Bedding Basics of Woody Ornamentals

Chris Adler
The most common woody and semi-woody ornamental crops grown in most greenhouses today include poinsettias, chrysanthemums, calibrachoa, euryops, hydrangea, roses and azaleas. What many bedding growers are overlooking is that there is a great opportunity to increase spring sales with forced shrubs. With a little horticultural confidence and some know-how, adding new woody varieties to inventory isn’t as complicated as it may seem, and ultimately benefits the bottom line. The following tips might just be the encouragement you need to try something new (and woody) in your greenhouse.

Woody tips
To begin a successful growing process for woody ornamentals, start with plugs planted in the summer or fall so that they can root out in pots. Allow a dormancy period in winter for forcing plants or to naturally grow out in spring. Dormant plugs can be planted in late winter for forcing in spring.

Although plant nutritional and cultural growing environments will vary from species to species, a constant feed of 100-300 ppm nitrogen will generally be sufficient. There are some varieties where pH is a concern; rhododendrons prefer pH on the low side, while lilacs prefer a more alkaline soil. Typically, 90% of varieties do fine with a pH of 5.8-6.2.

Optimal container media depends on three factors—the specific plant species being grown, the container size, and the environmental conditions in the production area. While nurseries generally use a pine bark-based media with woody ornamentals, the usual greenhouse peat/perlite medium formulations can also be used.

Woody ornamental disease pressures are similar to annual production. However, due to some hardwood species requiring a longer growing time, more chemical applications may be necessary. Most of the new varieties of flowering shrubs have been selected for disease resistance. Pest management for these varieties won’t have the intensity that growers encounter with poinsettia crops.

Plant growth regulators are not often necessary, but extremely effective on woody varieties. These can be most useful when plants are grown in a house with mixed crops and environmental or cultural growth regulations are difficult to control. PGRs are especially useful when height specifications are crucial. In this arena, daminozide, paclobutrazol and chlormequat (B-Nine, Bonzi, Cycocel) are commonly used. As with growing poinsettias, these growth regulators can often enhance the quality of the plant.

Trial to suit your needs
The breeding work for many of Spring Meadow’s new varieties of flowering shrubs have been trialed for color impact in 1- to 3-gal. pots in combination with landscape trialing. Some new woody ornamentals, such as the Cityline Hydrangea series, were developed with greenhouse production in mind. These compact hydrangeas were developed in Germany, where PGRs are prohibited. Growers may find it worthwhile to trial a forced shrub program for spring. Not all shrubs will work, but trialing fast-growing shrubs such as buddleia, Limelight hydrangea or Invincibelle Spirit hydrangea may create excitement in your greenhouse and with your customers. 

Chris Adler is the new plant coordinator for Spring Meadow Nursery in Grand Haven, Michigan.