Parenthocarpic Crops for High Tunnels

By Lewis W. Jett, Horticulture Specialist

Female squash blossom Male squash blossom
Figure 1 Squash has separate female (top) and male (bottom) flowers

Parenthocarpy is development of a fruit without pollination. Parenthocarpy could be a genetic trait or induced by environmental conditions such as low light and cool temperatures. Many greenhouse cucumber varieties and some summer squash can set parenthocarpic fruit. Parenthocarpy may be of particular interest to high tunnel producers since early-season cucumber and squash production is often limited by bee activity within the high tunnel. Cucurbit pollen is very heavy and sticky and is only carried by pollinating insects. Moreover, cucurbits are monoecious, meaning there are separate male and female flowers on the same plant (Figure 1). Cucurbit flowers may be open for only 6 hours and pollen viability rapidly declines.

Bees are necessary to cross pollinate most varieties of squash. Parenthocarpic varieties of cucumbers and squash do not require cross pollination for fruit set and are well-suited to high tunnel production.

Table 1. Cultivars of parenthocarpic cucumbers and summer squash

Vegetable Cultivars
Cucumber Camaro, Corona, Diva, Tyria, Tasty Jade
Cucumber (Beit alpha) Sultan, Rocky, Socrates, Timor
Zucchini Cavili, Defender, Dundoo, Parthenon, Venus