The idea of floral clocks emerged in the 18th century. Carl Linnaeus, Swedish botanist and father of modern taxonomy, observed that flowers opened and closed under three sets of different circumstances:
- some open and close in response to weather
- some open and close in response to length of day
- some have set times for opening and closing unaffected by weather or day length
Intrigued by the observation that some flowers adhered to a clocklike fixed schedule of opening and closing, Linnaeus introduced the idea of floral clocks in Philosophia Botanica in 1751. He researched the opening and closing times of native wildflowers he observed in landscapes around Sweden and illustrated a circular living clock placing the flowering plants at the hour of the day they opened.
Over the centuries scientists have discovered much more about the circadian rhythms of plants first noticed by Linnaeus. A complex set of factors combine to signal a flower’s opening and closing including cell biology, light, temperature, weather, and evolutionary adaptations.
Setting Your Floral Clock
Select a sunny location for your clock. In essence you are creating a sundial with flowers. Many clock flowers keep time only with exposure to sun.
When making the family’s first floral timepiece, place plants in portable pots to make easy adjustments for latitude and seasonal changes in light. After carefully watching and recording the opening times of flowers and fine–tuning placement of plants the first year, specimens can be installed permanently the second year.
Join hands and form a circle in the site selected. The circle could be 3 to 6 feet in diameter. Mark the circle with a garden hose or flour before preparing the soil.
Divide the circle into twelve sections like the face of a clock. Place a post, birdbath, or sundial at the center of the circle. Edge the perimeter of the clock in rocks or low growing non-spreading plants like alyssum, candytuft, or thyme.
Floral Clock Flowers Shopping List
Flower selections for your clock will depend upon your area’s USDA hardiness zone and the close observation of flowers in your yard, at botanic gardens, nurseries and along the roadside. Times in the chart below are approximate flower opening times and should be attuned to your latitude.
Below is a list of flowering plants in sequence of the approximate opening times of flowers:
- 03:00am – Convolvulus
- 04:00am – Blue flax, salsify, spiderwort, umbrella milkwort, dogrose
- 05:00am – Buttercup, chicory, corn poppy, goatsbeard, japanese morning glory
- 06:00am – Cape marigold, catmint, dandelion, daylily, morning glory, iceland poppy
- 07:00am – African marigold, balloon flower, catnip, st. bernard’s lily
- 08:00am – Fringed pinks, scarlet pimpernel
- 09:00am – Catchfly, marigold, moss rose, mullein, sandwort, yellow gentian
- 10:00am – California poppy, ganzania, gold star, strawflower,
- 11:00am – Calendula, passionflower vine, star of bethlehem, sweet pea
- 12:00pm – Ice plant, wild daisies
- 01:00pm – Carnation
- 02:00pm – Acanthus-leaved thistle, rock pink
- 03:00pm – Vesper lily
- 04:00pm – English plantain, four o’clocks
- 05:00pm – Jimson weed
- 06:00pm – Evening primrose
- 07:00pm – Evening campion, flowering tobacco, fig marigold
- 08:00pm – Evening catchfly, night blooming stock, night phlox
- 09:00pm – Dame’s rocket, moonflower, schizopetalon milky way
- 10:00pm – Night blooming cereus
Creating a floral clock requires planning and persistence but the finished timepiece can be an heirloom. Share the seeds with others who wish to customize their own floral clocks.
How accurate will the floral clock be? Only time will tell!
To celebrate the family’s accomplishment and to dedicate the floral clock garden, host an evening primrose party commingling family and friends face to face with flowers.
