Summer Squash Cultivar Selection for High Tunnel Production – Vegetable Crops Hotline

Summer Squash Cultivar Selection for High Tunnel Production

Warm-season vegetables like tomato, cucumber, pepper etc. often receive premium prices if they were sold at farmers’ markets earlier in the season. The same happens on summer squash, with the different fruit shape and color, summer squash provides a great diversity to the market. High tunnels that  are planted with warm-season vegetables are often closed to maintain heat inside the structure in the spring. Growers often hesitate to bring beehives to high tunnels because of the increased production cost and potential worker safety concerns. Under such circumstances, crops that can set fruit without pollination (parthenocarpic) have an advantage for early-season high tunnel production. Previous studies indicated parthenocarpic character exists in some summer squash cultivars. But such information is not always clearly indicated in seed catalogs. Without knowing the information, farmers may miss the opportunity of growing summer squash and targeting for an early harvest in high tunnels.

In the spring 2018, we selected 6 summer squash cultivars (Cavili, Dunja, Golden Glory, Multipik, Noche, Partenon) that had previously shown high percentages of setting fruit without pollination. Three-week old transplants were planted in a high tunnel at the Southwest Purdue Agricultural Center in Vincennes, IN on April 2. Seedlings were planted on black plastic-covered beds with an in-row plant spacing of 2 ft apart. Side-walls of the high tunnel were closed until mid-May.

Cultivar Multipik developed the earliest female flowers on April 9, which was about 10 days earlier than male flowers. Other cultivars either developed male and female flowers around the same time or developing male flowers earlier than female flowers around April 20. Cultivar Multipik had the greatest number of aborted female flowers while cultivar Golden Glory had the least number of aborted female flowers prior to mid-May. Cultivar Cavili and Partenon were harvested the earliest. The first harvest was on Apr. 29. The first harvest of all the other cultivars was on May 4. Harvest lasted from April 29 to June 11, all cultivars had yields above 6 lb/plant. Figure 1 shows the yield of the cultivars. Cavili had the highest yield (8.58 lb/plant) although it was not significantly different from other cultivars. Multipik produced the greatest number of straighneck fruit with smaller sizes compared to the other zucchini cultivars.

The trial showed that all the six summer squash cultivars evaluated in this study are suitable for growing in high tunnels without insect pollination for early-season production. Since trellis summer squash is more difficult than trellis tomato and cucumber, growing summer squash in high tunnels takes more space, especially when plants develop large canopies, which is also the reason we ended the harvest on June 11 considering field-grown summer squash would enter the market shortly, thus it was less valuable to grow summer squash in high tunnels.


Reiners, S. 2014. Producing summer squash without pollination-ranking varieties. 2014 Conference Proceedings. Cornell University. Jan 28 2020 <>

Figure 1. Yield of summer squash cultivars in the high tunnel evaluation

Figure 1. Yield of summer squash cultivars in the high tunnel evaluation



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