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Mini Watermelon Research Benefits California Farmers

The Issue

Four types of watermelons are available in supermarkets. Older diploid (seeded) watermelons, grown since 1629, weigh 18-35 pounds. Large seedless triploid watermelons weigh 15-22 pounds and have been popular since 1988. Icebox-size melons, 6-12 pounds, have been available since 2000. The newest melons are seedless mini or “personal” watermelons, sometimes called “palm” melons.

The new triploid one-serving melons, weighing 3-7 pounds, became widely available in markets in 2003. Besides the smaller size, advertisers tout its thinner rind, which means more edible flesh. California growers started growing the personal-size melons, but research was lacking for recommended varieties, quality characteristics, pollinators and spacing requirements.

What Has ANR Done?

UC Cooperative Extension farm advisors Richard Molinar and Shannon Mueller began evaluating varieties in 2003 and 2004 at the West Side and Kearney Research and Extension Centers in Fresno County. In 2005 their research expanded to include evaluating plant spacing, fertility requirements, and a location in Hollister with the cooperation of farm advisor Aziz Baameur. They looked at 10 varieties, five plant spacings from 12 inches to 48 inches, and five fertilizer rates ranging from 0 to 300 pounds of nitrogen.

They evaluated varieties for yield, Brix (sugar), rind thickness, rind color, individual melon size (weight and diameter), and flesh color. Certain varieties were consistently sweeter than other varieties at all locations. Flesh color, also an important factor, ranged from dark red to orange-red. The two most significant and variable factors were the rind thickness and overall melon size. Since the melons are small, a fairly thin rind is desirable to maximize the amount of edible flesh, however this must be balanced with the handling and shipping distance since the thinner rinds leave the melons more susceptible to bruising. The variety Petite Perfection consistently had one of the thinnest rinds (0.6 centimeter), whereas Valdoria and Betsy had thicker rinds (1.5 centimeter). Research is ongoing to evaluate newer varieties and to identify more specifically the optimum plant spacing, fertility requirements, and pollinators for the ‘best management practices’ of this crop.

The Payoff

Growers have needed research facts to help decide

Personal-size watermelons are an expanding market, with California being one of the major producers. UC's work has been instrumental in helping growers make preliminary decisions on which varieties will perform well in different climate zones of California, what kinds of yields can be expected, and what quality characteristics are important to the broker, shipper, retailer and consumer.


Supporting Unit: Fresno County

Richard Molinar, (559) 456-7555, rhmolinar@ucdavis.edu; or Shannon Mueller,(559) 456-7261, scmueller@ucdavis.edu; or Aziz Baameur, (408) 282-3127, azbaameur@ucdavis.edu