Quick answer: Morro Rock Trees and Geology — Trees on this coast live with fog, salt, wind and thin soil, and the work that keeps them healthy is decided by those conditions rather than by a calendar written inland. Structure, clearance and the root zone are what a tree here needs looked at, and small work done early is what keeps a tree out of the emergency list.
Field note. What we see on this coast is that the trees people worry about are usually not the ones in trouble: the pine with a clean crown and a lean that predates the house is often sounder than the tidy tree that has been quietly drowning in its own root zone.
On the other hand, there is no schedule that suits every tree — the same species on two sides of one street can need opposite care, which is why we look before we recommend.
The absence of trees on Morro Rock is not a mystery and it is not entirely about wind. It is about what the rock is made of, how it fractures, and where water can be.
The material
Morro Rock is a volcanic plug: the cooled throat of an ancient volcano, exposed as the softer surrounding rock eroded away. The rock is a rhyolite — fine-grained, silica-rich, and hard. That hardness is the first problem.
Hard rock weathers slowly. Soil forms from the breakdown of minerals, and a rock that resists breakdown produces soil at a rate measured in centuries per inch. The rock has been exposed for a long time and has produced very little soil in all of it.
Where the water goes
Rhyolite fractures in cooling joints — roughly vertical cracks where the plug contracted as it cooled. Those joints drain. Rain that lands on the rock runs down a fracture rather than soaking into pore space, because there is no pore space.
A plant on the rock therefore has two problems: almost no soil to root in, and whatever water arrives leaves vertically. The species that survive in that are the ones that can root in a crack and tolerate drying completely between rains — lichens, small ferns, and a few succulents.
Chemistry
Rhyolite is silica-rich and low in the base cations that plants need. It is not toxic, it is simply poor. The mineral nutrients that a plant requires — calcium, magnesium, potassium — are present in small amounts and released slowly, and the organic matter that would hold them cannot accumulate on a surface that sheds water.
Contrast this with the shale and sandstone of the surrounding hills, which weather faster, hold water, and produce the soils that the oak woodland grows in. Two hundred metres apart, two different worlds.
What the talus does
At the base of the rock, fallen blocks have accumulated in a talus slope. That material has more surface area, more fractures, and organic matter that has blown in and collected. It holds water. Which is why the vegetation starts at the base rather than on the face, and why the base has a scrub community while the face has almost nothing.
Those scrub plants are the ones worth noting for planting on difficult sites nearby: they are the species that have solved the problem of growing on ground that is mostly rock and wind.
The wind, which is the second constraint
The rock stands where the marine layer funnels through the gap between the hills, which makes it one of the windier points on this coast. A plant on the rock face is subject to salt aerosol arriving at speed, and the salt is not washed off because there is no soil to dilute it.
Which is why the vegetation on the rock is concentrated on the leeward side and the crevices where the salt load is lower.
What this teaches about planting nearby
The lesson for a garden anywhere on this coast is that substrate and drainage come before species. A planting on shallow, fast-draining ground over hard rock behaves like a planting on the rock, regardless of what the soil map says, and the species that succeed are the ones adapted to that condition rather than the ones the garden centre recommends.
Where the site is genuinely shallow over rock, the right approach is root zone remediation in a small area rather than a broad planting, and the choice of species is the subject of salt-tolerant planting.