Poinsettia Cultural Tips
Poinsettia Cultural Tips
Christmas may be five months away but growers are already busy with the crop. The following information appeared in The Poinsettia; Journal for Poinsettia Professionals. Issue 9.
Successful poinsettia propagation begins with quality cuttings. Good quality cuttings are the result of properly managed stock or mother plants. Top Quality cuttings are produced by growing stock plants under optimum environmental conditions that encourage healthy growth.
Cutting maturity affects root development. Cuttings that are either immature or overly mature are difficult to root. Good quality cuttings root rapidly and uniformly. Cutting maturity is determined by timely pinching of the stock plants. For most cultivars, cuttings are best taken 6 weeks after the stock plants' last pinch. Therefore, it is important to schedule planting and pinching of stock plants to ensure optimum maturity when the cuttings are removed. Some poinsettia cultivars seem to root easier if taken 5 weeks after pinching, while many others are of proper maturity if taken in 7 weeks.
Take cuttings 2 to 3 inches in length (5 to 8 cm) when stock plants have reached optimum maturity. Measure cutting length from base of the cutting to the growing tip. A 2 to 3- inch cutting will have approximately two mature leaves. The stem diameter (caliper) of cuttings varies among cultivars, but stem caliper of 1/4 to 3/8 inch (6 to 10 mm) is desirable. Stems can be cut at a leaf node or in between nodes, since roots develop from the base of a poinsettia cutting with or without a leaf node.
Pinching Poinsettias
A poinsettia plant will grow unbranched for some time before the laterals appear due to a process called apical dominance. To create branched poinsettia, a pinch (removal of the apical meristem) is required. Three different types of pinches can be performed: soft, hard, and soft pinch with immature leaf removal.
When a soft pinch is performed, only the growing point is removed leaving young growing leaves on the plant. These leaves produce hormones that can inhibit bud break and lateral shoot development. As a consequence, soft pinched plants tend to produce 2 to 4 laterals, upright in habit. Soft pinch is usually used only on short, weak plants with little growth after the planting of a rooted cutting. A hard pinch is preferable. At least 1.5 inches of the growing point should be removed. If a soft pinch is required, remove some of the immature top stem leaves (just below the point of pinch) to overcome partial dominance. Remember that new cultivars branch easily and the desired number of nodes should be left on the plant.
Occasionally, at the time of pinching, some of the buds may have broken and started growing. These shoots should be removed. We could devote the whole newsletter to poinsettia fertilization. The following is just a reminder of some of the common problems growers encounter.
Calcium. Important for plant health and strength. Also important to avoid bract leaf necrosis (burn). Some growers think about calcium only to avoid the latter problem ignoring the former. This element moves into the plant with the water used for transpiration. Adequate levels of calcium early in the season, when temperatures and transpiration are high, will contribute in having adequate calcium levels in the plant tissues. Sometimes, calcium may be deficient despite the fact that it is present at levels considered to be acceptable in both soil and plant tissue. The deficiency may be caused by an excess of magnesium. The ratio calcium:magnesium should be 3:1. Growers who like to apply Epson salts (to add magnesium) should keep this in mind. (Photo 1)
Molybdenum. Poinsettias have higher molybdenum requirements than other crops. Apply at least 0.1 ppm of this element throughout the whole poinsettia cycle using a soluble fertilizer that contains this micronutrient. Applications of this element can also be done through sprays. (Photo 2) (Photo 3)
Fertilizer levels for dark leaf poinsettias. Poinsettia cultivars with dark foliage require less fertilizer levels than light foliage cultivars. For cultivars such as Freedom, keep growing mix electrical conductivity (EC) below 2.0 mS cm-1 (for light leaf cultivars, EC should be maintined below 3.0 mS cm-1). Keep in mind that if the EC reaches levels below Fertilizing Poinsettias
1.2 mS cm -1, you should fertilize.
