Field of Science

So you want to identify a plant?

Recent comments about the Friday fabulous flower demonstrate once again how different are the perceptions of "professional botanists" and most everyone else. When faced with an unknown plant your choices are to ask a professional (and please remember that a tip sufficient to purchase a halfway decent bottle of wine, or about 10% of a botanist's monthly salary, which ever is larger, is only polite) or use some sort of plant identification manual. Picture books are OK for amateurs, and this includes the physician that was thumbing through a Peterson wild flower field guide as yours truly entered the local poison control center after having been urgently summoned to identify an ingested plant. The Peterson wild flower guide for the NE North America is a quite nice enough book for hikes, but bloody hell, if your life depends on it, you be heading for trouble. Imagine the reaction if said physician caught the Phytophactor thumbing through a picture guide called "Appendectomy made easy" with a patient just waiting for my assistance. Oh, the asymmetry would be amazing! So when advanced students take plant identification they use a field guide like the 900 page (no pictures) Manual of Vascular Plants of the NE USA. This manual employs what we in the plant ID biz call keys; tables of choices, usually two, and if you consistently make the right choice based upon what you observe, it leads to a family, a genus, and a species. Ta da! But as my students soon discover, you must be both careful and discerning to be successful. Identification begins by categorizing the basic characteristics which places you into a key that will lead to a family identification. Here's the list of characteristics for selecting general keys (sections). Note that the authors rather expect that you can recognize pteridophytes, monocots, and woody plants right out of the gate. And while the floral characteristics look pretty picky, this is just the beginning. One of my students this spring only made two errors all semester! You can admire his proficiency, but in this business experience really really counts, so the big guy (PP) is still the big guy where is counts the most.
Section 1 – General Key to other sections
Section 2 – Pteridosperms & Clubmosses (non-seed vascular plants)
Section 3 – Gymnosperms
Section 4 – Epiphytes and branch parasites
Section 5 – Inflorescences modified into bulblets or tufts of leaves
Section 6 – Monocots
Section 7 – Dicot trees, shrubs, & woody vines
Section 8 – Herbaceous dicots; unisexual flowers
Section 9 – Herbaceous dicots; perfect flowers, no perianth
Section 10 - Herbaceous dicots; perfect flowers, one whorl of perianth, inferior ovary
Section 11 - Herbaceous dicots; perfect flowers, one whorl of perianth, superior ovary
Section 12 - Herbaceous dicots; perfect flowers, calyx & corolla present, two or more ovaries
Section 13 - Herbaceous dicots; perfect flowers, calyx & corolla present, inferior ovary (1)
Section 14 - Herbaceous dicots; perfect flowers, calyx & corolla present, flowers bilaterally symmetical, one superior ovary, & stamens more numerous than divisions of the corolla.
Section 15 - Herbaceous dicots; perfect flowers, calyx & corolla present, flowers radially symmetrical, one superior ovary, & stamens more numerous than divisions of the corolla.
Section 16 - Herbaceous dicots; perfect flowers, calyx & corolla present, flowers with separate petals, one superior ovary, stamens as many as petals or fewer.
Section 17 - Herbaceous dicots; perfect flowers, calyx & corolla present, flowers radially symmetrical, corolla tube present, one superior ovary, stamens as many as lobes of the corolla.
Section 18 - Herbaceous dicots; perfect flowers, calyx & corolla present, corolla tube present, either very bilaterally symmetrical OR stamens fewer than lobes of corolla.

For the record, both shoot stars and nightshades would be found using Section 17; the snowbell would be in Section 13, except it is a woody plant, so you would use Section 7 (and so is Solanum jasminiodes except it isn't in this manual at all).


Phil said...

For a fine example of the perils of plant identification errors, take a look at celebrity chef Anthony Worrall Thompson's lethal salad recipe at

The Phytophactor said...

Thanks for the link, Phil. Toxic henbane substituted for the spinachy white goosefoot is quite a mistake in taxonomy, and further illustrates the problem of using common names. Henbane, fat hen, henbit, none are related. Even worse when unrelated plants have the same common name!

Pat said...

I saw a children's cookery programme last week that was supposedly serving nettle soup. The plants on the plate had lovely purple flowers. Luckily the deadnettles are not poisonous, though they taste much worse than the true nettle.

What was even worse was the use of the nettle that late in the year and not liquidising with potato, oil, pepper and garlic.

Warthog Thompson's mistake was in blather not actually mistaking the identity of the plant in front of him, though it doesn't reassure someone eating at his restaurant. He is still in business, apparently.

A monkshood jelly was spotted by a knowledgeable cook at the last moment before it was sold at a bake sale. Can't remember where that was but it would make a lovely purple colour.

I have seen random aloes being sold as [i]Aloe vera[/i]. Some aloes have been used as arrow poisons so might not be good to use on cuts. My Mum was horrified that I made a fuss but the lady in charge was quite grateful for the info and changed the labels.

Mary said...

As the happy amateur who said that your American snowbell, Styrax americanus *reminded me* of a shooting star, I'd like to say - what fun would it have been had I said that it reminded me of the flower of a plant of the same family?

Nevertheless, I enjoyed your lesson in taxonomy and envy your students who have access to a book such as Manual of Vascular Plants of the NE USA, which helps them key out the plants of their area. If you know of an equivalent book for the neotropics, I'd be thrilled to acquire it! Gentry's book usually gives me a good start, but sometimes that's as far as I get.

Reading the comments here makes me think of another plant family with lots of edible and lots of poisonous members - the Apiaceae. Back in the area where I grew up, water hemlock, Cicuta maculata was treacherous to cattle and sheep and was reported to have killed people who mistook it for wild carrot, Daucus carota, or water parsnips Berula erecta.

The Phytophactor said...

Now, now Mary, please take no offense. It's hard for me to shift out of the professor mode. Al Gentry was a brilliant guy who could make your head hurt and his field guide represents his own idiosyncratic way of understanding things (we collaborated many years ago before his untimely death). Unfortunately no one wishes for a nice field manual for NW South America more than me. The review of Tropical Plants of Costa Rica indicates that this is a pretty but organizationally flawed field guide, and maybe too big to boot.

Mary said...

Thanks for pointing me toward the review of Tropical Plants of Costa Rica. I have the first edition and did use it quite a bit before I found the Gentry book, but I was also frustrated by the organization. As you said, once you know the plant, reading about it (and enjoying the excellent photos) can be enlightening. It also helps me confirm an identification made by other means.

Really, though, there's no systematic way to identify a plant using this book. If the photo catches your eye, then read the description and see if it matches the plant in your hand. Fine, but hardly systematic.

Further, in the first edition anyway, if you think you know the family, you have to find a hidden family index and then go through the species listed for that family. These are, of course, scattered throughout the book, and it's pretty awkward.

So, these days, I almost always start with your scary-sounding friend Gentry and go from there.

Maybe you could come up with the desired manual!