This section is from the book "The Gardener's Monthly And Horticulturist V23", by Thomas Meehan. See also: Four-Season Harvest: Organic Vegetables from Your Home Garden All Year Long.
Will you kindly allow me to make a few remarks in reference to the treatment of this subject in your columns? They should be repotted and started into growth about the beginning of May. Pot them in some good rotten sod with a little mixture of sand, and in the pots you intend for them to bloom in. Take them outside about the latter end of May and plunge them in the ground two inches below the surface in a southern exposure where they can have full benefit of the sun. Let them make a fair growth before you commence pinching the leading shoots back; keep pinching back from time to time as required until nearly the middle of August. Take care in the meantime to lift them out of the ground two or three times during the summer as the roots are apt to grow through the holes at the bottom of the pots; if so they should be cut off each time of lifting. If this service is not attended to, the roots will grow down in the ground some distance during the summer, especially where the soil is light and where the plants are lifted; finally it will give them a severe check, they will lose a quantity of leaves in a few days, and the result is you have generally poor puny looking heads of bloom.
After bringing them into the greenhouse, which should be done about the latter end of September, they should not have any less than 60° of heat at night, if possible 70° in the day time. Water then once a week with manure water. It is a great advantage to them and will amply repay you with finer heads of bloom. Manure water applied to other plants occasionally will make them bloom more freely.
I have been treating my Poinsettas this year in this way, and the result is highly satisfactory. I have a few good specimen plants with bracts or leaves that surround the flower from one foot to sixteen inches in diameter. Although they are plants that lose their leaves considerably, if you place them on a back shelf on the stage and set other plants in front to hide their stems, the Poinsettas look very effective and graceful with their brilliant scarlet leaves overlooking the front row of plants.