There are many ways to build garden resilience using annual crops: diversity in crop type, diversity in variety, diversity over time (repeat sowings of crops over the season to spread the risk) but adding perennials into the mix of food plants adds an extra layer of resilience. Obviously perennials include food producing trees and shrubs which, once established, keep on producing year after year.
Here though I’m going to concentrate on perennial vegetables and what they have to offer. Because perennial forms of vegetables have an established root system then they are able to withstand adverse weather events (that are likely to be increasingly more common as a result of climate change) and also predation by pest species better than annuals and also often start producing earlier in the year or spread their production more evenly over the year. Obviously the time and length of harvest depends on the type of perennial. Sea kale for example is a leafy perennial brassica and its shoots and leaves can be harvested over a long period from spring onwards, Jerusalem Artichoke on the other hand is a plant which forms tubers underground and these can only be harvested in the winter. They do last over the winter however and can be left in the ground and gradually harvested if your garden is not too wet or can all be harvested and stored in damp (non treated) sawdust and then eaten over a period of several months.
Koanga Institute holds a number of perennial vegetables which we make available either as seed (for example Sea Kale or Globe Artichoke) or through our Perennial Back Order System. Plants sold under the perennial back order system are sold as plant material (not seed) at the appropriate time of year for that plant. The collection includes many diverse items such as perennial onions and leeks, garlics (which although are cultivated on an annual basis are really perennial), strawberries, potatoes (again which are grown on an annual basis), kumara and a variety of tubers and other plants.
The group of plants sent out in the Spring is particularly diverse and includes plants we have offered for several years such as Yacon (Polymnia sonchifolia), Jerusalem Artichokes (Helianthus tuberosa), Yams (Oxalis tuberosa), Chinese Water Chestnuts (Eleocharis dulcis), and Chinese Artichokes (Stachys affinis), as well as Alpine Strawberries (Fragaria vesca), Solomon’s Seal (Polygonatum commutatum), Sorrel and Horseradish which are relatively new additions to the collection. As well as the food producing perennials we also have some perennial support plants in the collection such as Comfrey (Symphytum officinale) (both regular comfrey and a new addition Evergreen Comfrey) and some flowering plants such as Dahlias and Gladioli that add to the general diversity of the garden or orchard and, in the case of Dahlias, are absolute magnets for bees.