Thunderhead Japanese Black Pine

'Thunderhead' Japanese Black Pine at U.T. Gardens in Knoxville

Thunderhead (Pinus thunbergiana) is a choice shrub variety of Japanese Black pine. This medium-sized evergreen shrub conifer grows 10 to 12 feet high and 12 to 15 feet wide (in 10 - 15 years). Its distinctive cottony terminal buds and dark green densely packed needles are architecturally beautiful in the fall-winter landscape.

“Billowy emerald clouds” best describes the needle foliage on Thunderhead pine.  Silvery white candles (shoots) grow 10 - 12 inches long in response to warm spring temps.  The shoots reach their full length by late May. Branches are rigid and its lower needles are mostly retained.

Desired location is in full to partial sun and in moderately acidic soils that are well-drained. Provide a minimum of 6 hours of sunlight. Plant in late winter to early fall from container or balled and burlapped (B&B) stock. Allow 1-2 years to become established after planting; afterwards drought and heat tolerant.

Feed annually in late winter with 10-10-10 or equivalent granular fertilizer. Pruning is rarely necessary except for desired shaping and sizing. Cut back new shoot growth (“candles”) around late May to early June before needles are fully expanded.

Disease and pest problems are rare when properly sited. Thunderhead is highly tolerant of wind, drought, and salt spray. Provide shelter from harsh winds to minimize off-color in winter. Availability is primarily from specialty conifer nurseries on-line or in the southeast region.

Thunderhead Japanese black pine is loved for its low maintenance and its dark evergreen foliage. This shrub pine conifer deserves a place in your landscape.

Arkansas Amsonia - 2011 Perennial Plant of the Year

Since 1990, the Perennial Plant Association (PPA) has annually selected one outstanding perennial for gardeners to enjoy. Last week, at the annual PPA Symposium in Portland, OR, members selected Arkansas amsonia (Amsonia hubrichtii) as the 2011 Perennial Plant of the Year.
Why wait until next year to purchase amsonia? It is available now through many garden centers, mail order, and on-line nurseries. Amsonia begins its rapid growth in early April. A month later, the 3 foot tall and wide plants are blooming. Pale “bluestar” flowers bloom over 2-3 weeks in the southern Appalachian region (USDA zones 6 and 7).
Flowering is just a prelude to its other attributes. Blue-green, fine textured summer foliage is devoid of serious disease and insect problems and is deer proof. In October, its foliage turns a spectacular lemony yellow. To achieve maximum autumn foliar impact, plant three or more amsonia spaced 3 to 4 feet apart.
Amsonia forms strong stems under full day sunlight; branches are weak or floppy in partial shade. It grows in any well-drained soil with a pH range from 5.6 -6.8. Established plants are heat, humidity, and drought tolerant.
Furthermore, don’t overlook another perennial favorite, bluestar amsonia (A. tabernaemontana), which will be featured in a future blog.

Plumleaf Azalea -This Gardener's Choice

Plumleaf azalea (Rhododendron prunifolium) has been blooming in my garden for the past ten days. This species is a late July - early August bloomer in northeast TN. The bright orange-red flowers of this native azalea light up any garden spot whether in full sun or partial shade. Provide some additional shade in southern climes (zones 7-b and 8). A dark red flower selection is available.

It grows in any well-drained soil type- sand, silt or clay. My two established shrubs receive little nutritional care. Shrubs are irrigated during severe drought periods, such as we are in currently.
Plumleaf azalea is an Alabama/southwest Georgia native, but is winter hardy in the southern Appalachian region (USDA zones 6-7), and further north (zone 5). It seems almost soil pH insensitive, although likely prefers an acidic range between 5.4 to 6.4. No diseases and insects pests trouble it. Flowers are not fragrant, but do attract numerous butterfly and bee pollinators.

Pruning is rarely done on my 15+ year old plant purchased at Callaway Gardens. Plumleaf azalea grows 8-10 feet tall, but I maintain it at 6 by 6 feet tall and wide. An errant branch is occasionally clipped back into the fold.