Thursday, February 14, 2013

Answer: What kind of flower is it?

Short answer:  It’s Calendula arvensis, also known as the “field marigold.” 

T-shirt awards:  

Joe at 7:35AM called it Calendula officinalis (which is close enough that I’ll accept that answer). See details below.  

Khilbelink at 7:37AM named it correctly as Calendula arvensis

Unknown (aka “Julio”) at 7:47AM got VERY close by calling it a Malmequer flower (but when you translate “Malmequer” it means “marigold” in English, which is close, but not quite precise enough).  Sorry, Julio.

Sean at 7:53AM also figured out it was a Calendula arvensis

So… Sean, Khilbelink and Joe… send me an email and I’ll get those t-shirts to you! 

What I did to find the answer…

Since I knew the stem was “square” I did a search for:

   [ square stem plants ]

and found that Mint plants (in the family Lamiaceae) have square stems with rough, aromatic leaves.  But when I read a bit more, I found that all Mint flowers are shaped a bit like pea flowers—with a couple of fused big petals below and free upper petals. 

This flower clearly wasn’t like that.  This one looked more like a sunflower or an aster, both of which I already knew are in the Compositae family.  (Other composite flowers include sunflowers and dandelions.  They all have a center set of tiny flowers with petals arrayed around the center, just like our mystery flower.)  

But I did the search for orange mint flowers anyway, hoping that this one might be an odd one in the family.  My next query was:

   [ mint plant orange flowers ]

I switched to Image search and scanned down a bit.  Here’s what I found about 5 rows down… a flower that looked a LOT like the one I was after. 

This suggested that it was a “marigold calendula officinalis.”  That was a great clue—so I started looking up “marigold” and “calendula” and “officinalis” as search terms, quickly finding out that “marigold” is a common name of a large number of flowers, while Calendula officinalis is the name of a specific kind of flower that looked a lot like the one I had in my hand.  This was great! After only a couple minutes of searching, I seem to have a real clue about the flower.  

But now I wanted to find an extremely authoritative source that would give me a positive ID for the flower.  My next search:

   [ California wildflowers ]

led me to the website, a site I soon discovered is associated with UC Berkeley and a whole bunch of people with extensive California botanical experience.  (And, to their credit, they document ALL of the flowers in California, the weeds, the invasive species, and the native flowers.)   I started noticing that they had fantastic images... ones that looked just like mine.  
Image from CalFlora of Calendula arvensis.
Note the similarities in leaves and the tips of the petals
which have the same indentations as in my
photos of the flower.  
Image from CalFlora of Calendula arvensis.

So I checked on their site for Calendula.  This is part of what I found:

Not only are there many different kinds of Calendula in California, none of them are native, and some are invasive.  Well, that certainly seems the case here—they took over that hillside in a big way. 

As you can see, both C. officinalis and C. arvensis look like the flower in question.  Which one is it?

If you spend any time at all looking around at flower identification sites, you quickly find that they all end up pointing to the Jepson Manual ( ) which is THE bible of plant identification. 

So let’s look them both up in the Jepson Manual.  That’s pretty easy, but then you end up with these two descriptions side-by-side. 

C. officinalis L. POT-MARIGOLD
Finely hairy.
Stem: slender to ± coarse, sparingly branched.
Leaf: sessile, <= 15 cm, ± thick; base generally clasping.
Inflorescence: heads erect at maturity, flowers closing at night.
Ray flower: ray pale yellow to orange.
Disk flower: corolla generally 5–6 mm.
Fruit: 10–20+ mm.
2n=14,32. Uncommon. Escape from cultivation in disturbed areas, occasionally from seed mixes; < 500 m. Central Coast, San Francisco Bay Area, Outer South Coast Ranges, South Coast, San Bernardino Mountains; native origin unknown. Mar–May
 C. arvensis L. FIELD-MARIGOLD
Finely glandular-hairy.
Stem: slender, <= 60 cm.
Leaf: petioled; blade <= 7 cm, ± thin, becoming sessile distally.
Inflorescence: head nodding at maturity.
Ray flower: ray yellow to orange.
Disk flower: corolla generally 2.5–4 mm.
Fruit: 3–12 mm.
2n=18,36,44. Uncommon. Escape from cultivation in disturbed areas, sometimes established from seed mixes; < 200 m. c Sierra Nevada Foothills, Central Western California (except Inner South Coast Ranges), South Coast, expected more widely; native to c Europe, Mediterranean. Mar–Apr

So… how do we decode this?

Two key items leap out at me when reading these descriptions.  First, C. officinalis is described as “finely hairy” and having “sessile” leaves.   Second, C. arensis is described as being “glandular-hairy” with “petioled” leaves. 

If you look up “sessile,” you’ll find that it means the leaves attach directly onto the stem of the plant without any intervening stalk. That intervening stalk is called a “petiole.” 

Below I’ve highlighted a part of the one of the images that makes it pretty clear these leaves are in fact  “petioled.” 

I think this pretty much determines it:  Our flowers are Calendula arvensis, aka “field marigold.” 

Search lessons

Let’s face it—I got lucky with the image search.  (Especially since the stem was really pentagonal, and not square.) 

If I had NOT discovered the calendula family that way, I would have had to start searching for image collections of golden-yellow Bay area wildflowers, probably filtering by image color.  But the process would have been the same—find something that is a near match, then double and triple check on the details of the flower. 

As you see, I spent some amount of time looking for great reference materials ( and the online Jepson Manual).  Just matching pictures isn’t really detailed enough to give authoritative answers on plant identification questions. 

When the flowers actually bear fruit, I’ll take a few pictures and measurements… and determine if they’re really those of officinalis (at 10-22mm) or the smallish ones from arvensis (3-12 mm). 

Searching on! 


  1. Thanks Dan and congrats to the winners. I must admit that I should have clarified the color of the flower. I thought it was yellow but I also thought it could border on orange and I should have asked. Lesson learned, know the facts first.

  2. The previous post's photo of the flower held in a hand shows that the leaves are sessile. What you're calling petioles in this post are stems. The flower (in the daisy family, what we commonly call a "flower" is the whole inflorescence) is also erect in all your images. I think you've got C. officinalis.

    1. Kylee -- I agree that the one I've labeled in the picture is a stem, but the other leaves are attached by petioles, no? (When does a stem stop being a stem?)

  3. The stem's always a stem, but it's not always easy to identify without a lot of experience with plant body plans. People are frequently surprised that potatoes are stems, for instance! The petiole is part of the leaf, so the thing to look for is that only a leaf blade is attached to the petiole, not more stems and leaves. This does get hard to determine in the case of some compound leaves, but on something like a maple leaf it's really obvious: the leaf blade is connected to a stem-like part that falls off the tree at the same time and is one piece with the rest of the leaf.

    One important thing to know is that any time you have a leaf attached to a stem, you have a bud above the leaf. The thing that grows out of the bud is a stem, always. So I think what we see in the photo you posted above, to the right of that red ellipse, is a leaf and a stem that has grown out of the bud above it, and another leaf on that stem. I don't see definite petioles in any of your photos. You're right that it's a bit of a judgment call sometimes, but the leaf blades I see go right down to the stems ("clasping"), and that's supposed to be an officinalis trait according to Jepson.

    On the other hand, the arvensis entry says the leaves become sessile distally, which would be up by the flowers where we're looking. I realize you called this solved already, but examining the leaves way down at the base would help make a definite ID. If the blade goes away before the leaf connects to the stem, that would support your arvensis hypothesis.

  4. How exciting!

    what email address should I use to contact you? or is that a search project all on its own? ;)