January 2009

Crop Culture Report: Pentas Graffiti Series By Jessica DeGraaf

Few annual varieties withstand the rigors of heat and drought and maintain a reputation of resilient beauty quite like pentas. The flowers, more commonly known as Egyptian starflower, are native to northeastern Africa and thrive in very hot and dry conditions. A variety of soft and vibrant colors are now available, offering alternatives to petunias and marigolds for summer color.

Variety Information

The Graffiti pentas series is a well-known seed variety from Benary. Its wide color selection ensures that Graffiti is both versatile and beautiful. The most dramatic color in the series, Red Lace, offers bright-scarlet flowers with glistening white stigmas, giving the appearance of lace floating over the flowers. With its bright colors and abundance of nectar, Graffiti pentas are a sure attractant for butterflies and hummingbirds throughout the summer months.

Scheduling

Graffiti pentas are a sure winner for late-spring and summer sales windows. Crop times given below are from transplant to flower from a 128-cell plug. A 41/2-inch pot will need seven to eight weeks to finish, while a 6-inch pot will require nine to 10 weeks. A 10- to 12-inch pot will require 11 to 12 weeks. High light levels and heat will reduce crop times.

Germination

Sow seed in a media with a pH range of 6.5-7.2. Maintain uniform soil moisture levels and humidity levels above 95 percent. Stage I temperatures of 75- 80¡ F optimize germination. Maintain a pH range of 6.5-7.2. Do not cover seed, as light increases germination rate and improves seedling uniformity. Begin light fertilization with 25- to 50-ppm nitrogen. Continue Stage I conditions for seven to 10 days.

Plug Culture

Gradually reduce temperatures to 70-75¡ F during Stage II (seven to 10 days). Increase fertilization levels to 50- to 75-ppm nitrate nitrogen in a well-balanced mix. Increasing light levels to 1,000 foot-candles improves seedling quality and plug uniformity. During Stage III (14 to 21 days), gradually lower temperatures to 65- 70¡ F. Increase light levels to 2,500 foot-candles, and feed at 75- to 100-ppm calcium nitrate in a well-balanced mix. Keep plug pH between 6.6 and 6.8 for both Stages III and IV. During Stage IV, increase fertilization to 100- to 150-ppm nitrogen and decrease temperatures gradually to 62- 67¡ F. Do not allow soils to remain saturated during plug growth.

Growing On

Grow on at temperatures of 65-70¡ F. Fertilize weekly at 100- to 150-ppm nitrogen in a well-balanced mix. Monitor soil pH levels, and maintain a pH above 6.5. High light levels promote branching and flower initiation.

Cultural Hints

Pentas roots release hydrogen ions into the soils, which will drop the pH to toxic levels if not monitored and adjusted if necessary. Maintain pH levels between 6.5 and 6.8 to avoid magnesium deficiencies or iron toxicity. If magnesium levels are too low, leaf puckering will occur. Overwatering in combination with cool temperatures (below 50¡ F) delay flowering.

Plant Growth Regulators

Bred to be naturally compact and well branched (12-15 inches), the Graffiti series does not require plant growth regulators to finish a premium crop. Graffiti pentas can be produced on tighter bench spacing allowing for more cost-effective production.

Insect and Disease Control

Thoroughly cleaned production space will help to keep insect and disease occurrences down during production. Conduct weekly scouting counts to keep insect populations at a minimum.

The most common insect pests of pentas are thrips and aphids. Fungus gnats can also be problematic if soil remains too saturated.

Pentas prefer a very porous, well-drained soil. Excessive soil moisture increases the risk for pythium and phytophthora infestations. A fungicide drench may be applied after plants have rooted into the pot. As always, maintain good drainage and air circulation to prevent problems.