid? Again, not good.
Blossom-end rot is easily identified as a brown, leathery rot developing on or near the blossom end of the tomato. It starts with a dry, brown lesion the size of a dime and generally increases in diameter as the condition worsens.
One sign of overwatered tomato plants is drooping stems and foliage. Wilting occurs when the soil holds more moisture than the roots can take up but it can also mean the soil is too dry and the plants need water.
Water correctly: Do not overwater. The first week tomato plants are in the ground, they need water every day, but back off watering after the first week, slowly weaning the plants down to 1 to 1.5 inches of water per week.
In general, the infected leaves exhibit irregular shaped water soaked lesions in between the veins, which later turn to light tan, necrotic and dark brown. Infected plants may wilt and die. Stems also shows sunken, necrotic lesions. The vascular system shows brown streaks.
Baking soda isn't a good solution for preventing blossom end rot. If your soil pH levels are low and affecting the tomato plant's ability to absorb calcium, adding this kitchen pantry staple might raise them. However, this will be a temporary effect, and the amount you might need to use could harm your plant's health.
Foliar Spray
Commercial foliar calcium sprays (calcium acetate, calcium nitrate, and calcium chloride) are the quickest remedy for acute calcium deficiency, as plants absorb nutrients more efficiently through leaves than through roots.
SYMPTOMS: Blossom-end rot is characterized by a large, brown to black, dry, leathery area at the blossom end of the tomato fruit. The first symptoms appear as small, water-soaked areas, which resemble bruises, on the blossom end of immature or green fruit.
Some growers prefer to use a high-phosphorus fertilizer, indicated by a larger middle number. You can also keep things simple with a fertilizer especially formulated for tomatoes – usually with a ratio like 3-4-6 or 4-7-10. Most importantly, don't over-fertilize. Too little fertilizer is always better than too much.
Symptoms of calcium deficiency include stunted plant growth, leaf curling, dark leaf veins, weakened plants, and blossom-end rot in fruits. Fruit plants like tomatoes and peppers may develop dark, sunken areas in the fruit.
Blossom end rot is caused by a calcium deficiency in developing fruit. Fluctuating soil moisture due to overwatering or drought, high nitrogen fertilization, and root pruning during cultivation are conducive to blossom end rot.
As a stop-gap measure, spray tomato plants with a calcium solution made for blossom-end rot. Follow label directions. Apply two to three times a week, beginning when the first blooms appear. This is not a long-term fix, but it may salvage your crop until you can take the steps mentioned above.
Even though coffee grounds provide minor amounts of potassium, phosphorus, calcium and magnesium and very minor amounts of iron, copper, manganese and zinc, these nutrients aren't supplied in sufficient quantity to satisfy plant needs.
Again, about a month after planting, you'll need to replace the nutrition in the soil to keep plants growing strong. Miracle-Gro® Raised Bed Plant Food, with added calcium and micronutrients, is just the right plant food for raised bed growing and is the perfect complement to Miracle-Gro® Raised Bed Soil.
To ensure a consistent nutrient supply throughout the growing season, it's common practice to apply calcium nitrate fertilizer at regular intervals, typically every 2-4 weeks, especially for high-demand crops like tomatoes. Frequent applications help replenish nutrient levels as plants grow and absorb nutrients.
Second when tomatos begin to appear and are about 1 inch in diameter lightly sprinkle baking soda around each plant to make them sweeter. Repeat this process again when tomatoes are about half grown.
Soil that contains a lot of sand doesn't hold water well and dries quickly. Because of this, tomato plants growing in sandy soil may need to be watered more often, about every three or four days. Clay soil, on the other hand, holds water well. Plants growing in clay soil usually only need to be watered once a week.
Blossom-end rot occurs when cell wall calcium “concrete” is deficient during early fruit development, and results in cell wall membrane collapse and the appearance of dark, sunken pits at the blossom end of fruit.
Spots of various sizes occur on the stem, at or near the soil level and on the roots. These spots may vary in color from gray, brown, black, or even bright red. Frequently, these fungi cause the tips of fibrous roots to decay. Wilting, dieback, and poor vigor are common symptoms.