Cucumbers and other vine crops are monoecious. Monoecious plants have separate male and female flowers on the same plant. Male and female flowers are similar in appearance. However, the female flowers have small, immature fruits at their base. Pollen is transferred from the male to the female flowers by bees. When properly pollinated and fertilized, the female flowers develop into fruit. The first flowers to appear on cucumbers and other vine crops are male. Female flowers appear shortly after.
Gynoecious varieties are special hybrids which produce predominantly female flowers. Seeds of a standard monoecious variety are commonly included in the seed packet to ensure adequate pollination. (The seeds of the monoecious variety may be dyed or placed in a separate packet.) Gynoecious varieties often outproduce standard varieties when a pollenizer (monoecious variety) is present.
There are also parthenocarpic cucumber varieties. These varieties develop fruit without pollination. As a result, the non-fertilized fruit do not contain seeds. Parthenocarpic varieties must be isolated from standard varieties to prevent cross-pollination and seed development.
Cucumbers will not cross-pollinate with squashes, pumpkins, muskmelons, or watermelons. Cucumber varieties may cross with one another. However, the quality of this year’s crop is not affected. (An exception is the cross-pollination of parthenocarpic varieties with standard varieties.)
What is the difference between a ‘monoecious’, a ‘gynoecious’, and a ‘parthenocarpic’ cucumber?
Monoecious cucumbers produce both male and female flowers on the same plant.
Gynoecious cucumbers produce only female flowers and require the planting of a male pollinating plant nearby.
Parthenocarpic cucumbers are usually hybrids grown from the seed that came from the cross of two parent varieties. Their flowers are all female and their seedless fruit is produced without pollination.
If you save your own seed, you should plant cucumbers are that are monoecious. They are open-pollinated (not hybrids) and do not require a male pollinating plant. They are usually pollinated by bees and other beneficial insects, so row covers must be removed when flowers appear to allow access.