1.Too hot – One of the most common reasons why a cucumber is bitter is due to heat stress. If a plant is stressed due to heat, it may start producing bitter cucumbers.2.Uneven watering – Another possibility for what causes bitter cucumber is if a cucumber goes through alternating periods of drought and overwatering, the stress from this can cause the plant to produce bitter fruit.3.Temperature fluctuations – If the temperature fluctuates dramatically from one extreme to another over an extended period of time, the plant may start producing bitter cucumbers.
There are four reasons why a cucumber gets bitter. First is when the weather is too hot. Plants experienced heat stress. Second is uneven watering which means overwatering of the plants or a plant get drought because of lack of water. Third is temperature fluctuations, a condition in which weather converts from one weather to another. Fourth is its heredity. This simply means through genetics. There are some possibility that once you plant a cucumber from the start and it is bitter already, that will make the next generation of the plant to become bitter also.