(Besides horsetail, the other words that could have followed loathers were chelators, chlorates, clathrose, helarctos, trochleas, trehalose, isotheral, and plethoras.)
There are at least two words that can follow HORSETAILS. (Add an M or a P.)
Mac, I'm assuming you are assisted by some program?
Do either of the two answers involve thor?
SCoates, the point of this particular game is to add a letter to the previous word that will form a single word that can be found at
www.m-w.com - or at least isn't rejected at
www.m-w.com ...