Sunday, April 06, 2014

Cactus Spines

Weather: High winds, dry air, and morning temperatures cold enough to threaten the peach flowers; last rain 3/16/14.

Last Sunday afternoon, I saw Russian thistles blowing by my window. From where I sat, they had to be at least ten feet off the ground. One landed in the black locust some seven feet up.

What’s blooming in the area: Peaches, cherries, crab apples, flowering quince, forsythia, daffodils.

Beyond the walls and fences: Bright green Siberian elms, alfilerillo, western stickseed, purple and tansy mustards, dandelions. Needle grass green about four inches.

In my yard: Bradford pear; sand cherry fragrant; spirea, lilacs, beauty bush leafing.

Animal sightings: Small birds.

I haven’t heard bees around my peach tree like I usually do when it’s in full bloom. I’m told, they don’t like wind.

Weekly update: The spines on the cholla cacti I brought from Abilene, Texas, in the 1990s seem much longer this spring. One is a different species than the local one, but the other looks the same.

I don’t know why.

People’s understanding of cacti is conditioned by perceptions formed by other plants.

Angiosperms have roots, stems, leaves, flowers and seeds. Of these leaves are the most important, because they perform the photosynthesis that keeps a plant alive.

Cacti are plants. Therefore, they must have roots, stems, leaves, flowers and seeds. Only they don’t have leaves. The stems handle the food production, and they do it at night like a grass, rather than during the day.

What the cholla and prickly pear in my yard do have that is unique to the plant family are the spines.

For years, conventional wisdom has said the spines were leaves whose purpose had been diverted to survive desert conditions.

Now, some who’ve actually looked closer have found cacti have microscopic leaves and that the spines are dead, woody cell matter that rises above the areoles where the leaves exist. They aren’t actually wood, but woody fibers.

Conventional wisdom posits the spines shade the green stems. That’s probably true of the hedgehog cactus that’s growing in my yard, but the ones on the cholla and prickly pear are too sparse.

An alternative suggestion is spines exist to protect cacti from herbivores. They certainly keep away the humans who make those comments. But, rabbits know how to eat prickly pear.

And so do grasshoppers. And so do birds.

Several years ago, a great mound of dirt appeared near one of my cholla, and the other one started to die.

Last fall, I noticed a mount near a cactus field on the prairie

This year, when I went walking on the prairie, I found every single prickly pear had a mound of dirt around it where some animal had burrowed under to get to the roots.

I noticed many of those cacti had long spines.

Botanists final suggestion is spines exist to direct water to the roots. Dripping is something they can observe.

What they can’t observe is what happened eons ago when the plant group was evolving in South America. Better knowledge of the Miocene, especially the early years when temperatures were still warm, might explain spines better than modern analogies.

Notes: J. D. Mauseth, MausethResearch: Cacti website sponsored by the University of Texas.

1. Spines on cholla brought from Abilene, Texas, 15 March 2014.

2. Spines on local cholla, 2 April 2014.

3. Flower on local cholla, 18 June 2009.

4. Flower on the other cholla brought from Abilene, Texas, 10 June 2013, with some kind of bee.

5. Flower on prickly pear down the road, 7 June 2013.

6. Hedgehog cactus in my yard, 2 April 2014.

7. Prickly pear nibbled by rabbit, 24 June 2008; young pad hasn’t developed many spines yet.

8. Cholla in my yard with seed pod (tuna) eaten, 2 April 2014.

9. Animal mound in my yard near a cholla, 23 December 2010.

10. Animal mound on the prairie, 21 September 2013.

11. Prickly pear on the prairie, attacked by burrowing animal, 20 March 2014.

12. Prickly pear flower eaten by a grasshopper, 7 June 2013.

13. Russian thistle lodged high in a black locust growing with Dr. Huey roses. These are thorns that deter.


Vicki said...

Very interesting post. Even with all those spines to protect them, the animals figured out that you tunnel under them to get to them. How very interesting. An interesting analogy is that no matter how many steel, barbed wire or electric fences we build on the Mexican border, tunnels are built under them to get what they want.

DragonsLady said...

A couple of weeks ago when I came to Espanola, I saw one Russian thistle caught on a power line near the Santa Clara medical building. It looked like Mother Nature wanted to keep planes or helicopters away from the cables. When I returned later the thistle was gone.