Horseradish

Armoracia rusticana. A hardy perennial root crop (zone 4), well known for its use as a condiment. Leaves are also widely used in pickles and ferments, to add flavour and preserve crispness of cucumbers. If planted in the spring, some root will be harvestable in the fall, but harvest will be bigger if roots are allowed to establish. Can grow in full sun or partial shade; prefers moist soil (but not very wet).
When buying horseradish, you will get several pieces of root; each will grow a plant. This allows to quickly start a sizeable patch. Plant in deeply cultivated soil to obtain the straightest roots. Roots can grow as long as 2 ft and as wide as 2 inches. Note that plants may become invasive, since they grow back from the smallest piece of root. To prevent spread, do not till the soil near the plant, and consider growing in sunken containers.