Perennial Solutions: Hydrangea macrophylla ‘Cityline Venice’

February 22, 2011 - 14:57

This improved hybrid livens up the landscape with bright color and is sure to make an impression at garden centers across the country

Over the past several years, many growers have added hydrangea to their product lines. Hydrangea produce large, bold and brightly colored flowers that are unrivaled in garden centers and landscapes, not to mention they are fast and relatively easy to grow.

In recent years, breeding efforts have brought several improved H. macrophylla cultivars to the marketplace making hydrangea even more desirable for growers to produce and market. Franz-Xaver and Konrad Rampp of Germany developed a series of hybrids marketed as the Cityline series. One of the outstanding cultivars in this series is Cityline Venice.

‘Cityline Venice’ is a compact big-leaf hydrangea, which forms attractive mounds reaching a very manageable size of 12 to 36 inches. This improved hybrid is maintenance free and requires no pruning, which improves the number of flowers produced in subsequent summers. Blooming occurs on old wood; if pruning is performed to shape the plants, it should be done by early August to allow adequate time for flower bud development before the plants go dormant. ‘Cityline Venice’ develops large 4-inch fuchsia colored flowers in the summer, which are held nicely atop tight sturdy stems. The glossy foliage is attractive and highly resistant to foliar diseases.

Hydrangea prefers to be grown in areas with light to medium amounts of shade and moderately fertile, well-drained soils with adequate moisture. They can tolerate more direct sunlight provided enough irrigation is provided. ‘Cityline Venice’ is suitable for landscapes throughout USDA Hardiness Zones 5 to 9 and AHS Heat Zones 9 to 3. Provide protection during the winter months in colder climates.

‘Cityline Venice’ is a great garden plant that livens up the landscape with bright color. This cultivar of big leaf hydrangea is versatile and can be used in perennial or shrub borders, in groupings or masses, in containers or mixed containers, and can be harvested as fresh or dried cut flowers. With its compact growing habit and flower power, ‘Cityline Venice’ is sure to make an impression at garden centers and in landscapes across the country.

Propagation

Hydrangea ‘Cityline Venice’ is propagated from softwood cuttings. Propagation of this cultivar is illegal and is strictly prohibited. Patent Information: Cityline Venice Hydrangea macrophylla ‘Venice Raven’ USPP10,928.

Production

‘Cityline Venice’ is most commonly produced in 1-gallon or larger- sized containers. Growers commonly plant one liner, ranging from 50-cell up to 5-inch liner, in the center of each pot. The liners should be planted so the original soil line of the plug is even with the surface of the growing medium of the new container. They perform best when they are grown in a moist, well-drained growing mix. Hydrangeas are planted at various times of the year (spring to fall) depending on the container size and market date.

Hydrangea ‘Cityline Venice’ is programmed to have pink blooms; however, under certain circumstances the flowers may appear blue. The coloration of hydrangea flowers is primarily influenced by the presence or absence of aluminum. If aluminum is present within the plant, the blooms will be blue and if it is absent, the flowers will appear pink. To maintain the pink coloration of the flowers, avoid using mineral soils in your substrate, do not use fertilizers that contain aluminum, use fertilizers with high phosphorus levels (which helps prevent aluminum uptake), and maintain pH levels of 6.0 to 6.3 (reduces the availability of aluminum). When the pH levels are low (<5.8), it may be necessary to apply flowable lime or potassium bicarbonate; be sure to rinse the foliage after application to prevent leaf spotting with the residues. Growing them with high pH levels (>6.5) tends to lead to iron-deficiency chlorosis.

Hydrangea requires an above average amount of irrigation and does not tolerate extended periods of overly dry growing conditions. Never allow the plants to wilt, as they will lose their lower leaves and have reduced quality characteristics. It is best to keep them uniformly moist, but not consistently wet. When irrigation is required, water them thoroughly and allow the substrate to dry slightly between waterings.

Fertility can be delivered using water-soluble or controlled-release fertilizers. Growers using water-soluble fertilizers either apply 100 to 150 ppm of nitrogen using a constant liquid fertilization program or 250 to 300 ppm as needed. Controlled-release fertilizers can be top-dressed onto the media surface using the medium rate on the product’s label, or incorporated into the growing medium prior to planting at a rate equivalent to 1.25 to 1.5 pounds of elemental nitrogen per yard of growing mix. Decreasing the fertility levels by about half (by leaching or omitting fertilizer applications) during the last two weeks of production (when the plants start to show color) will increase the postharvest life of the flowers.

With its compact growth habit, it is usually not necessary to manage plant height during production. The height of ‘Cityline Venice’ can effectively be controlled by providing adequate spacing between the plants. If the plants need to be toned, applications of B-Nine (daminozide) at 1,000 to 2,500 ppm can be applied during production until just before the plants begin to show color. Do not trim the plants during the same year they are to be sold or the flower buds will be removed.

Insects and Diseases

Generally, hydrangea can be grown relatively free of insect and disease problems. Aphids and spider mites are the most common insects observed feeding on them. The most common diseases are Botrytis and powdery mildew. Other insects and diseases that may be observed on hydrangea include bud rot, four-lined and tarnished plant bugs, leaf spots, rose chafers, rust, snails/slugs, thrips and whiteflies. Routine scouting will allow for early detection of these pests and can be useful to determine if control strategies are necessary.

Forcing

The first consideration to keep in mind when forcing hydrangeas is that they only produce flowers on old wood. The second factor to remember is that they require cold for flowering. After vernalization, the time to force ‘Cityline Venice’ is a function of temperature.

The two most common methods of growing hydrangea are to plant them in the late summer the year before they are to be sold and vernalizing them in the final container or potting them in the spring using vernalized liners. Planting them in the late summer is most commonly done when growers are producing large container sizes (8-inch and up). Hydrangea can be quick-cropped in the spring when growing them in one-gallon containers and when large liner sizes are used.

At the onset of forcing (following vernalization), provide temperatures of 55 to 60° F night and 65 to 75° F day. Warmer temperatures tend to decrease plant quality. At these temperatures, ‘Cityline Venice’ will reach flowering in approximately eight weeks. If flowering plants are desired before mid-May, it will take an additional two to three weeks for them to bloom. Decreasing production temperatures as they approach flowering will intensify the coloration of the blooms.

Availability

This series is exclusively available through the Proven Winners ColorChoice brand of flowering shrubs. Liners can be obtained only from licensed Proven Winner propagators including Spring Meadow Nursery Inc. (www.springmeadownursery.com). Finished containers are widely available from many reputable greenhouses and nurseries across the country.

About The Author

Paul Pilon is a horticultural consultant, owner of Perennial Solutions Consulting (www.perennial-solutions.com), and author of Perennial Solutions: A Grower’s Guide to Perennial Production. He can be reached at 616.366.8588 or paul@perennial-solutions.com.

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