What Grows There :: Hugh Conlon, Horticulturalist, Garden Advisor, and Photographer

Amur Cork Tree

Posted by Hugh on November 16th, 2017

Amur Corktree at Biltmore Estate, Asheville, NC

Summer foliage of Amur corktree

Amur corktree (Phellodendron amurense) is native to Northern China, Korea and Japan (USDA hardiness zones 4-9). Amur corktree is a fast growing, upright branched tree that makes an excellent yard or shade tree. Corktree grows in a wide range soils, and tolerates soil pH between 5.0 to 8.2. It does best in moist, well-drained soils, but it can stand dryer soils and conditions. It is drought tolerant and does well in areas of high heat and cold.

Amur corktree was a good choice for use on large properties such as golf courses, industrial sites, and urban parks where its wide shallow rootsystem has room to grow. Roots rarely interfere with underground utility lines as will sycamores (Platanus) or willows (Salix). Use as a street tree is questionable as corktree does not prosper in compact droughty soils. Its pinnately compound foliage is also tolerant of many air-borne pollutants common in urban environments.

The spreading branches of corktree cast lots of shade. This medium sized tree will reach heights of 30 to 50 feet, with its branch spread similar to its height. The tree is often seen multi-trunked. A second corktree species, Lavalle corktree (P. lavallei), is almost identical in all traits except branching that tends to be more upright.

Corktree is dioecious, e.g., a female tree produces inconspicuous flowers that give rise to sweet drupe fruits. As its common name suggests, Amur corktree exhibits distinctive porous (spongy) bark texture. Leaves, when crushed, emit a variety of scents that some described as “citrusy”.

Cultivars:

‘His Majesty’ (P. sachalinense x P. amurense) – male, fruitless, broadly vase-shaped, yellow fall color),

Eye Stopper ™ (P. lavallei ‘Long Necker’) – selected for bright yellow fall color; slightly less corky bark

Macho® (P. amuerense) – vigorous male, fruitless, broadly vase- shaped, tree.

Shademaster® (‘PNI 4551’) – male fruitless with glossy foliage,

Superfection™ (‘Supzam’) – male fruitless, upright-uniform branching habit

Important Note: Amur corktree is considered invasive in parts of the northeastern U.S. where it may outcompete native species.

The Great Little Bluestems*

Posted by Hugh on November 12th, 2017

Little Bluestem Fall Color at NC Arboretum, Asheville, NC

Summer foliage

Little Bluestem (Schizachyrium scoparium) is an attractive prairie grass native in southeastern or southwestern areas of the U.S. It is exceptionally hardy (USDA hardiness zones 3-9). Heights of the species (including inflorescences) vary from 2 – 2.5 feet tall and many cultivars grow 3-4 feet tall. Its late summer to fall foliage is a kaleidoscope of pastel colors and later coppery tones.

Stems of Little Bluestem stand rigidly upright and do not lay down during the winter, particularly after multiple snow falls, . The species is slightly variable in foliage features and the hairiness of its floral racemes. Over the years plant breeders have developed cultivars exhibiting more intense reddish foliage in autumn (see below).

Little Bluestem is tough and adaptable, tolerant of wide fluctuations in soil moisture levels through the seasons. It grows in both acidic and alkaline soils. A new seeding establishes quickly on steep banks, slopes, and restoration plantings as well as in meadows, prairies, and mixed plantings. Little Bluestem also provides food and shelter for wildlife, including birds and butterflies.

Little Bluestem performs at its best in full sun. In early spring cut back an established seeding for appearance and to allow new leaf blades to fill in. Feed a slow-release fertilizer such as Nutrikote™, Osmocote™, or equivalent. Shade, too high fertility, and too much moisture will result in floppy growth and poor seasonal color.

Little Bluestems Cultivars

‘Blaze’ grows in an upright shape and sports blue green summer foliage. Fiery fall colors are a mix of reds and purples, along with hints of orange and pink.

‘Carousel’ (PP20948) has a low broader shanc and grows strongly upright through the winter.

Blue Heaven® (‘MinnblueA’) is a robust, tall with bright variation. It starts out with light blue foliage in the spring and deep pink, later and burgundy red hues from late summer to fall.

‘Prairie Blues’ offers improved durable blue-gray fall color.

‘Smoke Signal’ offers narrow, refined, blue-green early summer foliage with deep red tones in late summer, and deeper red-purple in fall.

‘Standing Ovation’ (PP25202) has sturdy, thick stems that stands up to high winds and pounding rain; fall colors are mix of stunning reds and oranges.

‘The Blues’ struts stunning blue foliage accented by red stems thru summer; fall colors are a mix of purple, orange, and shades of blue.

Special note: The scientific name of Little Bluestem was formerly Andropogon scoparius.

*Some information in this blog furnished by Shannon Currey, Hoffman Nursery (wholesale grower) in Rougemont, NC near Greensboro.

Lantanas For Sunny Gardens

Posted by Hugh on November 8th, 2017

Lovely planting of lantanas

Mixed container including lantanas + petunias + junipers

Lantanas (Lantana x) are favorite bedding plants, particularly in southern and western U.S. gardens where summers are hot and long. Lantanas are generally planted in flower gardens, but can be grown in containers, including hanging baskets. Plants bloom from late spring until the cool days of fall arrive. Some environmentalists classify them as invasive because birds feed on the abundant berries and distribute the seeds over many miles.

Lantanas like full sun and can grow upright, mounded, spreading , and even trailing depending on cultivar. Feed newly set transplants with a slow release fertilizer such as Osmocote™ or Nutrikote™. An alternative feeding program is to apply a water soluble product such as Miracle-Gro™, Peters™, or Daniels™ every 6-8 weeks from planting time up to late August. Lantanas prosper in a slightly acidic soil.

In areas with long growing seasons such as Florida, Texas or Southern California (zones 9 to 11), plants may be trained into various topiary forms, including miniature trees. Here, lantanas are dependable shrubs or perennials. In cool temperate regions potted plants may be moved to a cool protected place such as a garage or unheated sunroom to overwinter.

Flower heads are small globes of tiny florets. Cultivars come in a wide array of colors from rose pink, yellow, orange or a combination of many flowers. Popular cultivar series include Luscious®, Lucky® and Bandana®. Bandanas grow shorter, about 24-30 inches high, depending on the cultivar. Some gardeners prefer the cultivars ‘New Gold’ and ‘Miss Huff’ that produce sterile seeds and are not invasive.

Disease prevention of problems is always your best alternative. Set lantanas in well-drained soil with good air circulation around plants. Lantana may on occasion succumb to root rot or powdery mildew, particularly when summer weather is unusally wet.

Sooty mold, caused by insect feeding by aphids, mites, and whiteflies, turns leaf surfaces and stems black. Problem pests can be sprayed with several kinds of pesticides or washed off. Plants can also be troubled by tiny sap-sucking lacebugs whose damage leads to leaf drop.

Lantanas are deer resistant and the flowers are favorites of hummingbirds, bees and butterflies. Berries can be toxic to pets and humans and leaves may cause a rash for some people.

Unappreciated And Underplanted Sawtooth Oak

Posted by Hugh on November 5th, 2017

Sawtooth oak on ETSU campus in Johnson City, TN

Foliage in early fall of sawtooth oak

Sawtooth oak (Quercus acutissima) is a medium-sized deciduous oak that exhibits traits similar to both the white oak and red oak sections. Indigenous to China, Korea and Japan, sawtooth oak has naturalized in some parts of the U.S. (USDA hardiness zones (5?)6-9). Sawtooth oak grows 40-60 feet tall and wide with broad spreading branches and rounded canopy.

Leaves of sawtooth oak are frequently mistaken for chestnut (Castanea). Long (5 to 7 inches long), lance-shaped, glossy dark green leaves are chestnut-like. Leaf veins are well defined, each ending with a single bristle on the margin (leaf edge). Fall color is variable, ranging from an attractive golden brown to undistinguished pale brown. Dead leaves tend to persist through most of winter.

Long stringy, yellowish-green catkin flowers in separate (male open first) and female catkins appear in early to mid-spring before leaves emerge. Flowers are not ornamentally significant.

Sawtooth oak grows in average well-drained soil and in full sun. Fertilize in late winter with a slow release product such as Osmocote™ or Nutrikote™. The tree tolerates summer heat and humidity. Chlorotic or yellowed leaves is common in neutral to alkaline pH soils in summer. Compared to most oak species, it is moderately pest resistant.

Its corky ridged gray bark matures to a black fissured bark over the years in this long-lived oak. Sawtooth oak this medium to large oak is not planted enough. It is an exceptional shade or specimen tree in residential or park settings and is also found lining parking lots, median strips and roadways.

Acorns are oval in shape and start to form start in 10-12 years after planting. Cap covers nearly two-thirds of nut with hairy scales that are prominently reflexed. Acorns ripen in early fall and are an important wildlife food source.

Geraniums Enjoy The Cool Autumn Season

Posted by Hugh on October 30th, 2017

‘Americana Pink’ geranium

‘Rocky Mountain Red’ geranium

Annual geraniums (Pelargonium x hortorum) are popular bedding plants in the garden or in all kinds of containers including window boxes or hanging baskets. Color choices include red, pink, rose, salmon, orange, lavender, violet, or white.

High summer heat is challenging for all geraniums. Some types of geraniums stop blooming completely and perk up when autumn’s cool temps return. Over the past quarter century plant breeders have given gardeners better heat-tolerant types. Some of the best are the Maverick™ and Orbit™ seed series; the Americana™, Eclipse™, and Rocky Mountain™ cutting series; and the interspecific hybrids marketed as Caliente™ and Calliope™.

In the spring, plant geraniums outdoors after all threat of frost has passed. Plants are spaced about 8 to 12 inches apart (depending on variety) and at the same depth as in the flat or pot. Mulch around plants to retain soil moisture and suppress weeds. Regular deadheading of spent flowers encourages additional blooms. Avoid frequent overhead irrigation, as this may result in leaf and flower disease outbreaks.

Geraniums must have a moist, humus-rich, well-drained soil and should be planted in a garden receiving at least 6 hours of direct sunlight. Let the soil go slightly dry between waterings. Do not overfertilize. Feed them with a slow-release, granular fertilizer once in spring or with a water soluble fertilizer such as Miracle-Gro™ or Jacks™ 2-3 times during the growing season.

Geranium cuttings root easily from cuttings in fall and can be over wintered as house plants.

Tis The Season For Ornamental Kales and Cabbages

Posted by Hugh on October 27th, 2017

Flowering kale and cabbage and pansies in container at Biltmore Estate, Asheville, NC

December at the Dallas Arboretum

Ornamental cabbage and kale (Brassica oleracea) are very close related to the same vegetables that we eat at our kitchen table. They are edible, just not as tasty. Plants are biennials, e.g. they produce leaves one year and flower the following spring. Ornamental kales have deeply cut serrated or ruffled leaves while leaves of ornamental cabbage are rounded leaves. Rosy to creamy white leaf colors are at their finest in full sun and temps fall into the upper 20’s and low 30’s.

Plants grow 18 inches tall and wide in either full to partial sun. When grown in warmer climes (zones 8 and warmer), partial shade is preferable. Kales and cabbages prefer a moderate acidic soil pH between 5.8 – 6.5. Irrigate plants weekly if rainfall is subpar.

By early spring plants have bolted (flowered), and leaves become torn and ragged. Aphids, cabbage loopers, and leaf rollers are troublesome in many growing areas. Mildew may cover leaves if fall weather is warm and humid. Cabbage loopers may destroy the foliage. An “owlet moth” deposits her eggs on foliage and the green worms (larval stage) quickly chew into the leaves. Frequent spraying with Sevin® or dusting with Bt (Bacillus thuringiensis), a natural bactericide, is effective. Insects are fewer in the cooler months. Rabbits are a secondary problem and should be fenced out.

Plants are very heavy feeders, and should be fertilized frequently for optimum growth. Plants properly hardened off plants can usually survive most winters in zones 7b and points further south. Drastic sub-freezing dips in temperature may burn leaf edges. Ice storms can destroy the planting.

I strongly urge the purchase of one gallon size plants over six packs of 4-inch pots. Smaller plants rarely reach full size before the biting cold wintry air arrives.

Leading varieties:

Kale:

‘Red Bor’ grows up to 3 feet tall with deep purple ruffled leaves.

‘Peacock Red’ and ‘Peacock White’ form large open plants up to 2 feet across with feathery leaves.

‘Red Feather’ and ‘White Feather’, similar to ‘Peacock Red’ except leaves are larger and less serrated.

‘Nagoya Red’ and ‘Nagoya White’ strut heavily ruffled foliage.

Cabbage: ‘Osaka Red’, ‘Osaka Pink,’ and ‘Osaka White’ – colorful wavy-edged leaves on tightly packed, 12 inch high compact heads. Top center rosettes turn bright purple, pink, or white with green outer leaf edges.

Fall Trimming Of Perennials

Posted by Hugh on October 23rd, 2017

Christmas fern -winter evergreen

Miscanthus ‘Morning Light’-late winter

You do not need to cut perennials back in the fall, but many gardeners do so as part of the garden cleanup. Don’t rush the job. Leaves of many perennial plants continue to produce and store carbohydrates in crowns and roots until they go fully dormant. Wait until after the first hard frost or until leaves have turned yellow or brown before cutting back plants back. The old growth may also carry over diseases, particularly mildews and botrytis and re-infect new spring growth.

There is no hard fast rule how far to cut back plants. For most perennials, prune them back to about 2 to 3 inches from the ground. Cutting off at ground level may damage the plant crowns where the new shoots emerge in the spring.

Do not cut back evergreen perennials such as assorted ferns, coral bells (Heuchera spp.), and lenten roses (Helleborus spp.) in the fall. You may trim off spent flower stems and any tattered and dead basal leaves. For most vines, wait until they are completely dormant before trimming them back. Trim them high, leaving at least 6 inches and more.

For some perennials which grow shrub-like, it is best to wait until late winter. However, the following perennials may be injured: silver mound (Artemisia), butterfly shrub (Buddleia), Blue mist shrub (Caryopteris), lavender (Lavandula), and Russian sage (Perovskia). With these perennials, wait until new spring growth starts to emerge before clipping off the old growth.

Again, it is not necessary to cut perennials back in the fall. Many perennials also provide winter interest to an otherwise drab landscape. Examples include ornamental grasses, coneflowers, goldenrods, and evergreen ferns. Ornamental grasses are architectural wonders. Lastly, seeds from coneflowers (Echinacea), blackeyed Susans (Rudbeckia), globe thistles (Echinops), goldenrods (Solidago), and yarrows (Achillea) are important food sources for overwintering birds.

Plant American Beautyberry For A Fall Show

Posted by Hugh on October 20th, 2017

American beautyberry at NC Arboretum in Asheville, NC

Colorful fall fruits

American Beautyberry (Callicarpa americana) is a loose open growing shrub valued for its spectacular fruits in the fall (USDA hardiness zones 6-10). The growth rate of this native shrub is rapid, eventually reaching 4-7 feet in height and 4-6 feet in spread within 5 years after planting.

Beautyberry thrives in a moist, humus-rich, mildly acidic, well-drained soil and in a mostly sunny spot in the garden. It will grow well in partial sun, although fruits are not as showy in shady areas. Group several plants together for better fruit numbers.

Small clusters of pink flowers are born in the axils of the leaves from late June thru August and mostly go unnoticed. Flowers lead to a showy display of brightly colored fruit clusters that will catch your eye and those of friends and neighbors. The magenta to violet berries are 1/5” in diameter. Leaves may turn faint pink or yellowish in fall before dropping.

Beautyberry requires little annual care (other than pruning) after its first year in your garden. Feed annually with 10-10-10 granular fertilizer (or equivalent). Lay down a fresh 2-3″ layer of mulch as a weed preventative and to conserve soil moisture. It is not troubled by any significant disease or insect problems. Beautyberry is propagate by vegetative cuttings or from seed.

Every 2-3 years, in late winter or early spring, this vigorous growing shrub should be pruned to control its size and shape. A multi-year unpruned shrub may also be severely cut back to within 6 inches from the ground. It should flower and bear lots of fruits by fall.

No question that beautyberry is most valued for its spectacular fruits. Berries are important food source for many species of birds and other wildlife. Summer flowers attract butterflies.

Native beautyberries are not frequently found at garden centers that prefer selling the Asian cultivars.

Planting A Rock

Posted by Hugh on October 17th, 2017

“Planted” Landscape Rock with Fall Pansies

Boulder for sale at local garden center

A well placed landscape rock or boulder is a perfect garden feature. Planted properly, the boulder appears to emerge naturally from the bowels of the earth. The crowning achievement is when mosses and lichens find a home in its crevices or when vines crawl over them.

Boulders may exhibit seams of color(s), deep crevices, and/or have jagged or rounded edges. Is the rock, stone , or boulder best displayed from a vertical or horizontal position? Boulder may provide multiple landscape uses from a child climbing over it or the gardener looking for a comfortable sitting stool.

A recent addition to our garden is a 250 pound rock (photo on left). Our stone has a broad muscular base and a flat gray/blue face (side facing the street). On rainy day the darker blue color comes forth. A couple of strong friends help move, orient, and set the rock in its permanent spot. We “posed” our rock, turning it to catch its showiest side(s) from inside the home and curbside. Neighbors, joggers and and dog walkers get to view the muscular side from curbside.

A wide shallow hole was dug around the base to “root” and support the boulder firmly. Plant your rock shallow! Its mass (bulk) and weight, along with gravity, will eventually settle a heavier boulder deep. On soft ground, add 2-4 inches of gravel or sand and tamp it down for firmer base. Be absolutely certain that the rock is firmly anchored and will not tip or roll and hurt a young child climbing over it.

Around the rock you may wish to plant low growing plants such as pansies, flowering bulbs, sedums, coral bells, cranesbills, astilbes, or ferns.

Restful sitting place at Biltmore Estate in Asheville, NC

‘Youngii’ White Bark Birch A Novelty Tree For Small Spaces

Posted by Hugh on October 13th, 2017

‘Youngi’ birch at NC Arboretum in Asheville

Newly planted ‘Youngi’ birch

Young’s Weeping European Birch (Betula pendula ‘Youngii’) is small graceful tree with willowy pendulous branches (USDA hardiness zones 3-6). Nurseries often train the very pliable branches and trunk of grafted seedlings into unique novelty shapes.

Plant this miniature 12 to 20 feet tree specimen near a deck or patio where it should receive mostly morning sunlight. Fall foliage turns bright yellow. In late winter 3-inch male catkins, hanging from its slender branches swell, a sure signal that spring is close at hand.

The key to growing Youngi (or any white bark birch) successfully is to maintain a stress-free growing setting. This noveltry tree requires more care and pesticide spraying than most landscape plants. Unfortunately, twigs and branches are highly susceptible to bronze birch borers and leaf miners which turn leaves brown by late summer unless sprayed every few weeks. Apply the proper insecticidal controls and cultural conditions for best growth.

When planted in cool temperate areas of the U.S., particularly in northern tier of New England and Midwestern states, European birches live several decades. The tree’s leaf canopy is not dense and surface roots tend to dry out rapidly. Irrigate deeply the first growing season to develop an extensive root system. Maintain a 2-3 inch mulch depth around the root zone to cool surface roots. Weekly summer irrigation also aids in cooling the ground. Feed with slow release fertilizer in early spring.

Pruning, if needed, should be performed in summer to early fall and do not prune excessively. Spring pruning should be avoided as sap will bleed profusively from pruning cuts; sooty mold disease frequently follows, growing over sweet sap and blackening the beautiful white sap. Avoid excessive pruning, e.g. removing more than 20% of total branching. Pruning at the wrong time also can lead to borer infestations.