Culture Report: Begonia Megawatt Series By Bart Sneek

Open the door to earlier spring begonia sales with this new mega- sized option.

When it comes to flower sales, greenhouse growers know: It’s all about the timing. Getting the right product into stores for maximum sell-through means selecting flowers that can draw shopper attention as well as thrive during the season to help a gardener be successful. One class of plants that is on the rise for today’s shopper is interspecific begonia. A stunner in sun or shade, begonias fill landscapes and baskets with the color gardeners seek with minimal attention or maintenance.

Starting off begonia season is BabyWing, which is fast to market and perfect for early-season sales. Next, growers looking to “fill the gap” between early and later begonia sales have an early crop option with the new Megawatt series from PanAmerican Seed. Megawatt has non-stop flowers spring through fall, thrives in heat and humidity, and tolerates drier periods between waterings. Plus, its sturdy flower stems hold blooms above the foliage for superior show in ground and in large-size containers. Finally, as the selling season heats up, growers can finish with deliveries of popular Dragon Wing for main season begonia baskets.

Crop Timing for Scheduling Landscape Begonia Programs

Table 1. Crop time.

NOTE: Due to daylength sensitivity, when producing during summer with daylength 13 hours or longer, add two to three more weeks for Megawatt Green Leaf varieties.

The introduction of Megawatt lets growers supply customers with a full, high-impact begonia assortment throughout the whole selling season. And with unique colors like Pink Bronze Leaf and the new Red Bronze Leaf for 2018, Megawatt opens the door to earlier spring sales for landscapes, baskets and big tubs. Here are a few additional production guidelines for growing Megawatt interspecific begonia.


Stage 1 (10 to 12 days). Use a well-drained, disease-free soilless medium (pH 5.4 to 6.0, EC 1.0 mS/cm). Sow one pelleted seed per cell in 288 or larger plug tray. Water thoroughly to completely dissolve the pellet, but do not cover at sowing.

Maintain night temperatures at 62 to 67° F and days at 65 to 75° F. Average daily temperature (ADT) should be 65 to 70° F.

Light is not required but is beneficial for uniform germination. Keep the media moist (level 5) during germination; Megawatt is very sensitive to drying out during the early stages. Maintain 95 to 97 percent relative humidity until cotyledons emerge. A saturated media and high humidity is critical to germinate successfully.

Stage 2. The optimum temperature is 72 to 75° F. Light up to 2,500 foot-candles. Continue to keep the media very wet (level 5). Do not stress plugs. Begin fertilization at five days out of germination chamber.

Stage 3. Temperature and light remain the same. Keep media moisture medium wet to medium (level 4 to 3). Do not allow the seedlings to wilt. Increase the fertilizer rate to 2 (100- to 175-ppm nitrogen) once a week as soon as the plugs have begun to root out. Apply a balanced ammonium and nitrate-form fertilizer as needed to encourage growth and balance the media pH.

Stage 4.
Temperature can be decreased to 65 to 67° F. Increase light up to 5,000 foot-candles. Moisture can be reduced to medium dry (level 3). Avoid excess humidity later in the plug production, as this will create disease conditions. Fertilizer is the same as stage 3.

Growing On to Finish

Megawatt is a facultative short-day plant. It flowers faster under short days (10 to 12 hours). All interspecific begonias are daylength sensitive — long days will delay flowering. Megawatt Green Leaf varieties are two to three weeks slower to flower in long days. Megawatt Bronze Leaf varieties are less daylength sensitive than others, and long days will only delay flowering four to seven days.

Megawatt Green leaf varieties are more vigorous than Bronze Leaf varieties. They require slightly heavier growth regulator rates than Bronze Leaf varieties.

Apply paclobutrazol spray for height control, especially for 6-inch or smaller containers. Spray rate can be up to 5 ppm, depending on environmental conditions, plant growing stage and varieties.

Start with paclobutrazol 2 to 3 ppm (0.5 to 0.75ml/l 0.4 percent formulation) spray about two weeks after transplant. If needed as plants grow bigger, apply higher rate of 4 to 5 ppm (1.0 to 1.25 ml/l 0.4 percent formulation) two weeks later when grown under warmer or longer daylength conditions. No pinch needed.

Bart Sneek

Bart Sneek is senior global product manager for the EU Region of PanAmerican Seed. For more production tips and full culture details on these plants and more, visit