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Does Hogplum Pay Rent?

Plants that “make their own luck” are a fascinating bunch. Many improve their own circumstances, or, an ecologist might say, generate “autogenic positive feedback.” Today’s example from a windy walk in the scrub is the way single plants, or even better, clumps, capture blowing leaf litter and make their own compost. Any gardener worth their snippers can list the marvels of compost.

A natural mulch volcano around Varnishleaf.

Clump of Gopher Apple acting like a leaf catcher brush.

Peelbark St. Johnswort catches waterborne debris.


Have the actual benefits of this sort of thing ever been tested and demonstrated? Yea, but what’s more fun than digging around in in Google is walking around in nature. Often if you think about an ecological possibility—making it “the theme” of a stroll— you can make your own comparative assessments. Does the plant send roots into its personal compost? Do this with compost look healthier than those without?


A twist in this topic is root-parasitic plants, one’s that grow alongside hosts and divert goodies from the host roots. The downside for the hosts is obvious, but maybe paying rent too? Observers have shown or speculated that while host helps the parasite grow nice and leafy, the parasite sheds its leaves into the shared compost zone. It might even help block wind. Maybe free compost benefits the host more than the cost of the root mischief. Not that I have any proof, but locally the scrub-dwelling root parasite Hogplum (Ximenia americana) comes to mind.

Hogplum growing a leafy contribution. By John Bradford.

Hogplum underground thievery. By R DeFilipps (1969).

 
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Posted by on November 10, 2024 in Uncategorized

 

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It’s Vine-Eat-Vine in the Scrub…

Unless you’re a Smilax


Darwinian competition is rough business:  frogs eat flies, snakes eat frogs, hawks et snakes, and Love Vine eats other vines in the scrub.   In case you don’t know Love Vine (Cassytha filiformis), it is that yellowish spaghetti vine festooned all over other plants in scrub and additional habitats. It forms massive tangles smothering and parasitizing all beneath.  

Love vine bothering its neighbors, by John Bradford

Love Vine penetrates its plant victims with little suckers called “haustoria” and sucks out sugar and water. 

Haustoria at work, JB

  Not nice, but it gets ahead in the world.    Love Vine probably came here all the way from Australia, pollinating itself to make the intercontinental hopscotch easier.   Tiny thrips, insects that parasitize the Love Vine, ride in a stowaway space between the fruit wall and an outer covering of fleshy birdfood.  Apparently the birds help the vine AND the thrips get around.   All well and good, but what interested me today is seeing in the scrub that a different vine, Earleaf Greenbrier  (Smilax auriculata), not only seems immune from the Love Vine, but also uses it to rise above the tangle  into the sun.  The invulnerable Smilax climbs up the Love Vine unmolested, and snakes along the top of the Love Vine to enjoy an easy path above all the shade, crowding, and parasitism below.

Smilax ignoring Love Vine. Can’t catch me!

It gets a little more complex.  Another  vine in the scrub (and elsewhere) is Muscadine Grape (Vitis rotundifolia).  The grape resembles Smilax in overall habit, stem diameter (when in scrub), climbing ability, leaf size, small plain clustered unisexual flowers, and making “bunches of grapes.”   Unlike Smilax, however, the grapevine falls prey to Love Vine.

Above: Grape is not immune!

Smilax comes out on top

Why the difference?   Most woody plants have their water-conducting and sugary-sap poorly protected just under the bark.  Easy pickings for creepy Love Vine.    But Smilax is different:   its stem is built like cables within cables.   (Because It is a monocot if that matters to anyone.)  If you cut across the stem  and look end-on, the plumbing is deep within the stem and surrounded by a hard  protective sheath.     No parasite is going to break into that!

End view of Smilax stem magnified. The green circles surround the sugar pipes. The big blue rings circle the protective sheath. The large open ends within the sheaths are water pipes.

Don’t get me wrong. No suggestion here that the Smilax stem internal structure is a special adaptation to block Love Vine specifically (although it might have a lot to do with protection in a broad general sense). So do those thorns. Think of it as a chance thing…lucky Smilax winds up in a habitat with a stem structurethat just happens to offer an advantage against would-be competitors such as grape, or maybe species long-gone because of not having the “right stuff.”

 
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Posted by on June 8, 2024 in Uncategorized

 

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