This is an old myth, but it keeps coming up. And it is indeed a myth.
The concept is that you should keep melons and cucumbers several rows apart in the vegetable garden or they will cross and that will ruin their taste, giving melons a cucumbery taste and make the cucumbers taste odd.
What lends credence to this myth is that cucumbers (Cucumis sativa) and melons (Cucumis melo) are in the same genus, Cucumis, so it would seem logical that they might cross. However, they no more closely related than a human and a chimpanzee. Cucumbers, notably, have 14 chromosomes while melons have 24. Plants with widely divergent chromosome numbers can rarely cross and if ever they do, the offspring are generally sterile. In this case, no crossing is possible. The two species separated from a common ancestor over 10 million years ago and have never mixed since. Pollination between them is simply no longer possible.
To confuse things further, there is a vegetable sometimes called a cucamelon (Melothria scabra) that certainly sounds like a hybrid between the two, but the tiny watermelon-shaped fruits are not the result of hybridization. Rather the cucamelon, also called mouse melon and Mexican sour gherkin, is an entirely different species and evolved far from the others, in the New World (cucumbers and melons originated in India). All three are in the same family, the Cucurbitaceae, but that’s their only link.
And just to clear things up, the watermelon belongs to yet another genus in the same family. Its botanical name is Citrullus lanatus and no, it will not cross with melons, cucumbers or cucamelons. Nor will squash (Cucurbita pepo), also a Cucurbitaceae, cross with any of the above.
What About Cantaloupes and Honeydew Melons?
Yes, they will cross. And so will any other true melon (muskmelon, Piel de Sapo, Casaba, etc.). All belong to the same species, have the same chromosome number and cross readily.
That said, even if you grow them side by side, that won’t alter their taste … not that year. Crossing doesn’t alter the taste of the fruit, which remains that of the female parent. However, any seeds saved when two types of melon are grown nearby may well be hybrids and their taste and form could easily be altered … next year, when they are sown. A safe isolation distance for melons is generally said to be ¼ mile (400 m).
For more on isolation distances for vegetables, read How to Keep Vegetables from Cross-Pollinating.
But I Grew Melons and Cucumbers Together and My Melons Tasted Weird
Yes, melons are notorious for their ability to take on funny tastes when the conditions are not to their liking. So, if your melons taste off, it’s probably because it was too cool, too hot, too rainy, too dry, the soil was too poor, too acid, too alkaline, etc. Certainly not because they crossed with some other vegetable. Melons are just finicky plants. Illicit hybridization has nothing to do with their altered taste.
So, don’t worry about different vegetables changing the flavor of their neighbors during the current season … unless you grow corn. More about that here!