By Robin Y. Rivet, for Let’s Talk Plants! August 2022.
Eucalyptus – Thank Them Or Yank Them?
The battle continues. Do you love or loathe Eucalyptus? What about Corymbia or Angophora? Or didn’t you know that the term Eucalypts includes them all? Over 900+ related species exist, and although most originate from Australia - it’s a very big continent. Their native climates vary widely, and likewise do their habits, sizes and appearances.
From my perspective, the vast diversity of the various genera and species (like many geographical divides), should make us pause and peer closer at what we’re actually arguing about in California.
Why admire them?
Many are statuesque skyline specimens, and others augment western monarch butterfly habitat in California. Some species are champions of carbon sequestration, drought tolerance, fast-growth, wind breaks, cooling shade and a reliable source of essential oils. Many species have stunning flowers, aromatic foliage and capsules so unique – they defy description. Eucalypts typically resurrect quickly after fire, frost or years of low rainfall, with some scientists suggesting these traits make them good candidates for mitigating climate change, or perhaps useful as rapid, regenerative energy sources.
What’s not to like?
Eucalypts also get accused of extreme flammability, allelopathy, limb breakage, water guzzling and toppling. They get blamed for being invasive, litter prone, pest-ridden, and basically an undesirable non-native plant that was imported into California for commercial timber profit – a plan that failed.
But how much is true?
If you sift through the myths, scientific research, biology and history – persuasive conclusions are difficult to pin down, and there seem to be “experts” taking both sides on many of these issues. One thing seems certain to me. They are fascinating and beautiful trees. After all, those two words are defined by the beholder.
What about San Diego’s Eucalypts?
Balboa Park showcases about 35 species of eucalypts, and to my knowledge, few spread without human assistance. Eucalypts supply shade from UCSD to Ramona, and numerous parks welcome them, including the heritage “Eucalyptus Park” in Spring Valley. Meanwhile, fire risk, water costs and spiraling hot temperatures are on everyone’s minds. The 2003 Cedar fire was an example where eucalyptus were victims of finger-pointing and misguided topping and knee-jerk removals, although Cal-Fire later released photos to show that the trees were not to blame for overall losses. After the initial inferno swept through, red-hot embers blew quickly along paved corridors toward all too flammable homes in Scripps Ranch – igniting wood fences, fascia and siding – primarily man-made products. This post-fire photo from Cal-Fire shows large, unburned eucalyptus stands flanking the torched residences.
Eucalypts can be large, so it’s assumed they drink a lot, but most trees know how to find nearby water sources. Like all species, their roots spread wide, but that also helps keep them upright. And, the notion that they’re more dangerous than our native pines and oaks is essentially not backed up by statewide tree failure data.
Typically grown from seed, the genera also exhibit phenotype plasticity – which essentially means they have good genetics and adapt well. This recent report illustrates the nuanced complexity and potential rewards of using eucalypts to increase biodiversity and resilience, so if you’re fortunate to own one, here are some plants that may survive underneath them.
I particularly revere the red ironbark, and remain a CA eucalypt advocate for many situations.