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

Growing Japanese Maples In Containers

Posted by Hugh on February 25th, 2021

Many slow-growing and compact cultivars of Japanese maples (Acer palmatum) and full moon forms (A. japonicum) grow for 3-5 years in containers. Japanese maples develop a decorative canopy, and their lacey foliage turns yellow, orange and/or red in autumn.

Most Japanese maples perform well in partial to full day sunlight, but not in full shade. Most grow happily under a tall open canopy of nearby large deciduous trees or around the eastern side of your home or patio. Many are very winter hardy in zone 4 and parts of 5 where they’re situated in sheltered locations such as an enclosed courtyard. Their low winter root temperature is rated + 5°F (-15°C).

When not properly sited, the tender spring foliage is vulnerable to frosty nights, drying winds, and strong sunlight. Leaves may scorch, shrivel, or burn on the edges if not adequately watered.

Japanese maples are not heavy feeders and should not be over-fertilized. Feed with a low nitrate nitrogen fertilizer and avoid products containing high amounts of ammonium nitrate and urea. In the spring add fresh mulch or compost to the surface. Mulch will also aid in retaining moisture.

Select small compact growing cultivars for container planters in range 5 – 6 feet tall and wide. Choose wide squat containers (terra-cotta, stone, or plastic) as opposed to narrow tall urns to avoid blow-over on windy days. Minimum pot size diameter should start at 12–18 inches (30–45 cm). Choose pots with light colored surfaces which reflect rather than adsorb the heat from sun.

Recommended cultivars that grow well in containers are: Crimson Queen, Fireglow, Garnet, Inaba Shidare, Kamagata, Mikawa Yatsubusa, Oshu Beni, Osakazuki, Sango Kaku, Red Dragon, Seiryu, Shaina, Shishigashira, and Tamukeyama.

Spring move outdoors (in cold regions): Late winter and spring is the tricky period time to judge outdoor temps. Container Japanese maples are moved outdoors as the buds begin to open. Be prepared to move the tree back into shelter during nights of hard frosts. The usual spring transitional period may last 2-3 weeks long.

Japanese maples often require minor spring/summer pruning for a neat appearance. Root pruning and repotting should take place in the early spring prior to the emergence of new leaves.

Finally, every 3 years, consider upsizing your Japanese maple to a larger container along with added potting soil.

Eastern Bluestar (Amsonia)

Posted by Hugh on February 21st, 2021

Eastern Bluestar (Amsonia tabernaemontana), aka blue dogbane, is a native herbaceous perennial that is becoming more popular with U.S. gardeners (USDA hardiness zones 3-9).

Eastern Bluestar (MT Cuba Trials in May 2019)

This erect, clump-forming plant produces terminal, pyramidal clusters of ¾ inch, soft light blue, star-like flowers in mid- to late-spring atop erect
2-3 feet tall leafy stems. Narrow, willow-shaped, dull green foliage may turn an attractive yellow in fall. The plant can be cut close to the ground or left for winter interest.

Eastern bluestar grows best in full sun. A plant in part shade will likely need to be staked due to its weak floppy form. Cut back stems after flowering to create a round, neater appearance. This species is less drought tolerant than A. hubrichtii.

Hummingbirds, large carpenter bees, hummingbird moths and butterflies visit the flowers in mid-spring. Generally, deer do not trouble Eastern bluestar. The latex sap is mildly irritating to humans. The plant appears to be unappealing to rabbits, deer, insects, slugs, and most other garden pests.

Cultivars of Eastern Bluestar:

‘Blue Ice’ looks very similar in appearance to the species except grows much more compact (1.5 feet tall and wide. Spring flowers are dark lavender-blue.

‘Short Stack’ is a dwarf cultivar that grows to only 10-12 inches tall and 18 inches wide with sky-blue flowers. Foliage may be susceptible to rust.

‘Storm Cloud’ start out with near-black stems and silver-veined dark green leaves in spring which lighten to olive green by early summer. Light pale blue flowers bloom from late spring to early summer, and may rebloom. It may be subject to rust.

‘Seaford Skies’ is a hybrid cross (A. hubrectii x A. tabernaemontana) discovered growing in Seaford, Virginia. Plants average 2-4 feet tall and 2-3 feet wide. Sky blue flowers develop atop 36 inch erect stems may attain 5 feet.

Willow leaf bluestar (var. salicifolia) also called bluestar, is native to the southeastern U.S., is often overlooked by gardeners. Plants average 3 feet in height and spread with dark green, narrow and willow-like leaves that turn clear yellow shade in autumn. Star-shaped flowers are pale lavender blue.

Twenty Highly Dependable Small Landscape Trees

Posted by Hugh on February 15th, 2021

In small landscapes, where growing space is limited, a number of outstanding trees may be planted. Several are also examples of great spring or summer flowering trees. U.S. native species are designated N. Additional landscape traits include:

Grow under 30 feet in height and underneath power lines).
Winter hardiness across the U.S. (USDA hardiness zones 5-7).
Most, particularly cultivars, are resistant to problem diseases and insects.
Suitable for either residential & commercial plantings.
Good heat and drought tolerances; all require good soil drainage.
Clean, blemish-free summer foliage, some displaying outstanding fall leaf color.
Dwarf forms suitable for container growing.
None are invasive.

Japanese maples (Acer palmatum) – many selections under 30 feet
Queen Elizabeth hedge maple (Acer campestre ‘Queen Elizabeth’)
Amur maple (Acer ginnala)
Paperbark maple (Acer griseum)
Serviceberry (Amelanchier x grandiflora)(several cultivars) N
American hornbeam (Carpinus caroliniana) N
Redbuds (Cercis canadensis) (several cultivars) N
Chinese Fringe tree (Chionanthus retusus)
American Fringe tree(Chionanthus virginicus) N
Flowering dogwood (Cornus florida) N
Chinese or Kousa dogwood (Cornus kousa)
Winter King green hawthorn (Crataegus viridis ‘Winter King’) N
Carolina silverbell (Halesia diptera) N
Crape myrtles (Lagerstroemia x indica) –select from four size categories ranging from 5 to 30 feet
Southern magnolias (Magnolia grandiflora) – dwarf forms ‘Teddy Bear’, ‘Kay Parris’ N
Star magnolia (Magnolia stellata) – multi-branched habit
Crabappples (Malus spp.) cultivars – crabapple (select disease resistant cultivars) – ‘Adams’, ‘Centurion’, ‘Donald Wyman’, ‘Prairie Fire’, ‘Sugar Tyme’, Japanese flowering crab (M. floribunda), et.al.
Okame flowering cherry (Prunus ‘Okame’) cherry; also P. ‘Accolade’; ’First Lady’
Yoshino cherry (Prunus x yedoensis ‘Yoshino’)
‘Kwanzan’ flowering cherry (P. serrulata ‘Kwanzan’)
Japanese Tree Lilac (Syringa reticulata)

Most, but not all trees listed above are sold at full service garden centers. Fringetrees (Chionanthus spp.), Japanese tree lilac (Syringa reticulata), silverbell (Halesia), and hedge maple (Acer campestre), and specific cultivars may be purchased from on-line specialty nurseries.

Winter-blooming Wintersweet

Posted by Hugh on February 6th, 2021

Wintersweet (Chimonanthus praecox) is a landscape shrub offers four seasons of landscape interest. Also called Japanese allspice, this deciduous mid-sized shrub typically grows 10-15 feet tall and 8-12 feet wide and blooms during winter (USDA zones 7-9). You can also risk planting wintersweet in a protected courtyard garden in Zones 6 to minimize freeze injury to flowers.

Wintersweet, native to China, deserves to be planted more in the U.S. Fragrant yellow flowers (1 to 1.5 inches across) are a prelude to spring forsythia. Bloom period is mostly determined by the precise weather conditions at the time. For example, in mountainous areas of Tennessee, NC, and VA, normal bloom time is mid- February. Bare branches may pop into bloom during an unseasonal 4-5 day warm spell in late December or January.

Each flower has numerous showy tepals which range from sulfur yellow to pale yellow along with a purplish-brown center. The spicy scented blooms catch your breath. Flowers on the cultivar ‘Lutea’ display a deeper yellow color.

Rough, glossy green, opposite, elliptic-ovate to ovate-lanceolate leaves (up to 6 inches long) emerge in spring. Leaves turn yellow in fall. Branches produce spicy yellow flowers with purple-brown centers on branches clad with a few persisting leaves.

Seed pods are 2 inches in length and gradually ripen to pink. In fall, the foliage turns bright yellow. Some flowers may open prematurely and get nipped by winter’s onset. No serious disease and insect problems trouble winter sweet shrubs.

Prune wintersweet in early spring before leaves unfold. Most of the cuts are renewal types, e.g., to remove older wood to reduce height and spread. Snip off dead or broken branches at any time. Add 1-2 handfuls of a granular fertilizer such as 10-10-10 or equivalent.

Seven Shrubs That Bloom In February

Posted by Hugh on February 1st, 2021

If you have ever dreamt of creating a year-round landscape garden, here are seven fine shrubs to start with. These shrubs bloom in late winter and are also important to early insect pollinators — native ground bees, bumble bees, and butterflies. In USDA hardiness zones 7-9, winter temperatures begin to moderate and some shrubs burst into floral life.

Chinese paper bush (Edgeworthia chrysantha) – a deciduous suckering shrub that typically grows to 4-6 feet tall and wide. In February
Tiny, apetalous, tubular, yellow flowers are densely packed flower clusters open in February. Short-petioled, lanceolate-oblong, dark green 3-5 inch long leaves are attractive (zones 6b-10).

Carolina Jessamine (Gelsemium sempervirens) – sweetly scented, golden yellow flowers cover the cascading, fine textured foliage from February to April. Moderately deer resistant (zones 6-9).

Chinese Witchhazel (Hamamelis x intermedia) represent crossing two Asian witchhazels (H. japonica x H. mollis). Plant grows 6-12 feet tall and wide and suckers freely at the base. Recommended cultivars are ‘Diane’, ‘Jelena’, ‘Orange Beauty’, ‘Primavera’ and ‘Westerstede’. Moderately deer resistant (zones 5-9)

Winter honeysuckle (Lonicera fragrantissima) – small fragrant white flowers appear in midwinter on this 10-12 foot tall vigorous shrub. Note: rated “invasive Florida and Texas where winter temperatures are mild; not so much in zone 7 and colder areas further north (zone 4-10).

Wintersweet (Chimonanthus praecox) – highly fragrant yellow/slight red blotched flowers appear in late January; prefers rich, acidic, moist, well-drained soils in part to full shade; 12 feet by 10 feet deciduous moderately drought tolerant shrub (Zones 6 to 9).

Sweetbox (Sarcococca hookeriana ‘Humilis’) – a suckering 4-6-foot evergreen shrub with numerous small fragrant white flowers set against glossy boxwood-like foliage; spreads very slowly by stolons in shady landscapes (Zones 6 to 9).

Winter daphne (Daphne odora) – an evergreen, densely branched,
3-4 feet tall shrub with rose-purple or white, fragrant flowers in mid- to late winter. Fragrant 2-inch long tubular flowers are a half-inch across and are usually white; pink or lavender varieties also available; long blooming in late winter and early spring (Zones 7-9).

Evercolor® Series Of Japanese Sedges

Posted by Hugh on January 26th, 2021

Japanese sedges (Carex oshimensis) are fine-textured variegated sedges that typically grow in a low, grass-like mounded clump to 10-16” tall and wide. This tough colorful sedge was originally found growing in dry woodlands and rocky slopes throughout Honshu Island, Japan. Brownish flower spikes, mostly inconspicuous, form on triangular stems in spring.

Japanese sedge are evergreen across the southern U.S. They’re long-lasting and easy to grow! Evercolor® series of variegated Japanese sedges are the result of breeding from Pat Fitzgerald, at Fitzgerald Nurseries in Kilkenny, Ireland. This collection of seven cultivars (to date)have been introduced so far. They are hardy in zones 6-8, but are being evaluated in USDA zone 5. Plants are evergreen through most of their growing range.

Sedges are grass-like plants, mostly preferring sites with moist, rich soil and in part shade. Once established in one growing season, these sedges tolerate dry shade, accompanied by intermittent watering during dry periods. Foliage colors are richer in partial shade than in full sun. Plants spread are propagate by rhizome division in early spring.

Evercolor® series make exceptional ground covers, as well as bedding and specimen plants. They are planted in mixed containers and window boxes, as billowy plant mounds spilling over the edge into a path or billow up (mound) in a container or window box. Spacing varies with cultivar. Group these sedges as edging along paths as specimen accent plants. Sedges can be planted along the edges of streams or ponds, and in rock gardens.

Evercolor® sedges grow 12 inches high and 12-18 inches in spread in shade or part shade in moist to average soil with good drainage. Water well after planting and regularly until established after one year. Trim back all last year’s growth in late winter. No serious insect or disease problems trouble sedges and are deer resistant

‘Evergold’ is the original variegated form grown noted for its arching, ornamentally attractive foliage. narrow leaves with broad, creamy, yellowish-white center stripe and bordered by thin dark green margins.

‘Everillo’ – a cascading mounding fountain of lime green leaves deepen to yellow-gold later in the summer.

‘Everest’ – more vigorous sport of ‘Evergold’ with green center and crisp snow-white edging.

‘Everlime’ – a mound of leaf blades with deep green centers flanked by lime green margins.

‘Eversheen’ has distinctive lime yellow striped foliage, all in a neat flowing mound.

‘Everoro’ – leaf blades emerge lime-green and turn golden yellow late in the season.

‘Everlite’ – rich green leaf blade edges and broad white center stripe.

Carex ‘Eversheen’ + ‘Purple Pixie’ loropetalum at Dallas Botanical Gardens

Carex ‘Everest’ at Atlanta Botanical Gardens

Update On Coral Bells

Posted by Hugh on January 20th, 2021

Coral bells (Heuchera spp) or alumroot are Tennessee natives. They represent an almost limitless choice of foliage colors, sizes, and forms (USDA hardiness soils 4-9). The biggest chore a gardener has is selecting what cultivar(s) to plant. There is over one hundred to choose that range from grow 8 to 12 inches in height and 1 to 2 feet spread. The coral bell color palette is a landscape designer’s dream plant. Should I mention that some varieties bloom exceptionally well.

Foliage color choices range from lemon yellow to green to nearly black, that may be glossy, matted, or marbled. Spring / summer flowers stand above the foliage. Flower stalks may reach 2 to 3 feet in height. Coral bells are suitable in most any landscape situation from mixed borders, mass plantings, and containers.

In the south, heuchera plants are best in an open woodland setting, but can tolerate a fair amount of morning sunlight. Plant in a humus-rich, moist, well-drained soil. In the north, coral bells grow well in full-day sunlight. In southern gardens, coral bell hybrids with a Heuchera villosa bloodline are longer-lived where heat and humidity are major issues.

Additional choice: Plant breeders have successfully crossed heuchera with its botanical cousin Tiarella (“foam flower”) to produce a more tougher shade plants (written as “x Heucherella”).

Northern gardeners have found that a layer of winter mulch helps protect the plant crowns in zones 4 and 5. Heuchera and x Heucherella exhibit good drought tolerance. During the dry portion of the growing season, supply an additional 1- inch of water weekly. Avoid planting heucheras in wet soggy soils.

Heuchera and x Heucherella clumps should be dug up and divided every 3-4 years in early spring. Heuchera and x Heucherella are generally left alone by deer and rabbits. However, when populations are exceptionally high, these critters will eat any plant, including coralbells and their relatives.

In general, heuchera and x Heucherella are not troubled by disease and insect problems. Foliar nematodes may disfigure leaves in late summer. There is no suitable control measures against nematodes. Black vine weevil is reported to be a problem in the Northwestern U.S.

In southern gardens, some cultivars may be damaged by summer dieback identified as Sclerotinia fungus. Suggestion: gardeners should talk with one another to select cultivars that perform best in their region. Good air circulation is the best preventative to avoid diseases.

Favorites in my Tennessee Garden: ‘Citronelle’, ‘Caramel’, ‘Apple Spice’, ‘Georgia Peach’, ‘Southern Comfort’, Primo® ‘Black Pearl’, ‘Berry Timeless’, and two H. villosa hybrids: ‘Autumn Bride’ and ‘Bronze Wave’.

New Landscape Roses With Exceptional Fragrance

Posted by Hugh on January 15th, 2021

Over a century of rose breeding has rewarded gardeners with so many gorgeous garden roses: hybrid tea, grandiflora, floribunda and shrub types. Rose breeders have concentrated on plant vigor, flower color, disease resistance, and greater numbers of flowers over the growing season. Over the years, floral fragrance has been mostly ignored.

Brindabella® Purple-Prince (Photo courtesy of Suntory)

In the past two years two new rose series have come to market with incredible fragrance along with improved disease resistance.

At Last® rose (Rosa x At Last®) is a highly fragrant, fully-petaled rose with no-spray disease-resistant landscape rose. No spraying is required to enjoy a non-stop display of large, sweetly perfumed sunset-orange blossoms from late spring through frost. Handsome, glossy foliage and a vigorous, rounded habit makes it ideal for use in the landscape or the flower garden (USDA hardiness zones 5-9). Introduced by Spring Meadow Nursery (wholesale).

Brindabella™ Pink Princess (Photo courtesy of Suntory)

Brindabella™ roses is a series of shrub roses from Australia. They exhibit a bushy habit, 3-4 feet tall and wide and possess excellent disease resistance to black spot and powdery mildew. Their colorful blooms are doubled and highly fragrant. Blooms are produced in flushes from spring into fall, and no deadheading is required. The plants have a bushy, upright and sometimes semi-weeping habit. They reach at maturity, making them ideal for low hedges, spots at the edge of a mixed border, and containers.

Brindabella® roses are low maintenance and vigorous in a small package. They are well suited to home gardens and commercial landscapes. For beauty and fragrance Brindabella roses know few rivals. Roses are selected for their beauty, disease-resistance and vigor. Roses require 6 or more hours of direct sun per day and fertile, reasonably moist soil. They benefit from an occasional feeding during the growing season. Extra hardiness (Zones 4 – 9). Introduced by Suntory Flowers.

Six current Brindabella varieties for both home gardens and commercial landscapes are:

Dawn™ – fragrant salmon colored blooms with hints of apricot.
First Lady™ – lavender pink double flowers
Purple Prince™ – purple double flowers
Pink Princess™ – frosted pink double flowers
Red Empress™ – crimson red to dark fuchsia double flowers
Touch of Pink™ – pale pink centers & white outer whorled doubled flowers

Plant Awards Of 2021

Posted by Hugh on January 10th, 2021

NGB Perennial of the Year – Monarda (Beebalm)

For 2021, the National Garden Bureau (NGB), the non-profit organization promoting gardening in North America, has announced the five (5) plant classes that will be featured in the 2021 “Year of the” program.

Annual: Year of the Sunflower
Vegetable/edible: Year of the Garden Bean
Perennial: Year of the Monarda
Bulb: Year of the Hyacinth
Flowering Shrub: Year of the Hardy Hibiscus

Hosta of the Year – ‘Rainbow’s End’ a small- to medium-sized hosta. It is a sport of Hosta ‘Obsession’ boasts very thick, glossy, canoe-shaped leaves with bright golden streaky centers surrounded by a wide, green/black border.

Perennial Plant of the Year: Calamint (Calamintha nepeta subsp. Nepeta) – a member of the mint family (Lamiaceae), native to southern Europe north and west to Great Britain. Plants grow up to 18 inches tall and wide, and work well as a front border or a rock garden planting.

Calamint – 2021 Perennial Plant of The Year (PPOY)

Posted by Hugh on January 1st, 2021

Too begin a new gardening year, the Perennial Plant Association has named calamint (Calamintha nepeta ssp. nepeta) as the 2021 Perennial Plant of the Year. One landscaper designer describes calamint as “a cloud of confetti, tiny white flowers”. Plants are dotted with masses of tiny white (or pale blue) flowers from early summer to fall.

White flowers of calamint in summer garden (Photo credit: Midwest Groundcovers)

Calamint is a member of the mint family and a close cousin of catmint (Nepeta faassenii), another PPOY award winner. Flowers in turn attract loads of small butterflies. Undemanding, this low-maintenance deciduous perennial is native from Great Britain to Southern Europe. It grows best with good soil and air drainage (USDA hardiness zones 5-7).

Calamint grows 15-18 inches tall and wide in full sun and in average garden soil. It exhibits a low mounding or bushy habit, ideal for the front of the border, rock gardens, and more.

It exhibits above average drought tolerance once established. You may shear back lightly if desired to create neater habit or refresh spent blooming stems. Once a 1-year establishment period, calamint exhibits good drought tolerance.

Calamint (photo courtesy of Midwest Groundcovers)

Calamint stays disease and pest free. It blooms throughout the summer and its aromatic foliage is deer-resistant. It is an ideal companion planted with other late summer blooming perennials as fall anemones (Anemone), asters (Symphorocarpus), obedient plants (Physostegia), turtleheads (Chelone), garden phlox (Phlox paniculata), and ornamental grasses such as ‘Northwind’ switchgrass (Panicum), Little bluestem (Schyzacharium), and muhly grass (Muhlenbergia).