CULTURAL TIPS

By Dr. Claudio Pasian
Department of Horticulture and Crop Science, OSU

Poinsettias

Bract edge burn. A reminder to growers that this problem can be prevented with calcium chloride sprays, once a week at 400 ppm. Sprays should start soon after bracts begin showing color. In addition, growers should reduce fertilization two weeks before shipping. Do not ship plants wet because Botrytis can worsen the problem. Prevention is the only solution; when symptoms are visible, it is too late.

Poor bract color. Bract color intensity is a function of temperature and light. It increases at high light levels and lower mean temperatures. It fades under the opposite conditions. It is advisable to decrease temperature the last two weeks of production to 60 - 62 F. Plants that were grown at high light levels during Fall tend to have brighter red colors.

Lateral branch breaking. New research conducted by Dr. Faust (former Professor at Tennessee Univ, now at Clemson) indicates that environmental conditions to which stock plants are exposed have a strong influence on this problem. Stock plants grown at high temperature and low light levels will produce cuttings whose laterals will break easily. Here the solution is to grow stock plants cool and at high light levels or purchase cuttings that come from areas in the country where such conditions exist.

Easter Lilies

Next year, Easter falls later than it will for many years to come. Growers will have to plan for the extra time they will have available. If well handled, this situation should allow growers to have excellent quality Easter lily plants (grown at cooler temperatures). By forcing plants properly, growers will be able to increase the number of flowers per plant.

According to Dr. Richard McAvoy, University of Connecticut, one way to use the extra time available is to prolong the cooling period. Bulbs must be vernalized at 40 - 45 F for six weeks or 1000 hours. You may prolong this period without any negative effect by reducing the temperature in the cooler to 32 - 34 F after four to five weeks at 40 - 45 F. Temperatures just above freezing will retard development without affecting quality. This low temperature can be held up to four weeks. After that, raise the temperature to the normal 40 - 45 F to complete the six weeks of vernalization. Be sure that the cooler performs properly. The temperature inside the cooler must never dip below 32 F. Use a thermometer to check temperature in different spots of the cooler!

According to Dr. Wilkins, floral bud initiation is a progressive event. After the first set of primary floral buds has been initiated on the perimeter of the meristem, additional secondary floral buds may be initiated as a second whorl of buds. It is believed that optimal temperature for secondary flowers is 44 - 45 F for 'Nellie White'. Temperatures may be lowered in mid-January if Easter is late or if timing is adequate to develop secondary flowers. This lowering of the temperature must occur after flower bud initiation in order to avoid affecting flowers. In addition to dissecting bulbs, you can tell bud initiation by noting when stem roots are beginning to break out.

Finally, if you have extra time, you can store plants with open flowers in coolers. However, keep in mind that it is not advisable to store plants for periods longer than two weeks.

Water pH and Chemical Efficacy

Both too low and too high water pH can impact the effectiveness of some chemicals. Two examples are Phyton 27 and Florel. The ideal pH of a Phyton 27 ready-to-use solution is 5.5 - 6.5. This pH will ensure effectiveness and plant safety.

Florel is also more effective if the solution is prepared with water whose pH is around 5.7. Check the pH and alkalinity of water before use and, if necessary, reduce pH by adding some of the commonly used acids to neutralize alkalinity.

If your irrigation water has either too high or too low pH and alkalinity levels, contact the manufacturer of the product you want to apply and ask for any restriction regarding pH of the spraying solution.