By Peter Beiersdorfer
Tuesday, September 15, 2026 – 7:00 pm Pacific Time (California)

Members and visitors can attend in person in San Francisco,
or watch on Zoom.

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Program Description

When we read that some species of Lithops (or some species in any other genus) has been found to be synonymous with another species, or is actually a hybrid, we tend to accept that this determination has been made by a diligent researcher and has a basis in fact. In the course of his research on Lithops, Peter has found that this is not always a good assumption. By carefully reading old accounts of the discovery of different species, and tracking them down with all the clues available, he has found that quite a few plants have wrongly been cast aside by what he calls taxonomic malpractice, when they are in fact perfectly good species. Bringing valid taxa back is of utmost importance for conservation – species that are discarded no longer need to be protected and are truly on their way to extinction; their status of non-existence will be self-fulfilling. In his presentation, Peter will share his adventures in search of plants that have been “legislated out of existence” by armchair botanists peddling misinformation.

About our Speaker

Following his retirement from paid research in physics, Peter has switched to unpaid research in botany. Since the end of 2020 he has been spending about 9 weeks per year in Namibia searching for Lithops, although recently he also ventured back to the Canary Islands. At his home in Livermore, Peter propagates plants from seeds and cuttings, including mesembs and bulbs from the winter rainfall areas of Southern Africa and many cactus species from South and North America.

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Meeting Agenda

7:00 Mingling and announcements
7:30 Formal presentation starts promptly with Society business
7:35 Show and Tell Table
7:50 Leg stretch
7:55 Featured presentation

Show & tell table 
Succulent: Conophytum and Lithops
Cactus: Uebelmannia 
Caudiciform-Pachycaul: Ipomoea & Pyrenacantha
plus anything else that’s looking good or in flower.

Featured grower: PB&J Cacti & Succulents (Peter and Jaan)

Snack table: Some basics are provided by the club, but we suggest bringing something to share every couple of months if you partake regularly. As a thought, we are often short on drinks. 

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Watch Online

On Zoom: Register or join the meeting in progress.

We will attempt to simulcast on our YouTube channel.

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