Sometimes poinsettias are prone to lateral stem breakage. The crop may look healthy and the roots look good, yet an occasional branch will wilt for no apparent reason. There are several possible causes for this condition. Varieties can differ in susceptibility. The most sensitive plants are those with lower laterals that grow perpendicular to the stem. For example 'Freedom' may be more susceptible to stem breakage than plants with strong upright growth habit (v-shape) such as 'Success', 'Prestige' and 'Red Splendor'. One of the most significant factors that contribute to a plant's susceptibility to lateral stem breakage is the cutting diameter at planting. Research has show that cuttings 4.5 mm in diameter or less have twice as much breakage compared to cuttings with a diameter of 7.5 mm or greater. Other reasons for stem breakage are:
- If too many nodes were left on the poinsettias during the pinch, lower branches may be shaded and grow in a more horizontal position putting pressure on the junction of the branch and the main stem.
- Not enough calcium was used in the fertilizer program resulting in weak shoots.
- Poinsettias were pinched too early resulting in side branches growing too long.
- Low light levels during the vegetative growth phase after the pinch causing weak lateral branches.
- Lack of care when hand watering can cause a small physical break at the junction of the branch and main stem that is not observed until the branch wilts. The branch feels like a “loose tooth”, still attached, but the vascular system is broken.
Although this condition usually occurs late in the production cycle or during shipping, it can occur at any time. Once the branch is wilted, it will not recover. It will have to be gently removed.