Leaves of differing taxa can be very very similar and sometimes nearly indistinguishable from one another. They also change with growing conditions (light, nutrients, etc). Floral features won't change so much; they provide a uniform comparison. Flowers are almost much more intricate and have more features to compare.

Okay, I will be the thick-headed one and say again, why?

Helianthus tuberosus and H. grosseserratus are very similar species that are distinguished by smooth stems versus hairy stems. If you key this out by traditional methods you would start with the same flower characteristics and at some point after many other similar characteristics you would get to smooth vs. hairy stem and have your species.

But if the plant is not in bloom and you have never seen the plant in bloom, you are out of luck. Yet the charactieristic that separates the two species is present through much of the growing season.

If keying systems were topsy-turvy and left flowers for last, you would still be able to eventually separate similarly-foliaged species when the bloom is present. But other plants could be id'd without blooms.

V.

Because many keys are based on type specimens rather than field use. Not having blooming flowers is an issue for many keys, but it's something we usually have to live with.

However, not being familiar with those species, what you say makes no sense. If you are keying only between the two species, then all other characteristics that are the same will not come into play in the key and the distinction will be between the stems. There is also no law that you have to go by the exact order in the key. You can use identifying features of the specimen you are trying to identify, narrow it down to a couple potential species, then use the key from there. Missing of identifying features can come into play, even with non-floral plants. For example, in trying to key out a bryophyte, with no sporophytic generation present we are limited to the gametophytic characters, and with ferns if the sporangia are not yet formed we are lacking an important identifying character. Keys really only can go so far.

Keys definitely have their limitations, and this is one of them.

Maybe if I give the specific example of what I'm facing, it would make more sense.

The plant I'm trying to ID is an herbaceous perennial that has already bloomed. The plant is 6 feet tall, has square stems that are reddish, and opposite leaves that are ovate. The lower leaves have two small leaflets at the base of the leaf. Flowers are borne on panicles that are up to 6 inches long, generally with three stems in a group.

But since I have no idea what color the flowers were or how many parts they had, I cannot begin to use the keys that I have. The square stem, the height and the flower panicles make this rather distinctive compared to other vegetation normally found in our area, so it would seem to me that this should be easy to name, but I keep hitting dead ends because of the lack of flower information.

It just seems to me that there would be a use for a plant id key that is driven by other characteristics first.

V.

"It just seems to me that there would be a use for a plant id key that is driven by other characteristics first."

There are indeed such keys ... you need to look around the literature ... and I agree with everything Catalina has said so far ... it also helps to know your plant families which are based on flowers but also on fruits and other features ... if you new for example the unknown you are working on is Asteraceae ... well you have eliminated a couple of hundred thousand plants ... ofcourse there are still 14,000 or so members of Asteraceae BUT how many in your area of the country in the habitat you are collecting in with the features you have described ?? ...

As I said there are sometimes keys that work with characters other then the flower ... often someone like your self will develope such a key look carefully in the library ect and build your own collection of botanical floras ...

Flowers are indeed important so it is not simply to make things difficult ... many features of plants overlap ... flowers and fruits and seeds often contain the "stamp" that sets plants apart ...

Take heart ... you may get stumped this season but by next you will be the wiser and if you keep notes and make collections YOU will be identifying unknown plants in your area even without flowers ... or even leaves ... that is you will develope an expertise ... but you have to pay your dues !!

Good Day ....

well, now u have something to do for the winter. :) key away...

seriously tho. i feel ur pain sister. im in the field alot and u come up to a little plant with nuthing but a few half dead leaves and u think, 'man ill bet this is sumthing neat but there is no way im going any farther than forb'.

i think one of the main reasons is the diversity of the plant kingdom. there are a few types of leaf config but every plant (to a certain degree) has a specific flower. u got the flower and the rest is easy.

another reason is that alot of ppl keying to family and go from there. and certainly there is a wide diversity of morphology in families.

i think u are also id'ing a problem as it relates to local flora. think how many plants there are in the world that are alternate (or slightly so) and ovate leaf? in ur neck of the woods it may only be a couple but looking at the eastern range of the usa, that isnt much of a start. and book sellers wanna sell to the eastern seaboard, not to just Veronicastrum-ville Ill.

lastly, i think its funny that we can send an SUV to Mars but still dont know what the heck (or how to id it) is in our own back yard. and no one pays u to name that little forest edge weed so unless u have had botany taxonomy class or someone in the know has shown u the way, ur stuck. yet ppl will pay 55$/month for cable.
imho, there should be an 'ARMY of ecology' (just gimmie 1/100th of what the military spends) doing work like this in every part of the world. instead of blowing the place apart, spend a few $$$ and put it back together. fixing, id'ing, saving, understanding, cleaning and monitoring. oh, my mouth is watering...

alas, back to the real world :)

froggy

We have 15 sunflower species in my state and I'll bet further west there are many more. Some are glabrous some are pubescent. To simply start with these two traits is not definitive enough. I think that the keys are more efficient the way that they are.
When we go botanizing, we zero in on the species that are in flower or fruit. It is with the understanding that if a specie is past flowering, we may not be able to definitively ID it. The composites can be especially complex. To me, the process of elimination starts with the flower.
Sam

Flowers tend to have less variability and be more distinctive than non-flowering parts.

The big problem with keys is that, if you have an ambiguous trait or you make a mistake, you get led down a completely wrong track. An ideal key would be one that let you narrow down choices based on the suite of characteristics you were certain of.

There are non-flowering keys for some groups. Grasses, for example, sometimes have non-flowering keys for specific regions. There has been a lot of work recently on developing software that allows the user to select the known traits of a plant so the possibilities can be narrowed down. So far, those keys are mostly for small groups of plants or regions. Around here, for example, there is a publication called Weeds of the West which comes with a CD that lets you key a plant based on the characteristics you are confident of. It only works, of course, if the plant happens to be one of the weeds they've included.

Eventually, software keys will be more complete, but for now, you just have to muddle through. As you get more experience, you can often make a good guess about the possible families based on the "look" of a plant.

Here is where knowing a little about plant families can come in handy.
Generally speaking, square stems and opposite leaves would immiediately bring to mind either something in the mint family or verbena family. If the plant smells when leaves are crushed you can bet on a mint. If not bets are on a Verbenaceae of some sort. With the height I might think Verbena hasata but more ovate leaves may indicate Verbena stricta. The former should be in wetter areas, the latter (althought reportedly not as tall as 6') likes dryland areas.

I found this after most of the discussion but I enjoyed reading this thread. I will add that the reproductive characters of plants (flowers, fruits, seeds) tend to change slowly through evolution. Not only do leaves and stems change quickly in response to the immediate conditions, as noted earlier, but they change relatively fast in evolutionary time. This is why the flowers of the various species in a genus, and even in a family, look rather similar. The flowers and a few other clues, as Rosa described above, will narrow a wide range of choices quickly.

Key authors use whatever they think will take you to plant name the quickest. I have a book on the woody plants of northwestern South America with keys that pay very close attention to the trunk characters of rain forest trees because it is so hard to see their leaves and flowers.

The problem I run into with some of the technical works is that they use both the flowers AND the fruit in the key. And of course, usually both aren't present at the same time. I did some volunteer work on a plant census in the NYC area a couple years ago, which took place over the course of several years, and actually went back and re-visited some plants several times to get a look at the different stages to try and get an accurate ID, which was kind of neat. I have to confess I don't usually have much luck with keys, except down at the species level.

I know it's probably too late now, but the next time you run into a problem like this, Veronicastrum, post a picture (or even just a description) on the Name That Plant Forum. We love a challenge...

WW

"The plant I'm trying to ID is an herbaceous perennial that has already bloomed. The plant is 6 feet tall, has square stems that are reddish, and opposite leaves that are ovate. The lower leaves have two small leaflets at the base of the leaf. Flowers are borne on panicles that are up to 6 inches long, generally with three stems in a group."

Purple loosestrife ?

Here is a link that might be useful: Google: Purple loosestrife

Veronicastrum and all others should certainly heed the words and advice of both Catalina and Mojave. Both appear to have a sound base in plant taxonomy and their approach is rational.

Veronicastrum gave enough info to id the plant. Rosa made the right call. Even after blooming, one can distinguish one Vervain from another by leaf and fruit morphology. Even on Sept 1, one can occasionally find a late-blooming plant, perhaps one has been cut back or broken earlier in the season. Sure sounds like Blue Vervain to me. One note, ours are usually covered with mildew starting right about now.
Sam