How do I clean an old macrame plant hanger?

Hand wash with vinegar, baking soda and some dish soap. Rinse until water runs clear, then hang in shower or bathtub to drip dry.

Do you have any of those mesh bags for washing delicates in the machine? You could put the plant hangar in one of those, and wash in your machine on delicate, using a product like OxyClean.

I'd handwash especially if it has any wood beads (as vintage hangers often did.) You can also hand soak in an OxyClean solution. Rinse well then hang to dry.

If your hanger is made of brown jute, I would not use water to clean it. This will make it rot! I have many jute hangers and I just spray with Frebreeze to make them smell better.