Whenever I grow Cucurbita Moschata the plants show excellent resistance to powdery mildew and there is no sign of infection. Meanwhile my Zucchini breeding lines and some varieties that are supposed to have IR(Intermediate Resistance) will die if I don’t use fungicide.
I’ve been thinking of hybridizing Cucurbita Moschata with Cucurbita Pepo to get a hybrid that is fully bush like zucchini with no vines but that is also highly resistant to powdery mildew. I don’t really have experience with interspecific Cucurbita Hybridization except for one cross I attempted last year(Cucurbita Moschata x Cucurbita Maxima). I got fruit set both ways but the seeds I harvested seemed immature(They were just filled with fluid) while seeds form other, self pollinated fruit were just fine.
Will a cross between Cucurbita Moschata and Cucurbita Pepo work better than Moschata x Maxima? What about Cucurbita Argyosperma? Can it cross more easily than moschata with pepo? Does it have higher or lower disease resistance to powdery mildew than Cucurbita Moschata?
All I know is that out of maxima, moschata (argyosperma should be almost same as moschata) and pepo, only pepo x maxima is next to impossible (but not quite impossible) both ways. Other crosses should work as well as you could expect interspecific crosses to work. Only experience I have is moschatas last year that only had females at start and as consequense were mandatory crosses with either pepo or maxima (can’t tell which). In that case fruits made at most some full seeds, but some fruits made none. I have no knowledge if they germinated. Did you try @ThomasPicard ? In any case that’s what you should expect. Not too difficult, but might take several crosses to get enough seeds to play with.
Cucurbita moschata and Cucurbita argyrosperma cross fairly readily. This year I am growing for the second time in a row the variety called Gold Striped Cushaw which is Cucurbita argyrosperma and it was from seed saved from an open-pollinated squash. It appears as it was crossed by the bees with one of the Cucurbita moschata landraces that I was growing last summer. The fruits are much more shortened than they were last year. I only have two plants for the reasons that (1) they don’t keep as well as the Butternut species and (2) I only wanted to have a few to do breeding work with them. It’s my intention to transfer the very colorful gold pattern to some medium sized Butternut types that have long keeping qualities. See the attached photo for how the vines look with the color patterns on the leaves.
There is a commercial hybrid of Cucurbita maxima x Cucurbita moschata called Tetsukabuto which is sold by Johnny’s Selected Seeds in Maine as well as some other seed companies. If you are going to be attempting crosses between the two above species I would recommend that you get this variety to use as a “bridge” between crosses. My experience with this interspecies hybrid is that I can generally cross it in either direction, but the plants of this only have female flowers so you will have to choose a male from your other parent and then plant out the offspring the next year and try to select for plants that have both male and female blossoms on the same plant. You might have to backcross one generation to get full fertility, but if you grow a large enough population you might not need this step. There will be lots of genetic segregation in any such breeding projects using this Winter Squash as a parent.
I have never been able to cross a Cucurbita argyrosperma and a Cucurbita pepo although I have tried it around 30+ years ago.
I have seed for a Cucurbita moschata x Cucurbita pepo that I received in the spring of 2025 and was able to make crosses in either direction to Butternut and the Summer Squash types. If I remember correctly I think I even succeeded with some Cucurbita argyrosperma as well, but I would have to check my notes on that. I will have some BC1 seed of the above this fall for other squash breeders if they are interested. (Assuming I don’t get an early fall frost, which can happen.)
Thanks. I will definitely try next year
As I have discovered, interspecies crossing in squash is possible, but it comes with challenges. Beyond being a hands-on gardener, I’ve been a passionate reader since childhood. I have devoured Joseph Lofthouse’s Landrace Gardening as well as Carol Deppe’s Breed Your Own Vegetable Varieties (bless her), drawing heavy inspiration from the Maximoss and Moschamax projects.
Last year, I spontaneously crossed the interspecific hybrid Sprinter F1 (as the mother) with C. maxima. I harvested three fruits pollinated by Sunshine F1 and one unexpected fruit by Sweet Meat Oregon Homestead (SMOH). Only one long-lasting Sunshine F1 cross remains. So far, all fruits have yielded flat, sterile seeds. If this last holdout happens to contain any viable seeds, they won’t make it into the ground this season, but they will definitely reinforce next year’s polycross with genetic bridges.
Direct crossing between Cucurbita pepo and Cucurbita moschata is extremely difficult and highly unreliable under normal conditions due to genetic incompatibility barriers, usually resulting in aborted embryos. However, these genetic walls can be breached using a bridge species, where more compatible species clear the path for the problematic ones—a sort of “smuggling gene transfer through chaos.”
That is exactly why I use Cucurbita argyrosperma (specifically a cross of Nipon Island and Cushaw Orange Striped) as a 5% “mentor bridge” in my breeding pool (60% moschata, 20% maxima, 15% pepo, 5% argyrosperma). C. argyrosperma has partial genetic compatibility with both pepo and moschata. It acts as a genetic diplomat, absorbing pollen grains from both species, facilitating wide crosses, and opening the floodgates for gene transfer in subsequent generations that would otherwise be blocked.
If you want a reliable evolutionary mix between these species, you cannot rely on a simple dual cross. You need to create a multi-species polycross pool with an explicit interspecies bridge to coordinate the chaos.
If there is interest, I can share my full plans on the forum. I have an almost finished, multi-page manual titled “Landrace Squash Otín 2026 – Year One,” packed with cross-linking strategies and my own technical hacks.
I consider last year’s simple crosses as “Year Zero,” yet growing in my harsh conditions (560 m a.s.l.) brought fascinating insights. Aside from the exceptional shelf-life of the last remaining fruit, I witnessed incredible resilience from the SMOH cross. I didn’t even know the fruit existed until I literally tripped over it in the dead leaves after the first frost. That fruit then went on to ripen inside my apartment for several months.
Perhaps I am a bit naive with overly ambitious plans, but I will keep pushing forward despite any failures.
For next year, I have chosen the commercial interspecific hybrid Autumn Crown F1 as a maternal line. With this year’s mothers, there is zero risk of self-pollination due to total male sterility. Next year, that risk will be present, but their fertile pollen will simply become a calculated component of each respective cocktail, diluted within the massive volume of other varieties.
If anyone here can share or trade any interspecific hybrids, I would be thrilled to include them in next year’s trial.
P.S. It’s fascinating that even though this last fruit is genetically three-quarters C. maxima and only one-quarter C. moschata, the peduncle (stem) looks and behaves completely like a C. moschata.
It might be interesting to hybridize Cucurbita Pepo with Cucurbita Argyosperma to transfer hullless seed traits to Argyosperma. There are Cucurbita Argyosperma varieties that have been selected for huge seeds/ high seed yields and Cucurbita Argyosperma seems to be much more disease resistant than Cucurbita Pepo
You might be better off sticking with just moschata, and picking lines that have compact architecture and crossing to lines with zucchini-like fruit traits eg tromboncino. I reckon this would make selection for desirable traits much easier and achievable in fewer generations.