What’s this plant? Gardeners aren’t the only ones who find themselves wanting to identify a particular flower or shrub. Hikers like to learn the names of wildflowers, new homeowners want their landscape labeled, and most of us just get curious at times. With my new job (answering plant-related questions, either identifying them or diagnosing a problem), I’ve been identifying a lot of plants lately (if you missed it, I’m now working for a gardening app), and I’ve learned some tips.

There are two approaches to plant ID. The easiest for a non-botanist involves noticing some eye-catching feature and then either flipping pages in a colorful field guide or searching the internet for that attribute. Most wildflower guides are arranged by color, simplifying this process.

For example, I had been getting a lot of flowers that look like deep orange dandelions. To identify these flowers I simply typed “orange dandelion” into my Google search box and did an image search. Voila! My first try gave me a number of flowers just like the one I was trying to ID. I could reply that the photo was of Orange Hawkweed (left), a noxious weed—or maybe it’s Orange Agoseris, a wildflower. They look nearly identical in the photos.

When faced with two extremely similar plants, more detail is needed. Are the stems hairy? How are the leaves arranged? Do the petals end in a neat point, or are they somewhat fringed? You can also look at where the plant is growing. Perhaps one is a xeric species that prefers dry hillsides, while the other loves damp riparian soil. The more details you note, the more you can be sure your ID is correct.

Then there are the plants that leave me completely baffled. I can’t even name the family it’s in, much less the genus or species. That’s where a dichotomous key comes in handy.

If you took high school biology, chances are you learned about keys. They ask questions like, “Are the leaves needles? Are they scales that hug the stem? Or are they flat and broad?” If you answer that they’re needles, the next question might be, are they directly attached to the stem, or are they in bundles? If you answer that they’re directly attached, then it might ask if they’re flat and flexible, or square and stiff? If you answer that they’re square and stiff, the key will tell you that you have a spruce tree.

Keys are a godsend, but there’s a catch. Usually you start out well. Are the leaves opposite or alternate? That’s pretty clear, even in a photo. Are they lobed, or unlobed? Most of us can recognize a lobed leaf (such as a maple or oak) vs. an unlobed leaf (think cherry tree). But then we run into trouble. It may want us to examine the leaf scars to see if they meet across the stem or not. You may have trouble differentiating between a row of opposite simple leaves and a single, compound leaf. You may be asked about the flowers or seed structures. If all you have is a photo, or if your plant isn’t in bloom, you’re stuck. Could I have used a key in this case? (Can you ID these weeds? Yeah, me neither.)

Given the limitations of photographs, I do most of my plant ID using the first approach. It’s not always easy.

In my plant ID job, people use their iPhones to send in pictures of a mystery plant. Taking a good photo with a phone can be tricky. A typical shot might be of a blurry branch and leaves in the foreground, but no longer attached to the plant it belonged to; the barbecue in the background is nice and sharp. Or, they wanted to include the whole tree, all 40 feet of it, so they backed up to fit it all in. The result is that the leaves are a blurry, uniform green mass. Here’s a photo I received. Can you identify this plant? (The answer is below.)

I think some people stick the camera up to (or among) the leaves to take the picture, making it impossible to distinguish between a tree and shrub—or is it a groundcover? One gardener clearly rototilled their weed patch and then took some photos of the weeds, chopped into pieces and half buried in the dirt.

Happily, most people send in perfectly acceptable photos. I love it when I can learn about a new flower, or figure out some obscure disease. I didn’t recognize this pretty flower when I first saw the picture. The photo was taken in the mountains west of Boulder, Colorado. However, a web search (I typed in “purple flower long stamen” and did an image search) turned it up on the first try. That’s when I shout halleluiah and jot down the name so I can grow it in my own yard. If this is new for you too, it’s a Lacy Phacelia, Phacelia tanacetifolia.

What we really want are one or more clear, focused photos showing the size and shape of the plant, some individual leaves (both top and bottom), how they’re arranged on the branch or stem, and a close-up of a flower or seed pod if possible. Ideally, they’ll include a note about the plant—is it a houseplant? Is it cultivated (e.g., purchased from a nursery) or was it growing wild?

When we get something like that, I want to hug those people. If you’re trying to identify a plant on your own, now you know what to look for.
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By the way, the mystery photo is the cone from an alder or birch tree. Did you identify it correctly? I have no idea what plant in the top photo is.