The Q&A Archives: Poinsetta

Question: What is the best soil combination to use when re-potting Poinsettas. What type of fertilizer is best? Are Poinsettas acid loving? Is that similar to Gardenias need for acid in the soil ('Miracle-gro')? The Poinsettas will be potted in terra-cotta pots, and will be kept outside. I live approximately 8 blocks from the ocean in San Diego, California.

Answer: Poinsettias can be used in landscapes as accent plants or informal flowering hedges, as container plants for patios and decks, and as cut flowers for interior decorations. They should be planted in areas where they receive full sun most of the day. However, it is essential that they receive no light at night during the bud-setting period. Poinsettias require a long, dark period before they will initiate flower buds. Normally, they set flower buds in early October when nights are becoming increasingly longer. If the dark period is interrupted with the light from a window, street light or any other light source, flowering will be markedly delayed or the plant may not flower at all. Just a short period of light during the dark period is enough to delay or prevent flowering. This should be kept in mind when poinsettias are used in the landscape, and they should be planted in areas that will completely dark during the night.

Poinsettias grow best in moist, well drained, fertile soils. However, they will grow satisfactorily in a wide range of soils, including sand and clay. Soil pH should ideally range from 5.5 to 6.5, but it need not be adjusted if between 5.0 and 7.0. The soil must be well drained because poinsettias will not grow well in wet areas.

A general rule in planting is to dig a hole 1 foot (30.4 cm) wider and 6 inches (15.2 cm) deeper than the root ball. Backfill the hole with enough soil so that the plant will sit in the hole at the same depth as it was growing in the container. Firm the soil to prevent settling, then gently place the plant straight in the hole and fill around the ball with soil. Water thoroughly while planting to remove air pockets. Mulch around plant with organic materials to conserve moisture and help control weeds. You can also grow poinsettia's in containers; use a commercial potting soil rather than garden soil. Potting soil is typically neutral in pH so you shouldn't have to adjust the pH.

Today's poinsettia cultivars respond favorably to an abundant supply of fertilizer and adequate moisture. Neglecting to fertilize them will result in yellow leaves and ultimate loss of most of the lower leaves. Plants should be fertilized monthly, starting in March. Use a half-strength dilution of liquid ferilizer to avoid salt burn. Feed every 2-3 weeks during the growing season. Stop fertilizing in mid-September.

The soil should be kept moderately moist at all times. Frequency of waterings will depend greatly on weather conditions.

Poinsettias should be pruned in early spring after blooming is over and the danger of frost has passed. They should be cut back to within 12 to 18 inches of the ground. Pinching the plant during growing season will result in a compact plant at flowering time, rather than one with a few long, unbranched canes. After four weeks or when it is 12 inches long, new growth should be cut back, leaving four leaves on each shoot. This procedure should be repeated every time the new growth develops until about September 10. New growth after the last pinch will usually grow to a length of 8 to 10 inches and, in the first week of October, will initiate flower buds.

Hope this answers all your questions!

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