Spanish Needles, Beggarticks

19 May

Bidens pilosa

(including populations traditionally called Bidens alba)

(Bidens means two teeth. Pilosa refers to hairiness.)



Wildlife was abundant today in the Kiplinger Natural Preserve where John and I greeted a friendly osprey, fiddler crabs waving their fiddles in the mangrove mud,  a young land crab posing as a giant spider, and a photogenic corn snake too quick for photos.


Got eggs?

Anyone who knows me knows that I find the rare attributes of common species far more interesting than roaming to see rare species.  It takes work to know the species literally in our own back yards, including Kiplinger.   You couldn’t have a commoner weed than Spanish Needles; they are everywhere, and the yellow and white flower heads decorated the trails (and our socks) today.

Bidens alba

Spanish Needles by John Bradford

We all know this species, if not as a wildflower, at least as the source of sticktights in our shoelaces and pants cuffs.  They have been known to disperse in the clothes dryer from the trousers of an innocent botanist to his spouse’s apparel, eliciting muttering.  The stickers are well designed, a pair of barbed devil horns on the tip of the seedlike fruit.

Bidens alba horns


The fruits of this and some other members of the Aster Family have a second oddity, studied in depth by botanist O.J. Rocha in the mid 90s.  It is something you can see easily while walking the dog.   The headlike fruit cluster has two different types of fruits, or intergrading extremes.   Those at the center of the cluster are longer (let’s call them the central fruits) than those toward the edge of the cluster (edge fruits).

Bidens alba fruiting head

Cluster of fruits.  The central fruits are larger than the edge fruits (small one in circle).

The two fruit types have different jobs. The long central fruits  germinate quickly, and are more quickly relocated away from the mother plant.   Their job is to get far away, and spread the species now.

Bidens alba bare middle

Older fruit clusters.  The central fruits are disappearing.  The edge fruits remain.

By contrast, the edge fruits are reluctant to germinate, probably resist taking in water,  tend to require light to sprout, and cling to the mother plant.     Their job is to repopulate the home site eventually, persisting for who knows how long in the soil waiting for the prior generation to perish and open new opportunity.  Their requirement for light is apparently the cue that the parents have vacated. It would be fun and easy to compare the longevity of the two different fruit types buried in the soil.

Ever notice how Spanish Needles always look free of insect damage, even when the plants around are in tatters?   The species is a witch’s brew of toxins, including poisons researched as potentially destructive to human tumor cells.  One ingredient is PHT (phenylheptatriyne).   PHT smites your foes by destroying membranes.  Everything has membranes so the effect is broad spectrum, beating down such enemies as membrane-bound viruses, bacteria, insect pests, probably us, and competing vegetation.  Contrary to advice by those who feel the most interesting thing about wild plants is eating them…a penchant I’ve never fathomed…just fuggedaboutit!  Unless you are the dainty sulfur butterfly using today’s species as larval host.

Bidens alba 2



Posted by on May 19, 2017 in Uncategorized


5 responses to “Spanish Needles, Beggarticks

  1. theshrubqueen

    May 20, 2017 at 7:38 am

    I have a love/hate relationship with this plant and use it in flower arrangements. Very interesting about the seeds – something i will never be rid of.

    • George Rogers

      May 20, 2017 at 10:22 am

      Be a lover not a hater. And I’ll bet it lasts almost forever in a floral arrangement,

      • theshrubqueen

        May 20, 2017 at 4:08 pm

        Always a good plan, am planting a mostly natives perennial border!

  2. Laure Hristov

    May 20, 2017 at 10:51 am

    I just pulled out a large clump this morning on my morning walk in my Pj’s through the garden and of course, didn’t realize that is where those sticktights come from! Needless to say been pulling them out all morning. Should have read this first LOL!

  3. Steve

    May 25, 2017 at 10:41 am

    I have chickens, and they love to eat Bidens. However, they won’t eat the leaves off the plant unless it has been pulled up or cut. George, any theory as to why this might be the case? When pulled, could the bad tasting phytochemical dissipate? I hear rabbits also enjoy eating Bidens.


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