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Native Plant Society of Texas

Prairie Rose Chapter

Deep Dive: Mexican Hat courtesy Lady Bird Johnson Wildflower Center

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Deep Dive: Mexican Hat
Bunch of Mexican hats in the field
Zooming past wildflowers along roadsides or glimpsing them on a bike ride or jog is pleasant enough. But there’s a wealth of plant intel — and some pretty otherworldly eye candy — available if you stop and take a closer look, which is what we did with Mexican hat (Ratibida columnifera) as our model.

An unfussy, drought-hardy perennial, Mexican hats vary from entirely yellow to deep, rusty orange (with many combinations therein), all of which pop atop feathery green foliage. These plants are members of the aster family, but unlike many of their relatives (such as asters, daisies and sunflowers), Mexican hats’ disk florets (the ones in the center) adorn tall columns rather than flat faces.

On that note, let’s take a journey down the Ratibida rabbit hole and learn some plant anatomy.
 
Mexican hat showing two types of inflorescence
This image clearly shows the two types of flowers present on a Mexican hat inflorescence (or head): small disk florets on the central column (yes, those little things are flowers!) and ray flowers — the colorful drooping petals — around the base. Disk florets bloom from the bottom of the column to the top over a period of days.
 
Close-up of disk florets with corolla petals, anther tubes and pollen
Zeroing in on a collection of disk florets, we see brownish-orange corolla petals, chocolate-colored anther tubes and golden grains of pollen. Some anthers are closed, while others show exposed female stigmas curling out the ends.  
 
Close-up showing both make and female flower structures
Each disk floret contains both male and female flower structures. As the female style elongates within the male anther tube, pollen sacs rupture, and pollen is pushed out on stigmas with specialized fleshy bristles (most conspicuous on the far right and left of this image). This process is termed “plunger pollination” and is the main system of pollination within Asteraceae (the aster family).

One distinguishing feature of this process is that the female parts help present male pollen to pollinators, facilitating outcrossing (pollination with pollen from a different plant of the same species) and avoiding self-pollination. Once pollen is carried to the mature stigma of a different flower via wind or insects, fertilization begins. Eventually, a seed will be produced at the base of each fertilized floret.
Macro view of a single disk floret showing corolla petals, anther tube and yellow pollen
This macro view of a single disk floret shows corolla petals, an anther tube and plenty of bright yellow pollen. The clear-colored sacs along the anther are trichomes that secrete insect-repelling chemicals (which protect immature pollen from insect raiders).

Multiply that by several hundred ray florets per flower head and more than a dozen flower heads per plant, and it’s clear nature has a lot going on in plain sight — if we look closely (and a macro lens doesn’t hurt).

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**ARCHIVED POST AUTHOR: prairierose

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