Wednesday, April 5, 2017

SearchResearch Challenge (4/5/17): You mean.. they explode?

Crack.... Zing!

I'd been walking through a quiet and peaceful botanical garden when it sounded like something blew up not far from me.   What's going on?? 

A millisecond later I heard something whizzing overhead--an angry bee sound of something passing overhead at high speed.  

It seemed unlikely that anyone was shooting at me--this was the Waimea Arboretum after all--but I couldn't just ignore this high velocity drama overhead. 

Waimea Arboretum Pond

I DO remember seeing a sign about a "dangerous tree" on the garden pathway, but I'd just assumed it might fall down onto the path, not that it might fire high velocity projectiles in my general direction.  I thought it would be a peaceful stroll, not the wild west!  

Still, I should have suspected something like this.  Just a week before I'd been looking at the seed pod of a clover-like weed in my front garden.  To my surprise, when I touched the long, oblong seed pod, lots of tiny seeds zipped past my poking fingers and pattered on the nearby foliage.  Luckily, these seeds were about the size of poppy seeds, so there was no possible harm.  

I never did figure out what that high-velocity plant particle was in Waimea.  More generally, are there other plants like that?  Are there other plants capable of suddenly spewing out parts of themselves at high speed?  

The Challenges today:  

1.  Are there, in fact, dangerous trees that can somehow eject sharp bits of themselves, potentially hurting a human being?  (If so... HOW would it do this?  So far as I know, few plants - venus fly traps aside - are capable of much movement.)   

2.  More generally, are there other plants that can hurl seeds?  You can imagine this might be a handy evolutionary mechanism to have--but again, how would that seed-hurling mechanism actually work?  Do they have little plant muscles??   

Let us know what you discover.  It seems improbable, but I'll be searching with you this week, trying to see what we can discover about potentially dangerous plants!  

Search on! 

P.S.  BTW .... There was a bug in last week's Challenge.  When I wrote the Challenge, I know there was EXIF metadata on the last image--but something obviously changed.  I'm in the process of debugging it right now.  I'll let you know what I find out in an upcoming post. 


  1. My reply will have two parts, due to single-post character limits.

    A few years ago, I let a my only small section of backyard grass go untended before a remodel that would replace it with a patio. When it went to seed, I experienced a spectacular ankle-high show of seed-spouting fireworks with every step. Merely brushing against my pants was enough to set off the blasts. I thought I’d start with this search to try to identify that grass and go from there:

    [grass projectile seeds]

    But the fourth hit was an article that described the entire phenomenon:

    The article starts: “Some plants disperse their seeds forcefully by ejecting them. Sometimes the tension is so great, seeds may be ejected up to 200 feet away from the mother plant. This method of seed dispersal is called ‘ballistichory,’ a label that hints at the projectile-like emergence of seeds from their pods or capsules. This type of seed dispersal occurs because the fibers in the dried fruit pull against each other to create tension, and when the tension is great enough, the fruit splits open and the walls of the fruit spring back, flinging the seeds out with force.”

    It then listed four plant families that had significant ballistichoric seed ejection: Pea family (Fabaceae), Euphorbia (Euphorbiaceae), Acanthus (Acanthaceae) and Mallow (Malvaceae). "In the pea family are “Orchid trees” (Bauhinia spp.), (which) bear large pods that can fling seeds nearly 50 feet."

    I didn’t see any plant list for the Waimea Arboretum or Botanic Garden ... and no searches for those places and “dangerous tree” got any hits. But I thought your “dangerous tree” might have been a Bauhinia. Searching for [bauhinia ballistichory] gave this informative article (second hit) about two more capable exploding seed capsule trees:

    “One interesting example from the tropics is the genus Pentaclethra, a relative of Bauhinia. An experienced botanist reported that Pentaclethra was the only plant he knew whose pods opened so explosively and forcefully that they could break the sturdy oaken presses that botanists use to press and dry their plant specimens. For all its press-shattering strength, Pentaclethra throws its seeds only about 33 feet from the parent tree, which, ironically, is not as far as the gentle Bauhinia. Just for the record, the world champion ballistics title belongs to an African tree in the Legume family, Tetraberlinia moreliana, which throws its seeds almost 200 feet!”

    The latter may have come from the 1997 paper: “Explosive Seed Dispersal of the Rainforest Tree Tetraberlinia moreliana (Leguminosae - Caesalpinioideae) in Gabon” by Xander M. Van Der Burgt (now at Royal Botanic Gardens, Kew , Richmond); (Journal of Tropical Ecology - Vol. 13, No. 1 (Jan., 1997), pp. 145-151) (viewable with a free JStor ID here: )

    “The dehiscence (define: rupture) is caused by tension that builds up between the two valves during drying. Mature pods explode with a crack during periods of sunshine.”

    One tree he monitored produced an estimated 15,000-20,000 seeds, with 1.5-2% of those seeds projected over 50 meters away. The longest distance was 60 meters (nearly 197 feet). (With discussions of launch angle and wind-speed dispersions, this paper read almost like an analysis of a golfer testing drivers.)

  2. Part 2:

    Van Der Burgt’s paper also mentions that the exit velocity for the test tree was 37.1 meters/second … which was less than nature’s fastest: Hura creptitans, aka Sandbox tree or Dynamite tree, which launched its seeds at 70m/s (157 miles/hour). This may well be your “dangerous tree.” (It's sap is also poisonous.)

    Googling simply [“Sandbox tree” danger] turned up a host of articles and videos. Among the best: -- “Considered one of the most dangerous plants in the world, the sandbox tree isn’t suitable for home landscapes, or any landscape actually. … Sandbox tree fruit looks like little pumpkins, but once they dry into seed capsules, they become ticking time bombs. When fully mature, they explode with a loud bang and fling their hard, flattened seeds at speeds of up to 150 miles per hour and distances of over 60 feet. The shrapnel can seriously injure any person or animal in its path.”

    And two videos (although none show the H. crepitans seeds exploding):
    Hura crepitans ( ...
    and a Smithsonian Channel video (1:53) of several explosing-seed plants ( )

    The “Going Ballistic” article also succinctly described the ballistichory mechanism: “All of these plants rely on the drying of the fruit wall to generate tension. The wall of a ballistic fruit has at least two layers in which the woody fibers are oriented in different directions, usually at right angles. As the woody fibers dry, the layers pull against each other. When at last the fruit fractures along a predetermined seam or weak spot, the walls curl, throwing the seeds a considerable distance. … It is the drying of the fruit that supplies the tension.”

    So my answers to your questions would be:

    1) Several trees do eject their seeds with an explosive speed of 30-70 meters per second that can send them nearly 200 feet away. One could imagine that it might be hazardous to stand very close to one of the seed pods at the time of its ballistichoric dehiscense. Especially those of the Sandbox/Dynamite Tree.

    2) Yes, quite a few plants eject their seeds with explosive force. The mechanism (described in more detail above) involves increasing tension within a seed pod as it dries, and explosive ejection of the seeds when the pod eventually ruptures.

    Finally, After finding all this, I did not look further to identify the grass that I’d had in my back yard. :-)

  3. Replies
    1. 1. Are there, in fact, dangerous trees that can somehow eject sharp bits of themselves, potentially hurting a human being? (If so... HOW would it do this? So far as I know, few plants - venus fly traps aside - are capable of much movement.)

      First tried to find the clover-like seed you mentioned to know what we are looking for. This didn’t work at the moment. Then tried [“Waimea Arboretum”...] (... means tried different combinations.) Then I found out that the we can call the complex “Waimea Valley”.

      ["Waimea Valley" uncommon tree]

      The Waimea Valley Reveals Its Secrets

      Tried adding many “keywords” that didn’t work like: Velocity, projectiles. Also adding things like warning sign that didn’t work.

      Then decided to just a simple one and if that didn’t work then resting time.

      [explosive trees]

      There’s A Tree Covered In Spikes Whose Fruit Explodes Sending Sharp Seeds 100 Feet At 150 Mph!t

      The fruit of Hura crepitans opens with an explosive sound into segments, hence the name 'dynamite tree'. Seeds are dispersed up to 14 metres away.

      Results shows a video from YouTube and there, is recommended this one:

      Exploding Dynamite Tree Fruit

      Explosive seed dispersal in plants and trees

      [Hura crepitans "Waimea Arboretum"] and [Hura crepitans around(4) "Waimea Arboretum"]

      Massive Tree Pollen Explosion Explained Another new thing for me. Looks awesome.

      [list of explosive trees]

      Other kind of explosions

      [trees ballistic seed dispersal ]

      Page mentions: ballistic dispersal is common in legume trees of tropical African rain forests

      Then visited Waimea Valley site.

      cannonball tree, or Courouptia guianensis: This type of growth is called cauliflory, an adaptation enabling pollination and seed dispersal by animals that do not fly. Site has plenty of articles with different plants and trees.

      [Waimea valley trees ]

      Waimea has a good fruiting specimen of one of Hawaii’s rarest hardwood trees, the uhiuhi, Caesalpinia kavaiensis, from which we will be distributing seedlings. Found with Ctrl-F “Tree”

      [Caesalpinia kavaiensis]

      Caesalpinia kavaiensis is a rare species of flowering plant in the pea family, Fabaceae, that is endemic to Hawaii.

      Examples of Plants That Disperse Seeds by Shooting Them Remembering this, found that most probably, Dr. Russell heard this tree in Hawaii: Uhiuhi but not confirmation yet.


    2. Tried another way to find if Waimea has a Sandbox Tree or if Dr. Russell heard another tree. For this searched Waimea Valley Social Media. And when found it noticed #waimeavalley. I tried on Instagram because there show only images.


      This is the immature and mature fruit of Hura crepitans. Then searched #dynamitetree and found only 7 posts and one of those is from same user: thespeedofplant

    3. [sandbox tree seeds dangerous]

      What Is A Sandbox Tree: Information About Sandbox Tree Exploding Seeds

      1. The shrapnel can seriously injure any person or animal in its path. As bad as this is, the exploding seed pods are only one of the ways that a sandbox tree can inflict harm.
      2. Once fertilized, the female flowers produce the pods containing the sandbox tree’s exploding seeds.
      3. The tree gets its name from...

      Generic name derived from Native American...

      Hura in USDA

    4. Good Morning!

      As I mentioned before, I wrote to Waimea Valley asking for more data about our explosive trees. And, Josephine Hoh, Botanical Group Manager, mentions that Dr. Russell's tree could be either the rubber tree or the already known, sandbox tree. I didn't know rubber tree could explote. So searched , with bias as Dr. Russell tells, [Hevea brasiliensis explosion] to know more. She also mentions that maybe there are other trees but these 2 are the ones that she remembers.

      Thanks Josephine for sharing this information with us. And, thanks Dr. Russell, for helping us to discover and learn more about our world.

  4. [plant shoots ejects seeds]

    Violets, touch me nots, and squirting cucumbers all have one thing in common: They disperse their seeds by exploding. Here's some incredible footage of each one in action. video here: With dopey sound effects.
    Ballistichory (great new word to me) a label that hints at the projectile-like emergence of seeds from their pods or capsules. This type of seed dispersal occurs because the fibers in the dried fruit pull against each other to create tension, and when the tension is great enough, the fruit splits open and the walls of the fruit spring back, flinging the seeds out with force.

    Bet you heard this tree: Sandbox tree (Hura crepitans) sends its seeds hurling nearly 150 feet, and the exploding fruits create a loud noise comparable to a rifle discharge. Bishop Museum records it on Oahu as a high risk to be invasive. close up of the ballistichorical dispersion as far a 50 - 100 meters.
    The shrapnel from the exploded fruit can seriously injure any person or animal in its path. As bad as this is, the exploding seed pods are only one of the ways that a sandbox tree can inflict harm. The fruit of the sandbox tree is poisonous, causing vomiting, diarrhea and cramps if ingested. The tree sap is said to cause an angry red rash, and it can blind you if it gets in your eyes. It has been used to make poison darts.

    This is a dandy. jon tU

  5. almadenmike - comprehensive, informative write up - well explained, kudos - seed/spore dispersal is a vast subject - cattail seeds, mushrooms or maple seeds come to mind.

    not as pleasant a way to gaze around Waimea Valley as Dan experienced, but perhaps a safer way…?
    Waimea Valley
    a lily pad pond…
    recent water damage @ Waimea Valley
    Waimea Valley - lily pond… home to over 5000 plants
    pretty good fact sheet & pics = male & female flowers
    USDA pics
    in Honolulu, Hawaii
    the street view of the above wiki pic, showing that the sandbox/dynamite tree can live in a residential setting… Aloha 'āina

    Ramón (Ramón González April 5, 2017 at 2:06 PM) - regarding your EXIF example of Dan's turkey tracks… perhaps the photo's host makes the difference in this case - the "problematic" photos
    seem to be blogspot hosted… see the JIMV grab below… & comparison to WTCU/Petaluma image…
    so even though you are viewing that fron Dan's blog, the photo is hosted at a non-blogspot site… so the GPS info is still there?…
    image hosted at
    just in case you ever wanted to put a face to Jeffrey Friedl
    near Osaka - see the note about EXIF

    1. Hello Remmij! Good morning. Thanks for the photo with the explanation. I didn't check that and forgot with time that those photos hosted on I wonder why the EXIF data wasn't removed completely on Old St. Hilary’s chapel photo? I mean coordinates were removed but the date and other data still there to read with the extension you shared. Maybe the reason is why on other EXIF Viewers not even that was shown.

    2. I was searching [sandbox tree Hawaii] ["Hura Crepitans" Hawaii] ["Hura Crepitans" Waimea] and found Trees with addresses Here with Ctr-F "Hura" found the tree that Remmij already showed on Google Maps. Ctrl-F "Waimea Valley": 1 Albizia saman, Monkeypod Tree. Erythrina sandwicensis, Wiliwili Trees grove of 18 trees and 2 trees Reynoldsia sandwicensis, ‘Ohe Makai Trees

  6. impressive! & funny - especially if you are familiar with Casey's style - virtual SF - and out to the "N'Plex?" … think that is Hangar One in the background… clever
    (Sutro Tower in the background opening shots - 06 seconds in, on the right)
    is Google nudle now? or is that a parallel reality?

    ""Tribute to Casey Neistat and the fact that the hugely inspiring Vlogs are back!
    The video was made inside of the game Watch Dogs 2 by Ubisoft.
    This channel is mainly a German gaming channel; containing reviews, commentary's and other silly stuff.
    However for a more authentic depiction of a Casey Style Vlog,
    I chose to do the video in English.
    Forgive me for my poor English speaking skills.
    One could say my English is not the yellow from the egg ;)
    that's a good yolk…

  7. the science & math of dehiscence
    video example, ballistic Orange jewelweed pod
    Touch-me-not example
    Mechanical dispersal
    pokey trunks #7
    "You think that sounds dangerous? Try eating one of these bullet-like seeds and you’ll get serious stomach cramps, diarrhea, vomiting, impaired vision and a fast heartbeat. Eat two, and you can add delirium, convulsions, and even death. The yellow sap causes inflammation, in contact with the skin, and causes temporary blindness, if rubbed on the eyes."

  8. Postscript to my earlier comments:

    Today in my yard, I saw in an immature stage one of those weedy grasses that will in the summer explosively disperse its seeds. I took a photo of it and posted it to the Plant Identification Facebook group ... and within a minute someone posted an identification: Hairy bittercress (Cardamine hirsuta).

    A quick search on that name and "explosive" led to the cover article in the August 2011 issue of the American Journal of Botany: "THE MECHANISM FOR EXPLOSIVE SEED DISPERSAL IN
    CARDAMINE HIRSUTA (BRASSICACEAE)" by Kevin C. Vaughn, Andrew J. Bowling of the US Dept. of Argiculture's Crop Production Systems Research Unit (Stoneville, Mississippi) and Katia J. Ruel of the Research Center on Plant Macromolecules (Grenoble, France) --

    Here's a photo of the cover: ... and the illustration with caption:

    The article goes into fascinating detail of the mechanism, including comparisons with similar plants that do not have explosive seed dispersion.

    (BTW, Another new word for me: The elongated seedpod is known as a silique or siliqua (plural: siliques or siliquae).)

    1. looks like you have a potential food source/healing botanical - the Plant Identification Facebook group sounds like a valuable tool too…
      "This plant can be weedy or invasive."
      other names:
      "Chantruk-maan, Common bittercress, Hairy wood cress, Lamb's cress, Serampeti, Serampidi, Splitting Jenny, Sui mi qi, Tosanini vu, Vlaknesta gorva, land cress, hoary bitter cress, spring cress, flick weed, and shot weed (or lambscress, landcress, hoary bittercress, springcress, flickweed, and shotweed)."
      eat the planet
      healing weeds

  9. …so I guess the question is: how did Dan include EXIF Metadata on some of his photos previously on Blogger?
    re: EXIF — used [blogger photos missing gps exif info]
    "I guess social media sites would say that uploaded images are low res and are unlikely to be used outside their social media platform. The EXIF may also contain sensitive info such as where you live, give clues as to your movements (for example leaving home to go on vacation) and divulge when the photo was taken.
    Additionally, they may say that unwanted EXIF data in almost all the millions of images on their platform would consume unnecessary file space and add to download times."

    Adobe forum
    see Blogger section
    conclusion graphic
    did you know that social media sites strip images of iptc metadata?
    Blogger Help Forum
    2011 - Blogger removes GPS EXIF data from uploaded pictures

  10. from the last challenge:
    fwiw - the view looking toward Old St Hilary's Chapel from SF… hope Dan gets a pic - with EXIF info - from here soon…
    the inevitable "shakey" might be interesting.
    ~ 7 miles… on a clear day

  11. 21.635549, -158.054646
    Waimea Valley lily pond with the 'Hawaiian `Alae `ula which means “burnt forehead.”'*
    search lesson: don't assume an image came from the person using it and there isn't more information available…

    did come up with lat/lon for the Waimea image… there is more EXIF info on the original image, but no GPS on the WordPress posting either. Had to use GooMaps for that…
    and the description of the location in the blog post: "A “species and subspecies that evolved in Hawaii and are found nowhere else in the world.” The prize lay conveniently just beyond the ticket booth. I tried but couldn’t get a peek of any burnt foreheads in the pond without paying the $16/each entrance fee.. Worth every penny and more. And we’d only stepped five feet into the park."

    the large, un-cropped, version of the image Dan used, including burnt foreheads on the lily pads…
    also with drainpipe… (how do you select/find these?)
    fwiw, believe this area had a fair amount of flood damage last month. [iPhone 6 back camera 4.15mm f/2.2 Shot at 4.2 mm]
    Jeff's IMV of the image
    a difficulty shared with plants – many names, same thing:
    *Common Gallinule/Common Moorhen
    those are BIG feet
    different camera - Canon EOS 80D, EF100-400mm f/4.5-5.6L IS II USM Shot at 400 mm - Hawaiian Gallinule
    on GooMaps
    the pond photo location
    image from:
    a Portland birder - did Dan cross paths?
    Audrey has a birder sense of humor - "I didn't choose the bird life, the bird life chose me."
    most recently in Texas

    another renowned burnt forehead hangout
    feet & fish