August 15, 2009

1 - Some vegetable plants not forming fruits this summer.

Yard and Garden August 15, 2009


Why are pumpkin, corn, cucumbers, melons, and some other plants not yielding vegetables? They are blooming, hundreds of blooms, except the corn. The tomatoes, peas, carrots, radishes, and potatoes have produced vegetables. Three years ago the pumpkins, corn, cucumbers, and melons did yield a harvest.

- Cathy

From NMSU website


Your plants that are not yielding are plants that require pollinators. For several years we have noticed declines in wild honeybee populations due to several problems. However, bumblebees and other native bees have been pollinating many of our crops. This year's weather may have created a problem for pollinators. It remained quite cool for longer than usual, then suddenly turned cold. Precipitation has not followed usual patterns in some parts of the state and that may have interfered with pollinator activity. Based on the need for pollinators in the plants you have listed, this is my first guess as to why they are not setting fruit.

There are other potential causes such as over fertilization with nitrogen fertilizer (including manure) that can cause the plants to grow vigorously, but prevent the development of flowers and fruit.

The cold weather could have also interfered with the early development of fruit and the heat may have prevented mid-summer fruit set.

However, based on the list of plants not forming fruit and those that have, I consider pollination problems most likely. Tomatoes and peas do not require pollination, they are capable of self-pollination. Corn is also not dependent on pollinators; it is pollinated by wind, so if a lack of pollinators is the problem for the other crops, you should still see some corn developing. Perhaps they have not yet begun to produce tassels (male flowers with pollen) and silks (part of the female flower that produces the corn kernels). Over fertilization with nitrogen would reduce fruit set in tomatoes and may delay formation of corn. Since these tomatoes are forming fruit, I suspect pollination problems. However, if some parts of the garden were more heavily fertilized than other areas, then fertilization may be at least part of the problem.

Carrots, radishes, and potatoes do not require pollination because we do not eat the fruit that results from pollination. We eat the vegetative parts of these plants (roots and tubers). Heavy fertilization would have benefited them.

Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email:, office: 505-865-7340, ext. 113.


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