Have you ever taken a close-up look at an oak acorn? Usually we use the shape of the leaves to determine which oak we’re looking at. Sometimes it helps us to know whether the oak is evergreen or deciduous. We can also look at the acorn for help in identifying oaks.
The valley oak, Quercus lobata, has a long, tapered acorn. The cap or cup is thick and tubercled (warty). The acorn requires one year from flowering to the mature acorn.
The coast live oak, Quercus agrifolia, has a cap that covers over one-third of the nut. The cup has thin scales and is not warty. The acorn matures in the first year.
The black oak, Quercus kelloggii, has a cap that covers over one-half of the nut. The acorn matures in the second year.
— Katie Martin, UC Marin master gardener
