NEWS for North Dakotans
Agriculture Communication, North Dakota State University
7 Morrill Hall, Fargo, ND 58105-5665

September 2, 1999

[Editors: Please include byline when using this article.]

How Do You Pick A Ripe Watermelon?

by
Ronald C. Smith
Extension Horticulturist, North Dakota State University

One of the biggest challenges of late summer in our region is knowing when to harvest watermelons. The ability to recognize a ripe melon comes from experience and careful observation, but even large-scale watermelon growers can sometimes go wrong.

The watermelon industry has long sought a scientific way for determining ripeness, although it has generally been a fruitless quest! Sometimes growers are faced with the possibility that the 40,000-pound truckload of watermelons they just shipped will be rejected by the buyer--all because of the presence of a dozen unripe melons.

According to the August 1999 edition of the Growing for Market newsletter, students at the University of Delaware have designed a machine for testing ripeness. The machine is based on the old method of thumping the melon to see if it is ripe. Thumping an unripe melon will produce a metallic sound while the sound emanating from a ripe melon will be duller.

The Delaware students rigged up a device that thumps a watermelon and then measures the resonance of the sound. They have been able to correlate certain sound frequencies with sugar content. In general, the sound frequencies between 100 and 200 hertz correlate with the desired sugar content of about 8 to 12 percent.

The watermelon industry is no doubt holding its breath to see if the thumping machine survives field testing this summer. If the device proves reliable, it could be commercialized and sold to growers and supermarkets so that consumers could test the watermelons themselves.

That's still a long way off, though, for most market gardeners. Most still rely on two other time-tested indicators of melon ripeness:

• Look at the bottom of the melon where it rests on the ground. When this "color spot" goes from white to a light yellow, it is generally considered ripe.
• When the tendril nearest the melon turns brown and dry, it is probably ready to eat.

But even these indicators aren't precise. Only a melon's taste provides the definitive evidence as to its state of ripeness. Here's a nearly foolproof strategy: cut open several melons that appear to be ripe (based on the two time-tested standards), and then find the one with just the right taste. Note the color spot, the shine on the rind and the size of the melon. Harvest all those that have the same qualities.

I'm betting that's a test any kid would love to take!

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Source: Ron Smith (701) 231-8161
ronsmith@ndsuext.nodak.edu
Editor: Dean Hulse (701) 231-6136