Hi Fermi,
The Symphyotrichum pictured in the Crystal Range Flora thread is from a plant photographed in the wild. This is the ideal that I am striving for in our Sacramento garden. Above is Symphyotrichum spathulatum var. spathulatum blooming in our Sacramento garden on 17 July 2017. July 2017 was hot, ~ 2.0 F (1.1 C) above the 30-year average. In our Sacramento garden this species can bloom from July to September. Generally, the most flowers appear in late August and September.
Here is another specimen of Symphyotrichum spathulatum var. spathulatum blooming in our Sacramento on 5 September 2017. Temperatures during September of 2017 averaged -1.0 F (-0.56 C) below the 30-year average. So far I am pleased with my results with this species, however I am striving for something better. In our garden Symphyotrichum spathulatum responds well to applications of compost to the soil on a regular basis. Without compost the plants persist, but also decline markedly in vigor over time.
This species is common throughout the mountains of Western North America. It would likely thrive in gardens in Northern Europe. My guess is that Leena and Mariette would find this species easy to please in their gardens. I have never noticed much slug damage on our plants, but then even at the worst, we do not have great numbers of slugs.
For us that garden in much warmer climates the source of the seed is of great importance if we wish to have success with this species. Low elevation forms of this species are much more tolerant of extreme summertime heat. Garden populations respond well to repeated selection of the best plants.
The three varieties native to California are easy to distinguish from one-another. Variety yosemitanum has very distinctive linear foliage. Variety intermedium generally has 10-50 flower heads per inflorescence. Variety spathulatum generally has 3-10 flower heads per inflorescence. First generation plants grown in summertime hot, low elevation gardens can appear off-type from their seed parents. After a generation or two of selection plants can be selected that are more true to type. Plants producing pale flowers during hot weather is an issue that is more difficult to resolve. In our Sacramento garden growing the plants with morning sun, afternoon shade ameliorates this situation to a degree.
