Ask Mr. Smarty Plants

I think the key word there is going to be "reach." Cows are ruminants, and have stomachs divided into four parts to help them digest the very rough food available to them, with lots of cellulose in it. Their ordinary food source would be grass, but dairy cows are fed silage (fermented grasses, alfalfa or corn), hay and corn, although corn is now scarcer, because it's being used to make ethanol. You don't even want to know what they get fed in feedlots. Obviously, what your neighbors have are cows that are expected to eat grass and maybe a nice snack of clover in their field. The grass supply may be low or they may just be shopping about for a bit of variety when they get to your fence. Wouldn't you prefer a nice tender bloom to grass? If you were a cow. Since they can digest all that really tough stuff, it's unlikely we're going to find a cow resistant plant, or even one they won't at least try.

So, the first thing we would suggest is that you plan to move your decorative garden plants far enough away from the fence that the cows can't reach them. Between that garden and the fence, a row of some fairly fast-growing native shrubs will provide both protection and a screen for the fence. They still will probably try to nibble the shrubs (the grass/flowers/shrubs are always greener on the other side), but if it's something pretty tough and hopefully tasteless (to a cow) maybe they'll decide to go back to grass.We're going to suggest some shrubs that can be attractive from your side and hopefully unappetizing on the cow's side. When you get down to it, though, a cow will eat just about anything, so you might want to measure how far a cow can get its head through your fence, and then allow for a shrub to grow in circumference, and plant it far enough away that the cow can't even get at the shrub. The bad thing about this is that it reduces your own garden size, but hopefully it's only one side of your yard that shares a fence with the cows.

Shrubs or shrubby flowering plants that have some blooms or interesting leaf colors are Lantana urticoides (West Indian shrubverbena, Malvaviscus arboreus var. drummondii (wax mallow), Rhus copallinum (winged sumac) and Viburnum acerifolium (mapleleaf viburnum). Shrubs that are more solid background for shorter plantings of flowers are Morella cerifera (wax myrtle), and Ilex vomitoria (yaupon). Any one of these or a mixture can be used as a decorative screening hedge. Just remember-measure how far the cow can reach and put the plants farther than that!

Lantana urticoides

Malvaviscus arboreus var. drummondii

Rhus copallinum

Viburnum acerifolium

Morella cerifera

Ilex vomitoria