Plant ID apps may be good but they are no match for an experienced gardener….yet
by Heather Raithby Doyle
Walking along a trail, or in our neighbourhood we may see a plant and wonder: “What is that?” Since many of us carry our phones with us, it’s easy to snap a photo and find out using one of the many plant identification apps.
Especially for those of us who are newer to gardening, plant apps are an amazing tool, tapping into a world of knowledge, and, ahem, making us seem more expert than we are. It is like having a botanist in our back pocket, so to speak. To top it off the apps, amazingly, are free. (Although it turns out that the most popular app in my small Facebook survey has a paid version for US$30 per year, but more about that later.)
As an example of an app’s proficiency, I used Google Lens this summer to discover, horrifyingly, that the beautiful delphinium-like plant that has been in my garden since we moved to the house sixteen years ago, is actually wolf’s bane (aka monkshood). For those who don’t know, and I didn’t, this is a type of murderously poisonous aconite that should not be touched let alone accidentally eaten as it was in a recent case in Toronto that sent 12 people to hospital. (https://www.cbc.ca/news/canada/toronto/suspected-poisoning-markham-restaurant-1.6566001 ) My wolf’s bane/monkshood
identification by Google Lens was confirmed by the experts in the Master Gardeners of Ontario (MGO) Facebook group, along with helpful hints on how to very carefully get rid of it.
But how trustworthy are these apps? In June 2020, a Rutger’s University study looked at the accuracy of six common plant identification apps downloaded from the Apple App Store including iNaturalist, Pl@ntNet, LeafSnap, PlantSnap, PictureThis and Plant Identification (all trademarked names). The purpose was to determine how well the apps could identify street trees. Researchers submitted four pictures of bark and leaves to the apps.
In this case the leaves, not the bark, proved to be the key to unlocking the correct information. The top apps were PictureThis with a 97.3% accurate to genus, 83.9% to species, and iNaturalist with a score of 92.3% accurate to genus, 69.6% to species. (https://scholarship.libraries.rutgers.edu/esploro/outputs/acceptedManuscript/An-analysis-of-the-accuracy-of/991031655349704646 )
Which plant ID app do you prefer? Take our opinion poll!
Not perfect, but pretty good results! When I posed a question asking which plant identification app people prefer on the MGO Facebook page, respondents to my non-scientific survey agreed, with PictureThis the hands-down favourite.
Alas, apps make it seem simple, but figuring out a plant species is not always straightforward.
Group expert, master gardener, and MGO Facebook moderator Laura Gardner had this to say about plant ID apps in general: “They are best for distinctive flowering plants…but accuracy drops with similar plants that need to have specific features examined more closely (ex. Aster phyllaries). A downside is too many folks accept the answer the app gives as absolute without checking other sources.”
“PictureThis has only been wrong for me a couple of times. I also like with the free version I can add the plants to a list of my garden plants. It helps a novice like me keep track,” says Facebook user Jen Lenoir Moyer. The free version does have persistent advertising however, and you must be willing to close multiple windows that pop up.
“I haven’t tried very many but I do find PictureThis to have a high degree of accuracy. Keep in mind that it’s only a tool and one does require enough knowledge to know when it’s wrong,” says Dianne Kerr in response to the query. She summarizes: “Very useful for an experienced gardener. Somewhat useful for a novice but all such tools are flawed.”
Google Lens also got some love from Margaret Kus for its breadth of data and the fact it doesn’t take up room on your phone’s hard drive. In my experience, Google Lens and PictureThis are easier to figure out than iNaturalist.
I asked group expert, master gardener, and MGO Facebook moderator Cathy Kavassalis on other ways people can boost their knowledge about plant identification:
“Most master gardeners begin their journey by taking courses in horticulture…This teaches us to look at key plant features of parts of the plant. For instance, we look at the shape of the leaves, the phyllotaxy (how they are arranged on the stem), leaf margins (is the leaf smooth or are there teeth on the leaf edges, etc), the veins (how they are organized on the leaf)...It is easier when there are flowers or fruit/seeds along with the leaves. The more features you can see, the easier it is to classify a plant and place it in a family or genera. From there you can focus on the species. Learning how to pick out plant families really narrows the possibilities…and books like Botany in a Day by Thomas J. Elpel are really helpful.”
Kavassalis says she uses apps but always approaches with caution: “For what it is worth, my favourite apps are Pl@ntNet ... and Google Lens. But the failure rate for all of them can be quite high on certain plants. When there are several similar species, I don't trust any apps.”
Since this is a relatively new field, machine learning is bound to get better. Kavassalis adds a game changer will be when developers program apps to ask for more details such as the presence of fine hairs, or number of stamen, which will lead to more accurate results.
In the meantime, don’t believe everything an app tells you, and enjoy the challenge of researching other sources or engaging with a knowledgeable gardener.
Don’t forget to take our opinion poll on your favourite plant ID app!