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Spring Bloom in Fall--It's a Problem

In today's SF Chronicle (January 1, 1917), I wrote about plants that bloomed last fall in San Francisco that ought not to have been blooming until spring, caused by continuing climate change.

While it's true that we typically have our warmest "summer" weather from mid-September to mid-October, this weather has been lasting longer than usual. Last fall, the warm days and mild nights lasted until near the end of November. We celebrated time spent outdoors in nice weather, but some of our garden plants reacted by blooming and leafing out as if it were spring. This is a problem for the plants, which put energy and physical matter into doing this, so that when spring really does come, they have less stored matter and food energy to do it all again. This weakens the plant, leaving it more susceptible to all kinds of setbacks.

Case in point is my apple tree, which has borne bountiful crops of delicious apples for 30 years. But recently it has been trying to bloom in fall. Then, because winters aren't quite cold enough, it blooms later than usual in the spring. And, because of the energy it used up in fall, it blooms more sparsely. Two years ago, it had practically no fruit.

Last year it did better, though not as well as it used to do. The photo below, which I sent to the Chronicle, but they didn't use in the paper, shows my tree last November, with a few last apples and last leaves till hanging on while blooms and new leaves opened all around them. Now, on January 1, all the new leaves have succumbed to cold, wasting all that effort.

Apple 11-17-16 Sq IMG_8892 copy

If you are growing other temperate plants in the Bay Area, such as cherries and plums (ornamental or fruiting), magnolias, lilacs, or azaleas, you may be having the same kind of problem. What's to be done to save our plants? Obviously continue to work against climate change, a movement in which California in general is doing well.  But we can also join an effort to record the changes, in which our regional data will provide extremely valuable evidence.

More data about how climate change is affecting plants in our region is especially important so that we are represented in a system that has so much more data from cold-winter regions.

There are two organizations that are seeking citizen science data. One is the National Phenology Network (, sponsor of the National Phenology Project. It studies both plant and animal species. Another, Project Budburst (, is studying only plant responses. Phenology is the study of what plants and animals do in response to seasonal changes.

Sending records to these databases is easy to do online. Log in, choose a plant, and tell them what it is doing on various dates. Children can do it at home and school classes can do it. Both web sites have curriculum information to help teachers fit the work into classes. It teaches observation, appreciation of plants, climate science, ecology, and how science is done

So as our new, and rather unnerving, year begins, please help observe and record what is going on with nature. Your reports will be powerful.


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Pam Peirce

Thank you for the report from Florida, I hear that real estate prices are still rising in Miami--along with the sea level-caused floods.

Perfect Plants

In Florida, we had the reverse. Winter was cold but warmed up quickly... but then cold came back! The early blooming trees bloomed and then the blooms went away, permanently! Very sad.

Pam Peirce

Hi Steve, It isn't that fall was especially warm last year, but that mild weather lasted longer than usual. Or, more specifically, it lacked the usual mid October cold spell. We didn't get a cold snap until nearly the end of November. I haven't checked the data. Maybe I will find some time and do that, but I trust to phenology. The few cold days we usually get in mid-October put the chard leafminers into dormancy and usually the cabbage white butterflies stop laying eggs on leaves of cabbage family plants too. Last year and this year, these phenomena were delayed. I notice because I usually put my chard out in September and keep it under row cover until mid October, and then I can uncover it. This year, I had to wait. Even more upsetting was that at the end of December I found chard leafminer eggs on my chard leaves again, so there must have been warm spells long enough to initiate their life cycle again. I haven't looked this week yet, but the rain should slow them down.
The mild Januarys or Februarys will certainly impact plants that are buiding up chill hours. Less chill might cause them to bloom late. At the same time, it will stimulate some plants that don't need chill to bloom early, and then perhaps have trouble when later months are cold again.
This winter, I also have self-sown common pole beans that germinated in the mild November weather and are climbing to about a foot and a half tall now. I have left them to see what will happen.


I am a scientist, but not a meteorologist.

I didn't think that it was particularly warm this or recent Falls. Is there meteorological data that bear this out? What has certainly been true has been our very warm January's for the past few years as the stubborn high anchored off the coast of Alaska. I wonder if these warm winter months affect the clock later in the year.

In any event, I was shocked by the robustness of this fall's (senescent?) bloom. It worries me...

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