Producing high quality trees requires a commitment to an extended growing season, considerable greenhouse space, and diligent pruning and crop maintenance. Some poinsettia cultivars are better adapted to this form than others, with strong stems and large bracts being desirable characteristics for trees.
The height of the poinsettia tree is directly dependent upon growing time prior to the first pinch. For taller trees (4 to 5 feet), rooted cuttings are transplanted in late May to early June. Trees can be double- or triple-pinched to attain the final shape and size desired for the finished plant. Double-pinched trees create an “umbrella” shape, while the triple-pinched trees have a more rounded “lollipop” form. The following guidelines can assist growers in producing exceptional poinsettia trees.
Plant rooted cuttings into 6″ / 15 cm pots. Establish these plants in a warm, humid environment to help develop an active root system and vigorous growth. Begin night lighting at the time of transplant to keep plants vegetative and minimize the potential for premature floral initiation. Stake plants at this time to prevent crooked stems, leaving at least one inch between the stem and the stake. As plants elongate, lightly tie them to the stakes, using floral tape or similar materials that will not girdle or damage the stem. Always maintain a margin of space between the plants and avoid crowding the crop. Space several times during the growth cycle to provide good light and adequate air movement for the development of symmetrical trees.
Before the roots of the plant begin to wrap themselves around the base of the pot, transplant trees into the final growing container (8 to 10-inch/20-25 centimeter pots for small plant trees, 12-inch/30 centimeter pots for larger trees). Produce trees under light intensities of 2500-3000 foot-candles / 26,900-32,280 lux, and avoid excessively high light that may cause heat stress or restrict stem elongation.
- Leaf and Shoot Removal
Remove the lower side shoots when they are approximately 2 inches long. Be sure to always leave the top 10 shoots on the plants to form the branches. Do not remove foliage until September, unless it is necessary due to insects, diseases, or chemical burn (phytotoxicity). To remove damaged leaves from the tree, cut the petiole about one-half inch from the main stem. The remaining petiole will dry up and abscise naturally without causing injury to the stem.
- First Pinch
The first pinch should be a soft pinch, removing one-quarter to one-half inch of the terminal growth. At the time of pinch, remove the top two or three immature leaves remaining on the plant. If the plant has split, pinch immediately below this split to induce new, vegetative growth.
- Second Pinch
The second pinch should be done approximately 4 weeks after the first. If this is a double-pinched tree, the lower shoots should be pinched to leave 3 to 4 nodes per stem, while the upper shoots should be pinched harder, leaving 2 to 3 nodes. If this is a triple-pinched tree, all shoots (upper and lower) should be pinched to 2 or 3 nodes each. At this time, increase the light intensities to about 5000 foot candles / 53,800 lux and use growth regulators as required to prevent stretch of the new growth.
For triple-pinched trees, the final pinch should take place about 4 weeks after the second pinch, and 2 to 3 weeks prior to floral induction. Trim each shoot to 2 to 3 leaf nodes. Remove any older foliage that may be shading the growth and development of new shoots.
- Plant Supports
Support the branches by loosely tying them to the support stake next to the main stem. This should be done near the time of the final pinch to avoid breakage of new shoots and stems.
Fertilizer requirements for trees will vary with the growing season. During the hot summer growing period, use fertilizer with high ammonium nitrate, additional calcium and magnesium. Once into fall growing conditions, a finisher-type feed (higher in nitrate nitrogen) is more appropriate. Avoid the buildup of soluble salts in the media, and monitor the nutritional status on a regular basis with media and tissue analysis.
- Packing and Shipping
Packing and shipping trees can be difficult due to their large size and potential for breakage. If trees are going to be trucked any distance, it is advisable to sleeve and box them individually. If trees are going to be delivered within a more local market, consider securing the pots in some type of larger container to prevent the tree from falling over, and sleeve the upper canopy with a large flared sleeve or plastic bag. Do not crowd the plants in transport to avoid damage to bracts and stems.
Poinsettia trees can be a challenge to grow, but these unique forms offer expanded sales and marketing opportunities.
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Recommended Cultivars: Advent Red, Autumn Red, Tikal, Prestige Early Red, Jubilee, Prestige Red, Peterstar, Classic, Red Velvet, Solstice, Polar Bear, and Polly’s Pink.
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