Dark depressed spots on the side of the flower are a sign of blossom end rot. This is a physiological (non-contagious) disease, the cause of which is a lack of calcium. According to experienced gardener Nikolai Vladimirovich Khromov, without urgent treatment, future fruits will rot.
This is why tomatoes suffer from blossom end rot in June.
A lack of calcium in fruits can occur for several reasons. The first is summer heat: at high temperatures, the plant evaporates moisture through the leaves much more slowly, and calcium from the soil moves to the fruits with greater delays. The movement of calcium can also slow down due to uneven watering – if you overwater the tomatoes once and then leave the plants without moisture for several days, the roots will stop absorbing calcium fully.
Also, calcium is not absorbed by plants in acidic soil, excess nitrogen, potassium and magnesium.
At risk of blossom end rot are the varieties Bull's Heart, Mazarin and Pink Giant. In the future, it is worth taking a closer look at varieties that are resistant to this disease: Mongol F1, Miracle of the Earth F1, Sanka, Benito F1, Nastenka.
Urgent help for tomatoes with blossom end rot
All ovaries affected by rot will have to be removed, since they cannot be cured – they will only absorb calcium, taking it away from healthy ovaries.
In the evenings, it is useful to spray tomatoes with a solution of calcium nitrate – 15 g of fertilizer per 10 liters of water. After a week, spray the plants again with this solution.
Root feeding is also possible. Add calcium nitrate (20 g per 10 l) to the water for irrigation and water 2-3 times at weekly intervals.
The expert also recommends chelated calcium – it penetrates tissues faster with a guaranteed result. And fertilizing with nitrogen and potassium should be stopped for a while.
