This section is from the book "The Gardener's Monthly And Horticulturist V23", by Thomas Meehan. See also: Four-Season Harvest: Organic Vegetables from Your Home Garden All Year Long.
It is the general belief among Pennsylvania farmers that laurel leaves are poisonous, and that the instinct of sheep will not prevent them from browsing upon them.
Recently I noticed the owner of a wood in this borough carefully cutting and removing every laurel bush previous to turning in a flock of sheep. I remember reading about fifty-five years ago of the case of a family a few miles from Philadelphia being poisoned by eating pheasants which had eaten laurel leaves. An examination of the gizzards disclosed the cause of the trouble.
A statement of the case was published in one of the medical journals of Philadelphia, and the physicians said that no danger would have resulted from the use of these birds had the entrails been removed soon after they were killed, but when several days had elapsed the poison had thoroughly permeated the flesh.
I believe it is not generally known that the leaves of the Ailanthus are poisonous, yet I have been assured by Spencer Neal, of Burlington, N. J., that he had three cows to die from eating them. In general it appears that the instinct of cattle prevents them from eating of these leaves, but in this case a rail was broken, the cows were reaching for corn in the adjacent field, the young ailanthus suckers were in their way, they ate them, and in a few hours were all dead.
[It seems proper to state that our doubts about the Kalmia being poisonous to sheep arises from the fact that chemical analysis has failed to find any poison in Kalmia leaves. Reflecting on this curious state of the case, it seemed to us probable that the character has followed the name. The European Laurel, Cerasus lauro-cerasus, is certainly poisonous to sheep. The poison, prussic acid, can be taken by the chemist from the leaves. Because the Kalmia has broad evergreen leaves, and because the Rhododendron and some other things have been called "laurel,"they must needs be poisonous. This is of course, but a supposition. In the meantime if there is poison in the leaves of the Kalmia, we should like to know by what name this poison is known to chemists? - Ed. G.M.]