A hybrid or a crossbreed shouldn’t be seen as some sort of cursed monster. It is completely innocent; it simply has a “mother” and a “father”. In fact, almost all varieties that gardeners try to keep “pure” today were originally created through crossing. With some, we no longer remember the process, but with others, we do. For instance, on the Czech website Permasemínka, in their “Pestré osivo” (Diverse Seeds) section, you can find the Painted Mountain flour corn. It was developed by crossing more than seventy heritage corn varieties rescued from indigenous peoples and homesteaders living in the harshest climates of the US and Canada. Its earliness is legendary.
The main trouble with commercially sold F1 hybrids is that you end up with seeds of a plant that might suit you perfectly, but you have absolutely no idea who its “mother” or “father” was. Seed companies keep this a secret so that we are forced to buy from them over and over again. If we knew the “parents,” we could simply cross them ourselves and stop generating such huge profits for the seed corporations. (Assuming both parents are open-pollinated; if they were F1 hybrids themselves, we would get hopelessly lost in our own ignorance.)
******
Therefore, we can categorize crosses based on whether we have full information about their origin or not. Some passionate seed savers, when selling hybrid seeds, openly share information about the “parents.” For example, Joseph Lofthouse, in his book Landrace Gardening (Food Security Through Biodiversity and Promiscuous Pollination), mentions that his ‘Paradise’ sweet corn (also an F1) has ‘Astronomy Domine’ as the mother, while the pollen is supplied by fathers like ‘Who Gets Kissed’ or ‘Ambrosia’.
*******
Personally, I would divide them into “unconscious crossing” (hybrids with a secret) as opposed to “conscious crossing” (with full information about the “parents”).
The third category would be “accidental crossing,” when who-knows-what flies in from who-knows-where, just as it happens naturally in the “wild.”
And the fourth would probably be “forced crossing,” where breeders compel plants that wouldn’t normally cross to do so under highly non-standard conditions. Mind you, this is not genetic manipulation like GMO (Genetically Modified Organism). It is still traditional plant breeding. I also understand that these seeds are not protected by patents, unlike GMOs. (These principles are beautifully described in Carol Deppe’s book Breed Your Own Vegetable Varieties, which I have mostly translated for myself, though I still struggle a bit with the appendix “801 Varieties of Interest,” especially matching the official and colloquial Czech names.)
*******
Then come certain overlaps. One of them is the “Dehybridization of Hybrids”—a long-term, multi-year process of selection and crossing, as described by the “blessed” Carol Deppe in The Tao of Vegetable Gardening as well as in Breed Your Own Vegetable Varieties.
Dehybridization can be “miraculously” shortened to a single year if a seller cheats and markets an open-pollinated variety as an F1 hybrid just to discourage you from saving your own seeds. Apparently, this used to happen—breeder Alan Kapuler referred to these as “pseudohybrids.”
In some commercial F1 hybrids, cytoplasmic male sterility (CMS) is intentionally introduced. This means that the subsequent offspring (F2) do not produce any pollen in their male flowers. There is a very high probability of this occurring in F1 hybrids of radish, sunflower, cabbage, kale, broccoli, and other brassicas, as well as onions, carrots, and parsnips.
Even so, seeds can still be produced if such a hybrid is pollinated by a different plant, but the male sterility continues to be passed down.
Although the genes for male sterility travel uncompromisingly along the maternal line, nature gives us breeders a powerful weapon in the form of genetic restorers (fertility restorers). These genes are carried in the pollen nucleus of many fertile Cucurbita maxima varieties. If this correct pollen hits a sterile mother during mass crossing (a polycross), it can override the sterility in the next generation, restoring full fertility and the ability to produce pollen to the plants.
*******
And now we come to squashes, watermelons, and interspecific hybrids.
Squash (Cucurbita) is a genus within the gourd family (Cucurbitaceae). The genus Cucurbita includes the following species: Cucurbita pepo, Cucurbita maxima, Cucurbita moschata, and Cucurbita argyrosperma(formerly C. mixta). And, of course, Cucurbita ficifolia (the fig-leaf gourd). Under normal conditions, these species do not cross with one another.
Then we have Citrullus lanatus, commonly known by its fruit as “Watermelon,” which is a somewhat distant relative of squashes—just one tier up, it is also a genus within the Cucurbitaceae family.
*******
Next comes “crossing with mild force.”
Breeders in Japan successfully crossed Cucurbita maxima and Cucurbita moschata, creating a hybrid sold under the name Tetsukabuto F1. In our country, hybrids based on the same principle are available under the names Sprinter F1 or Bolt F1—used as rootstocks for grafting cucumbers and melons. They are supposed to have male sterility. Joseph Lofthouse tried to breed subsequent crosses using Cucurbita maxima on one side and Cucurbita moschata on the other to provide the missing pollen to the mothers. It worked. He then selected for restored fertility and eventually for excellent flavor. He named his creations Maximoss and Moschamax. I’m sure you can guess why 
. In his book, he encourages others to replicate the process.
*******
So, I decided to join in and replicate the process under my own conditions.
After the last spring frosts, I sowed pre-germinated seeds of Sprinter F1 (Cucurbita maxima x Cucurbita moschata) directly into the garden within reach of C. maxima. On one bed, they were near Sunshine F1; on the other, at the far end of the garden, they were near Sweet Meat Oregon Homestead (SMOH) - or at least, that’s what I thought it was at the time. I did not perform manual pollination; the insects took care of it. Even though the plants had weeded beds, they only produced one medium-to-large fruit each (5.9 kg, 5.0 kg, 3.8 kg) of a dark, almost “black” green color. (The “SMOH,” which was sown about a month later, produced about 3 fruits per plant. Note: This was actually the interspecific hybrid Otín Maximoss, more on that in the next article.) On the bed with Sunshine F1, there were three plants, and all three individual fruits had a heavily wrinkled, warty surface; one fruit was more deformed on the side, likely from resting on its flank on the ground.
The fruit next to SMOH had a smooth surface with only a hint of ribbing, a spherical shape, and was smaller compared to the previous three (2.5 kg). Just like my other winter squash, these fruits are stored in a heated living space. The wrinkled fruits (crossed with Sunshine F1) are beginning to change color in patches, while the “globe” (crossed with SMOH) remains unchanged for now. (Note: It colored up later.)
*******
Breeders in Ukraine successfully crossed Cucurbita maxima and Citrullus lanatus (Watermelon), naming the result Kavbuz (кавбуз). It is an abbreviation of two words: watermelon = kavun (кавун) and squash/pumpkin = garbuz (гарбуз).
I bought the seeds from a German e-shop (natalino-shop.de), though they didn’t have them in stock just now. But they are offered elsewhere too. I couldn’t find any information anywhere on whether Kavbuz carries male sterility. I sowed the seeds. The plant grew, flowered, and set fruit. However, because I was about a month late with the sowing (due to manually preparing the bed for corn), combined with a strange summer and an early frost in September, the fruits were small and highly immature. (Slightly over three months of growth. Note: Otín Maximoss, on the other hand, produced multiple medium-sized fruits packed with seeds.) I harvested only one fruit from the Kavbuz plant, about the size of a coconut, only perfectly round. Throughout the entire storage period, the skin did not harden at all. A few seeds did form, but they were smaller than the ones I originally purchased. So, next season I will hopefully start on time using the purchased seeds from scratch, and hopefully, the season will be more reasonable too.
(Note: The article “With Interspecific Squash Hybrids, the Dam Seems to Have Burst, or Hybrid is Not a F-Word” follows. And well, plans are plans; I didn’t start on time, so my growing and breeding could be summarized by the motto “FOREVER RUNNING LATE” - but with a bit of a squint, it can totally be considered a “targeted” breeding strategy .)
If the text seems a bit austere or, on the contrary, overly bombastic, it might be the influence of the AI that helped me with the translation.
watermelon would look like.