A leaf is a leaf is a … rain gauge? Yup. Sort of. Brittlebush leaves act like Ma Nature’s precip monitor. The drier it is, the smaller and whiter the leaves it produces. If the soil dries up too much the leaves drop off altogether.
The we’ve-got-enough-water leaves are dark green, almost hairless. Turn up the heat and turn off the tap and that changes quickly — the next leaves to appear will be greyer and covered by white hairs. Those two factors keep the leaves from overheating by reflecting the sunlight. The tiny hairs also trap moisture.
I took the leaf shots this morning just as the rain started — the wet leaves really show the colour contrast.
Brittlebush is one of the most common plants on the Sonoran Desert. It grows in a half moon shape, like an upsidedown bowl. That shape and the profusion of eye-popping yellow flowers make it easily recognizable.
The image below shows what happens to a single bush when it moves into town and onto a lot where the owner waters plants. Wow. 🙂
Brittlebush Encelia farninosa
Chuparosa Justicia californica (aka Beloperone californica)
Palo verde Parkinsonia aculeata
I wrote recently about The Silk Road. This is the rest of the story.
How many mouths does it take to eat a tree? Not the wood. Just the leaves. All of them.
That’s what has happened in our corner of the world. Most of the aspen poplar have been completely defoliated by armies of small black caterpillars.
The caterpillars, or larvae, are the second stage in the life cycle of the Large Aspen Tortrix. The name Tortrix comes from a Latin word meaning to twist. When you see the leaves they’ve been feeding on, you can see why that name was chosen.
These photos and captions tell more of this tale …
Aspen defoliated by caterpillars of the Large Aspen Tortrix. The other leafy trees are balsam poplar which are mostly unaffected.
The start of the infestation — larvae have eaten much of the leaves.
Larva on a spruce branch. Strong winds and the search for more food sent larvae groundward on strands of silk. This one landed on a spruce tree.
Larvae that weren’t able to find poplar leaves to pupate in settled for spruce.
Tortrix larva beginning to spin silk on a poplar leaf in readiness for the next stage in its life cycle.
This larva is spinning silk on a balsam poplar leaf, drawing the leaf sides closer together until it is completely hidden. It will hide there, turning from an active leaf-eating caterpillar into a non-feeding pupa, the next stage in its life cycle.
Here’s an interesting grouping (L to R): a fully formed pupa, the larval skin it shed as it pupated, and a caterpillar beginning its transformation.
Some pupae have already split open, releasing the adult moths. I imagine we’re in for quite a show when the big hatch happens.
We’ve had defoliations in the past, but I don’t recall anything like this — it stretches for kilometres in all directions.
Although this feeding frenzy sounds disastrous for the aspens, it’s not as gloomy as one might expect. The trees are already sprouting new leaves and before long will look more like they should at this time of year.
Conditions this year are different. Winter was mild. Spring came early. It turned hot. Rainfall has been little and sporadic. Are we seeing the effect of climate change? Or merely a brief climatic blip?
It’s an ongoing evolutionary dance as we each strive to adapt to our world.
Large aspen tortrix Choristoneura conflictana
White spruce Picea glauca
Trembling aspen Populus tremuloides