Xanthium argenteum Widder (original description)
Xanthium bushii Widder (original description)
Xanthium californicum Greene & Widder (original description)
Xanthium californicum var. oligacanthum Widder (original description)
Xanthium canescens (Costa) Widder accepted as Xanthium spinosum L. (original description)
Xanthium chrysacanthum Costa ex Widder (original description)
Xanthium decalvatum Widder accepted as Xanthium strumarium L. (original description)
Xanthium inflexum Mack., Bush & Widder (original description)
Xanthium japonicum Widder accepted as Xanthium strumarium L. (original description)
Xanthium saccharatum Wallr. & Widder (original description)
Xanthium saccharatum var. silphiifolium Widder (original description)
Xanthium saccharatum var. speciosum Widder (original description)
Xanthium saccharatum var. wootonii Widder (original description)
Xanthium shullii Widder (original description)
Xanthium sibiricum Patrin ex Widder accepted as Xanthium strumarium subsp. sibiricum (Patrin ex Widder) Greuter (original description)
Xanthium spinosum f. laciniatum Scheuerm. & Thell. ex Widder accepted as Xanthium spinosum L. (original description)