Tom Karwin, on gardening | Identify this plant – Santa Cruz Sentinel



Take care of your garden

Every garden has “mystery plants” at one time or another… or maybe frequently. Some gardeners aren’t curious about anonymous plants, but others insist on knowing what plants they have.

As indicated regularly in this column, the botanical name of any plant gives access to printed or virtual information on its growing needs.

In addition, many plants are accompanied by stories about their histories, properties, special uses in native habitats or landscapes. With such basic information, they become more than ornamental objects.

Let’s go over the strategies for identifying the mysterious plants you encounter in your garden or in other situations. The objective is to determine the botanical name of the plant in order to better understand its past and, by extension, its future.

After locating a mystery plant in your garden, let’s get started.

The quickest and easiest identification strategy is to ask a friendly gardener who has grown the same plant. This approach works well when you are attending a gardening company meeting and meeting friends with random gardening experiences. Bringing a snapshot of your factory to such an event is a great icebreaker (or “soil breaker”).

The next step, when you think you know the genus of your mystery plant, is to ask a local genus specialist. Again, a gardening company offers opportunities to meet local gardening gurus, who are usually happy to share their knowledge. In a future column, we’ll list chapters from local gardening societies, most of which focus on selected genres.

The major upgrade to this approach, when you know the genus of your mystery plant, is to explore the plant directories on the websites of national gardening societies. Here is an incomplete list of these resources:

Iris: American Iris Society ( a searchable, freely accessible database.

Bulb Plants: Pacific Bulb Society ( click on “Wiki”) a free resource with details on individual plants.

Orchids: American Orchid Society ( the menu “All about orchids” and click on “Orchids from A to Z” searchable only by species and cultivar names).

Roses: Access to the American Rose Society ( requires a membership or annual fee).

We are gradually returning to face-to-face meetings with other gardeners, but we also have virtual resources for plant identification: artificial intelligence on real plants.

In last week’s column, I shared photos of a mysterious plant in my own backyard. A visitor to the garden suggested that I identify my plant using specialized software on her cell phone. The software, iNaturalist, has a solid reputation, but it has remained empty. After I was able to identify the plant (see below), I entered its name on the Naturalist website, which replied: “The current model of computer vision does not know this taxon …”

I then tried the software on my own cell phone, PlantSnap. He couldn’t face a full view of this tall plant (busy background) so I tried a photo of its leafy base. The software immediately identified it as an Agave, and suggested three possibilities, which I later learned were not correct.

A second PlantSnap search for a photo of the plant’s raceme was also unsuccessful, possibly also due to the troublesome background.

I then tried Google Images, a function of, in two separate searches. The spotting scope of my mystery plant left Google confused (again, background loaded). The close-up view suggested that the plant was a bromeliad (wrong!). Interestingly, Google also returned with a link to my column from last week, with the photo of my mystery plant.

The next step was a Google search using various keywords to display the images produced by the search (choose “Images” from the search results menu). Searches for “purple agave flowers” and variations led to scrolling through many images and ultimately spotting two agaves with very similar clusters but completely different leaves.

AI approaches to plant identification bring powerful technology to our service. Their results can be impressive, and I won’t let them go, but these tools are not yet ready to replace human intelligence.

I sent photos to three very knowledgeable succulent specialists, who all responded with what my plant might be. After checking their nominations on the Internet, they were all wrong. In all fairness, a snapshot of a plant isn’t as good as seeing it in real life.

I finally went to my “go-to” resource, the National Gardening Association’s Plant Identification Forum ( This is a free online service where a volunteer group of experienced gardeners monitor incoming mystery plant queries and respond when they can come up with identification. I received several responses within days, one of which identified my factory. This respondent also provided two web links that confirmed the identification.

Success! My plant is an Agave polyacantha, called Maguey de la Neibla (“Agave of the fog”). It is a rare member of the Agave family, which includes 270 species plus a number of natural hybrids. It was difficult to identify due to its relative rarity, but this is no longer a mystery.

Another respondent discussed the difference between agaves which are monocarpic (bloom, seeds, then die) and polycarpic (reproduce more than once before dying). My plant could be polycarpic, but we’ll have to wait and see what it does.

Bottom Line: The NGA Plant ID Forum is a useful resource, and the NGA website has a lot of useful information to explore.

Anytime you’re looking for plant identification with a snapshot of your plant, you’ll have the greatest success with a well-framed, well-focused, well-lit close-up photograph with minimal distracting background detail. Today’s digital cameras do most of the work, so you don’t have to be an expert in photography.

Improve your gardening knowledge

The Ruth Bancroft Garden & Nursery will present two webinars this month. For more information on registration, fees, and recorded replays, visit

“Gardening with the pollinators”, 10 am Saturday. Kim Young, Ambassador for the Xerces Society for Invertebrate Conservation, will talk about our pollinators and the importance of what we can do to ensure their survival.

“Essential Trees & Palms in Dry Garden” at 10 am on August 25th. This webinar will examine the selection of a tree / palm for its aesthetics and conditions, as well as the wide range of drought tolerant trees and palms that are commonly available., in partnership with the American Horticultural Society, has announced a series of interactive live virtual tours of notable public gardens. The next scheduled event is “Apple Celebration at Gamble Garden – Fun for the Whole Family” at 8:30 am Saturday. Gamble Garden in Palo Alto has a collection of garden “rooms” to explore, including a rose garden, wisteria garden, edible beds, pollinator garden, and a new watershed garden. For more information, visit

Enrich your gardening days

An occasional project to identify a mystery plant in your landscape could add an enjoyable, satisfying, and educational dimension to your gardening days. Enjoy your garden!

Tom Karwin is the past president of the Friends of the UC Santa Cruz Arboretum, the Monterey Bay Area Cactus & Succulent Society, and the Monterey Bay Iris Society, and UC Lifetime Master Gardener (certified 1999- 2009). He is now a board member and garden coach for the Santa Cruz Hostel Society. To view photos of his garden daily, To find an archive of previous gardening columns, visit


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