I've often wondered the same. Surely those who know all of these plants must have a photographic memory, right? I don't know any other way they could memorize and retain the knowledge of so many plants.

rp actually hanging out on this forum is a great way to get familiar with plants that we have not grown. There are folks like floral that have astounding general knowledge, Jay that knows native plants of NA, macanthros & gg that live on the west coast, fig_insanity and many others. I only know what I know but have learned a great deal here. Stick around!

"encyclopaedic botanical knowledge"?? No way! But several decades in the nursery industry and a professional career as a consulting horticulturist and garden designer has certainly left me with a pretty big mental plant database to which I refer. I also just seem to be very plant focused wherever I go and notice them, especially ones I might not encounter that frequently.

It's the weeds and natives that tend to trip me up. I recognize a lot of weeds but don't really care what they are :-) And a lot of native plants are not native to my locale so seldom seen and therefore not included in my personal plant database. Local natives are a different story.

I'm not able to id that many things, but a book about botany for gardeners helped me. I'm more ofen able to at least narrow down to family. I wish I could remember which book I had used but it was a long time ago.

Decades of botanical scrutiny and I still feel barely competent. Everywhere I go, I try to ID everything, so it’s all about kaizen.

My memory is far from photographic, and my knowledge far from encyclopedic. What I DO have is an insatiable curiosity (one reason I hang out here; thanks guys and gals!), and a broad general experience with plants. I've killed a lot more than I grow: I've grown over 3000 distinct plants (by genera/species/variety) at one time or another. That includes plants hardy, tropical, annual, perennial, et al.

When I run across a plant I don't know, I try to mentally file away its general impression, and when I ID it, I then research what the defining characteristics are for that plant family. What makes a malva a malva? Members of Malvaceae are easy, but you get the point.

Hang around here long enough and you actually absorb a lot by osmosis, lol. Once you narrow it down to family/genera, there are always plant keys...and Google.

I will admit to one geeky thing from my past. When I was in my late teens, I got a Wyman's Gardening Encyclopedia for Christmas. I read it cover to cover, annotated the margins, and spent years finding pictures of the plants I'd never heard of...and this was pre-internet. Yeah, it was VERY geeky.

Practice. Lifelong abiding interest, well since about age 3. No training.. I don’t make notes, either physcal or mental and keep no records. I remember walking routes by the plants rather than the scenery. . I’m very short sighted so I peer closely and see detail. The ipad is very good at zooming in. I frequently don't know what a thing is exactly but I can usually tell a plant family and then can take it from there. That said, I know nothing about plants from Africa, Australasia or Asia.

It certainly helps if people can describe scent, habit, size and texture rather than just posting a picture taken from above, or worse, from their car.