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

Zone 6 Hardy Camellias

Posted by Hugh on January 11th, 2020

In the Southern U.S., camellias are treasured for their showy flowers in the fall-winter landscape. Their glossy evergreen foliage looks great all year long. Hardy varieties are now available for zone 6 northern gardens (-10 to 0 °F). This means that gardeners in Tennessee, Kentucky, Virginia and most coastal cities in Eastern U.S. can grow camellias. Blooms measure 3-5 inches across with yellow stamens centers.

Depending on variety, flowering may last 4 to 6 weeks. Short periods of freezing temperatures can burn the blooms currently opened and those scheduled to open within a few days, but buds tightly closed may survive, swell, and open. Color choices include shades of red, pink, lavender, white and multi-colored flowers. Varieties vary in size, from 8 feet to 15 feet in height and 6 feet to 10 feet in spread. Annual spring pruning can alter plant dimensions.

Camellias like well-drained, mildly acidic soils along with adequate soil moisture. In northern areas grow shrubs in a partially sunny site or one with full morning sun and afternoon shade. Established camellias are moderately drought tolerant; irrigate during prolong dry spells in summer and fall. Fertilize camellias in early spring with a product labeled for acid-loving shrubs.

Modern day hardy camellias are interspecific crosses between C. oleifera, C. sasanqua, C. hiemalis, C. japonica, and C. vernalis. Camellias start blooming in early fall into very early winter and a second flowering period in March and April. Petals are shed and require no dead-heading. In northerly climes, zone 6 hardy camellias are planted and mulched anytime from early spring up to Labor Day (and no later).

Reward yourself by planting two or more camellias in your garden to flower during the transition periods in early fall and in late winter when temperatures are seasonally mild. Here are some favorites:

Fall Bloomers: ‘Snow Flurry’ (white), ‘Autumn Pink Icicle’ (clear pink), ‘Sweet October’ (white/pink tinge), ‘Winter’s Joy’ (pink double), and ‘Long Island Pink’ (light pink).

Mid-March/April Bloomers: ‘Pink Icicle’ (shell pink), ‘April Tryst’ (deep red), ‘April Remembered’ (4.5 in. wide (11 cm), semi-double pale pink-large flower), ‘April Rose’ (deep rose pink).

‘Snow Flurry’ Camellia at NC Arboretum in Asheville, NC

12 Woody Trees And Shrubs Perfect For Containers

Posted by Hugh on January 6th, 2020

Japanese maples, hydrangeas, hollies, boxwoods, camellias, and dwarf conifers are popular favorites to grow in pots. Often, they’re part of mixed plantings coordinated with colorful annual and perennial flowers.

If and when these outdoor trees and shrubs outgrow their pots, you have one of three options available: 1.) move plants into a bigger pot, 2.) repot the plant in the same pot after pruning back roots and shoot growth, or 3.) plant them in the ground.

Here are 12 plants (trees and shrubs) that are perfect for pot culture in residential landscapes. Note the USDA hardiness zones for each selection.

1. Cutleaf weeping Japanese maple (Acer palmatum)- lacy green or purple foliage in spring and summer and colorful fall color. Tree form is umbrella-like. Recommended compact varieties are ‘Tamukeyama’, ‘Crimson Queen’, ‘Garnet’, ‘Shaina’, among others (zones 6-9).

*Nandina domestica* in planters at Biltmore Estates, ASheville, NC

2. Hinoki false cypress (Chamaecyparis obtusa) – some favorites include ‘Crippsii’ (6-8 feet high) and ‘Verdonii (3-4 feet high). (zones 4-8).

3. Nandina or heavenly bamboo (Nandina domestica) – many varieties available from 2 – 6 feet. In southern climes, avoid invasiveness be selecting male only varieties. (zones 6-9)

4. Japanese yews (Taxus x media ‘Hicksii’) grows 9 feet tall and 6 feet wide in containers (zones 4-7).

5. Deodar cedar (Cedrus deodara) offer several shrub forms which are ideal for pot culture; recommend ‘Crater Blue’, ‘Feelin Blue’. (zones 6-9)

6. Dwarf Dawn Redwood (Metasequoia glyptostroboides ‘Schirrmann’s Nordlicht’) – this deciduous conifer grows 4-6 feet tall over 10 years. zones 5-8)

7. Japanese plum yew (Cephalotaxus harringtonia) – ‘Fastigiata’, dark-green, tight columnar evergreen; ‘Duke Gardens’ (4-5 feet high and wide); ‘Korean Gold’ (3-4 feet) (deer-resistant). (zones 6-9)

8. Dwarf camellias (Camellia sasanqua) – compact growing dark evergreen foliage; ‘Shishi Gashira’; ‘Yuletide’ (6 feet tall and high) (zones 7-9).

9. Panicle Hydrangeas (Hydrangea paniculata) – select smaller forms at 3-6 feet height such as ‘Little Quickfire’, ‘Little Lime’, ‘Bobo’ with showy cone-shaped flowers from mid-summer to early fall. (zones 3-8)

10. Tiger Eye® Sumac (Rhus typhina ‘Bailtiger’) -5-6 foot tall deciduous shrub or small tree with fine textured dissected chartreuse seasonal foliage. (zones 4-8)

11. Boxwood (Buxus sempervirens) – hardy hydrid forms are available including variegated form like Wedding Rings® and ‘Variegata’ (zone 5 -8)

12. Inkberry holly (Ilex glabra) – native evergreen hollies like
Strongbox® and miniature Gem Box® are highly dependable for pot culture. (zones 4-9)R

‘Sun King’ Aralia Named 2020 Perennial Plant Of The Year

Posted by Hugh on January 1st, 2020

Plants with golden foliage can brighten up almost any drab garden patch. Sun King golden aralia (Aralia cordata ‘Sun King’) is no exception, hardy in USDA hardiness zones 3-9. It is also known as Japanese spikenard and mountain asparagus. Under ideal conditions this thornless, rhizomatous, herbaceous perennial grows rapidly to 3-5 feet tall and as wide in a single season.

The golden compound foliage emerges in mid-spring and retains its bright color throughout the summer. Growth rate is rapid and dies back to the ground in late autumn. In mid-summer numerous small clusters of tiny white flowers shoot up, borne on 2 feet tall racemes. Lustrous purplish-black berries follow in the fall.

Sun King makes a bold almost tropical statement in a semi-shade garden. Grow it in a compost-rich moist soil and in ½-day sunlight (morning hours preferred). It is adaptable to a wide soil pH range. The foliage may burn in full day sun. In USDA zones 8 and 9, grow only in dappled sunlight to avoid foliage burn. Golden aralia should be kept mulched and irrigated over long summer dry spells.

Sun King aralia mixes well in large containers planted with green and other brightly colored foliage plants. It combines with variegated Solomon seal, hostas, brunnera (Brunnera macrophylla), lungworts (Pulmonaria spp.), coral bells (Heuchera spp.), and astilbes. Golden aralia is deer resistant and its tiny white flowers attract numerous honeybees.

A native of Japan, Korea, and China, ‘Sun King’ aralia was introduced to the U.S. by Barry Yinger.

Caution: Birds love the tiny berries, but they’re NOT edible for humans).

Arizona Cypress Standouts

Posted by Hugh on December 26th, 2019

‘Chaparral’ at UT Gardens in Knoxville, TN

Arizona cypress (Cupressus arizonica var. glabra) is a needle evergreen conifer native to the Southeast U.S. and is noted for its rapid growth rate. It is also grown as a Christmas tree and is rarely troubled by disease and insect problems. Depending on what part of the U.S. that you garden in, damage from bark beetles may occasionally happen.

Arizona cypress requires full sun for best growth and appearance. Varieties are hardy to 0 °F (USDA hardiness zones (5)6-9). Fertilizing this cypress should be stingy due to potential nitrogen burning. This conifer adapts to most soils, as long as moisture drainage is excellent. It needs very little maintenance. When planted in the landscape, Arizona cypress should be provided lots of room to achieve its cone-like or pyramidal form.

‘Carolina Sapphire’ introduced by Clemson University

Superior varieties include ‘Blue Ice,’ ‘Blue Pyramid,’ ‘Carolina Sapphire’, and ‘Chapparal’. Cultivars Blue Ice and Blue Pyramid tend to develop a tighter pyramidal habit compared to Carolina Sapphire or Chaparral. Chaparral stands out for its light sage-green, fine textured foliage. Carolina Sapphire struts blue-silver needles (not rated winter hardy in zone 5. At maturity, all four varieties may reach 45 feet tall and around 20 feet wide.

Its fabulous blue needle color is more intense during the cold days of winter and needle color is more washed out in shade. A one-year old established Arizona cypress tolerate fairly dry conditions year-round.

If you are looking for a privacy screen, tall hedge or screen, choose Arizona cypress. Plants are pyramidal in shape and definitely grow taller than wide. As a specimen plant ages, branches tend to open up. An old specimen almost takes on a weeping appearance.

Arizona cypress is a Christmas tree in the southwestern U.S. The seeds are eaten by ground squirrels, squirrels, and other rodents. Most years, pruning is often skipped. You will likely opt to remove an aberrant growing branch. Disease and insect problems are very minimal if the site is correct.

Poinsettia Care

Posted by Hugh on December 21st, 2019

Poinsettias (Euphorbia pulcherrima) have become a symbol of the Christmas and winter holiday season. Their colorful bracts (most people call them”flowers”) are actually modified leaves. The tiny “true” flowers are in the center of the bracts. Each year new poinsettia varieties hit the garden shops.

In the mid-19th century, Joel R. Poinsett introduced the poinsettia plant to the United States from Mexico. Poinsett was a botanist, physician and the first U.S. Ambassador to Mexico. In Mexico, poinsettias grow as hardy shrubs to 10-15 feet tall. In the U.S. plants thrive outdoors in south Florida and Southern California gardens (zone 9). In the warmer latitudes poinsettias are sometimes planted outdoors in late summer. Their vivid colored bracts add pizzazz to the late fall and winter landscape. Plants withstand night temperatures in the upper 30’s.

A member of the botanical family Euphorbiaceae, leaves and stems ooze milky sap when cut. However, no parts of a poinsettia plant are deadly poisonous. Some people and pets may be sensitive to the plant’s sap which may cause a skin irritation.

Tips on purchasing: before buying a poinsettia, know that the true flowers are fully formed and should be tightly closed at time of purchase. If the yellow pollen sacs have shed or the flowers have dried out, do not purchase. Once the flowers start to age, the colorful bracts soon decline. The plant may look poorly on Christmas Day.

Care In The Home: place your poinsettia near a sunny
south- or east -facing window of your house or apartment. Room temperatures should be between 65 to 75 °F. Poinsettias thrive in a well-drained soil-less media (potting mix). Check media for dryness every few days and water the pot thoroughly; allow any excess water should flow freely out the drainage hole in the container.

Do not leave your poinsettia sitting in water over 3 hours as it may injure the roots. Feed the plant every 2-3 weeks with a water soluble garden or house plant fertilizer @ one-half the rate on the package directions. Your poinsettia should continue to look pretty on the first day of spring.

Over 100 varieties of poinsettias are available at garden shops, grocery stores, and area greenhouses. Varieties come small, medium and large sizes and in colors ranging from traditional red, white, pink, burgundy, marbled, and speckled.

Tips On House Plant Nutrition

Posted by Hugh on December 16th, 2019

Fertilizers shelf at garden center

Iron cross begonia needs extra nutrient iron

Fertilizing tips for your house plants vary according to the individual plant’s need, home or greenhouse environment, and the season of the year.

Key elements that house plants require are nitrogen, phosphorus (P) and potassium or potash (K).

With few exceptions, tropical plants are low constant feeders, meaning using a water soluble fertilizer such as Miracle-Gro™, Schultz™ All Purpose Plant Food 10-15-10 or Jacks™. Feed at one-half package directions twice monthly. Orchids need fertilizing once monthly at the one-half rate.

Light quality and duration (photoperiod) coupled with the surrounding room temperature also are key determinants of a plants’s nutritional need. Late winter and spring flowering house plants benefit from feedings every 2-3 weeks during the period that they’re blooming. For example, African violets and other gesneriads spring into flower

When a house plant is blooming heavily, offer them a balanced diet on 1:2 :1 ratio every 2-3 weeks. Shade tropicals such as philodendrons, calatheas, peperomias, dracaenas, et.al. want little nutrition during the winter months.

Some house plants benefit being planted in an acidic-based potting soil (media) because they require some minor nutrients like iron and manganese. These elements are more available (soluble) is greater in acidic (peat-based) media. Ferns and begonias are examples.

In general, cacti and succulents can survive with little supplemental feeding. However, they grow and bloom more profusely when fed regularly. Feed them with a specialist cactus food that provides the right balance of nutrients. Avoid high nitrogen fertilizers as they can promote soft, weak growth. Apply cactus fertilizer every 2-4 weeks in spring and summer only.

Finally, special fertilizer products are available for certain plants that require minor nutrients like iron (FE), manganese (MN, boron (BO), and/or molybdenum (MO). Epsom salts, sold in pharmacies, is a good source of magnesium (MG).

Lipstick Plant (Vine) – Lovely Flowering House Plant

Posted by Hugh on December 11th, 2019

Lipstick Vine at NC Arboretum in Asheville, NC

Nothing brightens up a room more than a flowering plant. One of my favorites is lipstick plant or lipstick vine (Aeschynanthus spp.), a close relative of the African violet. The green leaf form A. radicans is very popular with shiny dark green leaves and orange, pink, purple flowering varieties.

Lipstick plant is a free bloomer, meaning that flowering is tied to how much light, humidity, temperature and fertility the plant is receiving. It produces with colorful flowers that emerge from dark buds like a tube of lipstick near the tips of the branches.

Proper care will reward you with good flowering. Lipstick plant enjoys a humus-rich potting mix (one designated for house plants) and good feeding program. Most house plant fertilizers manufactured by Schultz™, Miracle-Gro™, Jack’s™, and others are ideal. Feed lipstick plant every 2-3 weeks in spring, summer, and early autumn @ one-half the package rate. Autumn to winter feeding should be monthly as the plant undergoes a brief rest period.

Water the plant thoroughly and allow soil (media) to dry partially before re-watering the plant. Overwatering is a huge mistake. Lipstick vine will not bloom unless in a brightly lit room. Too much direct sunlight may burn the foliage. Room temperature should be around 68 to 80 °F. (20-27 °C.) for best flowering. This tropical plant may be injured at temps lower than 50 °F (10 °C).

A hanging basket is the perfect pot for growing a lipstick vine. Repot the plant annually, preferably in late winter. Mealy bugs, spider mites, aphids and white flies may be occasional pests. Safe organic pesticides like insecticide soap or neem oil will handle most pests.

Groom (prune back) long vines after flowering as needed. In late winter revitalize the plant by pruning it back by one-third to encourage new branching and re-blooming.

Over the winter heating season, maintain a room humidity around 40 – 50% by daily misting or run a room humidifier.

Downtown Street Trees With A Narrow Vertical Form

Posted by Hugh on December 6th, 2019

On the subject of land, Mark Twain wrote: “they’re not making any more of it”. This is particularly true in downtown urban areas where land to grow trees is usually very limited. Here are five tall trees that possess a striking vertical accent. Their upright branch habit does not take up much horizontal space. Trees are superb planting choices along wide avenues or boulevards. All five species adapt to the urban environment. They’re also fit into downtown pocket parks and small residential sites where there are no height restrictions like overhead utility lines.

During the first two years following planting, trees should be irrigated during dry spells (or every 2-3 weeks) from spring through late summer. All five picks are hardy in USDA hardiness zones 5-9.

‘Slender Silhouette’ Sweetgum (Liquidambar styraciflua ‘Slender Silhouette’) (USDA 5-9) is a narrow 35 to 50 feet tree that spreads only 8 feet wide. ‘Slender Silhouette’ produces very few nuisance gumball fruits so typical for other sweetgums. In some years, the yellow to red fall color is exceptionally nice. Bark develops deep furrows as the tree ages.

‘Beacon’ Swamp White Oak (Quercus bicolor Beacon) deserves more recognition. ‘Beacon’ is a tightly columnar upright branching, adapts to city environs, and mostly disease-free foliage. Fall color is yellow and persists for 2 to 4 weeks. Its mature height is 30 to 40 feet and 12 to 15 feet wide. Yes, this oak does produce acorns which can be a messy problem every 3 or 4 years unless picked up curbside.

‘Princeton Sentry’ Ginkgo (Ginkgo biloba ‘Princeton Sentry’) is a deciduous conifer (a true gymnosperm) that grows to 30-50 feet in height, although a rare mature 100 feet tree is possible after a century or more. Ginkgo’s two-lobed, triangular or fan-shaped green summer leaves are distinctive. It is a male (fruitless) variety. Fall foliage turns bright yellow and neatly fall to the ground to form a golden carpet around the tree.

‘Arnold’ tulip poplar (Liriodendron tulipifera ‘Arnold’) is a fastigiate grower to 50-60 feet tall and only 8 to 10 feet wide. Unusual light green and orange tulip-like flowers appear in late spring, most blooms hidden beneath the tree’s dense foliage. Fruits (seed pods) offer no value ornamentally. Its furrowed gray bark offers significant winter appeal.

Upright European hornbeam (Carpinus betulus ‘Fastigiata) displays a narrow, columnar form, especially when the tree is young. The tree’s middle (girth) gradually broadens into a tear drop or oval-vase shape with age. Mature tree size is 35 – 40 feet tall and 25 – 30 feet wide. Another hornbeam variety, ‘Frans Fontaine’ (40 ft. x 20 ft.), is also suitable for confined areas.

Space-Saving Vertical Shrubs

Posted by Hugh on December 1st, 2019

Try these slim and sleek varieties in a small space such as on patios or the front porch, in courtyards, or as a single specimens in narrow gardens or containers. Set them at the back of beds for space-saving walls and backdrops. Pot them up for container magic on the porch. All six plants grow best in full sun to part shade and well-drained soil. Shrubs requires little to no special care including pruning.

‘Sky Pencil’ holly flat-topped at High Point University

Landscape Uses: single specimen, allée, tall hedge, medium hedge, foundation plant, holiday foliage, containers. Choose any of the following:

‘Helmond Pillar’ Barberry (Berberis thunbergii ‘Helmond Pillar’) – deciduous shrub with a tight upright, columnar habit; features reddish-purple leaves (0.5 to 1.25 inches long) on spiny reddish brown stems. Mature size: 4-5 feet tall and 1-2 feet wide; highly drought tolerant and deer resistant. Alternative: ‘Sunjoy™ Golden Pillar’ Barberry– orange-red new foliage becomes bright gold in summer and orange-red in fall. Mature Size: 4 feet tall x 2 feet wide. USDA Hardiness zones: 4-9.
Roman Candle™ Podocarpus (Podocarpus macrophyllus ‘Miu’) – lovely Southern evergreen shrub with heat tolerant variegated creamy-white and green foliage; in a container, Roman Candle grows about 20 inches tall and 8 inches wide and is deer proof. Mature Size: 10-15 feet tall x 4-6 feet wide. Hardiness zones: 7b-10.
‘Sky Pencil’ Holly (Ilex crenata‘Sky Pencil’) – narrow, dense, multi-branched, columnar evergreen shrub with a rounded form. Mature Size: 5-10 feet tall and 1-2 feet wide. Hardiness zones: 6-8.
‘Dee Runk’ Boxwood (Buxus sempervirens ‘Dee Runk’) -broad-leafed evergreen with a very narrow, upright, pyramidal habit; oval, 1 inch long dark-green leaves. Mature Size: 10-12 feet high and 2-3 feet wide. Hardiness zones: 6-8.
October Magic® camellia – fits the tight garden spaces; deep green glossy foliage year-round along with pure white flowers. Mature Size: 4–5 feet high x 3–4 feet wide. Hardiness zones: 7 to 9.
‘Blue Point’ Juniper – maintains a dense, pyramidal form; prized for its lush blue-green foliage, looks good in formal garden landscape setting. Mature Size: 15 feet high x 3–5 feet wide. Hardiness zones: 4 to 9.

Uniquely Different Red Dragon™ Contorted Filbert

Posted by Hugh on November 26th, 2019

Uniquely Different ‘Red Dragon’ Contorted Filbert

‘Red Dragon’ filbert in Columbus, Ohio garden

European filbert or hazelnut (Corylus avellana) is native to Europe, western Asia and northern Africa where it is often found growing in thickets and hedgerows. Red Dragon™ filbert is an outstanding red leaf selection of contorted filbert (C. avellana Red Dragon™). This unique landscape shrub grows 6 – 8 feet tall and 5 – 6 feet wide. It is a good addition to urban gardens (USDA hardiness zones 4-8).

This red–leaf shrub was developed by the Oregon State University filbert breeding program. Currently, gardeners are losing the popular green leaf variety C. avellana ‘Contorta’, aka “Harry Lauder’s Walking Stick’ to Eastern filbert blight. Red Dragon filbert demonstrates superior resistance to the disease. Red Dragon also replaces ‘Red Majestic’, another red leaf variety that is also vulnerable to Eastern filbert blight.

Contorted filbert grows best in moist, organically rich, well-drained soil and in full sun to partial shade. It tolerates average garden soils. Prompt removal of root suckers improves plant appearance, avoiding a messy buildup or thicket.

Autumn leaf drop exposes its contorted branches and ornate floral catkins in early days of spring. Filberts are monoecious, e.g. individual male and female catkins (flowers) develop on the same plant bloom in the early days of spring (March-April) before leaves emerge. The 2-3 inch long yellow male catkins (flowers) stand out. The 4-inch elliptical or ovate leaves have doubly serrate leaf margins.

Red Dragon filbert retains its burgundy red leaf color until early summer and turn dark green. The foliage is also partly curled. Leaves are coated with tiny hairs and appear dusty by the end of summer. Fall leaf color is variable, often with yellow shades. Smooth light bark is gray-brown.

Nuts appear in terminal clusters of 1-4 and are half covered in ragged husks. Nuts ripen in late August and September that the neighborhood squirrels and birds should enjoy.

Red Dragon filbert may also be grown in containers. Disease and pest problems are few. Japanese beetles may rigorously attack the foliage in some areas of the U.S. Scale may also occur.

‘Red Dragon’ is grafted cultivar and is sold by e-commerce nurseries online. Red Dragon filbert requires little or no pruning; removed all root suckers and keep the shrub well mulched. ‘Red Dragon’ is sold either grafted or not. It is through e-commerce nurseries online.