Celebrating Sticky Seeds

Early autumn is a season of surprise and wonder.  Colors are changing and animals are scurrying all around, trying to check off all their pre-winter tasks.  For nature enthusiasts like us, it’s also a great time to appreciate the complex and sophisticated ways plants move their seeds around the world.

For example, there’s the unexpected prick of joy when you accidentally sandwich a heretofore unseen sandbur between calf and hamstring as you kneel down to re-tie your boot laces. 

(I think that’s the first time I’ve ever used the word “heretofore”.  I hope I used it correctly.  I would have used “previously”, but when I typed it out, the spelling looked wrong for some reason.  Brains are funny.)

Sandbur (Cenchrus longispinus).

Anyway, upon discovering the sandbur, you immediately stand back up, lick your fingers, and remove it (and its friends) from your pantleg.  As you have so many times, you ask yourself why licking your fingers helps it hurt less when you grab sandburs.  Surely, the surface tension of saliva can’t provide that much protection?  Regardless, seeing and feeling the sandburs is a terrific way to celebrate their particular seed dispersal strategy. Hurray for nature!

After you identify a winding path that will allow you to avoid more nearby sandburs, you step forward – only then remembering that you’d stopped to tie your boots.  That’s when you glance down and realize that your boot laces must have pulled loose when you walked through a patch of cockleburs a little way back.  Now, a cheerful cluster of cocklebur seed pods is tangled happily in your laces like spiny little meatballs in a plate of spaghetti. 

Cocklebur (Xanthium strumarium) along a wetland edge.

As you start to carefully extract the pods from your laces, you can’t help but marvel at the similar, but different architecture of cockleburs and sandburs.  Sandburs, of course have long, straight, sharp spines protruding in every direction from their mostly-spherical core.  Those spines have an impressive ability to penetrate nearly any material.

Cockleburs, on the other hand, have what look like dozens of tiny fish hooks sticking out of their football-shaped bodies.  Those hooks can poke through clothing (and boot laces), but they’re more likely to snag than poke, with the little hooks acting like a bunch of tiny grasping claws.  Of course, if they do manage to penetrate clothing or laces, the hooks also make it much harder to extract them.  It’s a really remarkable design.

The strategies of both cockleburs and sandburs are sure effective, you think, as you continue de-tangling your laces.  Also, it’s fun that both of them have “bur” in their names.  That, of course, brings back memories of learning the difference between burs, stickers, thorns, and spines at some point.  You obviously don’t remember what those differences are now – it’s been at least three or four years since you last looked that up and no one can be expected to retain information that long.  It’s fun to know there are differences, though.

Also, it’s weird that the word bur can be spelled with either one “r” or two.  You know that bur oak is definitely spelled with one, though people do insist on adding that second one, don’t they? 

Apart from the name of that tree, which definitely, always has only one “r”, you recall doing a little research a while back and learning that both bur and burr are considered correct spellings in certain situations.  There are burs that are seed pods and burs that are rough edges on metal and it seems to you that people argue whether those two should be spelled the same or differently.  Ah well, someone will probably figure that out and then people won’t have to argue anymore.

Close up, you can see the tiny hooks on the cocklebur spines (thorns? prickles? poky things?).

Anywell, you finish removing the last cocklebur (surely not cockleburr?) from your laces and leave the pods on the ground – having done them the favor of carrying them to a new potential home.  Isn’t it nice to play a helpful role in the dispersal of seeds?  You’re an actual conservation hero.

Well, hero, as you proceed through the prairie (by the way, you’re walking in a prairie), you take a detour around a big patch of tick clover plants.  You’re no fool, after all.  Tick clovers are beautiful, important wildflowers, but their seeds are like little Velcro packets that are good reminders of where the name “tick” clover comes from.  Taking on the role of a seed disperser is all fine and good, but you’re in charge of fixing supper tonight and won’t have time to both do that and scrape a load of tick clover seeds off your long-sleeved shirt.  A wandering deer will surely do the tick clover dispersal without you needing to become involved this time.

Side-stepping the tick clover takes you along the boundary between the prairie and a small adjacent woodland.  As you walk along that edge, a tentacle appears to lash out from beneath the trees and grabs onto your pants.  Startled, you pull away, but the “tentacle” leaves behind a linear string of small sticky pods.  You stumble slightly over a gopher mound, and as you catch your balance again, your leg is caught by two more of those tentacles, which turn out to be branches of the amazing stickseed plant.

Stickseed (Hackelia virginiana) hangs out mostly in woodlands, at least around here.

Stickseed has an even more descriptive name than tick clover.  The sticky “pods” carried by the stickseed branches are, as you oddly recall, actually clusters of four little “nutlets”, each containing little barbed prickles.  I dated a girl named Barb Prickle in high school, I think. 

I’m joking, of course.  Barb wouldn’t have given me the time of day.

Returning to the present, stickseed and its prickly nutlets are magnificent examples of nature’s innovation.  You know from experience that trying to rub the little nutlets off your pants will just cause them to roll along the fabric, never loosening their grip at all.  It really is a spectacular evolutionary achievement.  Well, you’ve owned these pants for almost four months now, so it was probably time to replace them anyway.  It’s a small (well, medium) price to pay for a front row seat to this lovely demonstration of seed dispersal mastery.

A close up of the nutlets with their tiny barbed prickles.
Stickseed seeds (and a little foxtail) on my hiking clothing.

You manage to pull one of the little nutlets loose to inspect it with the hand lens you always carry on a string around your neck.  Under magnification, the little prickles sure don’t look like they’d be as sticky as they obviously are.  As you’re pondering that, you turn to continue your hike and walk straight into a chest-high patch of tick clover. 

Well, look at that, will you?  The pattern of tick clover seed pods across the front of your shirt is really visually attractive. It’s like a free participatory public art project!  (Hm – the seed pods are not really pods.  What are they actually called?  Loments?  Loment segments? No one knows for sure.)  Either way, it’s loments like this that make you really ponder the awesome power of evolution.

This is Illinois tick clover (Desmodium illinoense) but there are lots of species with very similar sticky seeds (or loment segments).

You’ll have to pull those whatever-they’re-called off later, of course, because any that make it to the laundry will still be attached when the shirt comes out of the dryer.  Except, obviously, for a few that will detach and re-attach in fun, surprising places on other pieces of clothing.  That’s ok, picking tick clover seeds off a shirt later tonight will give you something to do while you’re browsing through the internet for new pants.

Speaking of tonight, look at the time!  All this marveling at the wonders of nature has taken the whole afternoon and you’d probably better get on the road so you can get home in time to make supper.  You’ve got leftover pulled pork in the fridge.  That, some fresh carrots, and a bag of chips will make a pretty nice dinner.  Maybe you’ll even stop at the grocery store on the way home and grab a nice jar of barbed prickles to complete the meal.

Photo of the Week – November 14, 2013

Last week, I took a short early morning trip out to my family prairie.  As the sun came up, its light was caught beautifully by the fuzzy seeds of various prairie plants, particularly stiff goldenrod (Solidago rigida) and dotted gayfeather (Liatris punctata).

A stiff goldenrod seed is ready to fall from a seedhead.

A stiff goldenrod seed is ready to fall from a seedhead.  Helzer prairie, near Stockham, Nebraska.

Species with fuzzy parachute-style seeds trade distance for time.  Their seeds can be carried far from the plant, giving them a chance to colonize new areas.  However, because the seeds have to be light weight, they tend to have short shelf-lives, and can’t survive for very long – they will either germinate quickly or die.  Bulkier seeds often have the ability to survive for years in the ground and then germinate when favorable conditions appear – but they don’t typically travel very far from their parent plant.  Life is a series of tradeoffs!

More goldenrod seeds.

More goldenrod seeds.

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And more.

And more.  In this photo, the contrast between the brightness of the seeds and the shadows behind the plant were such that the camera couldn’t capture it all, resulting in a black background behind the correctly-exposed seeds.

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Even after the petals (and even the seeds) fall, goldenrod flowers are still very attractive.

Even after the petals (and even the seeds) fall, goldenrod flowers are still very attractive.

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Dotted gayfeather also has short-lived, high-flying seeds.  However, once a new plant is established, it puts down deep roots (literally - as deep as 10-15 feet).

Dotted gayfeather also has short-lived, high-flying seeds. However, once a new plant is established, it puts down deep roots (literally – as deep as 10-15 feet).

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More dotted gayfeather seeds.

More dotted gayfeather seeds.