Living Arroyos

Acorn Season!

It’s acorn season, and we’re out harvesting! This year’s crop arrived fairly early, so we’re scrambling to collect as many as we can to ensure a good supply for planting later this fall and into winter.

A good stash of valley oak acorns along Tassajara Creek in Dublin.

A good stash of valley oak acorns along Tassajara Creek in Dublin.

We’re planting oaks from acorns rather than as seedlings – or even larger plants – for a number of reasons. Cost, of course, is important; acorns are free for the taking, though collecting large numbers does involve a fair amount of labor. Acorns are also easy to manage and plant,which makes them well suited to volunteer-powered programs like Living Arroyos. Most important, though, is that several studies have shown that oaks grown from direct-seeded acorns tend to grow healthier and straighter than plants grown in containers and transplanted. The reason for this is that as they germinate, oaks first put down a long taproot that reaches deep into the soil to secure moisture. Container-grown plants have to be managed very carefully to ensure that the taproot is allowed to develop normally before transplanting. We’ll be experimenting with a number of oak planting techniques over time to find the methods that work best for us.

Oaks are large, long-lived trees that will someday form the backbone of the landscape along many of the arroyos in our program area. We chose oaks for this role not only for their beauty and longevity, but also because they are among the most important of all California trees in terms of supporting other species. Their acorns provide food for an astonishing diversity of wild creatures, from acorn woodpeckers to bears (though we don’t expect to see many of those in the Livermore-Amador Valley).


Looking up through the canopy of a valley oak.

We’re focusing on two species, valley oak and coast live oak, for our plantings at the Stanley Reach site. Valley oaks are deciduous, and tend to grow fairly straight and tall. The tallest valley oak, located in Covelo, is also the tallest known North American hardwood at 151 feet. Old trees can be incredibly massive, with trunks up to twelve feet in diameter and long, drooping branches that often reach the ground. Valley oaks are endemic to (found only in) California.

live oak

UCC’s Apprentices in Ecological Restoration with a coast live oak.

Unlike valley oaks, coast live oaks keep their leaves year-round. Mature coast live oaks tend to grow more outward and less upward than valley oaks. Coast live oaks are near-endemic – their range extends a little way south of the border into Baja California. In the past Coast live oak acorns were a staple of the diet of numerous California Native peoples. Old trees of both species are magnificent, iconic elements of the California landscape, and we hope that someday our trees will feed, shelter, and shade future generations of wildlife and people.