Short Day Plants Flower Now

Certain flowers naturally bloom or can be induced to bloom in fall or winter due to the shorter day length by virtue of photoperiodism. Learn how you can manipulate this.

December 21, the Winter Solstice, is the shortest day of the year. Apart from signalling the beginning of winter, it is significant in flower gardening because some plants bloom only under short day (long night) conditions. It's not that they tell time or watch the calendar, it's based on photoperiodism. In other words, for these particular plants the flowering is based on the number of hours of continuous darkness they experience day to day.

Some plants flower under short day conditions, some under long day conditions, and some are considered to be day neutral. This means some flowers bloom in response to the short days/longer nights of spring or fall, some in response to the longer days of summer, and some can bloom any time regardless of day length.

For short day plants, how short is short? Twelve hours seems to be the cut-off and as a rule of thumb, 14 hours of darkness is typically recommended to induce flowering for short day plants. The short day plants will respond to these longer nights by setting flower buds and blooming. An important point to remember is that the darkness must be complete, continuous and uninterrupted: NO light during the "night" -- not one flip of the light switch, no glow from a streetlight, not one flash of a headlight.

Professional growers manipulate day length to force plants to set buds or bloom at a given time. The holiday poinsettias are a great example of this specially timed production strategy for short day plants. At home, you can manipulate your poinsettia into coloring by Christmas if you cover it or put it in a dark closet every night for about 14 hours of uninterrupted darkness beginning in about mid September and continuing every single day/night for weeks on end until it colors up.

More holiday plants you can manipulate this way are Christmas cactus and Kalanchoe, although I have found that these will bud and bloom without special treatment -- if left in a spare room with only natural light so they can sense the naturally shortening days. Otherwise, use the box or closet method.

Happy Solstice! MORE FLOWER GARDENS ARTICLES and FLOWER GARDENS BLOGS,TOO