Most cucumber varieties, including all open-pollinated varieties require pollination. In Europe and North America thousands of bee hives are annually carried to cucumber fields just before flowering for this purpose. The flowers of these 'open field' varieties must be pollinated by bees to set fruits. The cucumber fruits contain well-developed seeds when picked for market.
Various factors impact pollination such as scarcity of bees; rainy weather which keeps the bees at home; the use of insecticides which can kill the bees; high temperatures which can effect the pollen and make it sterile.
To allow controlled production of cucumbers in greenhouses new varieties have been developed that do not need pollination. These varieties produce higher yields, with a shorter maturity time. They are usually referred to as 'greenhouse' or 'glasshouse types'. They are also generally F1 hybrids and in Australia include the cultivars Dove, Raven, Starling, Falcon, Eagle, Hawk, Eros, Carmen, Polaris, Dalat 42, Saroya, Botero, Luna, Neptune and Cormoran.
These 'greenhouse' or 'glasshouse types' of cucumbers are usually seedless as they set and develop fruit parthenocarpically (without pollination).
On an average cucumber plant, the first 10 to 20 flowers are usually male, and for every female flower, which will develop the fruit, 10 - 20 male flowers are also produced. Plant breeders, looking to increase yields, realised that production could be increased if many more female flowers were being produced. This led to the introduction of 'greenhouse' or 'glasshouse types' that are not only parthenocarpic but also may be gynoecious, which means they have 100% female blossoms. So parthenocarpic (no pollination needed) cucumbers can either be gynoecious (100% female flowers) or monoecious (both male and female flowers). Parthenocarpic gynoecious types are generally more productive and produce fruits with smoother skins than the parthenocarpic monoecious types, which have both female and male flowers. Parthenocarpic monoecious types however, are generally more vigorous and produce fruit of better size and quality. Both types produce an excessive number of female flowers, so some flower 'pruning' may be needed.
Green Harvest does not sell any parthenocarpic 'greenhouse type' cucumbers. All cucumber types listed are only suitable for garden or field production.
The time cucumbers take to produce a harvest varies widely, anything from 35 to 120 days.