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

American Fringetree – A Spring Flowering Treasure

Posted by Hugh on April 28th, 2015

American fringetree

American fringetree (Chionanthus virginicus) is one of the finest spring flowering trees (USDA hardiness zones 4-9). Individual flower heads are large and billowy, snowy white, and very fragrant in the early evening hours. Flower panicles peak through the large leaves, and are large and showy compared to Chinese fringetree (which I also like).

Leaf sizes range from 3 to 10 inches in length and exhibit a high-gloss upper surface. Fringetrees rate above average disease and insect resistance. Seedling forms are quite variable in summer leaf colors (medium to dark green) and in fall leaf color (pale green, yellow, and brown). On occasion, individual fringetrees surprise with sensational autumn color.

In its early years plants start off slowly. Shoot growth may be wild and require pruning attention. Shrubs can be trained into 1 to 3 trunk trees through judicious annual pruning. Remove most, if not all basal suckers during the first 3-4 years. Staking may be required the first 1-2 years to develop a strong leader(s).

American fringetree is dioecious; male flowers are non-fruiting, while female flowers bear ½ inch long egg-shaped blue-black fruits (drupes). Seeds collected and sown in the fall germinate 2-3 years later. ‘Emerald Knight’, a male form, exhibits slightly upright branching and dark green leaves. Reportedly, ‘Emerald Knight’ may be propagated vegetatively.

American fringetree prefers full sun but grows okay in light shade with less flowers. Plant in a wide range of soils that are well-drained and lightly acidic. A 3 to 5 gallon plant will grow to 25 to 30 feet tall and wide in 20 years. Keep newly planted shrubs lightly mulched and irrigated. Two-year established plants demonstrate good drought tolerance. In southern climes fringetree performs better sited under light afternoon shade.

Caveat: People often confuse the name “fringetree” (Chionanthus) with “fringe flower” (Loropetalum)

New ‘Pam’s Mountain Bouquet’ Kousa Dogwood

Posted by Hugh on April 25th, 2015

Fused Bracts of ‘Pam’s Mountain Bouquet’ Chinese Dogwood (photo by Dr. Alan Windham, UT Plant Pathologist, Nashville, TN)

‘Pam’s Mountain Bouquet’ is a new Chinese dogwood (Cornus kousa) cultivar from the plant scientists from the University of Tennessee Dogwood Working Team (USDA hardiness zones 5-8). Mountain Bouquet is a near-white flowering form whose petal-like bracts fuse into near perfect squares. The cultivar blooms slightly later than other flowering dogwoods, helping to extend dogwood’s spring flowering season.

Mountain Bouquet tends to bloom heavily annually. Its unique fused bracts should become the point of conversation in your garden. About 82% of all bracts display some degree of fusion among the yellow-green colored bracts. UT plant scientists report that 80% of bracts were partially attached; 50% had all four bracts fused together. Mountain Bouquet is also highly resistant to powdery mildew and dogwood anthracnose foliar diseases.

The cultivar was discovered among a planting of seedlings at the University of Tennessee (UT) Arboretum in Oak Ridge, TN from seed gifted to UT by Ms. Polly Hill. ‘Pam’s Mountain Bouquet’ is a selection from the original seedlings.

Mountain Bouquet is expected to become available to homeowners in the next 3-4 years as nurseries build up their inventory. You may ask: “who is Pam?”. She is the wife of Dr. Robert (Bob) Trigiano who developed this amazing new dogwood.

Japanese Kerria Beautiful Old-fashioned Shrub

Posted by Hugh on April 23rd, 2015

Japanese kerria (Kerria japonica)

Kerria’s Winter Green Branches (Biltmore Estates, Asheville, NC)

Japanese Kerria (Kerria japonica) is an old fashioned shrub that never seems to go out of style (USDA hardiness zones 5-9). Some call it the “Yellow Rose of Texas”, although kerria originates from eastern Asia. Its showy yellow buttercup-like flowers bloom in spring, after the forsythias have finished. In winter you’ll fall in love with kerria’s graceful arching bright green stems.

Kerria is easy to grow and is highly adaptable to almost any garden locale. Depending on cultivar, it grows 3-8 feet tall and 6 -10 feet wide. You may opt to grow it in full or partial sunlight and it tolerates moderate shade. It develops into an excellent woodland plant, although flowering is less. Kerria adapts to almost any soil type, preferring a moist well-drained site.

Provide lots of room as this shrub tends to sucker freely; holding plant colonies in check may become a chore. Foliage may burn in full afternoon sun, particularly white edged variegated forms. Container grown nursery-grown plants may be set almost anytime from late winter to mid-autumn.

Keep the soil moist until the shrub becomes established after its first year. It suffers during long dry spells resulting in stem dieback. No fertilizing is necessary as nitrogen stimulates suckering and less flowering. Fall leaf color is insignificant.

Kerria should be pruned following spring bloom to maintain a desired size and to remove dead branches and twigs. Every few years kerria should be completely renovated following spring flowering; cut back the entire shrub to within 12 inches from the ground. Diseases and pests are rarely a problem.

Selected Cultivars:

‘Geisha’ – attractive yellow and white speckled variegated leaves.

‘Golden Guinea’- large single flowers and 4-5 feet tall shrub (commonly sold in U.S. garden centers).

‘Picta’ – white edged leaves; protect from afternoon sun in southerly areas; prune off reverted green leaf shoots.

‘Pleniflora’ (‘Flora Pleno’) – double flowered form with wicked suckering habit.

‘Shannon’ – produces larger single blossoms on 5 to 6 feet tall shrub.

Many New Beebalm Cultivars Continue to Roll Out

Posted by Hugh on April 21st, 2015

Monarda didyma at Kingwood Center, Mansfield, Ohio

Bee balms, aka bergamots or Oswego tea (Monarda spp.) are native to eastern North America (USDA hardiness zones 4-9). Plants are easy to grow, bloom beautifully, and multiply rapidly. They are treasured for their raging colored flowers and medicinal properties. Numerous bee pollinators as well as butterflies and hummingbirds favor the summer blooms.

The native M. didyma produces scarlet red flowers on stems up to six feet tall. New hybrid cultivars are crosses with the shorter M. fistulosa and/or early blooming lavender to pink flowers ofM. bradburiana. The resulting hybrids come in red, violet, purple, pink, and white.

Classic selections such as ‘Gardenview Scarlet’ and ‘Jacob Cline’ continue as standard bearers in the red beebalms. ‘Purple Rooster,’ ‘Raspberry Wine,’ and Grand Parade are rated the best in the purple category. ‘Marshall’s Delight’ (3 ½ feet height) and ‘Pardon My Pink’ (10-12 inch height) are two of the better pinks.

A new Sugar Buzz™ series includes ‘Bubblegum Blast’(hot pink), ‘Cherry Pops’ (cherry red), ‘Grape Gumball’ (vibrant magenta), and ‘Lilac Lollipop’ (lilac). All four cultivars are similar in size, mid-summer bloom time, and vigor. Their 12-15 inch size range fits perfectly into the middle of a flower border. The solid dome flowers sit atop strong, well-branched stems and all display above average resistance to powdery mildew.

Beebalms grow naturally in moist meadows, along rivers and streams, and in forest clearings. Surprisingly, they do grow near black walnut trees. Full sun is best, although plants do thrive in partial sunlight if air movement is adequate. Cutting plant(s) to the ground in late summer will stimulate fresh new growth.

Beebalms should be grown in a well-drained, compost-rich, moderately acidic (pH of 5.5-6.5) soil. They also prosper in containers filled with a porous peat/bark soil-less media mix. Plants are moderate feeders; three bi-monthly feedings of water-soluble fertilizers such as Miracle-Gro™, Nature’s Source™, and Daniels™ is adequate.

Deadhead old flowers for re-bloom a month or so later. Maintain moderate soil moisture levels. Irrigate plants in early morning so as not to encourage, powdery mildew. Aphids, spider mites, thrips, and whiteflies are a few common pests. None are fatal.

Wonderful Bellworts For Woodland Gardens

Posted by Hugh on April 18th, 2015

Late May foliage

Bellwort (Uvularia grandiflora)

The soft yellow bell-shaped flowers of bellworts (Uvularia spp.), aka merrybells, contribute to spring’s awakening in U.S. woodlands and shade gardens (USDA hardiness zones 3-9). On both U. grandiflora and U. perfoliata, flower stems pierce (pass through) the center of the leaves. A third species, (U. sessilifolia), nicknamed Wild Oats, grows in northern woodlands; leaves of latter are sessile (without a peduncle) and are not pierced by floral stem.

All are U.S. natives and bloom in April, May or June depending on regional location. Bellworts are members of the Liliaceae family, and are among the easiest of wildflowers to grow. Their nodding bell-shaped flowers are a springtime delight. Bellworts appear delicate looking, but are hardy and enduring. Over the years individual clumps colonize among themselves from thick fleshy white underground stolons.

Bellwort leaves are elliptic, glaucous (blue-green), and entire on 6-18 inch tall plants. Each solitary flower is just over an inch long composed of six soft yellow tepals (three petals and three sepals). Fruits (three-angled seed pods) form in the fall.

Plant bellworts in partial to full shade in compost-rich, moist, well-drained woodsy soil. Leaves turn clear yellow in early fall; it’s not unusual to observe some leaf burn on edges after a dry summer. Bellworts tolerate dry calcareous (limestone) sites after settling in for 2 years. No insect or disease problems are rare, but young emerging shoots may be damaged by slugs.

“Wort” is a name formerly given to plants used for food or medicine. Bellwort was sometimes used to cure throat problems.

Gomphrena (Globe Amaranth) For Summer Easy Color

Posted by Hugh on April 15th, 2015

Late summer display of Gomphrenas at UT Gardens in Knoxville, TN

Gomphrena at UT Gardens in Knoxville, TN

Gomphrena, aka Globe amaranth, is an annual bedding plant that blooms profusely in the summer heat and sun. Small ball-shaped flowers are clove-like in appearance. Many gardeners tend to ignore them at the garden center for showier flowering annuals. By mid-summer, a peek into your neighbor’s yard may cause to rethink that decision. Gomphrenas root down deeply and bloom way into the autumn, often without additional care. Dried gomphrena flowers are favorites of florists.

Depending on the choice of variety, plants grow 10 to 24 inches high and 12 to 16 inches spread. Their color palette includes purple, pink, orange-salmon, and red. Gomphrena’s small flowers are magnets for attracting butterflies and other nectar feeders to garden beds and containers.

Gomphrenas prosper in full sun and in average well-drained soil. Space plants a foot or so apart. Add a slow-release fertilizer to each planting hole. If summer leaves look chlorotic, 1-2 applications of a water-soluble fertilizer such as Miracle-Gro, Nature’s Source and Daniels will green them back up. Once plants are well established, water needs become minimal.

Gomphrenas attract very few insect pests and no diseases. Spider mites may be troublesome when weather is exceptionally dry. A blast of water to the underside of leaves reduces their populations without resorting to pesticides.

‘Fireworks’ is one of the new generation of gomphrena cultivars; one inch flowers appear as explosions of pink with yellow stamens. ‘Audray Bicolor Rose’ has two-toned flowers, rose colored at the base and white on top. The Las Vegas series (white, pink, purple) have been outstanding performers.

‘Audray Bicolor Rose’ gomphrena, Kingwood Center, Mansfield Ohio

Less Invasive Rose Of Sharons (Altheas)

Posted by Hugh on April 12th, 2015

‘Purple Chiffon’ Althea

‘Diane’ althea

In several states rose of Sharon or altheas (Hibiscus syriacus) are classified as exotic (non-native) invasive shrubs (USDA hardiness zones 5-8). Their seedlings are invading U.S. woodlands. Plant breeders are now developing less invasive cultivars.

The double-flowered altheas produce far fewer fertile seeds; stamens and pollen sacs are mostly embedded within the flower petals. Azurri Blue Satin® is a new seedless form with celestial blue blooms. Sugar Tip® althea is covered with light pink and white double frilly petal blooms; Sugar Tip’s variegated foliage is green with creamy white edges. Both cultivars grow 8-12 feet tall and 4-6 feet wide.

Most double-flowered altheas produce some fertile flowers and are much preferred over open single invasive forms. Among the best are Blue Bird (dark blue double), Blushing Bride (multi-pink shades double), Freedom (purplish-pink), and four cultivars in the Chiffon series (Blue, Lavender, Pink and White).

Over a quarter century ago, the U.S. National Arboretum released four tetraploid cultivars, called the Roman Goddess series. Diana (white), Aphrodite (rose), Helene (white/purple), and Minerva (lavender) are seedless forms.

Altheas grow best in full sun and in average, well-drained, pH neutral soil. Altheas are utilized as single specimen shrubs, or grouped together for hedging, privacy screening or border plantings. They attract butterflies and hummingbirds, plus deer generally leave altheas alone. Prune as needed to size and shape from late fall thru winter. Altheas bloom on current season growth. Apply a slow release fertilizer such as Osmocote™ and Nutrikote™ in early spring as new growth begins to emerge.

‘Sugar Tip’ althea with variegated foliage

Ground Nesting Bees Are Beneficial Pollinators

Posted by Hugh on April 10th, 2015

Ground Bee photo provided by Dr. Frank Hale, Entomologist at the University of Tennessee

Spring signals the return of many species of birds and the bees to yards and gardens. In early spring increased activity by ground nesting bees cause alarm for many people; dirt pile nests start appearing in bare patches in the lawn. They are beneficial pollinators in the garden.

Bees in the families Colletidae and Andrenidae represent the ground nesting solitary bees. They do not form hives. Solitary bees spend much of the life in the pupa stage in shallow underground tunnels or galleries; the queens live individually and raise their young. Ideal location for the nests are warm sunny grassless patches in well-drained soil; the ground should warm up quickly in the morning.

Nest or mound entrances are only a few inches across. Nests (holes) improve soil aeration holes that help in the downward movement of water and nutrients. Each spring ground bees abandon old nests, mate and build new ones. Many females may nest in the same area.

Ground bees pose little or no threat to people. Male bees comprise the majority of above-ground swarmers, and do not have a stinger. The mostly subterranean queens do have stingers, but rarely defend their nesting area. They are very docile and not likely to sting. However, if you are stung, persons with extreme sensitivity should always carry an Epipen to protect against an allergic reaction.

Ground bees are highly beneficial to your lawn and garden. To be rid of ground bees, you do not need to use pesticides. Lots of ground activity, from frequent tillage, mowing, or irrigation, will destroy nests. Simply watering the area will cause bees to move to another area.

Million Bells (Calibrachoa)

Posted by Hugh on April 8th, 2015

Calibrachoa ‘Liberty Hot Pink’

Calibrachoa ‘Double Amethyst’ container

Among gardeners “million bells” or “callies” are common names for calibrachoas (Calibrachoa x), spring-summer-fall flowering annuals; they’re closely relative of petunias (Petunia spp.). Low spreading plants are blanketed with small petunia-like flowers from spring until frost. Blooms hold up well to rain showers and do not need to be deadheaded. Plants are heat-tolerant and disease resistant.

Grow calibrachoas as you would petunias; they excel in containers and hanging baskets. Calibrachoas measure 6 to 12 inches high and 24 to 48 inches spread. Showy flower colors range from lavender, blue, red, pink, salmon, orange, yellow, white; blooms attract hummingbirds, butterflies and bees.

Calibrachoas grow best in full sunlight. In the deep south, a site that favors morning sun and afternoon shade is preferred. After the threat of spring frost has subsided, plant them in containers filled with a well-drained organic-based potting mix. Space plants 12 to 16 inches apart. If grown in garden beds, a moderately acidic soil is best; mid-summer leaf yellowing is a symptom of a high pH or alkaline soil.After planting add 2-3 inches of mulch. Overwatering or a poorly drained soil is the death knell of calibrachoas.

Supplement with a slow release fertilizer such as Osmocote™ or Nutricote™ according to package directions. Calibrachoas in containers may be nurtured with a water-soluble acidic fertilizer such as Miracle-Gro™, Schultz™, Daniels™ biweekly.

Aphids can become major pests on new growth. Freshen plants with a late summer shearing using a scissors or pruning shears. Clipping encourages renewed growth and flowering. Calibrachoas are very cold tolerant and usually survive into late autumn season.

Superbells, Minifamous, Alhoas, and Callies are popular series of calibrachoas.

‘Blizzard’ Pearlbush Is Superior Choice

Posted by Hugh on April 5th, 2015

‘Blizzard’ Pearlbush (photo courtesy of Dr. Tom Ranney)

Large flowered ‘Blizzard’ pearlbush

Once upon a time pearlbush (Exochorda spp.) was a popular old-fashioned spring flowering shrub. Its flurry of white flowers followed forsythia in early spring bloom cycle (USDA hardiness zones 4 to 8, excel in 7 & 8). New on the garden scene is ‘Blizzard’ (E. x Snow Day™) pearlbush. It is blanketed with large white 5- petalled flowers, twice as large as other varieties of pearlbush.

Blizzard pearlbush is an interspecific hybrid (tetraploid) of three Exochorda species and is the creation from Dr. Tom Ranney, plant breeder at the Mountain Crops Research And Extension Center in Fletcher, NC. This 5-6 feet shrub gem displays a distinctive upright branching form compared to taller and rankier varieties. Blizzard pearlbush needs little pruning to maintain its compact nature and may be trained into a diminutive tree. Pruning is best done in spring after flowering is over.

Pearlbush grows in any average soil that is well-drained and mildly acidic. Feed with a slow release fertilizer in late winter such as Osmocote™ or Nutrikote™. Early-spring branches are ideal for forcing inside your home. Pearlbush is highly disease and pest resistant. Spring-summer foliage is medium green and fall changeover is blah.

Pearlbush is native to China. For a great visual look in the spring landscape, set out multiples of Blizzard pearlbushes 5-6 feet apart to develop a short privacy screen or border.

Shop early as the availability of new Blizzard pearlbush may be limited at local garden centers this spring (under the Proven Winners (PW) logo).