March 2014 Culture

Perennial Solutions: Hypericum ‘Hypearls Compact Star’ By Paul Pilon

In recent years, the lines between plants marketed as herbaceous perennials and ornamental shrubs have become somewhat blurred. Many growers produce and market both perennials and shrubs in their commercial offerings. Hypericum ‘Hypearls Compact Star’ is a great plant that is typically categorized as a shrub, but it can easily be grown and marketed as a perennial.

‘Hypearls Compact Star’ has numerous appealing characteristics and landscape attributes. It offers beautiful deep green foliage in the spring, topped with yellow-gold star-shaped flowers in the late spring, followed by showy deep pink berries in the summer. These morphological stages lend well to marketing this plant over an extended period of time — from late spring through early autumn. Its compact size works well for both growers and landscapers; ‘Hypearls Compact Star’ grows 10 to 14 inches in height in containers and up to 18 inches tall in the landscape.

Once established, St. John’s-wort is heat tolerant and drought tolerant. It grows well in full sun to light shade throughout USDA Hardiness Zones 6 to 9. With its good texture and form, ‘Hypearls Compact Star’ can be used as a border or accent plant, in containers or in mass plantings. It attracts butterflies and birds into the landscape and is resistant to deer feeding.

With its multi-seasonal landscape appeal, reliable performance and ease of production, Hypericum ‘Hypearls Compact Star’ is a great perennial for sunny gardens, small places and containers. This often-overlooked perennial could help growers extend their retail sales into the summer and fall.

Propagation

Hypericum ‘Hypearls Compact Star’ is propagated from softwood cuttings. A U.S. Plant Patent has been applied for (USPPAF); propagation without permission of the applicant is illegal.

Stick 1- to 1.5-inch single node or tip cuttings into moistened propagation substrate. It is recommended to spray 1,000-ppm IBA soluble salts after sticking to improve rooting. Place the cuttings under a high misting regime for the first few days of propagation, then ramp down to moderate misting levels until approximately 10 days after sticking. Gradually reduce the misting further until the cuttings are rooted.

It is beneficial to begin constant liquid feeding with 75- to 100-ppm nitrogen at each irrigation, beginning 10 days from sticking. The cuttings generally require three to four weeks in the propagation environment. After the cuttings are rooted, pinch or shear the plants to promote branching. Allow three to four additional weeks for rooting and plant development prior to planting or shipping.

Production

‘Hypearls Compact Star’ are suitable for production in 2-quart to 2-gallon containers. To improve fullness, it is best to plant one to two liners per container in 1-gallon or smaller containers or two to three liners for 8-inch or larger pots. 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 grown in a moist, well-drained growing mix. Many commercially available peat or bark-based growing mixes work well provided there is good water holding ability and adequate drainage. Hypericum have an average to above-average water requirement. As the plants mature, they will require more frequent irrigations as they will dry out slightly faster. Avoid letting them reach a hard wilting point or foliage burn will occur. When irrigation is needed, water them thoroughly, ensuring the entire growing medium is wet or nearly saturated, and then allow the growing mix to dry slightly before the next irrigation is applied.

St. John’s-wort requires moderate amounts of nutrition. Fertilizers can be applied using water-soluble or controlled-release sources. Growers using water-soluble fertilizers apply 100- to 150-ppm nitrogen with every irrigation, or use 200- to 250-ppm nitrogen as needed. Controlled-release fertilizers are commonly applied as a top-dress onto the media surface using the medium recommended rate on the fertilizer label or incorporated into the growing medium prior to planting at a rate equivalent to 1.0 to 1.25 pounds of elemental nitrogen per yard of growing medium. Maintain the media throughout the production cycle with a pH between 5.8 and 6.4. Avoid feeding Hypericum after the berries are present; continuing fertilization after this point encourages the next flush of vegetative growth over the top of the berries.

With its compact habit, controlling plant height is not usually necessary when producing ‘Hypearls Compact Star’. Providing adequate spacing between the plants will reduce plant stretch caused by competition. If toning is required, spray applications of 2,500-ppm daminozide (B-Nine or Dazide) can be applied as needed.

Insects and Diseases

‘Hypearls Compact Star’ can be produced with relatively few problems from insect feeding or plant pathogens. Aphids, caterpillars and whiteflies are the most common insects observed feeding on Hypericum. Although St. John’s-wort can be generally grown without the incidence of plant pathogens, bacterial leaf spots, powdery mildew and rust diseases may be observed on occasion. Routine scouting should be sufficient to detect the presence of any pests or diseases and to determine if and when control strategies are necessary.

Scheduling

Hypericum ‘Hypearls Compact Star’ is typically grown and marketed for sales between early summer and early fall. Vernalization is not required for flowering. For best growth and flowering, it benefits from being produced under long day lengths.

Although, ‘Hypearls Compact Star’ can be grown as a traditional perennial or shrub and be transplanted in the summer or early fall and grown for sales the following spring, growers can also grow it in a single growing season. Transplanting into outside production sites in March or April (where weather permits) will result in marketable plants by early to mid summer. Plant them into the final containers in late May to early June for late summer or fall sales. It is recommended to trim the plants back at the time of transplanting and again about two weeks later to promote branching. For best appearance, do not trim the plants after July 1.

Availability

Unrooted cuttings and rooted liners of Hypericum ‘Hypearls Compact Star’ are currently available from Green Leaf Plants (www.glplants.com).