- THE FLORICULTURE VEGETATIVE CUTTING INDUSTRY 159
will stick the unrooted cuttings in their propagation area for 1 week
during which time the stem of cutting will begin to form callus tissue.
The callused cuttings are then removed from the propagation bench,
packaged and shipped to the customer who then finishes the rooting
process. The advantage of callused cuttings over unrooted cuttings is
the shortened propagation schedule, the improved success rate, and the
reduction in shipping-related problems. Callused cuttings can also be
directly stuck into the final container in which the plant will eventually
be marketed, thus eliminating the need for propagation materials and
the labor required for transplanting.
B. Poinsettia
Poinsettia cuttings follow much of the same procedures as geranium;
therefore, only the significant differences will be highlighted here. Poin-
settia stock-plant production requires about 6 months, which is the
same as for geranium. Poinsettia stock-plant production starts in mid-
February or March and ends in late July or August. This schedule is
completely opposite to geranium stock-plant production; thus, it is
possible for a stock-plant grower to fit two crops in the same green-
house in 1 year, that is, one geranium crop coupled with one poinsettia
crop.
Perhaps the biggest difference between poinsettia and geranium is
that poinsettias are not commonly threated by vascular wilts and
viruses; thus, a “clean stock” program is not required. While the san-
itation protocols for poinsettia are not nearly as stringent as for gera-
nium, pathogens, such as the bacteriumXanthomonas, can be serious
problems. Another unique characteristic of poinsettia is that they are
highly susceptible to whitefly (BemisiaandTrialeurodes) infestations,
so insect screening and an aggressive, preventative pest-management
program are absolutely necessary.
The process for starting a new poinsettia stock plant begins following
the end of the cutting harvest season in August when plants are then
flowered in December. The flowering plants undergo a selection pro-
cess for the characteristics of each particular cultivar. These selections
are then revegetated under long days to begin cutting production for
the production season following the current year. Thus, the selection
process occurs 1.5 years in advance of the cutting production.
Poinsettia is an obligate short-day plant with respect to flowering;
thus, stock plants must receive continuous long days to maintain vege-
tative growth and prevent flower initiation. This is accomplished by
providing night-interruption lighting from incandescent or compact