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Horticulture and Home Pest News
Horticulture & Home Pest News is filled with articles on current horticulture, plant care, pest management, and common household pests written by Iowa State University Extension specialists in the Departments of Entomology, Horticulture and Plant Pathology.

Poor Fruiting of Vine Crops

This article was published originally on 7/12/2013

Vine crops (cucumber, muskmelon, watermelon, and squash) are some of the most popular vegetables in the home garden.  While vine crops are easy to grow, home gardeners are occasionally disappointed in crop yields.  Poor fruiting of vine crops may be due to the plant's flowering habit, poor pollination, or blossom-end rot. 
 
Flowering Habit
 
Watermelon, muskmelon, squash, and cucumber are monoecious.  Monoecious plants have separate male and female flowers on the same plant.  Male and female flowers are similar in appearance.  However, female flowers have small, immature fruits at their base.  Pollen is transferred from male to female flowers by bees and other pollinators. When properly pollinated and fertilized, female flowers develop into fruit.  The first flowers to appear on vine crops are predominately male.  As a result, fruit production is poor when the vines begin to flower.  Vine crops usually begin setting good crops within a few weeks of flowering as the number of female flowers increases. 
 
Poor Pollination
 
For fruit to develop on vine crops, bees and other pollinators must transport pollen from male flowers to female flowers.  If female flowers aren't pollinated properly, the fruit begin to grow and then suddenly shrivel up and die.  Bees and other pollinators are less active in cold, rainy, or windy weather.  Fruit production may be poor during periods of unfavorable weather.  Fruit production may also be adversely affected by the use of insecticides in the garden.  Insecticides may kill bees and other pollinators visiting the garden.  To avoid harming bees and other pollinators, apply insecticides in the garden only when necessary.  Also, apply insecticides in the evening when the bees are less active. 
 
Blossom-end Rot
 
Blossom-end rot is a physiological disorder that occurs on tomatoes, peppers, eggplants, and cucurbits.  On summer squash and other vine crops, the blossom end of the fruit begins to rot and within a short time the entire fruit has rotted.  Blossom-end rot is caused by a lack of calcium in the developing fruit.  In most cases, there is no need to apply calcium to the soil.  Try to maintain an even moisture supply by watering once a week during dry weather.  Also, do not over-fertilize plants.  Uneven moisture supplies and excessive nitrogen inhibit calcium uptake.