A bit of agave magic
One of my favorite plants from our recent Santa Barbara trip to San Marcos Growers is Agave horrida. The clone most frequently seen in cultivation, tissue-cultured by Altman Plants, is very nice (here is Kyle’s specimen), but the San Marcos plants are even more beautiful:
 |
| Agave horrida from San Marcos Growers |
Take a good look at the photo above, especially at the marginal teeth and the spines at the end of the leaf tips. They’re light gray, right?
Imagine my surprise when I watered my plant:
 |
| Same plant with wet teeth and spines |
Whaaaat? The teeth and spines are almost black now!
Here’s a short video that shows the transformation even better:
What kind of alchemy is that?
I knew it had to be an optical phenomenon, and Google provided the answer: Agave teeth and spines change color when wet primarily because the water temporarily alters the way light reflects through their translucent outer layers. This highlights the underlying pigments and microscopic textures, creating a deeper, darker hue that vanishes as the teeth and spines dries out.
If your eyes are starting to glaze over, stop here. If you’re still mentally engaged, here is a closer look at the mechanisms behind this color shift, as per the all-knowing internet:
- Dry spines often have a microscopic waxy coating that scatters light, making the color appear muted or gray. When moisture is introduced, it fills these microscopic gaps, acting as a clear lens that allows light to penetrate deeper and reflect the natural melanin (dark color) of the spine.
- Some agaves absorb dew or rainwater directly through their spines and specialized cells. As the spine absorbs moisture, turgor pressure (water weight within the cells) increases, which can slightly expand the tissue and alter the color.
Physics was one of my least favorite subjects in high school. I won’t profess to know exactly what makes my Agave horrida change color, so I’m OK with calling it magic.
© Gerhard Bock, 2026. All rights reserved. To receive all new posts by email, please subscribe here.
Very cool!
ReplyDeleteIt is a bit of magic, I love hitting Ferocactus pringlei with a spray of water just to see the vibrant red spines pop. This is even more magnificent!
ReplyDeleteYes! Ferocactus spines become so vibrant when wet.
DeleteThat IS a dramatic shift!
ReplyDeleteRight???
DeleteOh, now that's fun--both the change itself and the science behind it. And of course your video. Thanks for sharing!
ReplyDeleteI love discovering and learning new things!
DeleteSo glad you made it back to San Marcos, and especially to snag such a beautiful agave. I've heard that clearing out inventory has gone a little slower than anticipated. Wish I had garden space and a small truck...
ReplyDeleteI hope the remaining plants will find a home instead of being trashed.
DeleteEither way, a beauty. Lucky you, what a souvenir from an awesome grower.
ReplyDeleteMy titanotas are blue with black teeth grown in shade; in sun, near-white and grey teeth--bleaching?-- or holding on to more moisture in shade?
I'm mourning the loss of San Marcos. --h.boo
I've noticed that, too. Titanota/oteroi teeth seem to change more readily and quickly than other agave.
DeleteI swear, every time I Google a cool plant, the San Marcos websites is one of the first links listed. So many wonderful plants no longer available. Kyle and I will do our best to continue propagating at least a few of them.