Not all the oaks in California

Muller oak, Joshua Tree National Park, California; September 2014

The first naturally growing oak I saw in California was in Joshua Tree National Park, just south of Los Angeles. Not a grand old tree like the ones from eastern USA I’d seen in picture books, but a gnarly shrub fighting for existence alongside succulents and desert ephemerals. Huddled near a stand of the local pine tree, the piñon (Pinus edulis), in the shadow of an ochre-coloured, rocky outcrop. 

I'm pretty sure it was a Muller oak (Quercus cornelius-mulleri), with its spiny, leathery leaves, growing the way oaks do in this part of the Americas. Keeping low to the ground and doing all it can to conserve water. Until 1981, this species was considered a variant of another Californian species, Nuttall's scrub oak (Quercus dumosa). 

Muller oak, Joshua Tree National Park, California; September 2014

Thomas Nutall, in case you were wondering, was a Yorkshire born biologist who travelled the length of the Missouri River and much of the Rocky Mountains and its hinterland, collecting new species such as Nuttall's scrub oak, which he named and described in 1842. 

Both oaks can be found in Royal Botanic Gardens Melbourne's expanding Aridland Precinct, beside Anderson Street, on the eastern side. Along with a few more leathery-leaves evergreen oaks from California, such as the scrub live oak (Quercus turbinella) and coast live oak (Quercus agrifolia; see also earlier post).

Coast live oak, Kyneton Botanic Gardens; June 2020

You can see a pattern emerging here in the common names, with terms like 'scrub' and 'live' reappearing. Scrub because these oaks are mostly shrubs or at best small trees. Live because they keep their leaves all year - or at least only dropping them when new leaves appear in late spring - rather than dropping them in autumn (or early winter) like most deciduous oaks. 

The Melbourne collection also includes an island scrub oak (Quercus pacifica), a name that says it all for this species from the Channel Islands of California. As well as a leather oak (Quercus durata), with a common name that celebrates another shared feature of most Californian species, the tough, leathery leaves. 

Leather oak, private garden on Bellarine Peninsula; October 2022

Engelmann's oak is there too but I've dealt with this species previously, and its common name is all about honouring a Californian botanist than telling us much about the plant. 

That's nearly all the Californian species in the Royal Botanic Gardens Melbourne's collection at the moment, but I expect more to come. There are 15 species of Quercus in that State (out of the 18 or so species found in the whole of western USA), and most will be suited to Melbourne's changing climate. They also make an appealing garden specimen if you like a little ruggedness and individuality in your plantings.

Potentially, also an interesting addition to your produce garden. Acorns from the scrub live oak and coast live oak, along with those from the far taller valley oak (Quercus lobata; California's tallest oak) - which you'll find in the Oak Lawn as one of the replacements for the fallen hybrid white oak (Quercus alba, from eastern USA) - are a favoured food by the First Nations peoples of western USA. The acorns are pounded and cooked to remove tannins, with the flour used to make bread among other staples. 

Valley oak ready to planted out, RBGV nursery; May 2020

Oak woodlands were not only planted, pruned and knocked (to remove acorns, and probably also removing dead wood to help the tree grow), but the ground beneath them swept and weeded to encourage other productive plants. Fires were lit to clear some of the regrowth in between, encouraging the trees to be large, healthy, and easy to access and travel through. 

As a result, the landscape was not unlike the dehesa of Spain, where the managed oak woodland (in Spain of cork and ballota/holm oaks) is both productive for humans while retaining some semblance of its original, pre-human state. Perhaps also like parts of Australia. Local readers will be interested to hear that the first European travellers through the Yosemite Valley described the vegetation they saw as like ‘an English park’. Thanks to the fire burning practices of the first peoples... 

I'll finish with another of the taller oaks from California, and one only recently added to the Royal Botanic Gardens Melbourne collection. The blue oak (Quercus douglasii) grows in coastal mountains of California and like the valley oak, is deciduous. Like the valley oak, it also has edible and harvested acorns.

Unlike that species, the leaves are not always lobed and tend to be leatherier – so more in common with those scrubby live oaks. The leaves of the blue oak also have a slight blue-green tint – hence the common name. This oak is said to be the most drought-tolerant species in California, although I wonder about that when I consider where the Muller oak grew.  

Muller oak, Joshua Tree National Park, California; September 2014

Royal Botanic Gardens Melbourne does not have, as the song goes, all the oaks in California, but a goodly proportion, nevertheless.