Riverside winters are mild, but nights still drop. A cold frame stretches greens, herbs, and starts without committing to a full greenhouse footprint.
Pick a twinwall polycarbonate lid that holds heat and shrugs off Inland Empire sun. Set the frame on a level bed with good drainage, face the lid south, and crack it open on warm afternoons so seedlings do not cook.
Use it for lettuce and spinach from late fall through early spring, or harden greenhouse transplants for a week before they go into the yard. When you outgrow the frame, the same panel logic carries into a backyard greenhouse kit.
Shop cold frames and polycarbonate panels at Greenland Nurseries — free shipping across the United States, pickup at 8200 Victoria Ave.