You have been introduced to the first law of dealing with wildlife: repellents are not fences. You might want to visit this site to see why repellents don't always work: Why Repellents Fail
If a rabbit or woodchuck is eating the plants, you can use a cage or box trap and relocate the animal. Remember, you must have the permission of the property owner, private or government, onto whose land you are relocating the animal. If you choose not to relocate the animal, it must be disposed of in a humane way. Check with your wildlife agency or Cooperative Extension office regarding laws governing the taking of fur-bearing and game animals.
Look for deer tracks in the soil. If deer are browsing the plants, you may have to resort to a physical barrier to keep them out. In a small area, a 4-foot-high fence is usually sufficient. Fencing can also be used to keep out rabbits and woodchucks.
Try to define the type of browser you have. You may want to try sprinkling flour or baby powder around plants that seem to be next in line. You may, or may not, find tracks the next day. You would have to put down enough to make sure the culprit walks through it.
If you find you do not have wildlife visiting your plants, then the only other alternative would be insect visitors, perhaps cutworms. In that case, you may have to use an insecticide. Should that be the case, be sure to read and follow the labels and ask for help at your nursery in choosing the right product.
One of the problems with repellents is that their quality is not always consistent. Fox urine may sometimes be used as a repellent. Believe it or not, all fox urine isn't the same. It's not where the urine came from; it is what the fox was eating. Urine from meat-fed foxes is much more repellent than urine collected from foxes fed dog chow, and most commercial fox urine doesn't come from the wild. Herbivores are repelled by true signs of predators, and if our attempts to imitate them are not good, these attempts are ignored.
Visit the Wildlife Damage Inspection Decision Tree
for more assistance in identifying the culprit.