Reasons for Blossom drop a.k.a Flower drop 

A common concern we have been observing of late is in regards to flower drop. Today we attempt to throw light on the various reasons that are responsible for flower drop.

Flowers are generally grown for their vibrant and attractive colors as well as for their commercial value. In either case, these plants are grown with much love, and affection!! Even in the case of fruits and veggies, the flower further develops into the fruit and eventually the seeds. Flower drop would result in lower yield and economic loss. Thus, flower drop is a cause for much annoyance and concern to the gardeners/growers.

Why do flowers fall off?

Firstly, not all flower drop is a concern – for example, in the gourd family (cucumber, ridge gourd etc) male flowers naturally drop off from the plants after few days – once their main purpose of pollinating the female flowers is complete! Having said that, a healthy blossom that drops off suddenly is actually a ‘Blossom/Flower drop’

A cucumber Male flower – in our Research Centre!

 

 What causes Flower drop

It turns out that multiple factors often working together are responsible for this. Listed below are few of the major causes of Flower drop:

  • Environmental factors: 
    • Temperature fluctuation affects ‘pollen’ growth. At higher temperatures, pollen becomes dry while at lower temperatures pollen becomes non-viable, both leading to no pollination in flower. For example, in the case of solanaceous  family of plants ( which includes tomatoes, chilly, brinjal etc), Day temperatures >30˚C could cause flower drop.  Similarly, night temperatures >22˚C  or <11˚C could lead to flower drop.
    • Humidity plays a major role in pollen shedding and its transfer. Lack of moisture or sudden and excess watering at once create a stress condition in the plant leads to flower drop.
    • High RH interferes in improper pollen shedding and low RH makes pollen dry and it will not adhere to the stigma of the flower.
    • Light – lack or excess of sunlight exposure results in the poor setting of fruits.
    • Lack or irregularity in nutrition also creates stress in plants. Higher/lower concentration of Nitrogen fertilizer will lead to blossom drop.  A higher dose encourages the vegetative growth in the plant while a lower dose cannot support further reproductive growth in the plant.
    • Excessive Wind may carry away pollens or desiccate the flowers. It could also physically damage the plants by breaking the flowering branches.
  • Heavy fruit set: In order to maintain a balance in the plant system, the plant itself abort some flowers when it blooms in large numbers. This avoids competition for fruit development when plant food supply is limited.
  • Pruning: Excessive pruning of the plant limits the reserve food energy, thus reducing the flower production and fruit set.
  • Insect damage and disease: Small insects like thrips and flies ill-feed the developing buds/flowers. This could lead to bud/flower drop.
  • Improper pollination or lack of pollination – when flowers do not get proper pollination within a particular time period this causes the flower to fall off.
    Flower drop in potato plants

Tips to control flower drop

  • Grow varieties that are suitable to the region and climate (Ex. Varieties which can tolerate high/low temperature)
  • Ensure provision of proper macro and micro nutrition to the plants. Micronutrients such as Boron are important for flower development.
  • Regularly water the plants – in the right quantity depending on the climatic conditions. The growth medium should always be kept moist.
  • Monitor for pest activity at regular intervals

Sushma completed her B. Sc. from College of Horticulture, Hiriyur and M. Sc. from College of Horticulture, Bengaluru. She is an avid gardener with expertise across soil based and soilless gardening techniques using substrates.

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