I have poinsettia (Christmas flower) from last Christmas. It has many green leafs. I have been told that there is a special procedure how to make these green leafs become red. Does someone know exact procedure? Is it too late for this year Xmas?
In general terms, you need to make sure the plant has complete darkness for at least 12 hours a night - e.g. cover it up or something over night. However, during the day they need bright light so that they can absorb energy to create a bright colour.
But: the red colouring is part of the overall life cycle of the plant. The recommendations I have seen discuss the year round care of the plant, and the build-up to the Christmas colour starts in September, so I am not sure if you will be able to convince the plant to become red in the remaining 4-5 weeks.
@standgale is correct that you need to duplicate the natural life cycle in regards to day length. However there are other factors that are much more difficult to reproduce. Growers go to a lot of trouble and use a number of techniques such as:
- plant growth retardants to keep the plant compact
- special fertilizer and potting practices
- mist system
- slightly acid or neutral ph water
I have seen many people keep a poinsettia from the previous year but I have never seen it look as nice as they come from the grower. A good challenge for you.