What to do now
Mildest step first.
- Pick misshapen fruit and use it; it's safe to eat.
- Water deeply and evenly, wetting the soil at least 6 inches down, and mulch.
- If bees are scarce, hand-pollinate female flowers in the morning.
- Don't spray insecticide on open flowers; if you must spray, do it early morning or late evening.
Not sure this is it? Check other cucumber problems
Poor pollination
A cucumber fills out evenly only where seeds develop, so incomplete pollination is the usual cause of crooked, curled or pinched fruit. Iowa State says poorly shaped fruit are usually the result of poor pollination, and University of Maryland Extension describes fruit that is deformed or underdeveloped on one end, with some small fruit falling off. Illinois Extension explains why: when not enough ovules, the future seeds, are fertilized, the fruit doesn't develop properly. Cut a crooked fruit lengthwise and the thin end usually has few or no seeds. Poor pollination can also leave the inside hollow, which has its own page.
Weather and bees
Cucumber flowers need insects, mostly bees, to carry pollen, and weather decides how well they work. Maryland lists rainy or cool weather that keeps bees from flying, very high temperatures that injure flowers and reduce or kill pollen, and pesticide use that kills bees. Iowa State recommends choosing an insecticide with low toxicity to bees when one is needed and applying it early in the morning or late in the evening. Clemson Extension notes that the first 10 to 20 flowers on a plant are male and don't make fruit, so a slow start is normal.
Uneven water and low fertility
Water and food matter too. Illinois Extension notes that when water is short or unevenly available while fruit is developing, especially in hot weather, the fruit may not develop properly, and that low fertility is another cause; with a complete fertilizer may help. Clemson says misshapen fruit is often due to low fertility or poor pollination, and that cucumbers have shallow roots, so a uniform moisture supply is critical during fruit set and development. It recommends watering to moisten the soil at least 6 inches deep, watering at the base in the morning, and mulching. Don't overdo nitrogen: Clemson warns that too much encourages vines and reduces fruit.
Viruses and cucumber beetles
If the misshapen fruit come with mottled, crinkled or stunted leaves, suspect a virus. University of Minnesota Extension lists squash, cucumber and watermelon mosaic viruses, with fruit that are deformed and may show odd color patterns, blotches or rings. Texas A&M AgriLife Extension says cucumber mosaic makes new growth cup downward and can cover fruit with bumpy protrusions. Maryland notes these viruses are spread by insects, including aphids, and survive in perennial weeds, and that striped and spotted cucumber beetles can carry viruses as well as bacterial wilt. Infected plants don't recover. Pull them, control weeds, aphids and cucumber beetles, and choose resistant varieties next time.
Helping pollination
To improve pollination, Clemson suggests planting a variety of flowers around the garden to keep pollinators visiting. When bees are scarce, pollinate by hand in the morning, since each flower opens for only one day: pick a male flower, remove its petals, and rub the pollen onto the center of a female flower, the one with a tiny cucumber at its base. Where pollination keeps failing, Clemson suggests parthenocarpic varieties such as 'Diva', which set seedless fruit without bees. If you cover plants against cucumber beetles, Maryland advises removing the cover when flowers open, except for parthenocarpic varieties.
Read the whole label first: it must list your crop, and its directions (amount, timing, gear, bees, days before harvest) are the law. If this page and the label differ, follow the label.
Growing it again? When to plant cucumber for your ZIP code
- Cucumber BeetleYellow-green beetles chewing cucurbit leaves and flowers; rapid wilting may signal bacterial wilt transmission.
- Gray Mold (Botrytis)Gray-brown fuzzy mold on fruit, flowers, or stems — soft, collapsing tissue beneath the coating in cool, wet conditions.
- Damping OffSeedlings collapse at soil level with a pinched, rotted stem — happens quickly in wet, cool conditions.
- Spider MiteStippled, bronzed leaves with fine webbing on undersides; damage intensifies in hot, dry weather.
- Why does my zucchini flower but not fruit?Usually it's pollination. The first zucchini and squash flowers are often all male and fall off a day after opening, which is normal. If female flowers (tiny fruit at the base) open and then shrivel, they weren't pollinated. Hand-pollinate them, and watch for heat.
- Why are my cucumbers hollow inside?A hollow center usually traces back to poor pollination — too few seeds formed, so the seed cavity didn't fill. Heat, water stress and low boron or calcium can add to it. The fruit is safe to eat.
- Why are my cucumbers bitter?Bitter cucumbers contain cucurbitacins — bitter compounds that build up in the fruit when the plant is stressed, usually by drought, heat or uneven watering.
- Why are my cucumber leaves puckered, crinkled, or distorted?Puckered or crinkled cucumber leaves usually mean a mosaic virus (spread by aphids) or severe aphid feeding itself — check the undersides of leaves for aphid colonies before concluding it's a virus.
- Why are my cucumber leaves turning yellow?Where the yellow starts tells you the cause: old lower leaves point to low nitrogen or age, angular patches to downy mildew, fine speckles to spider mites, mottling to a virus, and wilting vines to bacterial wilt.