Sunday, September 4, 2016

Trichostema lanceolatum

Trichostema lanceolatum is pollinated primarily by woodland skippers, Ochlodes sylvanoides. (2016)
Most plants, without question, are first seen, but some are first smelled. While taking a walk through a local woodland clearing one day, a sudden strong scent of gasoline or turpentine wafted into my face. It had perplexed me for some time, until I discovered that the origin of the scent was from a plant. I have come to look for this plant every fall, as it is one of the last native plants to bloom here in the Rogue Valley of Southern Oregon (or at least the last to bloom in my neighborhood).

Trichostema lanceolatum (2015)
Trichostema lanceolatum Benth. (Lamiaceae, mint family), or turpentine weed, is an annual Western native from California north into Washington. The plants grow to a height of around ten inches, often branching from the base. The leaves are of a narrow and tapering to a point at the tip (hence "lanceolatum" or lance shaped). The entire plant is covered in dense hairs that secrete a resinous oil, the source of the strong scent which I think is more akin to gasoline than turpentine (or camphor, as another common name suggests).

Trichostema lanceolatum (2016)
The fascinating flowers of turpentine weed are one of the features that make this genus so interesting to me. A related species, Trichostema lanatum, are known as blue curls, presumably named for the flowers. The anthers and stigma are arched out away from the flower, awaiting contact with a pollinator (seen in photos far below).

Trichostema lanceolatum with seed pods (2015)
Flowers are borne on a type of inflorescence called a cyme. Multiple flowers bloom at once, moving up the stem as they seem to produce only a limited number of flowers per cyme. Each flower produces up to four nutlets which fall and germinate the following Spring.

Trichostema lanceolatum (2015)
Trichostema lanceolatum (2015)
Visible here is the flower structure, the anthers have yet to fully expand, or they have been damaged in some way and are deformed. You can also see the dense hairs, possibly serving multiple purposes. As seen in Madia elegans, the resinous hairs (or trichomes) probably help the plants retain moisture during the heat of Summer.

Trichostema lanceolatum variability (2015)
There is some variation in plant height and flower color. They range from a pale lilac to a deep lavender. Height is also highly variable, as well as branching. Some plants grow no taller than three or four inches with a single branch while others grow to twelve inches with over twenty basal branches. Competition from grasses or other plants probably have a lot to do with this, the largest specimens I have seen were bordering a gravel road and thus nearly completely free of competition as the compacted decomposed granite is too harsh for other plants to grow.

Trichostema lanceolatum (2015)
Many of the plants lean generally towards the South, the flowers all being arranged more or less on the same side. For perspective, the South is where the sun is as the days shorten. In winter, the southern exposed sites are the only places to receive a full day of sun, while exclusively northern exposed sites are permanently shaded through winter's entirety.

Trichostema lanceolatum (2015)
The habitat is best describes as hot, with what is suspected to be nutrient deficient soil, possibly serpentine (though I do not believe this plant is an indicator of serpentine). The oils secreted by this species and others have toxic properties to other plants, reducing competition. This could explain why the areas I have found them growing are so sparsely vegetated while the surrounding area is (comparatively, for summer) "lush." Growing in poor soil is also a technique some plants capitalize on since there is less competition by other plants.

Trichostema lanceolatum (2015)
Trichostema lanceolatum (2015)
Pollinators on T. lanceolatum (2016)
I have observed few native blooming plants in the area at this time of year, limited to Madia elegans, Achillea millefolium, and Eschscholzia californica, aside from the Trichostema. The most common flowering plant here, seen in fields everywhere, is the invasive European native Daucus carota, the wild carrot. This leads me to ask the question, is that all that native pollinators had to forage on? Were there once other wildflowers here for native bees, or is the near end of the pollinator season naturally deficient in native wildflowers, corresponding to lowered numbers of active native pollinators late in the growing season? Perhaps before European settlers made this their home, the few native plants that were blooming were more widespread.

Ochlodes sylvanoides (2016)
The most common pollinators of this species were without question woodland skipper butterflies, Ochlodes sylvanoides. Woodland skippers were numerous and frequently visited many flowers on each plant and on multiple plants, suggesting they may be the primary pollinators of T. lanceolatum in this region. I have spent hours observing these plants in different locations over the past two years, and the woodland skippers were and still are the most frequent and numerous pollinators to visit.

Last year I had assumed these butterflies to be primary pollinators of T. lanceolatum due to the morphology of the flower, the arching reproductive organs make contact with the top of the thorax nearly every time the skippers land on the flowers to feed on nectar. Pollen was visible on their backs while at rest, confirming my assumptions.

Ochlodes sylvanoides (2016)
An interesting characteristic of the flowers of Trichostema lanceolatum is that the reproductive organs swing down onto the body of the pollinator when they land on the flower, causing pollen to be transferred. When the pollinator departs, the stamens and stigma return to their original position.

Ochlodes sylvanoides (2016)
The woodland skipper is active in the fall. Being grass skippers (Hesperiinae) they use host plants in the grass family (Poaceae) including Bermuda grass (Cynodon dactylon), canary grass (Phalaris sp.), wildrye (Elymus sp.), and wheatgrass (Agropyron sp.) though that is not a complete list. They are native to the Western US as far east as North Dakota and north from British Columbia to Saskatchewan. During their relatively brief adult lives, O. sylvanoides mates, imbibes nectar, and lays eggs which hatch in a matter of weeks. First instar caterpillars hibernate through winter, complete their feeding in the spring, diapause in summer as fully grown caterpillars, then build their chrysalis and pupate til emergence in the fall.¹

Ochlodes sylvanoides with pollen on the thorax (2016)
The woodland skippers thorax, in my observations, made contact with the reproductive parts of the majority of the Trichostema lanceolatum flowers they alighted on. In a few instances when the skippers were at rest I was able to observe more closely and noted pollen on the throax of most, as seen in this photo. Crossing of pollen from one plant to the next is a highly likely scenario considering the rate at which these butterflies moved between plants.

Trichostema lanceolatum with a tiny hymenopteran (2015)
During my observations, I observed few bees visiting Trichostema lanceolatum, though this was uncommon. Small solitary wasps, Philanthus crabroniformis, though never landing on any of the flowers, had been active near the ground in the midst of the Trichostema. I suspect they have nests around and were hunting small sweat bees, and that in the absence of me they may visit the flowers too.
Small hymenopteran, magnified
I did, although rarely, witness a few different types of solitary bees visit a few of the Trichostema flowers. The photo of a tiny hymenopteram (above) was a happy accident because I did not see it when I took the picture! Difficult to tell from the photo whether it is a bee or a small wasp. I have on a few brief observations seen what may be either anthophorine or eucerine bees visit the flowers, far too swift for me and my camera.

Trichostema lanceolatum (2015)
I have received the testimonies of others that bumblebees or perhaps large carpenter bees also visit the flowers, and appear to fit morphologically. I don't doubt their effectiveness as pollinators, in fact the "buzz pollination" of large native bees is highly effective for the pollination of many natives (particularly those with very sticky pollen, released only by the intense vibrating of the wing muscles). But I did not witness any large bees visit the flowers during my initial observations. Such is the variability of time and place. Honeybees may visit the flowers, but this is extremely rare in my observations.

Trichostema lanceolatum (2016)

12 comments:

  1. Incredible blossom! Looks like the Skippers love it. My guess is Woodland Skippers - Ochlodes sylvanoides, but I can't say for sure. Did you note other butterfly species using it?

    ReplyDelete
    Replies
    1. Good call on the Woodland Skippers Stewart! I didn't see any other butterflies, in fact I haven't seen any other butterflies ANYWHERE in the garden. The skippers visit many nonnatives like Echinacea, Nepeta, Allium, and even Calluna vulgaris. The only other natives in bloom here are CA poppy and Madia elegans. One other native comes to mind: Verbena lasiostachys; it's still blooming in an irrigated bed. It gets a lot of pollinator attraction, including these skippers.

      Delete
  2. I once watched a black native bumblebee land on vinegarweed flowers. The curving anthers and stigma fit around the head of the bee (in between the eyes) so perfectly that in an instant I was saying, those two species co-evolved together. Bumblebee populations have declined but I would guess that two hundred years ago, they were the dominant pollinator for vinegarweed. The fit is truly amazing!!!

    ReplyDelete
  3. Fine work, Travis! Your photography and natural history observations have progressed dramatically over the past few years. You're doing a great job of visually isolating your subjects while still providing environmental context. Keep 'em coming

    ReplyDelete
    Replies
    1. Thank you very much, I am hoping it will some day put my readers lives in context with their natural surroundings (or lack thereof)

      Delete
  4. Thanks to your post Craig, this dialogue came back in my mailbox, with what seemed like good timing. In my Pacific Northwest butterfly group we've been having a discussion about a crash this year in Woodland Skipper numbers in western Washington, starting with Bob Pyle (Butterflies of Cascadia) reporting a crash in numbers this year at his place in SW Washington, and that dialogue comes up again as another observer, just now reports none this year in her garden in Seattle, when Woodland Skipper is one of 3 butterfly species she can usually rely on each year in her urban garden (along with Western Tiger Swallowtail and Cabbage White). My report from West Seattle is that they have indeed been harder to find than usual (though with an earlier start than usual), but can still easily be found (though not in the numbers I might expect), at the best times, in the best spots (on the Puget Sound beach with the abundant late blooming yellow Grindelia integrifolia - Puget Gumweed - Asteraceae - http://biology.burke.washington.edu/herbarium/imagecollection.php?Genus=Grindelia&Species=integrifolia (I always start on that site by scrolling down for G. D. Carr's exceptional photos highlighting diagnostic features).

    ReplyDelete
  5. great pix, thanks soooooooooooooooooooooooo much!

    ReplyDelete
    Replies
    1. You're soooooooooooooooooooooooo welcome!

      Delete
  6. Great post and blog!
    The plant's pollinators in California's Santa Cruz Mountains include bees, among them a strikingly blue-eyed digger bee that I photographed (see https://www.flickr.com/photos/25673579@N04/21964225438/in/photolist-zsUp13-yNBR6M and https://www.flickr.com/photos/25673579@N04/21530969483/in/photolist-zsUp13-yNBR6M/). I also observed other bees repeatedly visiting t. lanceolatum when I photographed woodland skippers last month at Calero County Park.

    ReplyDelete
  7. Skippers are abundant in my Gold Hill Pollinator Garden. I am growing a mix of pollinator plants for Gold Hill gardens as part of my Gold Hill Bee City Project of 100 gardens. I am gathering Milkweed seed to grow.
    I am looking for Heartleaf Milkweed (Asclepias cordifolia) to gather. Also garhering Showy and Narrow leaf to plant this fall as container plants for spring purchase for Gold Hill Monarch Way Stations.
    Your reports are very helpful to me. Don't make me get out my Jepson's Manual.

    ReplyDelete
  8. You may want to read the following paper by Spira (1980). It's a classic... https://www.jstor.org/stable/2442337?seq=1#page_scan_tab_contents

    ReplyDelete

If leaving a comment as "Anonymous," please leave your name or contact information.