Mary Gerritsen

Phone: 650-520-6039 Email:

Specialtiesconservation, world travel, miniature and much more
FormatOnline and in-person
Provides plants for sale?No


Mary has been interested in plants for most of her adult life, and has been growing orchids on and off for the last 40 years, despite several cross country moves as part of her “other life” as a biomedical scientist. Her passion for orchids was rekindled when she moved to the San Francisco Bay area in 1997 and attended an orchid show. Returning home with a few plants, she decided to join a local orchid society to learn more about taking care of them, and from these beginnings, her current passion grew exponentially! Now Mary truly has put her roots down, and has orchids in two greenhouses, five lath houses, her front porch, sun room, and anywhere else she can put them. Her collection of about two thousand plants, mostly species, is rich in masdevallias and other miniature orchids of many different genera. Mary has traveled extensively to see orchids in situ, including many countries in Central and South America, Southeast Asia, as well as Australia, Papua New Guinea, South Africa, Madagascar, Europe & Mediterranean islands, the USA and Canada. She has co-authored six botanical books with co-author and photographer Ron Parsons “Masdevallias, Gems of the Orchid World”, “Calochortus, Mariposa Lilies and their Relatives”, “A Compendium of Miniature Orchid Species” (a two book set), “A Bay Area Guide to Orchids and their Culture” “The American Orchid Society Guide to Orchids and their Culture”, and the recently released “The Compendium of Miniature Orchid Species, 2nd edition” (a four book set). Mary has served as president and vice president for both the Peninsula and San Francisco Orchid Societies, and is currently president and chief executive officer of the Orchid Conservation Alliance and a director of the Orchid Digest.

Talks and Abstracts


Miniature Orchids and How to Grow Them

A significant proportion of orchid species are far smaller than those typically thought of as orchids. This lecture focuses on the true jewels of the orchid family, the miniature orchid species, which can produce some of the most unusual, and often spectacular flowers. Mary and her co-author Ron Parsons have produced the most comprehensive illustrated reference (A Compendium of Miniature Orchid Species, Vol 1-4) for miniature orchids to date, with a detailed overview of orchid species and cultivars from across 117 genera. This lecture offers a selection of some of Mary’s favorites of the miniatures, featuring the beautiful photographs of Ron Parsons. The lecture covers orchid habitats, specific cultural considerations for smaller species, and some ideas for indoor orchidariums for both tropical and sub-tropical orchids.

Masdevallias: Selected Species and How to Grow Them

This huge genus, which belongs to the larger tribe of orchids called Pleurothallids, originates in the tropical Americas, from Mexico in the north, to Bolivia and Brazil in the south. A genus with more than 500 species, and new ones continually being discovered and described, it offers an incredible diversity of form, color and beauty. This is Mary’s favorite genus, and was the topic of her first book Masdevallias, Gems of the Orchid World, coauthored with Ron Parsons. The lecture features a selection of some of the most desirable species, a section on culture, and sources for more information.

Growing Orchids Outdoors in Coastal California

The coastal region of California, extending up to 50 miles inland and from the San Francisco Bay area south to San Diego, offers incredibly favorable habitats to grow an amazing variety of orchids, outdoors, year round. However, the many microclimates, with their variations in high and low temperatures, humidity, fog, wind, and light intensity dictate the selection(s) of orchids that will thrive in the outdoors. A major component of Mary’s book “A Bay Area Guide to Orchids and Their Culture”, this lecture offers a comprehensive survey of the microclimates of the Bay Area, and detailed information about the orchids that grow there. The lecture also features ideas about outdoor orchid structures, as well as growing orchids on trees and in other protected areas. Mary also has a more generalized version of the talk which is more relevant to regions outside of the bay area (e.g. central coast, southern California).

The Orchid Conservation Alliance: Who We Are, What We Do and How We Do It

Founded in 2004 as a California corporation and a 501(c) 3 tax-exempt organization, The Orchid Conservation Alliance (OCA) partners with organizations and foundations in orchid rich regions to protect the native habitats of orchids. Creating reserves preserves numerous orchid species, often including undiscovered forms, as well as the ecosystem in which they exist. Critical for orchid conservation in the wild, preservation of habitat protects pollinators as well as birds, amphibians, mammals, other plants, and even fungi. Since its inception, the OCA has raised nearly a million dollars to establish, support and protect orchid habitats in Ecuador, Colombia and Brazil. Partnering with other organizations such as the Rainforest Trust, the University of Basel and the Reserva: The Youth Land Trust has great expanded our conservation impact and to date, we can proudly state that we have created nearly 5000 acres of protected habitat in 7 different reserves. Mary was recently appointed president and chief executive officer of the OCA, following over a decade served on the Board of Directors and as Chief Financial Officer. This lecture will introduce you to the OCA, provide a little history of how the OCA began, present beautiful photos and videos from our reserves, and explain our fund-raising strategies. Additionally, the lecture presents information on the Orchids in the Wild tours, with lots of photos from previous trips and previews of the trips planned for the upcoming year.

Orchids of Madagascar

This lecture is based on two separate trips to Madagascar, and covers the different regions of this amazing island, focusing on the orchids, but also lots of photos about the incredible fauna (lemurs, chameleons, geckos, frogs, moths etc.) and flora (Baobob trees, spiny forests, Bismark, Dypsis and Ravenea palms, Pachypodium etc). The Orchid Conservation Alliance (OCA) now offers orchid tours of Madagascar almost every year, led by experts Johan and Clare Hermans. The latter half of the lecture features the region(s) visited by the OCA tour.

Orchids of Papua New Guinea

One of Mary’s absolute favorite orchid destinations, Papua New Guinea (PNG) offers an incredible visit to a country that is tangled in time. The lecture, based on three different PNG expeditions, covers the Port Moresby area (nature parks, the amazing cultural museum, Varirata National Park), the Western and Southern Highlands (Mt. Hagen area, also Mt. Wilhelm), New Britain, and the islands of the eastern cape (Normanby, Ferguson). Fantastic scenery, visits with some of the many tribes, a sing-sing, a moo-moo (traditional pig roast), birds of paradise, and of course, orchids. Expect incredible photographs of orchids in the wild, many rarely if ever seen in cultivation.

Orchids in the Lost World (Roraima Tepui, Venezuela)

Travel virtually with Mary on an amazing orchid adventure, a trek to the top of Mt. Roraima, the tallest, and probably the most magnificent, of the South American Tepuis. This “island in the sky” features the most amazing rock formations, primitive plants, curious carnivorous plants (Heliamphora, Drosera, Utricularia) and lots of orchids.

Orchids of Borneo

This lecture is based on three separate trips to Borneo and highlights the orchids of Mt. Kinabalu, Mt. Alab, Long Pasia, Mulu and the Kuching area. Lots of fantastic scenery, trekking with the indigenous people of Long Pasia into the inner rainforest of Sabah, and orchids everywhere.

Slippery Tales

A talk originally prepared for a Paphiopedilum Guild meeting, this lecture is a compilation of Mary’s various adventures to see Orchids in the Wild. As she was preparing the lecture, it became evident that nearly every time a slipper orchid was involved, there was some additional twist and occasionally mishap! Featuring photos and travels to see slipper orchids in Thailand, Sulawesi, Borneo, southern and western China, North America, Mexico and South America. This is one of Mary’s most requested lectures, and the audiences are left roaring with laughter and clutching their sides over her descriptions of the misadventures.

Orchids of Chiapas

This lecture is based on a trip that the Orchid Conservation Alliance offered a few years ago. It was organized by Dennis Szeszko, an intrepid orchid explorer and expert on the orchids of Mexico state and Chiapas. We visited a number of archeological sites, enjoyed the tropical habitats of eastern Chiapas, flew over the rain forest in small seater planes, explored the subtropical dry forests north of Tuxtla, and finally completed a nearly 20 mile, 4 day trek to the cloud forests of the El Triunfo Bioreserve.

Orchids of the Rio Negro

This lecture is based on one of the most popular of the Orchid Conservation Alliance’s Orchids in the Wild tours. We travel first to Manaus (Brazil) where we board the Otter, an Amazon riverboat specifically designed for travel up the black water tributary, the Rio Negro. The journey is in late May, when the flooded Amazon brings you up to eye level with the orchids. A completely relaxing, delightful and visually stunning journey.