Question
does the use of cedar bark on the lawn, vegetables or flowers have any detrimental effects?

Answer
Cypress, Pine, Cedar and Hardwoods are the four most common mulches on the market, usually byproducts from lumber mills.  Western, Northern and Western Cedar are all used as mulch.  (Eastern Red Cedar is NOT a Cedar, but a Juniper.)  Cedar wood is probably most famous for its longevity.  You can make outdoor furniture out of Cedar and leave it out, exposed to the elements.  You can build a deck out of Cedar.  The reason: Polyphenolic Compounds.  You smell that sweet, clean Cedar fragrance when you open a Chest made of it.

These natural acids dissolve in rain and soak the floor of high altitude forests.  Cedar is LOADED with a built-in natural defense system made of chemicals called Polyphenols.  There are THOUSANDS of different Polyphenols in Wood, Fruit and other places.  Put enough in plant leaves, and you find the plant repels Snails, Slugs and even grazing cattle.

But Polyphenols also resist attack from Bacteria and Fungi that break down Cellulose and Lignin in dead Trees.  That's why Cedar planks don't rot.  This is very good if you're growing Vegetables; researchers have found that a Potato patch, for instance, mulched with Cedar does not develop any of the common Fungal illnesses.

There's no place for Cedar on your Lawn.  But some homeowners might contemplate using some leftover bags as a top dressing or mulch.  Bad idea.  Earthworms are VERY uncomfortable around Cedar.  Poof! There goes the underground Fungal Hyphae.  Poof! There go all your beneficial Bacteria.  Plus the pH of Cedar is on the acid side -- bad for Lawngrass.

On a related subject, Mulch made from the Shells of Cocoa Beans can be hazardous to your Dog's health.  Reason: it contains a lot of Theobromine, a Xanthine Compound that smells just like Chocolate and is poisonous to Dogs and Cats.  Keep them away from it.  Better, don't use it.