Perennial Kale

Brassica oleracea

Perennial kales survive USDA zone 7 and warmer. Some varieties may survive north of USDA zone 7 if protected. Also called Tree kale Perpetual kale, Tree cabbage.

Varieties include:
Daubenton (B. oleracea var. ramosa)
Walking Stick (B. oleracea var. longata)

Another recently available perennial variety, Kosmic Kale, is hardy to about 10°F, possibly survives lower temperatures once established.

Common kales are biennial, usually grown as annuals. Will survive 25 to 28°F. Has overwintered in a cold-frame in USDA zone 6a, harvesting only lower leaves.

Tree Collards

Brassica oleracea

Purple Tree Collards (in photo) - Tree collards are a very rare perennial vegetable. Reaching over 6 feet (1.8 meters).

Michigan Tree Collard - A reported USDA Zone 6a cold-hardy purple tree collard from horticulturist, Ken Asmus in Michigan has survived lower Great Lakes winters. From: www.projecttreecollard.org and oikostreecrops.com

Mixed data on USDA grow zones is likely due to experiments on different varieties. 

Common collards are biennial in moderate climates returning in spring to make flower stalk and seed. Mildly cold hardy and usually grown as an annual in USDA Zone 6a. Survives below-freezing temperatures, but below 20°F may kill them. Plant in sheltered micro-climate (e.g., cold-frame).

Good King Henry

Mountain Spinach

Hablitzia tamnoides

Also called Caucasian spinach. Shade-loving native to Caucasus region. Hardy perennial (slow-growing first year).

Long-lived climber, grows 6-9 feet (2-3 m). A plant in Norrtälje, Sweden reported over 50 years old. Prefers to be out of full sun.

Raw or cooked. Young particularly delicious. Older good eating (not develop bitterness once mature), however leaves in full sun are better cooked. 

Wild Kidney Beans

Phaseolus polystachios

Also known as Bean-vine, Thicket bean, Wild bean. Perennial, herbaceous vine native to North America. Range extending across eastern temperate US to southeast Canada. Once common, now rare.

Frost hardy climber (20 ft, 6m). Some resistant to -30° F (-35° C). Long lived and deep rooted.

Multiplier Onions

Allium cepa aggregatum

Potato Onions - Among the most productive of vegetables. Yellow and white varieties. Grown only from division of bulbs. Can be perennial if left in the ground.

Shallots - Mild and popular. Grown from bulb or seed.

Walking Onions

Allium cepa proliferum 

Also known as Tree, Topset, or Egyptian onion. Forms clumps of bulbs. Evergreen in mild climates. Brown and red skinned varieties. Can be perennial if left in the ground.

Long stems have bulbils which, if they touch soil, will root. Bulbs and bulbils can be eaten.

Overwintering Onions

Allium fistulosum 

Also known as Welsh onion, grown as annual scallion. Divide clumps for spring scallions and for replanting. Can be perennial if left in the ground.

Dakota Winter - Hardy, perennial, green bunching onion. One of spring's earliest. 

Heshiko - Hardy bunching onion.

Evergreen Hardy - Reliably overwinters in Michigan. Exceptionally cold-hardy.

Cutting Celery

Apium graveolens secalinum 

Also called Leaf celery. Grown for its flavorful leaves and stems. Stronger taste than stalk celery. A very old herb.

Usually listed as biennial but has over-wintered in Great Lakes region (USDA Zone 6a). When grown as a biennial, lush foliage in first year (best for eating), sets seed in second year. Crush seed heads into soil for new growth.

Lovage

Levisticum officinale 

Hardy perennial herb, part of Apiacaea family (e.g., carrot, celery, parsley).

Ancient, once common, used in entirety for its leaves, roots, stems, and seeds.

Also reseeds readily, but not invasive.

Horseradish

Armoracia rusticana

Perennial known for pungent root used as spice and condiment. Root vegetable in mustard family (e.g., broccoli, cabbage, kale). Cultivated worldwide as spice and condiment. 

Large taproot and smaller offshoots. 

Sunchoke

Helianthus tuberosus

Also called Jerusalem artichoke Sunroot, Wild sunflower, Earth apple. 

Species of sunflower grown for its tuber that looks like ginger and taste like potato .

Spreads very readily. Rapid growth and ability to reproduce from buried rhizomes and tubers results in easy spreading.

Sorrel

Rumex acetosa

Also called Common sorrel, Garden sorrel, Spinach dock. Three commonly used for culinary use have similar flavor:

Garden sorrel (Rumex acetosa).
French sorrel (Rumex scutatus).
Red-veined sorrel (Rumex sanguineus).

French is less bitter, grows taller with smaller, more rounded leaves. Grown from seed or by dividing clumps. 

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Sea Kale

Crambe maritima

Also called Crambe, Sea cabbage, Sea colewort.

Shoots grow from roots. Tender shoots eaten like asparagus, and can be eaten raw. Large leaves prepared and used like spinach or garden kale (older leaves often bitter and tough). Fragrant blooms edible. 

Best in full sun, and in deep, well-drained soils.

Turkish Rocket

Bunias Orientalis 

Also called Turkish wartycabbage, Warty-cabbage, Hill mustard. 

Very hardy, in brassica family. Main edible part are young florets, cooked like broccoli raab. 

Incredibly drought resistant due to massive, deep roots. Tolerates part shade. Averages 2-3 feet tall. 

Black Salsify

Pseudopodospermum hispanicummex

Also called Spanish salsify, Black oyster plant, Serpent root, Viper's herb, Viper's grass, Scorzonera.

Nutrient-dense root vegetable. Grows in full sun in poor soils 1 to 3 feet (30-90 cm). 

Replaces potatoes in recipes.Treasured in Medieval era. 

Asparagus

Asparagus officinalis

Grown for its succulent, immature shoots. Produces spears 15 years or longer. Harvest spears when 6 to 8 inches tall.

Prefers full sun and soil that is slightly alkaline (pH of 6.5 to 7.5). 

American Groundnuts

Apios americana

Also called Potato bean, Hopniss, Indian potato, Hodoimo, America-hodoimo.

A perennial vine that bears edible beans and large starchy, protein-rich edible tubers. Above-ground vine is frost-sensitive, dies back completely after frost. In warm climates with long growing seasons, second year plants can grow as tall as 20 feet.

Full sun in USDA zones 3-7. 

Rhubarb

Rheum rhabarbarum

The fleshy, thick, sour, edible stalks (petioles) of species and hybrids. Often used in desserts like pies and jams.

The leaves are toxic and should not be eaten. May remain productive for five years or more.

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Welsh Onion

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Ramps

Allium tricoccum

Also called Ramson, Wild leek, Wood leek, or Wild garlic. A edible native wildflower and favorite of foragers. 

Ovoid-conical bulb that is 1-2 inches (2-6 cm) long. Typically produce cluster of 2-6 bulbs that give rise to broad, flat, smooth, light green leaves 8-12 inches (20-30 cm) long including the narrow petioles, often with deep purple or burgundy tints on lower stems.

Can take seven years to harvest from seed and three years from bulbs. 

Babington’s Leek

Allium ampeloprasum babingtonii

Rare perennial of the onion family. Edible young spring leaves and early fall bulbils.

Full sun, tolerate variety of soil types. Winter hardy to USDA zones 5-9. Slowly multiplies from underground bulblets.

Height to 5-6 feet (1.5-1.8 m).

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Brassica oleracea

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Spinach

Spinacia oleracea

Has vast array of varieties (cultivars). Super–cold-hardy leafy green.

Best grown as annual. However, there are extra cold-hardy varieties that can overwinter in USDA zone 6 or warmer and in a cold-frame.

Chard

Beta vulgaris

Also called Leafy beet, Mangold, Perpetual spinach, Silver beet. Has vast array of varieties (cultivars).

Best grown as annual. Hardy to about 15°F. Swiss chard may overwinter in mild areas. Has overwintered in a cold-frame (USDA zone 6a).