Allium platycaule aka Broadstemmed Onion

Allium platycaule, or broadstemmed onion, belongs to the Amaryllidaceae family. It is a small bulbous plant from the western United States. Kew places its native range from southern Oregon to northwestern Nevada. Plants For A Future also lists California within its range. It grows in a temperate climate. Wild plants occupy dry flats, loose scree, and sagebrush slopes. These sites lie at 3,937–9,843 feet [1,200–3,000 metres].

The plant reaches about 0.33 feet [0.1 metres] in height. Its bulbs form groups along a rhizome, an underground stem. Each bulb measures about 0.07–0.11 feet [0.02–0.035 metres] across. This low growth suits a place in cultivated beds. Flowers appear from May to June. Each flower has both male and female parts. Bees and other insects pollinate them. The supplied species account gives no flower colour or leaf shape.

Grow this onion in full sun, with soil that drains well. It does not grow in shade. Sandy and loamy soils both suit it. It accepts mildly acid, neutral, and mildly alkaline ground. The soil may be dry or moist. Plant the bulbs fairly deep, as Plants For A Future advises. That source lists USDA hardiness zones 5–9. It also gives UK zone 6, without an RHS hardiness grade.

The bulbs and leaves can be eaten raw or cooked. The leaves add an onion taste to relishes. Raw flowers can serve as a salad garnish. The seeds are another edible part. The account describes briefly heating seed heads in hot ashes. The seeds are then removed for eating. It rates the plant's food value at three out of five. It also records the juice as a moth repellent. Claims that the whole plant deters insects and moles remain reported uses.

Propagation uses seed or division. Sow seed in a cold frame in spring. Move seedlings into pots once they are large enough to handle. Keep young plants under glass through at least their first winter. Plant them out in spring once growth is strong. Divide plants in spring, or during their growing season. Let divisions establish under cover before planting them outside. Plants For A Future does not flag this species as weedy. The supplied evidence establishes no species-specific poisoning or pest problem.