Fall Special Indoor Treatment

Short-day plants, when kept in inside, pose a little extra challenge for gardeners.

These plants they need uninterrupted nights of more than 12 hours to be able to bloom (hence days of less than 12 hours, hence the name "short-day plant").

Their normal flowering time is autumn or winter, when the days are naturally short, but they do not always manage to flower in our homes due to the lights that their owners turn on at night in the room where they grow.

This additional lighting artificially prolongs daylight hours beyond 12 o'clock and inhibits flowering.

For these plants to flourish, You have to provide them with a place where there is no night lighting.

Short day plants


Billbergia nutans

Billbergia nutans

Here are some well-known indoor short-day plants:

    • Rhizomatous begonias (Begonia heracleifolia, B. × erythrophylla, etc.)
    • Begonia × hiemalis
    • Queen's Tears (Billbergia nutans)
    • Christmas cactus and autumn cactus (Schlumbergera spp.)
    • Chrysanthemum (Chrysanthemum × morifolium)
    • Christmas Calanchoe (Kalanchoe blossfeldiana)
    • Orchids (some species, such as Cattleya warscewiczii, C. mossiae, and Dendrobium phalaenopsis)
    • Poinsettia (Euphorbia pulcherrima)

When to start the long nights


long-nights-short-days

Nights have to be longer than days for these plants to flourish.

Logically, you would start giving your photoperiod indoor plants, to give them a more scientific name, the long nights they need to bloom at the same time as Mother Nature: from the autumnal equinox.

This would be around September 21 (September 22 in 2021) in the Northern Hemisphere and around March 21 in the Southern Hemisphere. (The exact date varies from year to year.)

Of course, you don't have to be precise at this point and you can delay the treatment for a week or two without seriously affecting flowering; however, delaying long nights too long can seriously delay it.

Techniques to lengthen the night for short-day plants


You have several treatment options to ensure that short-day plants flourish indoors:

  • If you have a sunny room that you never use at night, use it to house short-day plants in fall. Remove the bulbs from all the lights in the room or unplug them so no one can accidentally turn them on at night - even a brief interruption from their 12+ hours of darkness is usually enough to abort flowering.
  • Place the plants in front of a well-lit window in a room that is used at night and therefore is lit at that time, but put a barrier between them and the light source: a screen, a panel or even just other plants, something that prevents the light from the lamps reaching them. In this way, they will receive good light during the day, but none in the afternoon and at night. The place where you grow them doesn't have to be in total darkness at night, but it does have to be dark.
  • If you live in an area where there is no risk of frost, leave plants outside for fall until they start to show color or produce flower buds, then bring them indoors.
  • Place the plants under artificial lights (LED or fluorescent), use a timer so that the lights do not stay on for more than ten hours a day, and then surround the growing area with a box or other opaque material so that the outside light does not reach them. Or set up your little timed garden lights in a large closet.
  • The traditional technique is more complex. It consists of putting the short-day plants in a closet or opaque box each night, and then putting them back in a well-lit area each morning until they begin to show color. A typical schedule: put them in the dark at 6 in the afternoon, and put them back in the sun at 8 in the morning. The problem is that you have to repeat these actions every day for two or even three months, without missing a single time, including on weekends! If you miss a single night, it can prevent blooming! Good luck with that!

Beware of false information


attention warning 1 1If someone suggests you put your poinsettia or Christmas cactus in a closet for two months To force it into bloom (and the weirdest suggestions are being seen on Facebook lately, right?), ignore it. This will seriously weaken your plant. and it can even kill her. Remember that short-day plants grow in autumn and they need light every day.

Once you see flower buds appear, even if they are very small, you do not have to continue with the special "long night" treatment. Flowering has already started and will run its course. This way you can grow the plants in the same lighting conditions as your other plants.

Daylight ... in abundance


Although short-day plants need nights of more than 12 hours, that does not mean that they do not need sunlight during the day.

All of these plants need bright light with plenty of sun during the day to flourish well, especially since in many areas the sun is much weaker in fall than in summer. So a sunny window sill location would be ideal.

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