Arugula

Pecan trees produce juglone in smaller amounts than black walnut but can still inhibit sensitive plants like brassicas

White sage produces volatile compounds that can inhibit germination of some herbaceous plants including brassicas

Both are fast-growing annuals that compete intensely for nutrients and water when planted together

Black walnut juglone severely inhibits brassica family plants including arugula

Shagbark hickory produces mild allelopathic compounds that can affect sensitive crops like arugula