Avoid the dishwasher. Always.
Your wooden spoons will get darker; they'll get stained, dented, scratched (that's patina!), and they'll still work great and look beautiful. All you need to do is hand wash in warm soapy water and let dry. If your spoons gets dry (which they will over time), you can refinish them with some oil and wax solution. Any cutting board oil would work, most of them are mineral oil and some have some beeswax mixed in.
Check back soon - I'll have my own spoon oil available in my shop.