What is blossom-end rot? How can I prevent it?
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Blossom-end rot is a disorder of tomato, squash, pepper, and all other fruiting vegetables. You notice that a dry
sunken decay has developed on the blossom end (opposite the stem) of many fruit, especially the first fruit of the
season. This is not a pest, parasite or disease process but is a physiological problem caused by a low level of
calcium in the fruit itself.
BER, or blossom-end rot usually begins as a small "water-soaked looking" area at the blossom end of the fruit
while still green. As the lesion develops, it enlarges, becomes sunken and turns tan to dark brown to black and
leathery. In severe cases, it may completely cover the lower half of the fruit, becoming flat or concave, often
resulting in complete destruction of the infected fruit.
Calcium is required in relatively large concentrations for normal cell growth. When a rapidly growing fruit is
deprived of calcium, the tissues break down, leaving the characteristic lesion at the blossom end. Blossom-end rot
develops when the fruit's demand for calcium exceeds the supply in the soil. This may result from low calcium
levels in the soil, drought stress, excessive soil moisture, and/or fluctuations due to rain or overwatering . These
conditions reduce the uptake and movement of calcium into the plant, or rapid, vegetative growth due to excessive
Adequate preparation of the garden bed prior to planting is the key to preventing BER. Insure adequately draining
soil in the bed by adding needed ammendments, maintain the soil pH around 6.5 - a pH out of this range limits the
uptake of calcium. Lime (unless the soil is already alkaline), composted manures or bone meal will supply calcium
but take time to work so must be applied prior to planting. Excess ammonial types of nitrogen in the soil can
reduce calcium uptake as can a depleted level of phosphorus. After planting, avoid deep cultivation that can
damage the plant roots, use mulch to help stabilize soil moisture levels and help avoid drought stress, avoid
overwatering as plants generally need about one inch of moisture per week from rain or irrigation for proper
growth and development.
Once the problem develops, quick fixes are difficult. Stabilize the moisture level as much as possible, feeding with
manure or compost tea is recommended by many, foliar applications of calcium are of questionable value
according to research because of poor absorption and movement to fruit where it is needed but many have
reported that foliar application of magnesium (epsom salts) can effect added calcium uptake. Other various
suggestions consist of powdered milk, crushed egg shells tea, bone meal tea, Tums tablets, etc. but prevention is
the key. Some recommend removing affected fruit from to reduce stress in the plant.
BER should not be confused with fruit abortion or inadequate pollination although the symptoms may appear
similar. The onset of BER occurs only after the fruit is well on it's way to development while insufficient pollination
problems terminate the fruit while still quite small.