7 responses to “Ceanothus thyrsiflorus”

  1. Ron B

    Coastal Californian and Mexican species tender to cold, definitely not “very hardy” to it.

  2. Michael Wall

    For those who would like to read up more on this wonderful genus I highly recommend ‘Ceanothus’ by David Fross and Dieter Wilken, Timber Press 2006

  3. arlee

    The dye is green rather than blue, because the anthocyacins in this flower are over ridden by the other chemical components.

  4. Peter Warner

    Thank you for posting this article on one of the many species of Ceanothus common to northern California. I appreciate the attention to some of this species’ ecological significance.
    Its cold hardiness, and what constitutes “very hardy,” constitute anthropocentric quibbling over semantics: pertinent for the gardener, not so much for species other than from a very long-term perspective. Over the past 25 years, temperatures in coastal northern California have dropped below 20 degrees F on a few occasions, not very cold compared with inland locations, although that time period is but a very small sample size over the historical life of the Ceanothus thyrsiflorus genome. The species is hardy enough where it grows as a native shrub — planting it outside its ecological range (which includes consideration of additional factors such as geology, soil chemistry and structure, slope exposure, hydrology), as with many other gardening activities, is often an uncontrolled experiment. Most species of Ceanothus don’t grow in heavy clay, summer-wet soils.
    In Sonoma and Mendocino Counties, I’ve seen C. thyrsiflorus individuals ranging to over 8 meters tall. These are invariably located in small sunlit forest openings, where the shrubs seem able to sustain vertical growth despite being in competition for light with Douglas-fir, redwood, tanoak, bay, and other trees.
    I think “nitrogen fixing” could be explained a bit more accurately, as the plant doesn’t actually do this, but develops nodules on its roots that provide habitat for soil-borne filamentous bacteria, as with legumes, alders, and other plants. I don’t know the details, but perhaps the author has more information about the bacterium or bacteria symbiotic with this species and other Ceanothus species. In a related taxon (Ceanothus caerulea), the N-fixation appears to involve both non-fixing actinomycetes (filamentous soil-borne bacteria) as well as active N-fixing actinomycete in the genus Frankia (Ramirez-Saad, Janse, and Akkermans, Canadian Journal of Microbiology, Vol. 44; 1998). I think Frankia is the most common genus of actinomycetes that inhabit the root nodules of non-leguminous plants.

  5. Jim Litts

    Oft times anthocyanin color is dependent upon pH, or the degree of acidity. I believe transitions between blue, pink and green are the most common depending upon the actual anthocyanin involved. “Cyanin” in itself usually denotes both blue and green.

  6. Barry

    It depends what you mean by cold. If you mean “This can’t handle anything below 15F”, then sure, the coastal California species are going to have trouble. One variety of C. thyrsiflorus is hardy to 15F according to Las Pilitas nursery: in mediterranean California (this species has a number of forms and grows wild outside of the town I live in).
    Las Pilitas says that even Ceanothus arboreus, which comes from the channel islands of southern California (a very mild climate) can end up with severe burn at 15F but can survive at the roots at 0F and come back. This is a typical strategy for these plants, to regrow after the tops have been burnt off by fires.

  7. Barry

    Another thing to note about a lot of Ceanothus is that some of the hybrids can end up as small trees. At a previous house, I planted the hybrid Ray Hartman and in a few years it was over 10 feet tall. Gorgeous deep purple blue flowers. The variety can grow about 20 feet tall.
    Another nice thing about Ceanothus is that many species have really sweetly scented flowers. It’s not a strong scent, but you can notice it near the plants when they’re in full bloom (and many are entirely covered in flowers when they bloom).

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