Extreme Cold: High Mountains and Frozen Northlands

This region covers most of inland Canada as well as the northern U.S. plains and the Rockies. It corresponds with USDA Zones 1–3, and Sunset Zones 1, 44, and 45. Note that heavy snow cover can provide excellent insulation in this zone, but the short season and lack of hot summers are serious limiting factors.

Perennial in all of the Extreme Cold zone:

Helianthus tuberosa sunchoke

Hemerocallis spp. daylily

Matteuccia struthiopteris ostrich fern

Nasturtium officinale watercress

Oxyria digyna mountain sorrel

Rheum rubarbarum rhubarb

Sagittaria latifolia arrowhead

Perennial in warmer parts of the Extreme Cold zone, or perennial with protection:

Allium fistulosum Welsh onion

Allium tricoccum ramps

Allium tuberosum garlic chives

Apios americana groundnut

Aralia cordata udo

Asparagus officinalis asparagus

Bunias orientalis Turkish rocket

Chenopodium bonus-henricus good king Henry

Cicorium intybus chicory

Crambe maritima sea kale

Dioscorea japonica jinenjo

Dioscorea opposita Chinese yam

Laportaea canadensis wood nettle

Levisticum officinale lovage

Oenanthe javanica water celery

Petasites japonicus fuki

Phytolacca americana pokeweed

Polygonatum biflorum canaliculatum giant Solomon’s seal

Rumex acetosa French sorrel

Rumex acetosa ‘Profusion’ sorrel

Rumex acetosella sheep sorrel

Rumex scutatus silver shield sorrel

Scorzonera hispanica scorzonera

Sium sisarum skirret

Stachys sieboldii Chinese artichoke

Taraxacum officinale dandelion

Tilia spp. linden (as a dieback perennial in colder areas)

Urtica dioica nettles

Can be grown as annuals in the Extreme Cold zone:

Brassica oleracea acephala ‘Western Front’ perennial kale

Diplotaxis spp. sylvetta arugula

Solanum tuberosum & spp. potato