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Hi Bill,

My best friend just moved to Napa in January and I would love to come visit her. However, I am deathly allergic to eucalyptus, especially if it is blooming. Can you tell me about the bloom cycle and when that happens in Napa? Any help in advance would be greatly appreciated.

LG, Fredericksburg, Virginia I have sympathy for allergy sufferers, particularly because I am one. For me it started as “hay fever” — a grass pollen allergy — in my early teens here in Napa.

As a young retail nurseryman in my 20s, still here in Napa, the spring gardening fever — the rush of people buying plants and supplies — became a double challenge for me when my hay fever would act up. It coincided with the local hillsides turning from green to gold as the wild grasses released their pollen.

I remember a customer commenting, seeing me suffering with itchy, watery eyes, sneezing, and a runny nose, “You are in the wrong business!”

I had a hard time finding the right allergy medication and struggled through each spring for quite a few years.

Now, many years later, my hay fever has diminished. I don’t have that dread of spring the way I did then.

Tree pollens have never been a problem for me — maybe I am in the right business — but I know they are for many. The acacias are most notorious here, as they come into bright yellow bloom, usually in January. But LG’s eucalyptus allergy problem is new to me.

I had to think it over and check some references on blooming periods. Out of curiosity I contacted my colleague Marty Harris, the city arborist for Gold Coast City, near Brisbane, on the east coast of Australia. He confirmed that he fields calls from people complaining of allergy attacks when eucalypts come into massive bloom when it rains after a drought. Interestingly, he commented that eucalyptus allergy sufferers are of “Anglo-Saxon descent, which may suggest that some people of European lineage haven’t ever developed a tolerance in evolutionary terms.”

Here is my response to LG:

I’m a little frightened to be responsible for you having an allergy attack!

I looked up the blooming periods for the most common species growing here and found good help on the “CalFlora” website (a nursery in our area).

In short, most eucalypts bloom in winter to early spring here.

Here is what I found on blooming periods in Northern California:

— Tasmanian blue gum (E. globulus), probably our most common eucalyptus: October through March.

— Red gum (E. camaldulensis): February through March.

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— Red Ironbark (E. sideroxylon): December through February.

— Silver dollar (E. polyanthemos): December through February.

Their statements seem consistent with my observations through years of experience.

The eucalyptus blooming period seems to coincide with our rainy season when the hills are green.

There are occasional other eucalyptus species here in Napa Valley and quite a few more in the inner San Francisco Bay Area where winter low temperatures are milder, i.e., where more tender species won’t freeze to death.

So, it looks like you would be at low risk if you visit from April through September.

During those months the valley is green with vineyards and oak woodlands on the hills and mountains, but the grasslands and open areas on the hills are golden after the end of the rainy season, greening up again in December if we get good rainfall.

There is no guarantee of safety, so talk to your allergist and bring your allergy meds!

Bill Pramuk is a registered consulting arborist. Visit his website,, email questions to, or call him at 707-226-2884.