Would strongly suggest you get a copy of Michael Dirr's Hydrangeas for American Gardens. Dirr is the godfather/guru of hydrangeas, especially the rebloomers, and his book is invaluable. In fact, I highly recommend any and ALL of his books!!

I do have Michael Dirr's "Manual of woody landscape plants" revised in 1998, which has a section on hydrangeas, but it doesn't contain a basic overview of the varying types. As I look at it and read individual plants I do see them labeled with the same categories as the website I linked. I checked amazon for the book you recommend and it's pricey at around $50. I am really only looking to get a handle on the main groups and their basic traits. I read descriptions and see Aspera, Macrophylla and petiolaris and didn't know what that referred to. I'm getting a better picture as I read more.

Check out your library. They should carry it.

IMO, still worth buying if you are focusing towards a horticultural business of any type. Dirr's books are essentials of my gardening library.

The genus of Hydrangea probably contains much more than 50 types of hydrangeas, with the majority not being available here in the US in large, sustainable numbers so you rarely hear about them until a nursery imports and starts selling them. Dirr also limits the list of different types of hydrangeas in his book to mostly those sold in large numbers here. Some types of hydrangeas and close relatives that I have run into/seen pictures: Macrophylla (also known as Big Leaf Hydrangea, French Hydrangea, Hortensia, Milflores, Christmas Roses, Lacecap Hydrangea, Mophead Hydrangea, etc.); Arborescens (aka Wild Hydrangea, Smooth Hydrangea, Snowball Hydrangea, Sevenbark Hydrangea, Hills of Snow Hydrangea); Serrata: (aka Mountain Hydrangea, Blood-on-the-Snow Hydrangeas, Sawtooth Hydrangeas, Tea of Heaven Hydrangeas); Paniculata (aka Panicle Hydrangea, Pee Gee Hydrangea); Quercifolia (aka Oakleaf Hydrangeas); Aspera (aka Rough Leaf Hydrangea, Grape Hydrangea but Grape is used only when referring to sub-species Sargentiana); Involucrata (aka Bracted Hydrangea); Heteromalla (aka Woolly Hydrangea, Himalayan hydrangea or Chinese hydrangea); Petiolaris/Quelpartensis (aka Climbing Hydrangea); Sikokiana (aka Shikoku Mountain Hydrangea). Schizophragma (aka Japanese Climbing Hydrangea), Decumeria (Evergreen Hydrangea); Hirta (aka Nettle-Leaved Hydrangea); Cardiandra alternifolia/formosana (aka Herbaceous Hydrangea). Sorry for any typos. Listed in the order that I remembered them. ;o)

If you want to add Aspera, Involucrata plus the other vines/climbers to the list of hydrangea types to Plant Addicts’ list, you will then have the most often sold types here. Note: the hydrangea information in their website is not theirs but was purchased from someone else who had an unrelated website with that information/pictures. While they make corrections now and then, I have not seen them add much to the hydrangea information.

@luis_pr That's a curious note. Do you have a link to the original website?

Thanks

The original website was "absorbed" into plantaddicts.com and then was discontinued in the late 2010s… maybe. If you tried going to the old link back then, it automatically redirected you to plantaddicts.com and did not display the old website. The old URL probably still redirects or gives you a 'not found' error message.

That old (2001) URL for the website belonged to a then blogger/author/horticulturist/enthusiast called Judith King and her original website URL was hydrangeashydrangeas.com I lost contact with her since the sale of the website somewhere in 2015-2017??? Memory fails me. She used to live in Virginia and then Tenessee and went to work for Plant Addicts. Not sure if she is still there working though.

Consider going to Half Price Books to find cheaper, used versions of Dirr’s books with lower prices.