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Allium cepa
Growing calendar
Typical timing for central Japan (Kanto region). Shift it for your own climate, and record your actual dates.
Guides
- How to Grow Onions from Seed: Sowing Date and Seedling Size
- How to Plant Onions: Depth, Spacing and Soil Preparation
- Overwintering Onions: Frost Heave, Feeding and Weeds
- Onion Growing Calendar: Sowing Through to Harvest
- Onion Problems: Downy Mildew, Bolting and Split Bulbs
- When to Harvest Onions and How to Cure and Store Them
Common problems
Start from what you can see on the plant.
Pests and diseases (42)
Problems recorded for this plant, most serious first.
Onion Thrips
MajorPest
Fine white stippled scars run in vertical lines along the leaf surface, and the whole leaf eventually turns whitish. Growth stops and both yield and quality suffer.
Thrips
CommonPest
Silvery white to brown scarring spreads over leaf and fruit surfaces. Flowers discolor and drop, and fruit is left with keloid-like scar tissue.
Seedcorn Maggot
CommonPest
Emergence is uneven, and digging up seed reveals white maggots inside the seed or hypocotyl. In transplants the stem base rots and the plant wilts.
Bolting
CommonDisorder
A flower stalk rises from the center of the plant and the leaves turn tough and stringy, spoiling eating quality. Heading vegetables run to seed without ever forming a head.
Bacterial Soft Rot
CommonDisease
The crown or the head becomes water-soaked and soft, then collapses into a slimy mush. The rotting tissue gives off a distinctive foul odor.
Onion Yellow Dwarf
CommonDisease
Yellow streaks appear along the leaves, which twist and lodge easily. The whole plant is stunted and the bulb and leaf sheaths bulk up very poorly.
Leek Moth
CommonPest
White grazed scars and small holes line the leaf surface, and splitting the leaf reveals larvae inside. Damaged leaves snap easily and die back.
Downy Mildew
CommonDisease
Pale yellow to yellow-brown angular lesions form on the upper leaf surface with a gray-purple mold in the matching spot underneath. Lesions merge, the leaves die back and the plant declines early.
Fusarium Yellows
Disease
Yellowing starts on the lower leaves, the petioles twist and the plant leans to one side. Vascular tissue browns, growth stops, and heading vegetables may die without ever forming a head.
Late Blight
Disease
Dark green water-soaked lesions appear on the leaves and expand quickly into brown dead tissue. White mold forms on the underside and at the lesion edge, and dark brown lesions spread to stems and fruit.
Bacterial Canker
Disease
Leaf margins scorch and die back, and splitting the stem reveals browned vascular tissue. Scabby, bird's-eye lesions form on fruit and shoots.
Sclerotinia Rot
Disease
The crown, stem or head rots in a water-soaked way and is covered in white cottony mycelium. Black sclerotia later form inside and on the surface, and the plant wilts and dies.
Rust
Disease
Small raised orange-yellow to red-brown pustules form on both leaf surfaces, then rupture and release powdery spores. Heavy infection yellows the leaves and kills them early.
Southern Blight
Disease
The stem rots at soil level and white silky mycelium spreads over the crown and the surrounding soil surface. Brown sclerotia the size of rapeseed then form and the plant wilts and dies rapidly.
Anthracnose
Disease
Light brown to dark brown round lesions with sharp margins form on leaves and fruit, slightly sunken in the center. In wet weather salmon-pink slimy spore masses ooze out on the lesions.
Damping-off
Disease
The stem pinches in at soil level, turning water-soaked to brown and thin, and the seedling topples over. Infection before emergence makes the stand uneven with missing plants.
Root-knot Nematode
Pest
The plant wilts in the daytime and does not recover with feeding or watering. Pull it up and the roots carry beaded chains of galls of varying size with few fine roots.
Gray Mold
Disease
Water-soaked brown lesions form on flowers, fruit and leaves, densely covered by a fuzzy gray mold. Fruit rots and drops, and decay continues in storage after harvest.
Bacterial Spot
Disease
Small water-soaked spots appear on the leaves, later turning brown with yellowing around them. Fruit develops water-soaked or scabby spots from which rot spreads.
