There are now many apps that claim to be able to recognize a plant from your photo so I decided to run a test of some of the most frequently mentioned to see how they rated. When I've checked in the past, I’ve had some totally wrong and often bizarre suggestions that could easily confuse a beginning gardener!
I chose to test with 5 images of both common and not so common plants - a clematis, dahlia, peony, ligularia and Kirengeshoma all growing in my garden. Some of the apps have extra functions such as more information on the suggested plants and social sharing, but I did not look into these.
I used the same photos in each, plus I briefly looked at other apps that required subscriptions, and some that were hard to use, or so wrong on the first test that I didn't test further. These are listed at the end.
1. Clematis 'H.F. Young'
Garden Answers - greek thimbleweed, anenome blanda (clematis viticella 2nd choice)
Picture This - Lilac clematis, a species of Clematis. Botanical name Clematis patens.
PlantNet - Clematis vitcella L.
Plant Snap - Clematis integrifolia leaves.
2. Dahlia - either Bishop of York or Mystic Illusion
Garden Answers - blood trumpet, distictis buccinatoria
Picture This - Garden dahlia, a species of Dahlias. Botanical name Dahlia pinnata
PlantNet - Biden's pilotage L (dahlia not in any of the other suggestions)
Plant Snap - Dahlia australis
3. Peony - Sword Dance
Garden Answers - ranunculus asiaticus
Picture This - Chinese peony, a species of Peony. Botanical name Paeonia lactiflora
PlantNet - Paonia officianalis
Plant Snap - Rosa chinensis (note peony was the 2nd choice)
4. Ligularia dentata
Garden Answers - ligularia
Picture This - Summer ragwort, a species of Leopard plant. Botanical name Ligularia dentata.
PlantNet - Not found in this project. "May be Ligularia dentata"
Plant Snap - Ligularia dentata
5. Kirengeshoma - Yellow wax bells
Garden Answers - chayotes, sechium edule (squash)
Picture This - Yellow waxbells, a species of Kirengeshoma. Botanical name Kirengeshoma palmata.
PlantNet - Impatiens noli-tangerine L
Plant Snap - Kirengeshoma palmata flower
Picture This came out best overall. I was surprised that Garden Answers which I had used in the past and found very accurate as it sent the photos to horticulturists (though now for a fee), was by far the worst with only 1/5.
Other apps I looked at more briefly included: LeafSnap (so many ads!); Plantyx and PlantSpot (seem the same $30 for 6 months); Plant ID $52 p.a.; Smart Identifier (thought peony was a rose); Plant Identify $1.99 per day; Plant Scan direct from camera only); Plant Identification $5.49 p.a.; Plant ID $13.49 a month; Plantifier (wouldn't load image); Plant Identifier (no results for dahlia).
All these apps are for iPhone or iPad only. They all work with the current iOS version 13.3.1 as of April 2020. However many are also available for Android devices in the Google store. I always check the information in the app store for more information, i.e. who is the developer and where does it originate? This may indicate whether it is likely to have content relevant to Western Canada. Also what version is it and how often is it updated? Hopefully the blurb will indicate how many plants are in their system, whether an internet connection is required or whether there is a large database that needs to be downloaded to your device. These criteria also affect whether I will pay for an app. Many are only a few dollars but I was burnt when two of my favorites that cost over $20 each were not updated to work with updated iOS versions.