What is a solstice?
December 21st is the Winter Solstice, which marks the shortest day of the year. After this, each following day will be longer than the previous one. This will go on until the days are of equal length. When days are of equal length, they are called an equinox.
Short days, long days and in between…
So, even though December 21 marks the first day of Winter, the days are actually getting longer until we reach the Vernal Equinox, on March 21st, better known as the first day of Spring. After this date, the days will get longer each day until we reach June 21st, Summer Solstice This is the first day of Summer and the longest day of the year.
After June 21st, the days will get shorter each day until we reach the Autumnal Equinox, when the days are again, equal in length with the night. The days will now become progressively shorter until we are back to December 21st, our shortest day of the year.. In an earth year around the sun, we have two solstices and two equinoxes.
Photoperiod is important to plants
These day/night length markers are actually very important in the life of plants. This is known as photoperiodism. It is caused by photo (light sensing) receptors on plant cells. Proteins react causing hormonal changes, gene expression and growth signals.
There are short day, long day and day neutral plants. In fact, researchers have found that it’s actually the hours of darkness that trigger a plant to bloom more so than the hours of light.
Dombeya “Seminole” only blooms during short photoperiods. It will bloom until the days start to get longer again on March 21st. Also known as Florida Hydrangea, this beautiful shrub is a reliable winter bloomer here, Easy to grow, Dombeya is much appreciated for its color and as food for pollinators.
Short day plants
Some well known plants that bloom during the shorter days and longer nights are Poinsettia, Dombeya, Blue Sage, Christmas Cactus and Jacquemontia, but there are many more. Take a look in your garden to see what’s blooming. Chances are they are short day bloomers, and you will notice that once the equinox passes, they will stop blooming.
It’s interesting that we seem to celebrate holidays during a solstice or equinox.. The darkest day of the year is when we celebrate with festivals of lights. A coincidence? I think not.