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

February Blooming Hybrid Witchhazels

Posted by Hugh on January 26th, 2020

Witchhazels (Hamamelis spp.) are somewhat coarse, loosely-branched, medium to large, deciduous shrubs that typically grow 12-20 feet tall. (USDA hardiness zones 5-8). They are particularly noted for their strapped shape, often fragrant, mid- to late winter flowers which appear before the spring leaves emerge. Five cultivars were selected by Mr. Tim Brotzman, an Ohio nurseryman who has been growing witchhazels for over than a half century.

Witchhazels generally grow 12-15 feet tall with an upright, vase-shaped, ascending branches and a spreading habit. The sweetly fragrant long-lasting flowers appear in February and last into March. The bright green 5-6 inch circular leaves appear weeks later in spring. Yellow-orange to yellow fall color can be quite attractive in some years. The first three winter-flowering witchhazel are Chinese hybrid witchhazel (H. x intermedia):

1. ‘Jelene’– clusters of bright coppery orange flowers

2. ‘Diana’ – sweetly fragrant copper-red flowers

3. ‘Primavera’ – bright yellow, spider-like flowers with narrow 3/8 to 5/8 inch long petals

4. Chinese witchhazel H. mollis ‘Wisley Supreme’ – fragrant golden-yellow flowers

5. Japanese witchhazel ‘H. japonica ‘Shibamichi Red’ – is a relatively recent introduction of Japanese witch-hazel named after the well-respected Japanese nurseryman, Akira Shibamichi. Flowers open a bit on the late side of the February/March period to reveal unusually showy cherry red, strap-shaped petals which are highly scented. This variety grows more slowly and the blooms are a bit smaller than hybrid witch-hazels. The shrub attains a height and spread of 8 feet.

Witchhazels are best planted in a shrub border or woodland garden that receives at least one-half day sunlight. They’re valued for fragrant late winter flowers and good fall color. Clip and bring in an attractive winter bouquet that will add fragrance to your home.

No serious insect or disease problems trouble witchhazels. Occasionally, caterpillars and Japanese beetles may chew on the summer foliage. Witchhazels are deer resistant.

Ten Stars Of The Winter Landscape

Posted by Hugh on January 21st, 2020

Here are 10 reliable plants that shine in my Tennessee garden (Zone 6-b) during the winter season:

Witchhazels (Hamamelis spp.) –two species bloom in winter: (a). Vernal witchhazel (H. vernalis) blooms in mid- to late- January (zones 4-8). (b). Chinese witchhazel hybrids (H. x intermedia) dominate the month of February into March. – deciduous, large multi-stemmed shrub or small tree that grow 12 to 15 feet tall with wide spreading branching; select hybrid forms including ‘Jelena’ (coppery-orange flowers), ‘Diane’ (copper-red to red flowers), ‘Gingerbread’ (orange flowers), ‘Westerstede’ (yellow flowers), and ‘Pallida’ (yellow flowers). (zones 5-8).
Chinese Paperbush (Edgeworthia chrysantha) – their showy nodding flowers appear in late February into early March (zones (6)7-9).
Carolina Jessamine (Gelsemine sempervirens) – puts on a spectacular display of fragrant, bright yellow flowers starting in late February (depending on weather) and lasting 4-6 weeks, Sports semi- to evergreen foliage (zones 6 to 9).
Lenten Rose (Helleborus x hybridus) – modern day varieties have some gardeners ripping out those they planted 25 years ago. (zones 4-9).
Christmas Rose (Helleborus niger) – also noted for their long bloom period in some years starting in late January, most in February through mid-April. (zones 3-9).
Fragrant Honeysuckle (Lonicera fragrantissima) – Extremely fragrant (lemony), short-tubed, creamy white flowers often appear in mid-winter before the leaves emerge. Flowers are followed by small, somewhat inconspicuous, red berries. (zones 4-8).
Japanese Cornel (Cornus officinalis) (zones 5-8) and Chinese cornel (C. mas) (zones 4-8) – bloom the latter days of February or early March as prolific open about a week or so later.
‘Pink Dawn Viburnum (Viburnum x bodnantense) – puts on a late winter spring show of pink flower clusters followed by thick, lustrous, rich green foliage and cinnamon-colored branches. (zones 5-8).
Chinese wintersweet (Chimonanthus praecox) – yellow 1 ½ inch wide flowers with a purplish-brown center open with fragrant flowers (to 1” across) typically bloom in winter (December to January) on leafless branches. (zones (6)7-9)
Daphne (Daphne odora) – highly fragrant creamy-white, pink, or yellow blooms open in late winter and persist well into spring. (zones 3 to 10).

Ten Stars Of The Winter Landscape

Plant Disease Warning: Phytophthora ramorum

Posted by Hugh on January 16th, 2020

Rhododendron infected with
*Phytophthora ramorum* (Pr) (photo by Dr. Alan S. Windham)

Known as “sudden oak death”, this serious plant disease (Phytophthora ramorum) (Pr) from the West Coast kills oak and other species of trees. It has caused devastating effects on the oak populations in California, Oregon, and Washington, and is also present in Europe. Symptoms include bleeding cankers on the tree’s trunk and dieback of foliage.

Pr causes foliar blight/leaf spots over 80 susceptible landscape plants including: maple (Acer), Camellia, witchhazels (Hamamelis), mountain laurels (Kalmia), honeysuckle (Lonicera), magnolias (Magnolia), Japanese andromeda (Pieris), Douglas fir (Pseudotsuga), azaleas and rhododendrons (Rhododendron), lilac (Syringa), and viburnums (Viburnum).

All nursery plants from the West Coast are strictly inspected by the USDA for Pr. However, mistakes do happen. In the spring 2019 rhododendrons infected with Pr were shipped to some stores in Tennessee. Fortunately, the plants were quarantined and quickly destroyed.

Pr is a water mold fungus disease known as ramorum leaf blight, ramorum dieback, and sudden oak death (SOD). In certain areas of California and Oregon, Pr causes bark cankers on several oak (Quercus) and tan oak (Lithocarpus densiflorus). The bark cankers are fatal to oak and tan oak if the lesions girdle the trunk. Otherwise, trees that develop foliar blights and leaf spots do not die, but may serve as “reservoir” hosts for the pathogen.

Pr produces “bleeding” cankers on the trunks and branches. The formation of droplets of dark reddish brown liquid on the bark is not usually associated with bark cracks or insect holes. If the outer bark is scraped away, black zone lines surround dead areas in the inner bark. Once a bark canker girdles a branch or stem, the portion of the plant beyond that point dies. Tree death may occur within several months to several years after initial infection. Infected trees are attractive to opportunistic ambrosia and bark beetles, as well as secondary colonization by the sapwood decay fungus (Hypoxylon).

West coast nurseries are forbidden to ship susceptible host plants. All plants must pass inspection “free of Pr” can be shipped to other states. No chemical control measures are currently available.

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.