“Why are my cucumber plants not setting many cukes? The blossoms fall off before setting.” Question from Ron of Cashmere, Washington
Answer: There are several possible reasons that your cucumbers are suffering from blossom drop before fruit set. These include pollination issues, environmental stresses, and soil nutrient problems. Let’s take a closer look at these possibilities.
Cucumbers are dioecious. This means that they have separate male and female flowers on the same vine. Male blooms appear first on the vines and will open and drop. A week or two after the male flowers appear, you should start to see female blossoms on the vines. These are easy to spot because they have undeveloped baby cucumbers at the base of the flowers. It could be that not many of your female flowers have appeared yet. Check to see if the flowers that have dropped have little underdeveloped fruits at the base. If not, they are male flowers and your fruiting females may just be getting started.
Once you have both male and female flowers on your vines, bees pollinate the females. If your yard has few bees, fruit set can be a problem. Look for bees, and if you don’t see any, you may have to try moving pollen from the stamens of the male flowers to the central pistil of the female flowers. This is easily done with a small brush or Q-tip. Another option is to choose a self-fertile cucumber variety, like the award-winning ‘Diva’, which does not need pollinators for fruit set.
Cucumber Plant Stresses
Seasonal temperature extremes–above 90 degrees Fahrenheit and below 60 degrees Fahrenheit–can induce flower drop and inhibit fruit set. Too little or too much water can too, though in both instances you will see overall vine decline. There are also many cucumber diseases that can inhibit plant vigor and fruit set (click here for an expansive cucumber disease list), but once again, you will see signs of poor plant health.
Cucumber Nutrient Needs
Choose a vegetable fertilizer formulated for fruiting crops for vigorous fruiting. Soil that is too high in nitrogen can inhibit flower and fruit set. Cukes also need organic-rich soil with a near-neutral pH (6 to 7) grow to their fullest (Black Gold Garden Soil is a great soil amendment).
I hope that this info will help you determine the root cause of your cucumber problems. To learn more about cucumber growing success, watch the video below.
Black Gold Horticulturist