January 2009 Culture

Hakonechloa macra ‘Aureola’ By Paul Pilon

Ornamental grasses continue their popularity with growers, landscapers and consumers alike. Although the ornamental grass hakonechloa is not new to our industry, it is quickly being added into production by numerous perennial growers across the country. Hakonechloa, commonly referred to as golden Hakone grass, will definitely continue to gain popularity as the Perennial Plant Association (www.perennialplant.org) selected Hakonechloa macra 'Aureola' as its 2009 Perennial Plant of the Year.

There are numerous desirable characteristics that set this ornamental grass apart from traditional varieties. The most striking feature of 'Aureola' is its cascading variegated foliage, which resembles golden waterfalls in the landscape. It brightens up shady areas with its luxuriant, brilliant leaf coloration. The green- and yellow-striped leaves arch in the same direction and form attractive mounding clumps reaching 18 inches wide and 12-18 inches tall.

The color of the foliage varies slightly with the light intensity it is exposed to. The best and characteristic yellow-toned leaves are most pronounced when they are grown in locations with partial shade. Growing them in deep shade causes the variegation to appear lime green, and hakonechloa grown in full sun take on a sun-bleached appearance and may become scorched. This grass also provides seasonal interest in the fall as the foliage takes on an intense pinkish-red coloration, particularly on plants in partially sunny locations.

Hakonechloa is slow growing, gradually spreading by rhizomes, but is not invasive in the landscape. It grows best in slightly shaded, moist, woodland environments and does not tolerate poorly drained soils or extended dry periods. 'Aureola' is commonly used to cascade down slopes, drape over the edges of walls, as an accent plant, in mass plantings or in container plantings. golden Hakone grass is hardy in USDA Hardiness Zones 5 to 9.

Propagation

Hakonechloa is vegetatively propagated by division and is most commonly available to growers as rooted liners. They are usually propagated in the early spring shortly after new foliage appears. Division entails dividing or splitting the crown into smaller sections containing at least one stem and several adjoining roots. It is best to propagate them with cool temperatures and let them root gradually. Carefully manage irrigation during propagation to avoid overly wet or dry conditions.

Production

'Aureola' is most commonly produced in 1-gallon or smaller containers using rooted liners (72-cell or larger). It performs well in a wide range of bark- or peat-based growing mixes; it is recommended to use a medium with both adequate drainage and water-holding capacity. Avoid planting them during hot periods; if it is necessary to plant them under these conditions, provide shade to reduce plant stress and prevent foliage burn.

While transplanting, avoid planting them too deeply — always plant to match the original soil line of the plug with the growing mix of the final container. They are relatively slow to root and require careful water management until they become established. It is important to maintain even moisture levels and allow the medium to dry only slightly between irrigations. Prevent overly wet conditions from occurring. Established containers require average amounts of irrigation and can be allowed to dry out more fully between waterings.

They are light to moderate feeders. Fertility can be delivered using constant liquid fertilization, feeding at rates of 50- to 100-ppm nitrogen or 150- to 200-ppm nitrogen as needed. Controlled-release fertilizers also can be used to deliver nutrients using low to medium label rates, typically incorporating with rates delivering 1-11Ú4 pounds of elemental nitrogen per yard of growing medium. The pH should be maintained within the range of 5.5-6.0.

With its compact habit and growth characteristics, 'Aureola' produces attractive and manageable containers that do not grow out of control or require height-management strategies or plant growth regulators.

Pests and Diseases

Insect or disease problems are generally a rare occurrence with commercial hakonechloa production. Spider mites have been observed on golden Hakone grass but have not become problematic for growers. Leaf spots may be observed and are usually the result of exposure to high light levels. Where possible, provide at least partial shade during the afternoon to reduce plant stress. In the South, provide at least 50 percent shade during the late spring and summer months. Northern locations can provide less shade — 30 percent will suffice.

Crown and root rots are commonly observed. The onset of these diseases is often caused by improper planting practices (too deeply), poor irrigation management, high salt levels in the growing medium, poor physical properties of the media (namely too much water-holding capacity and decreased aeration), or growing the crop in the same container and growing mix for too long. Any of these conditions could lead to plant stress and the onset of root-rot pathogens. Choose a growing mix that has good water-holding and drainage characteristics and will not deteriorate or settle over time. Monitor the irrigation practices and fertility levels on a regular basis, making adjustments accordingly. When these measures are taken, most crown and root rots can be prevented.

Forcing

Hakonechloa is not normally grown and marketed as a flowering plant. They do produce airy clusters of inconspicuous flower spikelets in the late summer, but the characteristics of the foliage are definitely the selling point of this remarkable plant.

For plant establishment and faster growth, maintain average temperatures of 65-70¡ F; this is often provided using 70-75¡ F days and 60-65¡ F nights. Lower temperatures can be provided but will increase the production times significantly of this already slow-growing plant. The best growth and quality characteristics, such as leaf color, are obtained when they are produced at moderate light levels of 4,000-5,000 foot-candles.

With the extended time necessary to produce a full container, many growers plant hakonechloa during the late summer the year before they are to be marketed. Allow at least six to eight weeks for establishment and growth in the fall before temperatures get too low for active growth. When spring planting from a 72-cell plug, allow 12 to 16 weeks to produce a 1-gallon container or eight to 10 weeks for quarts.

Availability

Hakonechloa macra 'Aureola' is widely available from a number of propagators, including Hoffman Nursery (www.hoffmannursery.com), Skagit Gardens (www.skagitgardens.com) and Walters Gardens, Inc. (www.walters gardens.com).