Heterotheca’s Heterocarpy

Heterotheca subaxillaris

Golden-Aster, Camphor Weed

Asteraceae

This blazing 90 degree morning John and George* investigated red widow spiders, pine tree tip dieback, loblolly bay in fancy bloom, and mosses in Seabranch State Park near Stuart, Florida.  We botanize there often.

Feral hogs have stirred up patches of soil, with a consequence I always find interesting: pokeweed babies rising from the disturbed earth.   Pokeweeds are known for their heterocarpy, that is, differential circumstances for distribution and germination within a single species.   Many plants make mixed offspring in terms of how far the seeds or fruits will travel, or with seeds having mixed germination requirements and timing.  Reportedly in pokeweed some seeds are prone to sprout soon after release. Other sleep in the earth for decades until some hog stirs things up, even in a deep shaded woods unfit for pokeweed residence.  Some time ago in this blog we covered sea rocket, where half the fruit remains on the mother plant while the other half breaks free to go colonize new beaches.

Heterotheca subaxillaris (by John Bradford)

The heterocarpic flower in pretty bloom this week is named for its hetercarpy: Heterotheca means “different containers,” in reference to its two types of fruits. Sometimes called Golden-Asters, Heterotheca subaxillaris is a common local bright sunny yellow-flowered weed on bright sunny dry sands. This species has extreme tolerance for drought and heat. Heterothecas (grandiflora) are so tough they have become invasive pests on Mars-like volcanic lava fields in Hawaii.

The leaves are fuzzy and smelly, giving today’s plant the name camphor-weed. I like the fragrance, but how many people know what camphor smells like, or even what it is? I just Googled camphor so I arrogantly know much about it for the next hour or two. Fact is, Heterotheca is a one-plant chemistry lab with a wide array of pharmaceuticals.  The “family” of fragrances Heterotheca brings to mind are wormwood, marigolds, and sunflower leaves.  (They are all related, and the similarity may come from lactone sesquiterpenes, but who cares?)

The obvious function of the stinky, sticky, chemical-laden, glandular hairy covering is to deter herbivory. Nothing would want to crawl upon or eat  camphor-weeds!   And there may be a secondary advantage to the hairs—protection from sun and drying.  Look at the death valley habitat in the photo above.   Plant hairs insulate the leaf surfaces from drying wind, and they block sun, maybe even reflecting solar radiation.   I don’t know if this is true of Heterotheca, but some botanists have suggested that glandular hairs might make a “sunscreen” that can spread and protect the foliar surfaces.  Even better, in other fuzzy species of similar habitats the hairs produce water-retentive compounds to create a moisturizing gel when the rains come.   It would be fun to look into some of this in Heterotheca which is so hairy and so oddly happy in a solar oven. The structure of the hairs helps define the genus.  A mutant hairless Heterotheca would probably wither unprotected.

As for the heterocarpy, in a flower head, most of the “seeds” (achenes) have parachutes to blow away to colonize a distant disturbed sand pit.   Some of the seeds, however, have no parachute, and recolonize their home neighborhood.

Heterotheca achenes showing heterocarpy: one has a parachute; one is bare. One flies far away; one keeps the home fires burning.

*Sorta let the blog slide.  Lost my mojo when our awesome international blog friend Mary Hart passed away in the U.K.  But John and George have kept up the botany—John has been working on the Seabranch site linked above, with some help from George.  And George has been developing a companion site to an introductory botany course, with a lot of John’s photos.

 

Tough Bullies and Bungee-Jumping Worms

Golden-Asters

Chrysopsis scabrella

Asteraceae

Willow-Bustic on Hobe Mountain. All photos today by John Bradford.

Yesterday John and George continued a multiweek appreciation of Jonathan Dickinson State Park, exploring this episode mostly the scrub area around Hobe “Mountain” (big coastal dune).  The alpine vistas are postcard pretty, and the montane flora is joyous too.  Understand, this massive pile of white sand looks like something out of Arizona, complete with cacti, big agaves, and no doubt rattlesnakes.  Especially eye-catching yesterday in bud/early flowering were two different species of “Bullies”:  Tough Bully (Sideroxylon tenax) and Willow-Bustic (S. salicifolium).

The Willow-Bustic, alternatively encountered as a hammock species in our experience, stood out as one of the dominant woody species on the fulsome dune, and the Tough Bully made its impression as an old, weather-worn, lichen-covered individual in the middle of historical Camp Murphy.  CLICK   The kinky tree could pass for a small live oak, and looked old enough to have been around in the WWII heyday of Camp Murphy, and gnarled and sand-blasted enough to be straight out of Lawrence of Arabia.

Tough Bully on N base of Hobe Mountain

Tough Bully flowers yesterday (2/14)

At that site, and throughout scrubs and dry pinewoods, is a vibrant yellow presence right now, Coastalplain Golden-Aster, Chysopsis scabrella, a sand-loving, sun-drenched, indestructible yellow-flowered ray of sunshine in Florida and nearby Southeastern States.  The ability of this species to thrive baking on sugar sand is remarkable.  It flourishes blooming on bare open windswept sand where it almost  seems little else can survive.

Golden-Asters on Hobe Mountain

Not very exciting or photogenic, the root is a massive brush infiltrating the sand below.  The above-ground growth presents more to describe and photograph.   The early growth is a fuzzy gray-green rosette, leading some botanists to dub the plant a biennial, although the life cycle seems more complex than that.  A stem rises, oh let’s say, 2 feet from the rosette, and something curious happens, the leaves in the lower part of the stem wither, as though the plant in its extreme habitat sheds foliage it does not absolutely need, taking a little inspiration from cacti and other leafless or minimal-foliage desert plants.

Golden-Asters

Another Florida member of the Composite Family that likes to accumulate fragrant dead leaves along the stem is “Rabbit Tobacco.” SMOKE THIS   Every time I see the dry Golden Aster leaves I experience, but resist, an urge to try smoking them. (That would be beyond stupid, but stupidity does not always stop me.)   Interestingly, also, the soft pith in the center of the stem seems to fizzle out…again, the plant shedding all but necessary tissue?

The fruits

Around here the Golden Aster lives up to its name with a stunning late-winter canary floral display although flowering is not confined to this season.  In late winter, now, a new rosette (basal  leaf cluster) forms as a side-branch at the old plant’s base.  In a garden setting you might say it makes “offsets,” or “pups,”  not an uncommon behavior in desert species, for example agaves.

Plant with pup

So perhaps the Golden-Aster is an improved biennial…yes, it goes from rosette to flowering stem, maybe even in two years in the fashion of a biennial, but then remakes a new rosette based on the existing hard-earned and precious root system, and thus is sort of an immortal “biennial.”  How many years one root system generates  annual resurrections would be fun to know.

As John and I were photographing, and sniffing the fragrant foliage, and savoring the Golden Asters we noticed an entomological curiosity.  At the bases of the flower heads (the units that look like single yellow flowers) often a little whitish larva maybe ¼ inch long nestles in a little cup with its frass.  When disturbed, the wee stowaway bungee jumps on a silk thread.  (It probably leaps when the flower head disintegrates, rockin’ its dreamboat.)  We do not know what the hidden hobbit is.  John posted photos on BugGuide.net, yielding opinions of moth, although which species is not clear.  We’d love to know.

Annoyed stowaway emerging from opened flower head.

We’d love to know so much we placed occupied flower heads in containers hoping maybe we can “rear one out” for definitive ID.  In the meantime, there’s a mystery trespasser in the Golden Aster flower heads.

You never know!