We've tried most of the common deer deterrant methods. Most work temporarily.
We have found that the most effective deterrent is the use of Crystalized Coyote Urine. Here is how you do it. The product is sold under the name "Shake-away".. There are several formulations, so be sure to buy Coyote Urine, not Fox Urine.
Shake-Away All Natural Deer & Large Animal Repellent (Coyote Urine Granules) 28.5 oz size - $15.95 at Amazon.com.
Do not follow the directions on the label, as the product will wash away after a rainfall. Instead do the following:
Place two tablespoons of "Shake-Away" Granules in a small piece on knotted nylon stocking. Tie a piece of string around the nylon stocking piece to form a small ball - use a length of string of about 18" to have at least a 14" piece to use for tying to a support. Next, take a small disposable plastic glass (like a Dixie Cup) and punch a small hole in the center of the bottom of the cup. Thread the long end of the string through the hole so the nylon stocking is drawn up into the cup. The cup acts as a moisture barrier, so the odor of the Coyote Urine is not washed away by rainfall. Now tie the cups around the perimeter of the area you wish to protect, hanging the cups at about four feet above the ground. We space the cups about fifteen yards apart around the perimeter of our hosta beds. If hung in the spring, you will need to replace the Coyote Urine granules in mid-summer. We have had very little damage to our hostas using this method.
The only damage we have had is an occasional nip on fragrant hostas. Deer have a definite preference for fragrant hostas...we suspect they're "sweeter."
Large dogs can also be effective guardians of the hosta patch.