Can I use extension cords for permanent landscape lighting?

No. Extension cords aren’t rated for permanent burial or long-term outdoor use — they lack proper insulation, UV resistance, and water-blocking compounds. The National Electrical Code requires listed cable like UF (underground feeder) cable or direct-bury landscape wire for underground installations. Even in conduit, moisture can degrade an extension cord over time. Use UF cable or appropriate gauge landscape wire instead.