January 2010

Crop Culture Report: Impatiens SunPatiens Series By Garry Grueber

Until recently, any reference to impatiens often included a phrase like "the perfect choice for shady gardens." With the advent of New Guinea Impatiens more than 20 years ago, these varieties would at least tolerate some sunshine, although they still performed quite poorly under hot conditions.

The new SunPatiens bred by Sakata are truly the first impatiens that will perform brilliantly in full sun and sweltering heat — but also show more vigor and flower power in shady or cooler environments than their popular predecessors.

Available in three series and 15 varieties, SunPatiens offer myriad possibilities in bedding, window box, hanging basket and commercial landscape opportunities. Their ability to tolerate a broad range of light and temperature conditions allows for multiple seasons of enjoyment: spring through summer and autumn, until hard frosts end the display.

The Compact SunPatiens series is excellent in 4-inch, quart and gallon pots; they work well in mixed containers as well as beds, gardens, baskets, mass plantings and more. Spreading SunPatiens series works well in quart and gallon pots. Vigorous SunPatiens series is perfect for commercial landscapes, whether grown in specimen containers or in Elle or Jiffy pots and planted green.

Growing SunPatiens

SunPatiens and New Guinea impatiens may be similar in appearance, but they have substantially different cultural requirements. For best results, maintain high light levels, cooler temperatures and space sooner than for New Guinea impatiens. Since SunPatiens root twice as fast as New Guinea impatiens, direct sticking into the final pot size is also an easy option to save labor and materials.

Propagation

Direct stick. Direct sticking cuttings into final container (up to 5-inch pots) can decrease overall crop time by 10 to 14 days. With no need for transplanting, the root system can freely expand, producing a well-established root system more quickly. Use similar misting and light levels as outlined below for rooting in cells.

Rooting in cells. Stick one cutting per cell. SunPatiens root very quickly, and rooting hormones are not necessary. Initial light level should be 2,000 foot-candles, increasing to 3,000 foot-candles 10 days after sticking. Maintain soil temperature of 68-75¡ F. Mist heavily for the first three days and then only as needed to maintain turgidity. Misting can usually be stopped one week after sticking. Avoid overmisting; this depletes nutrients and invites disease.

Finishing

Potting. Plan on one plant per 4- or 6-inch pot. For 12-inch hanging baskets, plan on three plants per basket for fast cropping.

Media. Select peat-based, well-aerated mix. Optimum pH range is 5.8-6.2, with an EC of less than 0.7. Consider that the water-holding capacity that is best for consumer performance may be greater than what is ideal for production.

Irrigation/fertilization. Avoid excessive irrigation when plants are young. Feed with a complete, balanced fertilizer at 200-ppm nitrogen. A media EC level of 1.0-1.2 is a good target range. Provide periodic clear water applications if excess soluble salts accumulate. Subjecting plants to a strong wilt causes leaf scorch, especially under low humidity levels.

Temperature/humidity. SunPatiens grow well under a wide temperature range. Establish the crop at an average temperature of 64-66¡ F. Once established, optimum temperatures range between 68-85¡ F during the day and 60-64¡ F at night. Lower temperatures are possible but will prolong crop time. Provide good air circulation at all times. Maintain relative humidity below 70 percent to prevent diseases such as Botrytis or Myrothecium.

Light. Optimum light level is 5,000 foot-candles. Apply light shade only if light intensities cause greenhouse temperatures to exceed 85¡ F. Growing below hanging basket lines at lower light levels will reduce number of flowers and increase internode stretch. If producing outdoors under full sun, acclimate plants first to avoid leaf scorch, growing one week at 5,000 foot-candles before moving outdoors.

Pinching. Pinching is not recommended, as it delays flowering by one to two weeks and often results in a low, horizontal branching pattern.

Scheduling

Sunpatiens are a terrific crop for early spring through fall finish. From liners, a 4- to 5-inch container will need five to six weeks to finish, with 6-inch and gallon pots requiring seven to eight weeks; an 8-inch container needs nine to 10 weeks, while a 10- to 12-inch container will take 10 to 12 weeks. If using direct stick the finishing time will be reduced by approximately two weeks. Space the plants properly to avoid stretching.

Plant Growth Regulators

Rapid stretching occurs when canopies between neighboring plants grow together; control by providing adequate plant spacing and high light levels. SunPatiens respond well to Bonzi/B-Nine tank mixes or B-Nine alone.