I've grown dragon fruit before and from my experience, it typically takes around 12 to 18 months for the plant to start producing fruit after planting. However, this timeline can vary depending on factors such as the variety of dragon fruit, climate, and growing conditions. I've found that with proper care, including adequate sunlight, water, and fertilization, the plant can grow quite rapidly and start flowering within a year, followed by fruit production a few months later. Some varieties may take longer, up to 2 years, but with good conditions, you can expect to see your first fruits within a year and a half.