Tips on Poinsettia Production

	Pinched			Single Stem
	15 cm (6 in.)	13 cm (5 in.)	10 cm (4 in.)	10 cm (4 in.)
Plant Rooted Cuttings	July 25-Aug 7	August 7	Aug 15-20	Sept 5-15
Pinch	August 31	Sept 10	Sept 15-20

Poinsettia cultivars are classified by response time; the time required from the start of short days to flowering (pollen showing). They vary from 8 to 11 weeks. These timings are approximate, since the actual time required is influenced by light and temperature.

Early maturing cultivars can be intentionally delayed by providing long days past September 21. This can be achieved by lighting the crop using incandescent lamps. The photo period needs to be extended for more than 12 hours.

Care of rooted cuttings
When rooted cuttings arrive they will likely be under stress and a little soft. They have been rooted under reduced light conditions and high relative humidity and shipped in darkness. Shade these cuttings with 30 to 50% shade cloth (preferably green) for the first two weeks after potting. This is the time when plants are extending roots into the pot. Use mist, fog or light sprinkling to cool the leaves and raise the humidity during the day time. Under the very dry conditions in Alberta, growers must pay attention to the humidity in the greenhouse and adopt all possible means to increase it to avoid stress on rooted cuttings. Well-rooted cuttings can be given high phosphorus feed a week after planting. Many growers use 10-52-10 or similar formulation on a weekly basis. If you dissolve one gram of this fertilizer in one liter of water you will get 100 ppm of nitrogen, 520 ppm of phosphate and 100 ppm of potash along with some trace elements. A complete guide to nutrient management of poinsettia is available by writing to the author.

Watering
Poinsettia require up to a liter of water per day when it is bright and sunny. Watering depends on light conditions. The amount of water varies from the time when cuttings are planted and when plants are ready for market. More water is required when plants are rapidly growing but when weather is dull and cloudy they can easily be over watered resulting in root rot. In general, poinsettias will perform better if allowed to dry between watering. This practice will help them to keep compact and encourage good rooting.

Also remember that fertilization and watering go hand-in-hand. When it is hot you are using more water and thus more fertilizer and when it is cloudy and cool you are using less water and therefore, less fertilizer. You can increase or decrease the amount of fertilizer based on sunlight and growth of the plant. It is important to monitor salt levels in root zone by monitoring the electrical conductivity (E.C.) of leachate. Try to maintain a leachate E.C. between 1.8 and 2.5 millisiemens/cm.

Pinching
Follow the pinching guidelines given earlier. An important factor is that the roots should be visible towards the out side of the growing medium. For a programmed pinch date, it is normal to have some variation in plant maturity. Some plants will require a hard pinch to achieve the desired number of breaks, while others will require only a soft pinch.

In case of a hard pinch, several leaves and the growing point is removed. This type of pinching tends to produce rapid, even breaks. They have fewer problems with dominant shoots and a good spreading habit. One leaf is left for each lateral shoot desired.

In case of a soft pinch, only the growing point is removed and this type of pinching tends to produce slower breaks due to the continued apical dominance. Often, 2 to 4 large mother leaves will develop from which dominant shoots will arise. This produces a plant with fewer blooms, and a more upright canopy.

M. Mirza, CDCN
Greenhouse Coverings - August 1999