Start New Zealand spinach just after the last frost in spring to give the plants a long, warm growing seasons. This plant doesn't tolerate frost and fails in early, cool-season plantings. Give the plant 55 to 65 days of frost-free growing time.
Plan the spinach garden in a site with full sun all day, good air movement and quick drainage. Allow 5 to 10 feet of space for multiple New Zealand spinach plants. This plant doesn't become overly large but does best in airy, spacious plantings.
Amend the soil at planting to give New Zealand spinach rich, loamy and moist soil. Dig into the top 6 to 8 inches of soil and turn in up to 4 inches of organic compost. This vegetable thrives in soil with high organic content. Add 10-10-10 granular fertilizer, per manufacturer directions, to increase soil nutrition for rooting and growth.
Plant New Zealand spinach seeds 1/2 inch deep spaced every two to four inches in the row. Leave 12 to 24 inches between multiple rows for gardening space. Expect seed germination in 14 to 21 days.
Water New Zealand spinach with 2 inches of water every week to maintain soil moisture, and lay 2 to 3 inches of organic mulch over the soil to keep the foundation moist and warm.