WICHE: Cool nights and short days initiate bloom

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The flowering of many plants is initiated by how many hours of light and dark in a 24-hour period.

By Jeneen Wiche

There are many things that come together to allow plants to thrive. When it comes to plants native to our area, we are not required to go to great extremes to provide the ideal environment. An ideal environment, however, means a great many different things depending on what kind of plant you are.

This time of the year we can do a couple of things for some favorite flowering plants. The goal is to mimic a plant’s native habitat as closely as possible; this is difficult in our homes, but success is likely if you move some things outdoors through the remainder of autumn.

For many tropical flowering plants we can initiate bud set through managing day length and nighttime temperatures. Instead of sticking your Christmas cactus in the closet for 12 hours a day, try just leaving it in a dark corner of the yard for a few weeks.

The flowering of many plants (including some native species) is initiated by how many hours of light and dark the plant receives in a 24-hour period.

Likely the most famous tropical that is photoperiodic is the poinsettia. How many people have tried to initiate the bracts to turn red by sticking their poinsettia in the closet for 12 hours each day? I usually just buy new ones each December.

There are some other photoperiodic bloomers, however, that I hold onto year after year; and I have discovered a reliable way to get them to bloom that is quite simple. I leave many of the plants outside through the month of September (or later, depending on the weather) so that they can naturally experience shorter days, and longer, cooler nights.

The list of plants that spend some time chilling outdoors include Clivia, holiday cacti and several different species of orchids. I have had amazing success with this very simple plan. Follow the forecasted weather and take note of nighttime temperatures. If a couple of nights dip below the desired temperature, bring the plants in until conditions become desirable again.

The holiday cacti (the Thanksgiving, Christmas and Easter cactus) can be left outside to experience the longer and cooler nights of late summer and fall until nighttime temperatures drop consistently below 50 degrees.

There have been some years when the plants have already set visible buds on the stems while they are still in the protected corner behind the garage.

We typically think of orchids as being sensitive to the cold when, in fact, several species are quite appreciative of cooler temperatures then our homes offer. The very popular Phalaenopsis, or butterfly orchid, appreciates a light breeze and some cool evenings to about 55 degrees. Once nighttime temperatures drop below 55 degrees, bring the plant back indoors, provide bright light and fertilize with a balanced fertilizer every other week.

The Clivia also will benefit from some chilling. I leave mine out until temperatures dip below 50 degrees. Once they are brought indoors, I basically set them aside, in bright light, and check on them once a month. They have low water requirements in the winter and reward me with blooms based on this neglect.           

Water is another component for success. For many – although not exclusively – a dry period in the winter is recommended. This is when understanding the native habitat of a plant comes in handy.

If you come from a place where it rains all summer and is dry all winter, then this is likely what you will prefer in someone’s house in Kentuckiana.

Keep Clivia, Phalaenopsis and holiday cacti a bit on the dry side during the winter months.


Check out gardening columnist Jeneen Wiche’s work at www.SwallowRailFarm.com. You can find her columns also at www.SentinelNews.com/agriculture. She answers questions once a month in SentinelNewsPlus. To submit a question, send an E-mail to jwiche@shelbybb.net and type “Sentinel-News” in the subject field.