How to Build a Heat Lamp for Starting Seeds

Place your seedling tray into a tabletop greenhouse or dome propagator. These are available online or from home improvement stores. If you can't find a propagator or a greenhouse use a clear plastic container that fits over your seedlings. You'll need to drill a couple of holes in the plastic to allow a small amount of airflow. The goal is to keep warm air around the seedlings.

Insert standard, incandescent floodlight bulbs into a floodlight shop lamp. LED bulbs will last longer but they don't produce enough heat. Halogen bulbs produce more heat but may pose a fire danger if they're left on unattended. Use standard bulbs and add a second floodlight if you need additional heat.

Clamp the floodlight on a table or shelf close enough to the greenhouse that it heats the air inside. You don't want it close enough to heat the plastic itself. This may take a little trial and error. Add a second light if you have a large area to warm.