Bunching onions are perennial alliums grown for their mild green stalks rather than a swollen bulb. They mature faster than bulb onions, tolerate cold, and can be harvested over a long window, which makes them a reliable cut-and-come-again crop for small gardens.
They grow well from seed sown directly in cool soil and can be sown in succession every few weeks for a continuous supply. Established clumps can be left in the ground; divide them in spring or fall to multiply plants. They are shallow-rooted and need consistent moisture and weed-free soil.
Downy mildew
Yellowing on top of leaves with grey-purple fuzz underneath. Spreads rapidly in humid conditions.
Remove affected leaves. Improve air circulation. Avoid overhead watering. Copper spray as preventive.
White Rust
Raised white to cream-colored pustules on leaf undersides, with yellow blotches on upper surfaces. Infected tissue may swell or distort.
Remove and destroy infected leaves. Improve air circulation and avoid overhead watering. Rotate brassicas and avoid planting in previously infected soil.
Onion White Rot
Yellowing and dieback of leaves, soft rotting at the base, and a fluffy white fungal growth with small black sclerotia on roots and lower stems.
Remove and destroy infected plants. Do not compost. Avoid replanting alliums in affected soil for several years and rotate crops. There is no chemical cure once established.
Onion Thrips
Silvery streaks and stippling on leaves, distorted growth, and tiny pale insects hiding in leaf bases during hot, dry weather.
Spray plants with water to dislodge thrips, encourage predatory insects, and apply insecticidal soap if populations build. Keep plants watered to reduce stress.