By Jeanne Yacoubou, MS
In Parts 1 and 2 of our series on climate foods, The Vegetarian Resource Group introduced perennial vegetables and suggested general techniques to grow a perennial garden. In this article, we’ll help you select perennials that will most likely do well in your particular situation.
Beyond USDA hardiness zones: sunset climate zones
The USDA Plant Hardiness Zone Map is the standard way gardeners decide whether a certain species will do well in their yard. It is based on “the average annual extreme minimum winter temperature.” You determine your zone by zip code.
However, this method has limited usefulness because it’s only concerned about the temperature at which a plant could be killed by frost. It doesn’t consider all the factors involved in allowing a plant to thrive.
The Sunset Climate Zone system is a more robust measure to figure out if a plant species will do well in your yard. This rating takes into account:
- Length of growing season
- Timing and amount of rainfall
- Winter low temperature
- Summer high temperature
- Wind
- Humidity
- Sun exposure
Initially designed for gardeners on the West Coast, the Sunset system now covers the entire country.
When researching the best perennial vegetables for your yard, look for Sunset zone information to maximize your success. Eric Toensmeier’s book, Perennial Vegetables, on which the following recommendations are based, is an excellent source for Sunset information about uncommon perennials.
Best perennial vegetables for the Rocky Mountain states, northern plains, and Canada (USDA zones 1-3, Sunset zones 1, 44, 45)
It may be extremely cold and snowy for long periods, but herbaceous plants and roots do amazingly well snuggled under insulating snow. These are your best bets:
- Sorrel
- Good king Henry
- Groundnut
- Arrowhead
- Rhubarb
- Sunchoke
- Ostrich fern
- Watercress
Best perennial vegetables for the mid-Atlantic, Northeast, and Midwest (USDA zones 4-7, Sunset zones 2-4, 6, 11, 32-43)
Most perennial vegetables are from tropical countries but grow well in regions that typically have cold – but not frigid – periods in winter. Adding a thick (6-12 in.) layer of mulch around the base of plants helps protect them during cold spells in these relatively temperate areas.
Alternatively, growing perennials as annuals will maintain their productivity over the years. For instance, you can store edible roots or tubers in a cool (35-500F), dark basement or garage just like you do with potatoes. Take cuttings from herbaceous plants and keep them inside as houseplants over the winter, returning them outside in spring. Place them next to a window or under full-spectrum lights.
For plants that are very delicate, such as chaya, you may permanently grow them in a container that you place outside during the spring and summer but bring inside for the winter.
Lastly, for perennial trees and woody shrubs with edible leaves whose above-ground parts die after the first frost but where the ground won’t freeze, they will resprout new growth the following spring. These species – referred to as dieback perennials – include chaya, katuk, moringa, and cranberry and edible hibiscus.
For gardeners in this area of the country, the following tables list the perennials that can be grown as annuals.
Species that can overwinter inside from cuttings:
- Katuk
- Okinawa spinach
- Perennial cucumber
- Tree collards
- Sissou spinach
Species that can overwinter indoors as tubers:
- Achira
- Chinese arrowhead
- Oca
- Ulloco
- Water chestnut
- Yacon
Perennial vegetables that can be started from seed as annuals:
- Cache bean
- Cranberry hibiscus
- Lablab bean
- Malabar spinach
- Runner bean
For more information on methods used to grow perennials in cold regions, see the books Palms Won’t Grow Here and Other Myths by David Francko and Hot Plants for Cool Climates by Dennis Schrader and Susan A. Roth.
Best perennial vegetables for the hot and humid Southeast (USDA zones 8-9 and Sunset zones 26-28, 31)
Having originated from tropical regions, most perennials thrive in the Southeast. Bananas and chayote are prime examples. You could also cultivate yams, katuk, and perennial beans as dieback perennials. Growing taro in this area is easy.
Best perennial vegetables for the hot and arid Southwest (USDA zones 8-10 and Sunset zones 10, 12, 13, 29, 30)
Like the Southeast, the Southwest U.S. is ideal for growing most perennial vegetables. Moringa trees and chaya shrubs are perfect candidates for dieback perennials because of their edible leaves, joining the spineless nopale cactus frequently grown in gardens of this region. The drought-loving, 7-year lima bean is one of several perennial beans that thrives here. Several species of fruiting cacti, as well as pomegranates and mesquite, round out perennial gardens in the Southwest.
Key takeaways on perennial vegetable selection
Of the 100+ perennial vegetable species, there are sure to be several that can thrive under almost any climatic condition. Some others may be adapted to zones when grown as annuals or dieback perennials. To determine which would be best suited for your garden, research your options before planting.