How many words does a botanist have to say a plant is hairy? Canescent, ciliate, hirsute, hispid, lanate, pillose, pubescent, tomentose, villose: this is not a complete list, and most of these can be modified… but to take these in alphabetical order:
Canescent indicates enough usually soft, short hairs to give the plant a gray or hoary color. So Desmodium canescens is Hoary Tick Trefoil, and Scutellaria incana is Hoary Skullcap.
Ciliate means with a fringe of hairs. In the case of fringed loosestrife, Lysimachia ciliata, that fringe is only found on the leaf petioles. Blephila ciliata, Downy Wood Mint is described by The Flora of Virginia as having canescent stems, while Desmodium canescens has ciliate leaves. Oh, well.
Hirsute indicates a thick covering of stiff hairs. There are lots of plants with this name, of varying hairiness: Hypoxis hirsuta Yellow Star Grass is pretty visibly hairy; Cardamine hirsutis the non-native Hairy Bittercress requires more careful observation to find the hairs.
Hispid is like hirsute, but with fewer, stiffer hairs. The invasive exotic grass Arthraxon hispidus Joint Head Grass has stiff enough hairs for anyone, while Bristly Greenbriar Smilax hispida pushes beyond merely hairy.
Lanate means wooly, as in Velvet Grass, Holcus lanatus an invasive exotic that is nevertheless very pleasing to the fingers.
Pilose means covered with soft, straight hairs. This is sometimes the case with Symphyotrichum pilosum var. pilosum, which The Flora of Virginia describes as having stems that are “pubescent to pilose-hirsute or villous.” Now all we need are definitions of pubescent and villous. Onward!
Pubescent means covered with short, soft hairs. So if you feel the stem or leaves of the downy yellow violet, Viola pubescens, or examine them with a hand lens, you may detect the hairs there. If those hairs are lacking, you may have a smooth yellow violet, Viola pensylvanica, instead.
Tomentose describes densely matted wooly hairs, like those on the undersides of leaves of Princess Tree, Paulownia tomentosa, or Mockernut Hickory, Carya tomentosa.
Villous hairs are similarly long and may be shaggy but not matted, as on Hairy Alumroot Heuchera villosa or Carolina bushpea Thermopsis villosa.
Add in all the diminutives, like hirtellum, hirsutula, hispidulum, or puberulum, and the superlatives like villosissimum, and you have a topic that could be described as not just hairy, but tomentose!