Pumpkin Roots: What You Don’t Know Can Hurt You!

Terry Nennich, Extension Educator, University of Minnesota Extension Service, Clearwater County

Unknown to most growers, root systems of pumpkins are as large and extensive as the foliage. With trees, in general, what you see in growth above the soil is matched by root growth in the ground. The same situation exists with pumpkins. In a “one-of-a-kind” research project in 1927, John Weaver and William Brunder, botanists at the University of Nebraska, grew many different vegetable crops and, over time, excavated and mapped the course of the root systems. They published their work in a book titled “Root Development of Vegetable Crops,” published by McGraw-Hill Company, New York. To my knowledgy, no one since has attempted such a difficult task.

Vines of ‘Small Sugar’ pumpkin were about 16 feet long at maturity and the top 12 inches of soil were filled with roots. The taproot of mature pumpkins grew 6 feet deep and had 10 or more lateral branches that extensively branched outward for 5 to 17 feet or more. Many of these lateral roots were 2 to 4 feet long and all complexly and minutely rebranched, forming a “wonderfully efficient root complex”. The second and third feet of soil were also thoroughly filled with roots, with the fourth foot of soil containing many vertically descending roots. Plant size of pie pumpkins, like ‘Small Sugar’, may not be as large and vigorous as the jack-o-lantern types. It is probable that the root systems of larger pumpkins may be more extensive than those reported in this book.

So what does this mean to the pumpkin grower? Both cultivation and fertility practices must consider the developing root system hidden beneath the surface. Generally, pumpkin roots grow faster than foliage and root extension outward usually is equal to or greater than the vine spread. If cultivation is necessary, it should be done before the vines run over the ground to be cultivated. Cultivation must only graze the soil surface to avoid root damage. Later cultivation should be avoided entirely and a good herbicide program used for weed control. Pumpkin vines root in the areas between the planted rows and provide “shortcuts” for water and nutrients to enter the plant. Therefore, pumpkin vines shouldn’t be moved around unnecessarily. Broadcasting fertilizer within the space between planted rows may provide nutrition to support the rampant growth of pumpkins and help pumpkin fruits developing on satellite vines usually quite distant from the main plant.

Source: Dr. Robert J. Dufault, Vegetable Horticulturist, Clemson University

Co-Editors:Bill Hutchison, Department of Entomology, University of Minnesota, hutch002@tc.umn.edu
Jeanne Ciborowski, IPM Program, Minnesota Department of Agriculture, jeanne.ciborowski@state.mn.us
Cindy Tong, Department of Horticulture, University of Minnesota, ctong@extension.umn.edu
Production Editor: Suzanne Wold, Research Specialist, University of Minnesota, woldx018@tc.umn.edu

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Last Revised May 18, 2000.
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