Cucumis sativus
Give a cucumber heat, steady water and something to climb and it will out-produce almost anything else in the bed. Grown up a trellis the fruit hangs straight and clean and is easy to find, which is most of the battle: a cucumber missed for three days is a yellow marrow.
Pollinated by insects — fruit sets only where bees and other pollinators reach the flowers. Most varieties need insects to move pollen and each flower is open for a single morning, so a covered plant in flower sets nothing. Two exceptions: parthenocarpic varieties set fruit with no pollination at all and can stay covered all season, and all-female gynoecious varieties need a standard variety planted alongside as the pollen source.
Full sun and warmth. A cucumber in shade grows slowly and sets little.
Water deeply and regularly at the base. Uneven watering is the main reason cucumbers turn out bitter or misshapen.
Rich soil with plenty of compost dug in. Cucumbers are hungry and thirsty and root fairly shallowly.
Compost dug in before planting, then one nitrogen feed once the plant starts to run.
Cucumbers will sprawl on the ground perfectly well, but growing them up a trellis gives straighter cleaner fruit, far less disease, and a crop you can actually find.
Pick five to seven days after the flower, while the skin is still deep green and firm. Any yellowing at all means you left it too long.
Up in five to ten days in warm soil. In cold soil the seed rots instead.
The three weeks that decide the crop. Keep the seedlings covered and check them every day.
The vines run fast. Feed once as they start to run, and guide them onto the trellis weekly.
Male flowers open first, then females with a tiny cucumber already behind the petals. Take the cover off now.
Five to seven days from flower to picking size. This is when watering decides whether the fruit tastes good.
Pick every day or two until frost, or until powdery mildew takes the leaves.
Slicing
Picked at 150 to 200 mm for eating fresh. Thicker skinned than the greenhouse types and the most forgiving group to grow outdoors.
Pickling
Short blocky fruit picked at 50 to 100 mm, usually spined and thin skinned. Crops in a concentrated flush, which is what you want if you are putting up jars in one batch.
Bush or compact
Short-vined plants that need no trellis and suit a container or a small bed. They crop less heavily and over a shorter window than the vining types.
Burpless or long English
Long thin-skinned fruit bred low in cucurbitacin, so they stay mild where older varieties turn bitter. Many set fruit without pollination and can stay covered all season.
Stages affected: Germination · Seedling · Vegetative · At planting
A small yellow beetle with three black stripes that feeds on cucumber squash and melon. The chewing itself is survivable on an established plant, but the beetle carries the bacterium that causes bacterial wilt, and that is what actually kills the crop. On seedlings both the feeding and the infection risk are serious.
Stages affected: Vegetative · Flowering · Fruiting
A bacterium that blocks the water-conducting tissue, so the plant wilts and dies with the soil still moist. It is carried from plant to plant by cucumber beetles and cannot arrive any other way, which makes it one of the few diseases you prevent entirely by managing an insect. There is no cure once a plant is infected. Cucumber and melon are hit hardest; squash and pumpkin are less often affected.
Stages affected: Flowering · Fruiting · Harvest window
White powdery growth on squash cucumber and melon leaves, arriving in mid to late summer and spreading fast once it starts. It rarely kills the plant outright but it shortens the season: the leaves die back, the fruit stops sizing and the fruit still on the plant sunburns once the canopy thins.
Stages affected: Fruiting · Harvest window
Not a disease. Cucumbers naturally contain cucurbitacin, a bitter compound, and the amount rises when the plant is stressed by heat or by irregular watering. Some varieties carry far more of it than others. The fruit looks completely normal, which is why this is usually discovered at the table rather than in the garden.
Stages affected: Vegetative · Flowering · Fruiting
Mites under 1.3 mm that feed on the undersides of leaves and spin fine webbing. Populations explode in hot dusty dry conditions and after broad-spectrum sprays kill their predators.
Stages affected: Seedling · Vegetative · Flowering
Small soft-bodied sap-sucking insects that cluster on the softest new growth. They reproduce extremely fast in warm weather and are the main insect vector of plant viruses in the garden.