Many gardeners live in cold winter areas where it's not possible to grow vegetables all year long. Even if they could, most vegetables are annuals, which means they live for a season and then die. There are a few vegetables that are perennials that, under the right conditions, continue to grow all year long.
Tomatoes are frost-tender perennial vines. If you live where winters get below freezing the vines will die. Keep the plant growing all year by feeding it every month and making sure it gets at least 1 inch of water per week. Indeterminate types will grow and produce fruit under the right conditions all year long. Temperature and humidity control blossom set. Tomatoes stop flowering in extremely high temperatures. The pollen dries before it reaches the blossoms under low humidity conditions. Cut the tomato plant back by two-thirds if it has stopped producing. Give it a dose of fish emulsion or fertilizer and it should come back.
Perennial kale is a leafy green with a slightly bitter taste. The leaves are dark green and ruffled. Break off the flower stalk if one develops to keep the plant growing. It will grow in dappled shade and appreciates protection from hot afternoon sun. Harvest by snipping leaves from the plant, rather than cutting the plant entirely off. Perennial kale likes rich well-drained soil. Keep it growing throughout the year by covering with a sheet if a light frost is predicted. It will take some frost.
Serrano peppers are very hot with a fruity aftertaste. The peppers are from 1 to 2 inches long and red. The bush grows to 24 inches but can reach 36 inches. Keep the peppers picked and the plant will continue to produce. During winter months production slows down considerably and may stop altogether until the days get longer. It is frost tender and will die if exposed to frost. Covering the plant with a sheet may protect it if the temperatures don't drop much below freezing. It won't live if the temperatures are below freezing for more than a day or two. Keep it growing by feeding it monthly.
Artichokes grow on large plants with serrated leaves up to 3 feet long. The edible part of the artichoke is the immature flower bud. It's a member of the thistle family with a deep blue flower. The plant continues to grow after flowering in warm winter areas. In early spring new growth starts and the previous year's leaves start dying. Cutting them off focuses the plant's energy on the new leaves.