Horticulture

Notes from horticulture segments presented at select meetings

(excerpted and edited from Marilyn Pulk’s meeting minutes in the RGC Bramble Newsletters)

“Sweet Heidy”: The workhorse hardy geranium (zones 4-8). This beauty has a similar habit to Rozanne Geranium, growing from a central mounding crown up to about 18” high, but spreading up to 3 ft. ‘Sweet Heidy’ has large pinkish-violet flowers with a white center and dark purple veining that bloom for several months from mid-summer to fall. It works well weaving among taller, sturdy plants, or use along a wall where it will cascade over the edge. Geranium ‘Sweet Heidy’ likes to be planted a little deeply in average to rich, well-draining soil that dries out completely between watering. It likes full sun to part shade and is extremely drought tolerant and will actually falter in wet conditions so avoid too much water.

“Houki”: A spectacular blooming Tree Peony specimen. Houki produces rich, ruby-red flowers with prominent yellow stamens on woody stems. Paeonia suffruticosa, or Tree Peonies, are loved by everyone who has ever seen them in bloom. A deciduous shrub, not a tree, the tree peony is multi-stemmed with an upright spreading habit of growth. It grows at a slow rate, and under ideal conditions can be expected to live for approximately 20 years. Its relatively fine texture sets it apart from other landscape plants with less refined foliage. A mature shrub produces dozens of huge, long-lasting, silken blooms which delight the eye. Tree Peonies prefer evenly moist, well-drained soil with a pH close to neutral. Our soils are acidic, so we need to add lime when planting.

Unlike perennial peonies, remember not to prune this variety except to remove deadwood after it’s leafed out in spring and also remove spent flowers. Tree Peonies usually take 2-3 years to become established and bloom heavily, so be patient. If your peony is in the optimum sunny location with average, well-drained soil, you can expect it to reach a mature height of 5 ft. tall with a spread of 5 ft. and to see blooming from June to September. Peonies are light feeders and too much nitrogen may inhibit flowering. Just like their perennial sisters, botrytis disease also affects tree peonies, which is the primary culprit of unopened, black buds. Keep foliage dry during watering, especially during cool weather. Use fungicides to control outbreaks. With some care, Houki will provide years’ worth of huge double red (lightly scented) flowers that will be a focus in either the landscape or a simple vase. Maureen mentioned that there is some spectacular tree peony viewing in the Portland Japanese Garden for those in need of checking on mature tree peonies.

Daphne genkwa or Lilac Daphne: Like many spring-flowering shrubs the long, beautiful lavender-blue flower wands (which are perfect for cutting) appear first on this compact (maxed out at 7’ x 7’) shrub. This Daphne has a free-flowing, arching branch habit with interesting silky textured leaves in spring and doesn’t require much pruning. It is hardy to -10oC, is content in full sun to light shade, loves warmth (so next to the foundation) and requires good drainage. Unlike its cousin, Daphne odora, this one has no fragrance—one drawback. Like lilacs, it’s a good idea to add a little lime to the soil and stand back for the sensational spring show. Maureen thought this would look spectacular with an underplanting of daffodils which bloom about the same time.

Daphne genkwa
Daphne genkwa

Hydrangea quercifolia ‘Munchkin’: a tough oakleaf hydrangea as her cool plant of the month. With a 3′ x 3′ growth habit, this compact, dense stunner is perfect in smaller, height-challenged landscapes or containers. This plant is awash with a profusion of large flower clusters, held against dark green, deeply lobed oak-like leaves. Robust blooms open white and age to pink, remaining upright even after heavy rain. Foliage turns brilliant mahogany in fall. It also shows well in groups or as a hedge. One other plus…one site listed it as so compact that it hasn’t needed pruning in 5 years. A great plant!

Hydrangea quercifolia 'Munchkin',
Hydrangea quercifolia ‘Munchkin’,

Beautyberry Bush (Callicarpa bodiniei var. giraldii ‘Profusion’) and the blue Caryopteris “Sunshine Blue”:  Two very colorful and irresistible shrubs. First up, the beautyberry was described as an extremely valuable bush for winter arrangements, as the violet berries last until Christmas. Profusion is one of the most outstanding of all fruiting shrubs with dense cymes of small lavender flowers that bloom by the thousands in late summer. The blooms are followed in the fall by masses of those showstopper clusters of small violet-purple berries. These fruits may attract several species of birds to your yard as well. The bright color stands out, especially after the plant loses its leaves. It grows 8 to 10 ft. tall with slender, erect branches in zones 5 to 8. It is vigorous, upright, flourishes in sun or light shade and is relatively drought tolerant. Once established, prune every spring, as it flowers on new growth. Plant 10 to 12 feet apart. Purported to be deer resistant, but never foolproof on that score (mine has been eaten down and is now safely behind bars). Beautyberry is one shrub that’s really earned its common name.

Callicarpa bodiniei var. giraldii ‘Profusion’
Beautyberry Bush (Callicarpa bodiniei var. giraldii ‘Profusion’)

Caryopteris incana ‘Sunshine Blue’ (aka Bluebeard, Blue Mist Spirea). Inspired by Susan H’s luscious Caryopteris ‘sunshine blue’ that we all passed by on our way to the September’s meeting, Maureen found a copycat specimen to share. It’s advised to plant this lovely near a window to enjoy the fragrance and rich golden foliage with amethyst-blue flower spikes. A dramatic display planted in masses. It holds both golden foliage and clusters of delicate blue flowers resembling blue smoke or mist from hard-to-find midsummer color to late summer and until frost. This tough little shrub is seaside and salt tolerant in a sunny spot (Zones 5-8), as well as deer resistant (again, I had a problem). The blue flowers attract butterflies and stand out well in containers, but remember to provide good drainage as wet soils should be avoided. The blooms occur on current season’s growth, so prune hard in early spring after leaves appear to remove dead growth and encourage blooms. May self-sow lightly. Rooted stems may be separated from parent and transplanted in spring…a definite “special” plant possibility for plant sale.

Caryopteris-incana
Caryopteris incana ‘Sunshine Blue’

Azara microphylla (aka, vanilla tree, box-leaf Azara): It is a hard to find, fragrant, large shrub or small tree of upright growth (10 to 25 ft.) and notably fine-textured, dainty dark green, shiny foliage on whitish to dusty-colored stems—with leaves measuring only a quarter inch to an inch long. This is a shrub that grows well in zones 8-10. Site Azaras in cool sun or partial shade in well-drained soil with regular summer water. They are frost hardy in USDA zone 8, suffering possible leaf damage below 15F. Use in a container as a showoff specimen that can be moved around for the best places to appreciate the scent. Minute, almost unseen flowers are yellowish-green, intensely vanilla- or chocolate cookie-scented in late winter or early spring (December into April). For their fragrance alone this is a superb, hardy small tree to grow. The fruit is a tiny one-seeded berry a quarter-inch long, first reddish-orange, ripening in by July to a chocolate milk color, yet shiny and speckled; slightly bitter vanilla-flavored. With five of these bushes available, the room seemed to swell with the scent of chocolate. The much coveted shrubs went to five lucky members.

Azara Microphylla
Azara Microphylla

Harry Lauder’s Walking Stick bush (Corylus avellana ‘Contorta’ Red Majestic):  If you’re lucky enough to have this focal point specimen, you’re able to see several seasons’ worth of interest.  This upright, tree-like shrub, also known as a corkscrew hazel, has heart-shaped, toothed, mid-green leaves. Pendant catkins are borne in late winter and early spring.  Strongly twisted, spiraling shoots provide year-round interest.  This is an excellent specimen in either the ground or in pots and would look great in a cottage garden or Asian style landscape.  When the shrub reaches a good size—generally topping out at 10-15 ft. with an equal spread—the branches are used in floral arrangements.

Corylus avellana
Corylus avellana

This newer cultivar starts out with burgundy colored new growth, with great summer appeal, and then slowly fades to green with the fall yellowish leaf color typical to hazels.  Grow in fertile, well-drained soil in sun or partial shade. This is an ideal plant for alkaline soils.  Prune out unwanted suckers, which can be abundant and come from the root stock, so they’ll not be twisted.  Propagation can be done by layering in autumn or grafting in winter.  This specimen has trouble with powdery mildew, blight, canker, dieback, mushroom root rot, fungal spots, Gymnosporangium rust, bud mites, tent caterpillars and webworms

Polygonatum odoratum ‘Variegatum’: The National Garden Bureau Perennial Plant of the Year™ in 2013. Common Names include: Variegated Solomon’s Seal, Striped Solomon’s Seal, Fragrant Solomon’s Seal and Variegated Fragrant Solomon’s Seal.

 

Polygonatum odoratum ‘Variegatum’
Polygonatum odoratum ‘Variegatum’

Hardiness:  USDA Zones 3 to 8   Light:   Part to full shade  Soil:   Prefers moist, well-drained soil. Unique Qualities: Arching stems carry pairs of bell-shaped, white flowers in mid to late spring.  Variegated ovate leaves are green with white tips and margins. Yellow fall leaf color.

Uses:  This all season perennial offers vivid highlights in shaded areas of borders, woodland gardens, or naturalized areas. The variegated foliage along with its greenish-white flowers in is attractive in flower arrangements.

Polygonatum odoratum, pronounced po-lig-o-nay’tum o-do-ray’tum vair-e-ah-gay’tum, is native to Europe, Asia, and North America and is a member of the Asparagaceae family. It was formerly found in the family Liliaceae.  Regardless of its new location, members of Polygonatum are excellent perennials for the landscape. The genus botanical name (Polygonatum) comes from poly (many) and gonu (knee joints) and refers to the many-jointed rhizome from which the leaves arise. The common name Solomon’s Seal has several proposed derivations. The first is that the scar that remains on the rootstock after the leaf stalks die off in the fall resembles the seal impressed on wax on documents in the past. The second source is that John Gerard, the English botanist and herbalist, suggested that the powdered roots were an excellent remedy for broken bones. He also felt that the plant had the capacity for “sealing wounds”, which was why it received the common name – Solomon’s Seal.

Polygonatum odoratum ‘Variegatum’ grows 18 to 24 inches tall and will spread by rhizomes to form colonies. The oval-shaped leaves are carried on upright, arching, unbranched stems. The variegated leaves are light green with white tips and margins. Leaves turn an attractive yellow in the autumn. Sweetly fragrant, small, bell-shaped white flowers with green tips, are borne on short pedicels from the leaf axils underneath the arching stems. Bluish-black berries are sometimes present in the autumn.

Variegated Solomon’s Seal is a classic beauty for the shady woodland garden or the part-shade to full-shade border. It is a great companion plant to other shade lovers including hostas, ferns, and astilbes. The sweet fragrance will enhance that walk along a pathway on a spring morning. Flower arrangers will find the variegated foliage to be an attribute for spring floral arrangements. And finally, this all-season perennial offers yellow fall foliage color. There are no serious insect or disease problems with variegated Solomon’s Seal.  Plants may be divided in the spring or fall. The white rhizomes should be planted just below the soil surface. Polygonatum odoratum ‘Variegatum’ is a very easy perennial to grow and will enhance any shade garden, especially a more natural one. Let’s Go Garden! 

Snowberry shrub ‘albus’: A member of the honeysuckle family, is a popular native due to its decorative white fruit in the fall that birds like quail, pheasant and grouse enjoy. However, the berries can be toxic to humans. The snowberry shrub grows up to 3 ft. in height and spreads through extensive rhizome root systems, forming colonies of fruit-bearing plants. With these roots snowberries can be used to stabilize soil on banks and slopes, especially around water features. The flowers are white to light pink at the end of twigs and upper leaf axils. Tolerant of pruning, it can be grown as a medium to tall hedge. This versatile and practical native is a good choice for some decorative fall berries.

Snowberry
Snowberry shrub ‘albus’

Snowberry hancock ‘chenaultii’: Often referred to as chenault coralberry, is an East coast native that is an undemanding 2 ft. tall, 10 ft. spread workhorse that also helps with erosion issues. In late summer, small pink flowers appear, followed by rosy red fruit which persist well into winter. With a low spreading, selflayering habit it is easily grown in full sun or shade and a range of soils. As with the other snowberry, it can be kept under control by pruning the spread and the rooted stems can be easily chopped off and used elsewhere.

Coralberry
Snowberry hancock ‘chenaultii’ (often referred to as chenault coralberry)

Cotoneaster dammeri: Bearberry Cotoneasters are some of the most versatile shrubs in the garden that especially lend themselves to espalier treatment. It is a fast-growing evergreen low shrub with creeping branches. It reaches 12-16 in. in height. Leaves are elliptical and leathery, with very fine tips and entire edges, about ¾ in. long. The surface is glossy and dark green while the underside is graygreen. The leaves turn purple in autumn. The fragrant flowers are usually single or 2-3 together in leaf axils. They are white with pink outer sides, with about twenty stamens and purple anthers. The flowering period extends from May to June. Fruits are bright red berries, remaining well into winter. The root system consists of finely branched and very shallow roots. The branches form roots at nodes when they hit the ground.

Cotoneaster
Cotoneaster dammeri: Bearberry Cotoneasters

Wintergreen (Gaultheria Ovatifolia): is a species shrub in the heath family which is known by common names western teaberry and Oregon spicy wintergreen. It is native to western No. America from British Columbia to California. This is a small, low shrub with short stems. The pointed, oval-shaped leaves are 2 to 3 centimeters long and green. The plant bears small, solitary bell-shaped flowers, which hang like tiny bells, in shades of white to very light pink with reddish bracts. The fruit is a red berrylike capsule, which has been used in flavorings, oils and teas. Kalleen mentioned that these shrubs should be kept well watered.

Wintergreen
Wintergreen (Gaultheria Ovatifolia)

Beautyberry ‘Profusion’: Beautyberry shrubs grow up to 4 feet tall, with a slightly greater spread. The arching branches bear pinkish to light purple flowers in summer, which mature into their signature light purple berries in autumn (although the albafructus variety produces white berries). The shrub can be grown in sun or shade. The fall foliage of Callicarpa dichotoma is yellow, but the berries are the most outstanding feature. Since flowers appear on new growth, this shrub can be easily pruned for shape without disturbing the possibility of these beautiful berries.

Beautyberry
Beautyberry ‘Profusion’