The Biologist Is In: Novel Vegetable: Scarlet Eggplant

Tuesday, September 22, 2015

Novel Vegetable: Scarlet Eggplant

S. integrifolium "Pumpkin Tree".

Solanum integrifolium (or S. aethiopictum, the nomenclature is a bit confused) goes by a few common names depending on what variety you're working with. A type that is grown primarily for decorative use in the USA is referred to as the "Pumpkin Tree" (or "Pumpkin-On-a-Stick") because of the ripe fruit have the color and shape (if not size) of pumpkins. The orange-red color of the fruit is characteristic for the species. Many other red/orange eggplants you will find are varieties of the same species.

Most photos of "Pumpkin Tree" plants that you find online have lovely deep purple-black stems, which provide nice contrast to its bright orange-red fruit when dried and used in a floral display. My plant has the green stems typical of your everyday eggplant, marking it as somewhat distinct from most of the photos I come across. My seeds were saved from a dried fruit that I found in a bouquet a friend had brought over from her florist employer. I didn't note the color of the stems, but I'm assuming they were light in color.

Sautéed "Pumpkin Tree".

The fruit are widely reported as edible, though they're more bitter than the usual cohort of American vegetables. There are references to the vegetable tasting better before it has turned orange, so I decided to prepare a pair of simple dishes to compare them. The ripe and unripe fruit from the top photo were diced and then sautéed separately with olive oil and a dash of salt and ground long-pepper. The ripe fruit was squishier and made more of a mess on my cutting board than the unripe fruit. As the diced eggplant was cooking, I was surprised to find many of the seeds were popping like popcorn, leaping out of the skillet in the process. (They didn't gain much in size like popcorn, however.)

After each dish was done, I sampled a small bite. Between trying one and the other, I rinsed out my mouth with some milk. The mature fruit might have been slightly more bitter than the immature fruit, but both were far more restrained than either had been when tasted raw. The bigger issue for me was the grainy texture of all the popped seeds. I may try preparing a batch of them into a stir-fry or some other dish that would prevent the popped seeds from being so prominent in the final meal.

The fruit are a bit too small for easy preparation. A larger-fruited variety, like several sold at www.rareseeds.com, would be a better place to start if you're interested in this plant as a vegetable. [I have no association with www.rareseeds.com, but I do think they're a cool company.]

I have seeds for another variety of scarlet eggplant that I found at a Hmong farmer's market stand near the University of Minnesota. The fruit were small, round berries that were connected in chains (like how cherry tomatoes often are). I chatted up the salesperson about the fruit, as I had never seen them before and was curious about them. He said the elders' name for the plant was [Hmong]"Iab Lws" (I had to have him spell it out, as I don't speak the language.) and that it is culturally considered the ideal pairing with squirrel. The name translates roughly to "Bitter Berry", which is a perfectly descriptive name because the berry is rather bitter. I wasn't planning to buy any, but in appreciation for my interest in his crop and culture, he insisted I take a large bundle as a gift. I don't typically enjoy bitter vegetables, but I've started to appreciate their place in cuisine.

It isn't yet clear to me if "Iab Lws" is another example of S. integrifolium (or S. aethiopictum) or if it represents the ancestral species S. anguivi. I planted several seeds early in the spring, but the plants that came up got lost along the way. I do have a single plant of "Iab Lws" that was started roughly mid-way through the summer. Though small, it has been growing well and is now flowering. Hopefully it will develop fruit before the first fall frost. Even if it doesn't fruit, I should be able to at least get some nice photos of the plant.

Since "Iab Lws" and "Pumpkin Tree" are very closely related, they should cross very easily. Though many gardeners take great pains to ensure their different varieties don't cross, so they can preserve the varieties as historical artifacts, I tend to be a bit more flexible. It doesn't bother me if my varieties cross. In fact, my varieties crossing helps to ensure that what I grow every year will remain interesting. My "Iab Lws" has started flowering and I've moved it to be directly adjacent to my "Pumpkin Tree" plant in hopes of that a cross might happen. I could perform the cross manually, but right now it is more convenient for me to simply setup situations where insects will do the work of crossing for me.

"Iab Lws" and "Pumpkin Tree" are distinct enough (as mature plants) and there is no reason to expect that all alleles responsible for visible traits in one variety would be dominant over the alleles from the other variety. It should be relatively simple to identify any resulting hybrids early enough to isolate them and ensure self-pollination (of at least the later fruit). I'm really interested in what recombinations of the traits from the two varieties would turn up in the F2 population and in subsequent generations. Large fruit developing in elongated chains would be really cool (as well as useful).

S. integrifolium "Korean Red".

I recently came across a fruit for yet another S. integrifolium variety, "Korean Red". This variety has been bred primarily as a vegetable and the fruit are much less bitter as a result. The fruit is definitely denser than those of "Pumpkin Tree", suggesting to me that it would be much more useful as a kitchen ingredient. I'm holding off from cutting into this one because I want to let it mature its seeds for me to grow next year.

When the fruit had become very shrunken, I cut it open and extracted the seeds for final drying. The fruit residue smelled very sweet, without any of the bitterness I was expecting. I didn't actually taste the residue, so I'll have to wait for next year to tell if the scent was telling the truth about the fruit.

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