About Yellow

After checking on the irises last Friday, I went to hike Billy Goat A. I had one goal: get photos of eastern prickly pear cactus flowers. It wasn’t too long before I came across this underwhelming specimen. I had a look ’round and found more plants, but no more flowers. Figuring they needed another week, I hoisted the pack and continued along the trail.

And then suddenly I spotted this huge stand, blooming in the shade of a scrub pine (Pinus virginiana).




You can read more about Opuntia humifusa in this post from last August, (in which I wrote “it’s something to look forward to next summer” -success!). And read more about cacti in general in this post from March.


Many times I photograph a plant in order to show specific details, or give an accurate view of the plant for reference, so I try to get even exposure across the subject.



On this day, the flowers were glowing in the mid-morning sun, and the shadows cast by the plants heightened the effect.




All I wanted to capture was that beautiful yellow in the layers of translucent petals.




It was a busy day, so once finished I packed up the camera and headed back to the car. And then I spotted something completely new. Couldn’t get good photos (pressured for time, wind blowing, etc.), but I got enough to ID the plants later. Ends up they’re threatened and listed S1/highly state rare in Maryland. So guess what I’m doing this morning? More on that plant soon.

What Makes it a Cactus?

And, back to wildflowers.

The pictures in yesterday’s post were of beavertail cactus, Opuntia basilaris, one of the earliest blooming cacti in the Anza-Borrego region. It grows in many different habitats of the Sonoran and Mojave deserts, and is easily identified as an Opuntia by the characteristic flat pads that appear to be spineless. It’s further identified as O. basilaris by the pink flowers (other species’ flowers are yellow). About those spineless pads: they aren’t spineless. The spines are just very small. They’re also barbed. Since this is botany, there has be be a word for them. They’re called glochids.

Beavertail has a cousin here in the Maryland piedmont: eastern prickly pear (Opuntia humifusa).

Cactus is one of those botanical terms that’s often mis-used colloquially, referring to any succulent plant. Succulent just means that the plant has organs that store water, while a cactus is any plant that is a member of the cactus family, Cactaceae.  There are many succulent plant species in the world, but only some of them are cacti.

So what makes it a cactus?

A number of things, taken in combination. First, cacti have spines, which are modified leaves. Spines are not the same as thorns, which are modified stems, or prickles, which arise from epidermal tissue.

Since (with very few exceptions) cacti don’t have true leaves, photosynthesis happens via the stems, which are succulent and often cylindrical, globular, or pad-shaped.

the things that look like dots on the stem are the aureoles; zoom way in to see some glochids in the upper ones

The spines arise from structures called aureoles, which are a defining feature of cacti; no other plants have them. Aureoles also give rise to new stems (on branching species) and to flowers.

Cactus flowers are showy and usually radially symmetrical, with numerous petals and sepals (which can’t be distinguished from one another). They are also usually bisexual, with numerous stamens and a single pistil with an inferior ovary (which means that it is located below the petals and sepals).

With the exception of a single species, all cacti are native to the New World.

Weird cactus fact: there are cactus species native to the the rainforests of Central and South America. Yes, cacti grow in the rainforest, as epiphytes on trees where there’s little organic detritus to form soil and water doesn’t collect, a situation like an extremely localized arid-yet-humid microclimate. Isn’t that nifty?! The common household plant Christmas cactus (Schlumbergera species) is one example.

next time: more cacti

interesting reading
Spines, Photosynthetic Tricks, and Other Marvels of Cacti Evolution

Bonus Plant

I had a few goals for my second hike on the Billy Goat A trail:

  1. find spatterdock and get better pictures
  2. find orangegrass and get better pictures
  3. get better pictures of purple-headed sneezeweed and seedbox


So it came as a surprise and delight to find this before finding any of the above.

This is Opuntia humifusa, aka eastern prickly pear, the only cactus to grow wild in the state of Maryland, where it’s mostly a plant of the coastal plain. But that’s one of the neat things about the Potomac Gorge: you find things there that aren’t usually found in the Piedmont. Also, strangely, there are records for this plant in Washington County, in the ridge and valley physiographic province.

This species is fairly well distributed through the mid-Atlantic, the South, and the Midwest. It’s listed as endangered in Massachusetts, exploitably vulnerable in New York, special concern in Connecticut, and rare in Pennsylvania.

Being a cactus, it of course is going to like growing on thin, sandy, rocky, well-drained soils, and prefers full sun as well. The Illinois Wildflowers site says that one of the species’ biggest threats is invasion by woody vegetation (presumably because of shading). I found this stand in a somewhat open area growing amid scrub pine (Pinus virginiana) and shrubby St. Johnswort (Hypericum prolificum), in a surprising amount of shade. This is a good size specimen (a few feet across). I hope it can hang on a few more years.


Eastern prickly pear is also known as devil’s tongue, low prickly pear, and smooth prickly pear. Don’t let that last name fool you: it may look more or less smooth, but it has hair-fine spines that can cause a lot of pain.

As in Death Valley, I was there at the wrong time to see it bloom. You can see the shriveled flowers in the first picture. I did have a look ’round for other plants, but as there are signs all over Billy Goat A asking people to stay on the trails, I didn’t go far. (Bear Island is under tremendous stress from overuse.)

Oh well. It’s something to look forward to next summer.

Two Cacti, Not Blooming

beavertail cactus
Opuntia basilaris


cotton-top cactus
Echinocactus polycephalus


While exploring the area around the globemallow I came across two different types of cactus plants.  One was well in bud, so I made it a point to go back two days later, right before leaving for the flight home. No luck. Still in bud.


Beavertail looks a lot like the familiar prickly pear cactus (it’s in the same genus), but it lacks spines. There are four varieties; I have no idea which one this is. Here’s a picture of it in flower. [sob]

Cotton-top cactus is distinctive because of its form (polycephalus means “many heads”). You can see from this photo how it got its common name:

By the way, if you’re scrambling up a scree where cotton-top are growing, choose to pass the plants on the downslope. I figured this out just a few steps shy of one of the beasts, where sure enough I lost my footing and went for a bit of a slide. It could have been comic in a Road-Runner sort of way. More likely it would have been really painful.