Creating a floral clock

I'm always looking for something fun to do in my gardens. Poking around the internet turned up the idea of a floral clock. Carl Linnaeus, a biologist and physician in Sweden in the 1700s, observed that certain flowers opened and closed at different times of day. He developed the first floral clock by arranging plants in a circle to mimic approximate times based on these observations. One can find a list of the plants he used, but for our area, several of the plants are considered invasive, woody or not suitable for Northeast Tennessee climate. So for nerdy me, the search was on for plants that could work as a floral clock and to find any pearls of wisdom about how to develop the garden. Luckily, a cohort had already done some research and shared it with me. Keep in mind that rainy or cloudy days, along with extreme variances in temperature, will impact if and when a particular flower will open and/or close. Also, plants with different opening and closing times can be of varied heights, so planting them in a perfect circle may be less than ideal. As my cohort said: "This is not a precision instrument — it's a phenological sculpture." So, scattering plants around an area and still mimicking the idea of a clock may be a fun way to make an interesting garden. Additionally, some of the plants suitable for this project are annuals and some are perennials. That may actually bring more fun to the endeavor. Here are some tips on how to plan the garden. First, the clock location must have at least six hours of sunshine. Planting on a slope may be better for viewing, but it isn't necessary. In choosing plants, be sure to avoid invasives and try to find native plants that will provide double benefit for pollinators. Expect most of the flowers to generally bloom from May through September. Below is a list of flowers that can produce a nifty flower clock: Goat's beard (Tragopogon pratensis), a biennial perennial, opens early morning and closes late morning. The yellow flowers stand about 1 to 3 feet tall. Morning glory (Ipomoea purpurea) is an annual vine available is several colors, opens in mid-morning and closes at about noon. It makes a beautiful statement when supported by a structure. Field marigold (Calendula officinalis), another annual, has 1- to 2-foot-tall yellow flowers that open with the sun and close late afternoon. Rock purslane (Calandrinia spectabilis) grows about 8 inches tall, but the flower stems can reach 1 to 2 feet with magenta flowers that open in early morning and close when sunlight fades. It is grown as an annual in USDA zone 7. Moss rose (Portulaca grandiflora) opens only in strong sunlight. It is a low growing annual, only about 8 inches tall, and is available in several colors. Four o'clock (Mirabilis jalapa) opens late afternoon. It is a perennial pollinated by moths and hummingbirds. The plant height can be 18 inches up to 4 feet with flowers in several colors. Evening primrose (Oenothera biennis) is a biennial native perennial plant that opens at dusk. In its second year, tall (3 to 5 feet) upright stems display yellow flowers with a mild lemon scent that attracts moths at night and bees in early morning before flowers close. Flowering tobacco (Nicotiana alata) is a tall annual plant growing 3 to 5 feet with fragrant flowers that open at about sunset. The true plant may be difficult to find, but seeds are available. Plants sold in nurseries are usually a different species that are unscented and open during the day. Night-scented stock (Matthiola longipetala) is an annual 1 to 2 feet tall and easily grown from seed. The pale lilac to white flowers open in the evening and release a lovely, sweet scent. Moonflower (Ipomoea alba) opens fully at night as its name suggests. It is a vine with 8-inch white flowers that are well-loved by nighttime moths. It requires a support structure. In USDA zone 7, it is grown as an annual. To help fill in and provide more daytime blooms, the following native plants could be considered: blue mistflower (Calendula officinalis), black-eyed Susan (Rudbeckia hirta), butterfly weed (Asclepias tuberosa), coreopsis (Coreopsis lanceolata and C. tinctoria), and purple-headed sneezeweed (Helenium flexuosum). My sense of nerdiness also wanted to know why different plants open and close at different times. One factor is pollination. Flowers need to be open when their pollinators are at the peak of activity. For example, moonflowers are open at night when the moth that pollinates them is making its rounds. A reason for closing at sunset is protection from heavy dew that could damage delicate parts, protection from predators, and conservation of energy. Closing during cooler temperatures protects the plants by keeping them warmer. For more details about the plants described, go to North Carolina Extension Gardener Tool Box at https://plants.ces.ncsu.edu/find_a_plant/ or University of Minnesota at https://plantsearch.extension.umn.edu/searchplants/list?orderby=aCommonName. RESOURCES "Linnaeus' Floral Clock - Horologium Florae" https://www.uu.se/en/linnaeus-garden/our-plants-and-attractions/our-plants/linnaeuss-floral-clock "The Natural History of Plants – Their Forms, Growth, Reproduction, and Distribution" https://www.biodiversitylibrary.org/page/13623487 HOW DO I ASK A QUESTION? If you have questions for the Master Gardeners, submit them to us on our website at www.netmga.net. Click the link at the top of the page, "Ask A Master Gardener" to send in your question. Questions that are not answered in this column will receive a response from a Master Gardener to the contact information you provide.