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Tromboncino Squash

Like most home vegetable gardeners, I have fought squash vine borers for years. These frustrating pests of summer squash (Cucurbita pepo) often knock out yellow squash and zucchini in my Upstate garden by the end of June. My colleague Terasa Lott shared some great tips on dealing with them in her June 3, 2019 hot topic, Watch Out for Squash Vine Borers. I’ve tried most of the techniques with variable success, but it’s a lot of work and I usually just give up. But this year I decided to try something different, ‘Tromboncino’ squash.

Tromboncino is an Italian heirloom cultivar of the species Cucurbita moschata, aka the butternut squash. Most butternuts are grown as winter squash where the fruit are harvested when mature, sweet, and dense. Tromboncino squash, however, are harvested and eaten when the fruits are young and tender, like summer squash. The best part is that all butternut squashes are essentially immune to squash vine borer due to the species’ dense, solid stems. This trait holds for Tromboncino as well.

For years I’ve heard other gardeners sing the praises of Tromboncino squash, but I had never tried them. So, this year I ordered seed online and grew them for the first time. Today, on the last day of July 2019, after my “normal” summer squash plants are long gone, I’m still harvesting from the Tromboncino vines with no sign of vine borer damage.

Admittedly, I was a little doubtful that it would be a suitable substitute for summer squash, but I’ve been pleasantly surprised. The key is to harvest very young, tender fruits. I try to get them the day after the flowers drop from the fruit and I’ve harvested a few with the bloom still attached (the flowers are edible too). These young squashes fill in admirably for summer squash in most recipes. Their light green skin color and flesh texture are a little more reminiscent of zucchini than yellow squash. As the fruit grow larger, the flesh becomes denser and more similar to the texture of the familiar butternuts, but is still quite tasty. I haven’t yet allowed one to fully mature to see if they have the flavor and storage qualities of winter squash.

The biggest difference between Tromboncino and summer squash is in the growth habit. The plant, like all butternut types, is a vigorous vine. It could be grown on the ground, but trellising keeps the fruit off of the soil and allows them to elongate into their distinctive form. It also makes them very easy to find and harvest. I grew the vines up our deck railings, and it’s been fun to watch them grow and produce. Plus, the large, yellow flowers are beautiful and attract a number of pollinators.

For more information on squash, see HGIC 1321, Summer Squash; HGIC 1318, Pumpkin and Winter Squash; and HGIC 1256, Planning a Garden.

Tromboncino squash almost ready for harvest.

Tromboncino squash almost ready for harvest.
Cory Tanner, ©2019, Clemson

Harvested Tromboncino squashes (right) next to a yellow crookneck squash (far left). The young, tender fruits (middle) are great substitutes for yellow and zucchini squash.

Harvested Tromboncino squashes (right) next to a yellow crookneck squash (far left). The young, tender fruits (middle) are great substitutes for yellow and zucchini squash.
Cory Tanner, ©2019, Clemson

Sautéed Tromboncino squash.

Sautéed Tromboncino squash.
Cory Tanner, ©2019, Clemson

If this document didn’t answer your questions, please contact HGIC at hgic@clemson.edu or 1-888-656-9988.

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