November 14th, 2006
Cosmos bipinnatus

photo: Cosmos bipinnatus
2006-11-14. Cosmos bipinnatus. Austin, TX.

The first autumn I lived in Japan, before the equinox flowers bloomed, a colleague and his wife took me to have my photo taken in a field of kosumosu. At the time my ignorance of flowers was on par with my ignorance of Japanese. I had no idea what kosumosu were even when I saw them. I guessed that they weren’t Japanese because the word was written in the Japanese script used for foreign words.

photo: Cosmos bipinnatus
Cosmos bipinnatus. Kuju Flower Park. Oita-ken. Japan. My introduction to cosmos.

In fact, cosmos are from my part of the world–native to the American southwest and Mexico and sometimes called Mexican aster. Like another Mexican native poinsettas, cosmos bloom as the days are shortening. Flowers that can bloom as the days are grow shorter make perfect sense in Texas because fall is an opportune growing season.

Most sources I’ve read said that cosmos like heat and drought–they must be talking relatively. They’ve always performed best in the cooler fall for me (86F today). But the field of flowers photographed in Japan was probably planted just after the summer solstice for our September photo op. As for water, the ones that got the most during their early days in September are the ones that are producing the largest flowers now. Luckily, they like poor soil. My garden is all about poor soil.

Cosmos are among the easiest flowers to grow from seed. The seeds are large and they germinate quickly so they make excellent flowers for children to plant. Butterflies also love them. The monarchs have been completely ignoring the Asclepias in favor of the cosmos this week. I’ve seen two types of swallowtales sucking on them as well.

Floridata warns us to check with out local extension office to see if they are invasive. Apparently they are a problem in Missouri. Unlike other annuals I’ve grown from seed, cosmos has rarely self-sown in my yard. It’s the only fall-blooming annual in the meadow so I don’t mind buying a new packet of seeds each year.

by M Sinclair Stevens

6 Responses to post “Cosmos bipinnatus”

  1. From Kathy (New York):

    “Cosmos bloom as the days are shortening.” –Do you mean they are day-length sensitive, or just that they happen to bloom then? Cosmos are frustrating plants for us (me and my kids, who also like them) because they bloom so late in the summer. They are not at all frost tolerant, and there have been some years where I’ve not gotten more than a week’s worth of blooms before they were knocked down by frost. (Okay, so it was a late planting of cosmos, and an early frost.) I’ve learned to choose varieties that specify early blooming and to start them inside. We also occasionally get a self-sown plant, which in general thrives better but blooms later.

    Sorry. I meant to expand on that but it got late and I got lazy. I mean that they are day length sensitive–like sweetpeas but in reverse. At least that’s what I read in Lynn Coulter’s “Gardening with Heirloom Seeds” which I’m reading at the moment. I haven’t read it elsewhere. She says that cosmos almost didn’t catch on because they are very difficult to get to bloom in cold climates such as yours or England where frost comes before the days get short enough.

    Curiously most of the seed packets stress that they like hot weather and instruct us to plant them in the spring after the last frost. Those instructions must be directed to cold climate gardeners. I’ve tried them as late summer flowers (May/June in Austin) along with sunflowers and black-eyed Susans but they disappointed. However, the times I’ve planted them with the fall rains in late August or early September they’ve produced well in October and November.

    I’m theorizing, too, that “hot weather” means the 70s and 80s we’ve been having this November. My summer cosmos keeled over when the temperatures were in the 90s. Was that because of the temperatures or because I didn’t water them sufficiently or because the days were growing longer?

    In southern Japan, where I lived, they bloomed in August and September. Japan is very flower-themed and even though cosmos are not native there, the department store shopping bags and other decorations highlighted cosmos in August.

    Day length sensitivity is a concept I have trouble with. For example, although the days are shorter in winter, my garden gets more sun than in summer because the trees lose their leaves. If I planted cosmos in the summer in a shady spot would the cosmos think the days were short? I need to experiment more. Right now, the cosmos that grew the tallest and are putting out the most flowers are in the sunniest parts of the yard, getting perhaps 4 to 6 hours of sunlight a day. — mss

  2. From Pam/Digging (Austin):

    When I was just starting my back garden (which faces east), I threw out a packet of orange cosmos seeds among the new plants. They took off and filled in nicely while my perennials grew bigger. They were never fussy about our hot summers, but, as you noted, they bloomed best starting in early September through frost.

    Each year they reseeded prolifically, and finally I decided to take them out so the perennials would have the space they needed. The cosmos seedlings were easy to pull, but they kept popping up all summer, and I had to keep after them. A couple of years later, I still had seedlings coming up in the gravel around my shed, where I’d hauled off the carcasses of the larger plants, which dropped seed in route to the bin.

    I’m curious about your statement that the Japanese are flower-themed. I always think of Japanese gardens as green and structural, with few flowers. Yet clearly they enjoy fields of flowers. What were your first-hand observations?

    I wish mine would self-sow like that. I think it happened once but since it sprouted in the spring it had too much competition from the larkspur.

    I mean that Japanese culture in general is very sensitive to flowers and their seasons. (Formal Japanese gardens do not focus much on flowers.) However, from the chrysanthemum emblem of the Imperial family to the humble morning glory, flowers motifs are everywhere in Japan–and not just for little girls. In a formal Japanese room there is an alcove (tokonoma) in which a seasonal arrangement of flowers is displayed in front of a scroll. Japanese food is served on small dishes with designs peculiar to the season. A woman’s kimono and sash (obi) reflects her age and the time of the year in the choice of color, patterns, and designs. Just like our holiday decorations, stores and shops use images of seasonal flowers in their displays and on their shopping bags. Even old-fashioned playing cards (hanafuda–literally flower cards) have a flower motif.

    This is the progession of flowers roughly as I remember them. January/February: early-flowering plum (often dusted with snow); March: cherry blossom; April/May: azalea, rape; June: iris; July: hydrangea, morning glory; August: cosmos, pampas grass in front of the harvest moon; September: red spider lilies (in Japanese, literally equinox flower, higanbana); October: chrysanthemum; November, maple leaf; December, pine. — mss

    Japanese houses do not have much of a yard. The Japanese go to parks to enjoy flowers (the most famous occasion being the wild cherry-blossom-viewing parties in Ueno Park, Tokyo). The Kuju Flower Park was designed especially for picture-taking. They change out the fields four or five times a year and have platforms so that photographers can take photos from above showing their subjects surrounded in a sea of blossoms. One vacation we went on with my school in May was to the Osaka Flower Expo–a combination of flower displays and Six Flags-type rides. — mss

  3. From Annie in Austin:

    Thank you for the photo of the flower park and the explanation of flower-themed. Like Pam, I think of Japanese gardens as mostly green, because the Japanese gardens I’ve seen weren’t flowery like your field of cosmos, which reminds me of the poppies in Wizard of Oz.

    Maybe I’ll try Cosmos again. It reseeded in Illinois, beginning to bloom in the beginning of July, going on to September. Seedlings didn’t do well on the deck at the last house and I never planted it at this one. Did you ever see a variety called ‘Sea Shells’? Those used to be my favorite.


  4. From Craig:

    This has been one of my favorite posts. I worked for Japanese-owned companies for many years and learned to appreciate and admire their culture. I have not visited Japan but hope to go there at some point in my future. I would enjoy hearing more of your life there. Have you categorized your Japanese experiences into an archive?

    Oh, yeah…that was my first blog nipponDAZE — mss

    Plant sensitivity to day length is photoperiodism. Some plants, such as Pansies, are day-length neutral and can be flowered any time of the year. Others, such as Petunias, are long-day plants and can be flowered whenever the daylight hours are greater than the nighttime hours. Chrysanthemums (or Dendranthemas) and Poinsettias are short-day plants and can be flowered when the daylight hours are less than the nighttime hours.

    But how do they know the length of the day? Or is it the amount of light they receive? If, during summer they are in the shade and then in autumn when the leaves fall they get more hours of sun, does that trick them into thinking that the days are longer? (Sorry about the anthropomorphisms.) — mss

    One of my favorite groups are July-blooming plants like Monardas and Garden Phlox because they are long-day plants but will not set buds until after the summer solstice. So here is a group of long-day plants that can recognize the subtle difference of a few less minutes of light than they were receiving just a few short weeks before.

    Many countries in the tropics and sub-tropics have monsoon summers. The plants have responded by growing and being nourished during the rainy season and flowering in fall and winter when their flowers will not be marred. Many plants from Mexico are like that, especially Salvias and plants in the Melastomaceae (one of my all time favorite plant families). It would not surprise me to find Cosmos in that group.

  5. From Craig:

    I have bookmark folders labeled (with no originality) “blogs and “favorite blogs” and I bet you could guess which has more entries. nipponDaze was immediately saved into favorites. Thanks.

    It really is the day length and not the quality of received light. Shade and sun affect how plants grow and are incidental to flower timing. If I were a botanist or paid closer attention in my one course on it, I might be able to explain how a plant can count the minutes of light and dark and compare them. I also often anthropomorphize plants (and animals) and assign personalities to them. Heck, I even do that to garden beds, wondering why a collective bed is sulking or not growing in an expected way and thinking, “Why is it doing this to me?”

    And there are often sweet surprises. After gardening my first year here, a California poppy started growing. It was never planted and I don’t recall seeing it but it must have piggybacked with one of the plants I brought with me. It reseeds itself in the same spot and there is usually a single one growing there, as if they are taking turns. I like to think it is keeping me from being homesick.

  6. From Christopher C in Hawaii:

    Plants count the minutes and hours of the day or night with chemistry. I am no expert but I think I can convey the essense of how it works.

    The process of photosynthesis is a chemical reaction that drives many other plant chemical reactions and the production of all the other compounds a plant may contain. Let’s say there is a flower bloom chemical and a flower inhibiting chemical. As the day length changes the AMOUNT of these chemicals produced as a by product of the energy of photosynthesis changes. When the critical threshold of a flower bloom chemical is accumulated a plant will bloom. When the concentration of flower inhibit chemical is low enough the plant will bloom.

    Short and sweet plants have chemical clocks.

    Pretty cool explanation. So we can trick the plants–for instance by growing them in a greenhouse and adjusting the amount of time under the grow lights. I still wonder if sweetpeas that I planted in a spot that gets two hours of sun in October but six hours of sun (after the leaves fall) in December, will compute that the days are lengthening. Or must I wait until after the solstice to plant sweetpeas? — mss