Cucumbers popular throughout region (The Vegetable Grower)
(Editor’s note: Gordon Johnson is a vegetable and fruit specialist with the University of Delaware.)
Cucumbers are a popular crop grown throughout Delmarva for both fresh market (slicers, mini) and processing (pickles).
There are three flowering or fruiting types. Monecious cucumbers have both male and female flowers on the same vine with a higher number of male flowers compared to female flowers.
Gynoecious cucumbers have mostly female flowers and are sold as a blend with 5-15 percent monecious pollenizers included to provide adequate pollen.
Because most plants produce female flowers, they are more productive. Most of our acreage are gynoecious hybrids.
Honeybees, squash bees, bumblebees and other wild bees are important for proper cucumber pollination and fruit set for monecious and gynoecious types.
A third group is parthenocarpic cucumbers. Parthenocarpic cucumbers do not require pollination to set fruit.
They have no need for bee pollination and no need for a pollinizer which also increases yield potential.
They will be nearly seedless or have unformed seeds. They should be isolated from seeded cucumber types to increase productivity and maintain the seedless nature.
Parthenocarpic types should be considered when bee activity is limited such as in high tunnels, under row covers, or in very early plantings.
Parthenocarpic cucumbers have been available for many years and include many types used in protected culture (greenhouse or high tunnel).
Parthenocarpy has an advantage in that there is improved fruit set under what would be a poor pollination environment.
Parthenocarpic pickle varieties also produce more fruits per vine for once-over harvest and therefore can be planted at half the stand of gynoecious types.
The University of Delaware has been conducting trials on parthenocarpic pickles for over a decade and there is now a significant acreage of production in the region.
There are also differences in cucumbers in shape, skin, taste, and texture characteristics.
There are slicers and pickling types; long seedless European greenhouse types; thin skinned crunchy Beit Alpha middle eastern types; long Asian types; “burpless” types; non-bitter skinned types; spined, rough, and smooth skin types; green and yellow types; egg shaped type; and long curly Armenian cucumbers which are actually related to melons but eaten like a cucumber.
One of the major concerns with cucumber selection is disease tolerance or resistance.
Most varieties have good powdery mildew, scab, anthracnose, angular leaf spot, and cucumber mosaic resistance.
Fewer have resistance to other viruses that are often present, particularly in late summer (watermelon mosaic, zucchini yellows mosaic, and papaya ringspot).
The major disease that limits production from mid-summer on is downy mildew which comes up from the south on weather systems.
There are only a handful of varieties currently with tolerance to this disease.
In gynoecious slicing cucumbers, Bristol, SV3462CS and SV4719CS and associated pollenizers have intermediate resistance to cucumber downy mildew. In gynoecious pickles, Citadel, Peacemaker, and SVCN6404 with associated pollenizers have intermediate resistance.
Further advances are being made in public and private breeding programs for improved downy mildew resistance.
Cucumber direct seeding in the field on Delmarva starts in late April. Successive plantings can be made through early August.
Cucumbers may also be transplanted. Start transplants in the greenhouse three weeks ahead of transplanting.
On plastic mulch, planting starts when daily mean temperatures have reached 60 degrees.
Early plantings should be protected from winds with row covers or rye windbreaks.
Cucumbers for early production may be successfully grown in low tunnels with perforated clear plastic row covers or using insulating row covers on plastic mulch with drip irrigation.
Cucumbers are a potentially profitable crop for spring and fall production within a high tunnel.
Cucumbers mature in approximately half the length of time required for tomato ripening.
Cucumbers are also amenable to vertical trellising which increases production and quality.
High tunnel cucumber varieties are often parthenocarpic (requiring no pollenizers) although gynoecious varieties can also be used (with pollenizers).
Cucumbers can be established by direct seeding or transplanting.
Space plants 12-18 inches apart in-row on 42-48 inch bed centers.
High tunnel varieties can remain unpruned, though pruning can reduce pest infestation and improve marketable yield.
If pruning is done, the lower laterals (suckers) should be pruned on the bottom 2 ft leaving 1 or 2 stems per plant to trellis.
Greenhouse Production Varieties are usually parthenocarpic varieties bred specifically for the lower light conditions of fall, winter, and early spring. European “English” or “Dutch” types and Asian types are available.
Hydroponic nutrient solution systems are commonly used, and cucumbers are trellised with single or double stems trained onto twine.