How to Build an Outdoor Seed Starter Box

Cut the plywood into four sections, each 2-by-4 feet. Cut one of the 2-by-2s into four 2-foot pieces and the other two into four 4-foot pieces. Place the 4-foot pieces aside, since these are for the lid.

Place the four 2-by-4 foot sections together to form a box. Nail one 2-by-2 in each corner of the cold frame strengthening and stabilizing the corners.

Find a location for the cold frame with at least a half day of sunlight.

Dig a trench 6-inches deep in the front for the cold frame and taper it off along the sides. Place the cold frame in the trench and pack the soil against the sides, holding it in place.

Build a frame for the cover by connecting the four 4-foot pieces of 2-by-2s. Overlap the sidepieces to the front and back pieces.

Put the fiberglass molding pieces on top of the box frame. Place the 4-by-4-foot piece of fiberglass on top of the molding.

Drill holes every 6 inches through the fiberglass to prevent breaking it when securing it to the molding. Use screws to secure it in place.

Place the landscape fabric in the bottom of the box to keep the bottom of seed trays clean. This box holds eight standard nursery seed trays that measure 21-by-10-1/2 inches.