Whatever you call this fruit, it certainly is unusual.
The plant is similar to a cucumber or melon vine, which you can either allow to creep along in the garden or provide support. The fruits start out small and green, covered with horns. The young fruit is similar in color to the leaves, so it can be hard to spot and may come as a surprise while you are weeding or re-tying the vines. Ouch, yep, that was a horned melon all right. Each vine can produce up to 100 fruit. Ouch, there's another one! As the fruits grow and ripen, they change from green to whitish, then yellow, and finally orange.
Horned melons require very warm temperatures to produce a crop, so it's best for most gardeners to start the seeds indoors. The seeds are a bit fussy about temperature and will not germinate until they sense about 58F.
Once your weather stabilizes to above 60 F, you can transplant the small plants into the garden. Keep them well watered until established and add mulch once the soil warms to 75 F. I grew mine in a very large container in full sun, quickly learning that a strong support was needed. The vines were well behaved at first, staying within the confines of the provided support. Later they tried to reach over the fence where the beans were growing.
As for disease and pests, all I can say is that mine were not bothered by any insects. The mice, which always eat my strawberries, did not bother the horned melons. Near the end of the growing season, however, the vines suffered from wilt, as may happen with some other cucumber/melon relatives.
The plants do not like any amount of cold weather, so plan ahead to harvest before frost, but the fruit is very cooperative. Cold weather was approaching and I had to dash outside to harvest all the fruits even though they were still quite green. Here's the good part: If the fruit is kept at room temperature, not refrigerated, it will ripen and will keep for several months. Yes, you read that correctly. Being a skeptic, I just had to do a test with a few of my fruits. Yes, it's true. Some that were picked green in November lasted until early January. Here, have a look...; ;
As for the taste, hmmm. You can research and see what others think - that the fruit tastes like a cross between a cucumber/lemon/banana/zucchini. Some people hate it. Some are put off by the green color. Many don't like fruit that looks like a medieval weapon. Or you can just dig in and taste for yourself. The type of seed you plant, the soil/temperature/growing conditions, and other variables all contribute something different to the taste of the fruit. To me they tasted a bit like kiwi, but they were more fun to eat because I spit out each precious seed to save for next spring.
Each seed is surrounded by a lime green, jello-like sack (I don't know the technical term). The entire fruit can be eaten: rind, pulp, seeds and all. They can be eaten at any stage of ripeness, from green to orange. The leaves can be cooked and eaten like spinach. (Nope, I did not try that!) The fruit pulp contains vitamins A and C and iron and fiber. As with any food crop, please know the source of your seeds as there are "cousins" of the edible horned melon that are quite bitter and inedible (and possibly toxic).
I communicate daily with my Plant Sister who lives halfway around the world. It was she who first introduced me to the African Horned Melon. It was the trading of these seeds that started our friendship. She tells me that the rind of the Horned Melon is very high in Vitamin C. You can make Horned Melon Rind Tea rich in Vitamin C: Slice the rind, dry/dehydrate it, and store it in a glass jar in a dark cabinet. The seeds are available from Baker Creek and several other companies. If the seed package says 'Kiwano,' the fruit will likely be sweeter than an unnamed variety.
I ate the Horned Melon with a spoon as a taste test, then later mixed the pulp with plain yogurt (excellent), in a smoothie (very good), on ice cream (no, not so much - I still prefer chocolate), and on cake (everything tastes good on cake!). A few ideas for later: Horned Melon Salsa or a lovely green sherbet. I am told that some people make a "Horned Melon Martini" and in the southern part of the U.S. they make a "Blowfish Melon Cocktail." What's next? "Jelly Melon Shooters"?
Almost forgot, yes, the pulp can be strained and made into jelly. I have GOT to try that next year!
But for now I'm still working up the nerve to prepare Roasted Horned Melon as is done in their native country. Don't think there is a recipe for that in mom's Fanny Farmer Cookbook.
Edit: Update for the Horned Melon seeds planted Jan 30, 2014: 30 out of 36 seeds have germinated by Feb 5, 2014. These seeds were saved from the fruit grown in Savannah, picked in November while green, allowed to ripen indoors, and seeds cleaned by the fermentation method in water as for tomatoes.