When to Harvest Cucumbers
• Harvest slicing cucumbers when bright, green, and firm and 6 to 8 inches (15-20 cm) long. Harvest pickling cucumbers when 2 to 4 inches long–6 to 7 inches long for big pickles.
• Harvest lemon cucumbers just before they turn fully yellow. A yellow lemon cucumber will be seedy.
• Cucumbers will be edible any time after the flower drops off the end of the fruit.
How to Harvest Cucumbers
Don’t leave cucumbers on the vine too long; an overripe cucumber will be dull, less crisp, seedy, and bitter tasting. Yellowing at the blossom end of the fruit is a sign the fruit is overripe. Remove all overripe fruit from the vine.
Cut fruit from the vine with a knife or pruner. Pulling fruit from the plant may damage brittle vines.
It is important to harvest cucumbers frequently to keep the plant producing new fruit.
How to Store Cucumbers
Store cucumbers at 50°-54°F (10-12°C); a cool spot in the kitchen is best, not warmer than 59°F. Cucumbers will turn yellow and decay rapidly if not kept cool.
You can refrigerate cucumbers for about a week in the vegetable crisper of the refrigerator. Do not refrigerate cucumbers below 40°F (4°C). Dunk fruit in cold water or wipe them clean with a damp cloth then place fruit in a perforated plastic bag; this will keep the fruit from drying out. (Refrigerators are dry, not humid.)
Sliced cucumbers should be refrigerated in a bowl covered with plastic wrap to keep slices crisp and to prevent dehydration.
Cucumbers stored below 40°F will become pitted, yellow, and start to decay.
Avoid storing cucumbers with apples or tomatoes; ethylene (a natural plant hormone released in the form of a gas) given off by those fruits will cause cucumbers to yellow.
Best cucumber growing tips at How to Grow Cucumbers.