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

Yellow Flowering Magnolias

Posted by Hugh on April 6th, 2020

Deciduous magnolias (Magnolia spp.) are popular landscape plants because of their bright cheery spring flowers. Breeding efforts back in the 1970’s created a new class of deciduous yellow-flowering magnolias. In 1978, the Brooklyn Botanical Gardens introduced the first, Magnolia ‘Elizabeth’ (creamy white). Yellow magnolias are hybrid crosses between M. acuminata, M. subcordata, M. denudata, among species. Several are designated Magnolia x brooklynensis.

The thick fleshy petals on magnolias are called “tepals”. Depending on the cultivar, flower colors range from oft white, light pink, and yellow color shades of creamy to dark yellow blooms. Growth rate, bloom time, tree growth rate, and disease resistance also differ. The greatest concern is that many varieties bloom in very early spring and are susceptible to frost injury in U.S. hardiness zones 6 and 7.

‘Gold Star’, ‘Golden Gala’, ‘Stellar Acclaim’, ‘Sun Spire’ and ‘Sundance’ have light yellow tepals. ‘Goldfinch’, ‘Butterflies’ and ‘Elizabeth’ are among the earliest to bloom; ‘Elizabeth’ has one of the longest flowering periods. ‘Judy Zuk’ and ‘Yellow Bird’ exhibit dark yellow tepals and usually are among the last to bloom. ‘Woodsman’ exhibit unique multicolored pink, white and green tepals.

In an evaluation of 30 cultivars by Dr. Donna Fare, at the USDA Research Station in McMinnville, Tennessee, the now retired ARS plant scientist found ‘Carlos’ and ‘Gold Star’ grew the tallest selections at 23 feet (7 m) each after ten years. ‘Golden Gala’, ‘Gold Star’, ‘Carlos’, ‘Lois’, and ‘Yellow Lantern’ had the largest trunk diameters averaging 1 inch (2.5 cm) per year. ‘Sun Spire’ had one of the smallest trunk diameters and showed an annual increase of about 1.5 cm per year.

Yellow magnolias generally grow 30 to 40 feet tall and 20 to 25 feet wide at maturity. Plant a single tree as a specimen, or several in groupings along a drive or walkway. These magnolias make wonderful shade trees planted near patios, low decks and other outdoor living areas. Trees can also be grown in large pots, planters and containers of 18 inches or more in diameter.

Yellow magnolias are easy to grow in moist, well-drained, acidic, fertile soil and full to partial sun. Magnolias prefers full sun for best flowering in northern climes (Zones 4-7), and in partially shaded understory in the South (Zone 8). Pruning usually isn’t necessary; remove stray and broken branches after spring flowering. Fertilize in early spring with a slow release balanced product like Osmocote® or Nutricote®.

Double Take® Flowering Quince

Posted by Hugh on April 2nd, 2020

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Flowering quince (Chaenomeles spp) is an early spring flowering shrub treasured for its brightly colored blooms (USDA hardiness zones 5-9). Old fashioned quince shrubs produced small amounts of fruits (quince) which were gathered and made into yummy jelly in the autumn kitchen. Old fashioned varieties often grew 10-12 feet tall shrubs and produced small sharp thorns which made picking the fruits a challenge.

Now appearing in local garden centers are three new compact cultivars in the Double Take® series called ‘Orange Storm’, ‘Scarlet Storm’ and ‘Pink Storm’. They were developed by Dr. Thomas Ranney at North Carolina State University Extension Center in Mills River, NC. Plants grow 4-5 feet in height and about the same in width (120-150 cm).

Their large vibrant double flowers are stunning in the early spring landscape. Blossoms measure almost 2 inches across and are visited in abundance by bees. Leaves emerge after blooms drop off. Once shrubs are established, usually within 1-2 years, plants are very heat and drought tolerant. Branches are thornless and deer resistant. Double-Take flowered quinces do not produce fruits (quinces) and are easy to care for.

‘Orange Storm flowering quince (J.E.C. photo)

Double Take quinces are easily grown in average, moist, well-drained soil in full sun to partial shade. Best flowering occurs in full sun. They adapt to a wide range of soil conditions, but prefer well-drained loam soil. Plants bloom on old growth. Avoid heavy pruning. After flowering, quinces may be pruned as specimen shrubs, espaliers or hedges. Promptly remove root suckers to control possible spread. Feed with a slow release fertilizer such as Osmocote® or Nutricote® at package directions.

Mostly disease and insect free, quinces are fireblight and scab susceptible in some parts of the U.S. Double Take quinces are more disease resistant than the species. Aphids, mites and scale can cause significant damage to the new spring growth. Chlorosis (yellowing of foliage) can occur in high pH soils. Flower buds are susceptible to significant damage from early spring frosts.

Personal favorite: ‘Scarlet Storm’ with abundant double scarlet red flowers are real standouts.

Landscape uses: Spring flowering specimen or group in shrub border or cottage garden. Branches may be clipped into a low hedge. Collect winter wood to force winter blooming indoors. Branches make gorgeous cut flowers.

Siberian Wallflowers – Tough Winter Annuals

Posted by Hugh on March 26th, 2020

‘Citrona Yellow’ wallflower in Dallas Botanical Gardens

‘Bowles Mauve’ wallflower

In areas of the U.S. where winters are mild, Siberian Wallflower (Erysimum cheiri), (formerly Cheiranthus cheiri), is an early flowering favorite in the late winter garden. The species hails from Southern Europe (USDA hardiness zones 7-9). Many books list them as biennials and a few as “tempermental perennials”.

Wallflower is a woody-based herbaceous perennial subshrub in the mustard family (Brassicaceae). They produce clusters (racemes) of fragrant 4-petaled flowers in a showy floral display bloom in the early spring cool weather followed by narrow pendant dehiscent seed pods.

Wallflowers, depending on variety, grow to 6-24 inches tall and slightly less in width. Flowers (each to 3/4 inches wide) are mostly bright yellow or yellow-orange to brown, but sometimes appear reddish purple to burgundy. Bright green leaves (to 2-8 inches long by 3/4 inches wide) are narrow and pointed.

Wallflowers are easy to grow, adapting to most types of well-drained soil and in full to partial sun. Full morning sun is preferred in cool northern areas. Plant them in rock gardens. border fronts or in raised beds in late winter. Fertilize lightly after planting and when late winter/spring flowering begins. No serious insect or disease problems trouble wallflowers.

This biennial plant will self-seed; you may want to cultivate seedlings for next winter’s garden. Otherwise, sow seeds in spring for bloom early next year.

Wallflowers have naturalized in British Columbia, Washington and California. In the southern U.S. they’re just catching on.

Six Easy To Grow Spring Wildflowers

Posted by Hugh on March 21st, 2020

These six native wildflowers emerge in early spring in rich woodland soils. In gardens grow them in moist, organically rich soils in partial to full shade. Adding compost substitutes for fertilizing. All grow in moderately acidic to slightly alkaline soils (pH 6.0-7.5). Plants go dormant by early to mid-summer, earlier if soils dry out. Under ideal site conditions, all six will naturalize (colonize) by self-seeding. Early arriving pollinators, especially bumble bees are often seen working these spring wildflowers. No diseases or insects trouble all six wildflowers if site is correct.

Celandine poppy (Stylophorum diphyllum) grows in Eastern U.S. wildflower gardens (zones 4-8). Clusters of 4-petaled, yellow flowers bloom in spring atop stems, typically growing 12-18 inches tall. Blue-green, pinnately lobed foliage is silvery below.

Virgina bluebells (Mertensia virginica) is a native wildflower (zones 3-8). This clump-forming perennial grows 1-2 feet tall with terminal clusters of pendulous, tubular, sky blue flowers (to 1- inch long) open in early spring; bluish green 3-4″ long leaves.

Trout lily (Erythronium americanum) grows 4-6 inches high, foliage easily identified by their thick fleshy, mottled brown and purple leaves that mimic brook trout. Individual, nodding, bell- or lily-shaped yellow flowers (zones 3-8).

Bloodroot (Sanguinea canadensis) grows 6-10″ tall and may form large colonies over time (zones 3-8) in rich soil. Each flower stalk produces a single 2 inch wide, 8-10 petaled, white flower with numerous yellow stamens in center. Flowers open in morning, close at dusk and last 1-2 days. As the flower blooms, the leaf unfurls. Single palmate, deeply-scalloped, grayish-green, basal leaves, some measuring 9″ across, remain attractive into early summer.

Bloodroot (*Sanguinea canadensis*) in late spring

Twinleaf (Jeffersonia diphylla) is a clump-forming plant that typically grows to 8” tall when in flower in early spring, eventually reaching 18” tall in late spring when its fruits ripen. Its 5-6 inch long-stemmed, blue-green basal leaves are deeply divided into two lobes (look like two separate leaves). In early spring (April), its 1” wide white, 8-petalled, cup-shaped flowers bloom singly atop rigid 8” leafless stalks (zones 5-7).

Shooting star (Dodecatheon meadia) is an eastern U.S. native whose flowers appear like a shooting star plummeting to earth (zones 4-8). Of the six wildflowers listed here, it is the last to bloom in the spring. From each basal rosette of lance-shaped leaves come 1-4 sturdy, leafless, center flower scapes rising to 20″ high. Each flower scape contains 8-20, nodding, 1″ long flowers. Each flower comprises 5-reflexed petals and a cluster of yellow stamens. Flower colors range from white to pink to light purple.

Redbuds With Awesome Summer Foliage

Posted by Hugh on March 16th, 2020

**The Rising Sun™** redbud at The University of Tennessee Gardens in Knoxville

Native redbuds Cercis canadensis) is native to eastern and central North America (USDA hardiness zones 4-8). This small tree is a highly dependable small flowering tree. Redbud is typically a relatively short-lived tree, perhaps 20-30 years at best. Depending on variety, their lavender / pink/ white pea-like flowers emerge in early spring, usually a week or two before our native dogwoods (Cornus florida).

Fifty years ago, most U.S. gardeners were unwilling to buy redbuds. Over the past 25 years numerous varieties flaunting colorful foliage continue to arrive at local garden centers, the green heart-shaped redbud foliage is not valued for their foliage tree. The introduction of ‘Forest Pansy’ redbud in 1950 changed the way we utilized this wonderful native tree in the landscape. What followed has been “A Redbud Revolution”.

Listed in the colorful foliage category are nine modern day redbud varieties. At the end I have included two cultivars with unusual thick glossy leaves:

‘Alley Kat’ – green & white splotched foliage

Carolina Sweetheart™ (‘NCCC1’) – spring foliage emerges rich maroon, and slowly changes to shades of white, green, hot pink; ending green with faded white margins in late summer.

Flame Thrower™ – new leaves start out burgundy-red, turn bright yellow and green as foliage ages.

‘Hearts of Gold’ – spring’s golden yellow leaves turn to chartreuses in summer. Leaves may sunburn (scorch) during hot dry summer.

Merlot™ – fade-resistant dark burgundy foliage

‘Pink Pom Poms’ (PPAF) – thick, glossy green foliage and dark pink-purple, double pom pom-like flowers.

Ruby Falls® – weeping form with purplish red foliage.

The Rising Sun™ – apricot/gold foliage that rarely burns in the summer heat.

‘Whitewater’ ̶ weeping form with leaves that emerge mainly white with minimal flecks of green; foliage matures mostly green with flecks of white.

Thick High Gloss Green Foliage (C. canadensis var. texensis)
‘Texas White’ (white flowers)
‘Oklahoma’ (lavender-pink flowers)

‘Oklahoma’ (lavender-pink flowers)A

Smoketrees For Their Multi-Seasonal Appeal

Posted by Hugh on March 11th, 2020

Smoketree or smokebush (Cotinus coggygria) is a large shrub or small tree native from southern Europe to central China (USDA hardiness zones 5-8). Over time it typically matures to 10-15 feet high and wide. Depending on cultivar (see list below), smoketrees have oval leaves tinted in rich purple, gold, or green shades. Generally, they grow as multi-stemmed shrubs, but many gardeners choose to train them as small landscape trees.

Truly, the uniqueness of smoketrees are their wonderful flower clusters which offer the illusion of clouds of smoke. Individual flowers are actually insignificant. Additionally gold and purple-leaved cultivars are available along with green-leaved selections.

Smoketrees are best grown in full sun and in well-drained soil. Standard varieties can reach 10 feet to 15 feet in height. Pruning is key to keep their multiple stems in check and prevent a gangly plant appearance. Plant a single smoketree as an accent feature or group several as a tall deciduous shrub border or privacy screen.

Fall color is a mix of yellow, orange, and red shades. Those varieties with standout seasonal leaf color, like Golden Spirit® or ‘Royal Purple’, are grown solely for their foliage. In the fall all growth is cut back (coppiced) to 6-12 inches above the ground. New colorful shoots grow 4- and 6-feet tall in one growing season with no flowering.

This tree/shrub has proven to be a reliable performer in the garden, holding up well in hot, dry conditions once the plant is established. To repeat the billowy summertime blooms put on a real show for 3-4 weeks. What follows is the fluffy clouds then disperse throughout the yard and your neighbors. Some may find this objectionable.

Leading cultivars:

Golden Spirit® (‘Ancot’) grows with unique golden foliage that fades to lime green in summer before showing shades of orange and red in autumn; 10 feet tall and 6 feet wide.

‘Grace’ offers rich burgundy-purple foliage in spring and summer then orange-red fall color; grows 15 feet tall and wide.

‘Nordine’ is an exceptionally hardy form with burgundy leaves that develop red and orange shades in fall; 15 feet tall and wide.

‘Pink Champagne’ bears pink smoky flowers along with round deep green leaves that turns a mix of scarlet and orange in fall; 10 feet tall and 10 feet wide.

‘Royal Purple’ bear clusters of purple puffy flowers and red-purple foliage which turns scarlet in fall; 15 feet tall and 12 feet wide.

‘Velvet Cloak’ struts dark purple-red foliage, fading pale purple foliage may dull somewhat in late summer, and turns a fall mix of scarlet, orange and russet; 12 feet tall and wide.

Six Perennials For Dry Shade

Posted by Hugh on March 6th, 2020

Many of the following perennials tolerate dry shade but flourish in moist, well-drained soil. Each typically displays the richest foliage colors with a couple of hours of direct sunlight a day. All hold up well to dry conditions and are deer and rabbit resistant.

*Epimedium perralchicum* ‘Frohnleiten’ makes a wonderful groundcover

Barrenworts (aka Bishop’s cap, Fairy Wings) (Epimedium spp.) represent over 70 cultivars and new hybrid selections are arriving every year. No two cultivars seem alike in flowering and foliage traits. Species will vary from 6 to 20 inches in height and 10 to 24 inches in spread. Fairy wings, depending on species, may be evergreen or deciduous.

Sacred lilies (Rohdea japonica) are mostly evergreen perennials that grow 8-24 inches high depending on cultivar. Well-established clumps produce short-stemmed, creamy to greenish, white bell shaped flowers. Blooms, mostly inconspicuous, are mostly hidden within the dense leathery foliage. Red or orange ornamental berries follow in autumn and last through most of the winter. Plants prefer humus-rich well-drained soil, but cope with moderate periods of drought. (zones (5)6-10).

Ajuga (aka bugleweed) is a groundcover perennial with pretty spring floral spikes of cobalt-blue flowers and lovely foliage. Popular varieties include ‘Burgundy Glow’ (silvery green leaves splotched with pink/ burgundy/ white); Chocolate Chip (small, narrow green leaves spotted burgundy purple); Black Scallop (large purple leaves with high gloss). (Zones 3-9).

Lenten roses (Helleborus x orientalis) are so easy and so pretty in dry shady gardens with well-drained soil. Exquisite bowl- or saucer-shape flowers in white (often speckled), pinks, yellows, or maroon bloom for three months from mid-winter into spring. Their evergreen foliage is deer-resistant.

Geranium *macrorrhorizum* ‘Bevan’s Variety’

Bigleaf cranesbill (Geranium macrorrhorizum) is a resilient ground cover for dry shade. Its deeply lobed green foliage takes on shades of reddish-orange in fall. Popular varieties- ‘Bevans’ and ‘Ingwersen’s Variety’- bear pale pink blooms appear in spring. (zones 3-8).

Lilyturf (Liriope muscari) is an easy to grow perennial that tolerates a wide range of light and soil conditions. It copes summer heat, humidity and drought. Foliage is evergreen in warm southern climates (zones 7-10). Purple blooms (white variety also available) arise above the strap-like evergreen leaves in early autumn. (zones 5-10).

Rhododendrons You Should Be Growing

Posted by Hugh on March 1st, 2020

“A healthy plant in the right place with proper maintenance” is a rhododendron that has few problems. Rhododendrons and azaleas are acid loving plants meaning plants should be planted in humus-rich slightly acidic soil (pH 5.2 -6.5).

If the soil is not well amended, rhododendrons will have trouble surviving long term. Once planted, water during dry periods, feed lightly in the spring with a fertilizer for acid loving plants, and stand back and enjoy. Most varieties are hardy from USDA hardiness zones (4)5 through 7(8). Rhododendrons are potentially troubled by several disease and insect problems. Choose only the most dependable cultivars, many of which are listed here.

R. maximum (Rosebay rhododendron), 15’ x 20’ & larger Midsummer White to rose; shallow rooted; best in partial shade; var. roseum 4’ – 6’ x 6′ -10’ Pink to red; best in partial shade.

R. catawbiense ‘Roseum Elegans’ or ’English Roseum’ 4-6’ x 6-8’ Mid-summer large pink, almost impossible to tell apart.

R. catawbiense ‘Grandiflorum’ 6’ x 8’ Mid-summer; pinker form than Roseum Elegans.

R. catawbiense ‘Purpureum Elegans’ 3.5’ x 5’ Mid-summer; large, purple blooms.

R. catawbiense ‘Album’ 5’ x 7’ Midsummer White with green or brown margins.

R. catawbiense Boursault’ 6’ x 8’ Mid to late summer Darker Pink Vase shaped as gets larger.’

R. catawbiense ‘Lee’s Dark Purple’ 6-7′ x 7′-8′; deep purple with green-yellow blotch on petals.

R. catawbiense ‘Nova Zembla’ 3-6’ x 3-6’ Midsummer; deep red flowers, especially in shade.

R. x ‘Janet Blair’ (Dexter hybrid) 4′ x 4 – 5′ pinkish mauve with golden bronze blotch.

R. x ‘Chionoides’ (R.ponticum hybrid) 5’x 5’ Late spring to early summer; pure white with yellow blotch on petals; dark green, narrow leaves.

R. catawbiense ‘Cunningham’s White’ 7’ x 7’ Mid to late summer; White, rays of purple or brown; Foliage turns purple in the winter.

R. catawbiense ‘Scintillation’ 6’x 6’ Midseason; Pink, brown throat Fragrant, dense, glossy leaves. Foliage turns purple in the winter.

PJM Rhodendrons (Rhododendron x carolinianum) 4 to 6’ x 4 to 6’ very early spring March; ‘Olga’ (Pink), ‘PJM Elite’ (reddish purple), to original ‘PJM (Lavender); ‘Aglo’ (Pink) are leading varieties; purple winter foliage, loose open form as it matures.

‘Alleghany’ Viburnum – A Versatile Spring Flowering Shrub

Posted by Hugh on February 26th, 2020

Alleghany viburnum (Viburnum x rhytidophylloides ‘Alleghany’) is a hybrid cross between V. rhytidophyllum and V. lantana ‘Mohican’ (USDA hardiness zones 5-8). ‘Alleghany’ viburnum is rated a four season landscape shrub, with multiple year-round appeal including a durable semi-evergreen leathery foliage, dependable spring flowering, and showy fruits in fall and winter.

This lovely spring flowering shrub grows 10-12 feet tall and 12 -15 feet wide. Its dark green semi-evergreen leaves are resistant to bacterial leaf spot. Branch wood is coated with tiny gray-brown woolly hairs on stems and on the undersides of leaves. This medium sized flowering shrub is an excellent choice for privacy screening.

In most years leaves turn purplish in winter and persist through ice and snow into mid-February. In mid-April, showy creamy white flat-top flowers open at the ends of branches. Up close, flowers emit a faint unpleasant stale odor; otherwise observe from 6 or more feet away. Glorious clusters of dark red fruits fill the branch tips from late summer to early fall. The combination of fruits along with coarse green foliage are major autumnal assets. Red fruits ripen to black and numerous birds flock to this shrub for food and winter protection.

Alleghany viburnum prefers either full or 6- hours minimum daily sunlight for heaviest flowering. Moist, slightly acidic, well-drained soil is essential. A 2-year old established shrub exhibits above average drought tolerance. Fertilize in early spring with a slow release fertilizer such as Osmocote or Nutricote.

This large viburnum is available either as a large landscape size balled and burlapped (b&b) or smaller size container-grown plant. In early spring rake away old fallen leaves and mulch viburnums for a clean appearance.

This viburnum has no serious insect or disease problems. Prune, if necessary, after spring flowering and before July 15.

Best fruit numbers occur with cross pollination from Viburnum spp. parents or clones within the hybrid.

‘Alleghany’ Viburnum – A Versatile Spring Flowering Shrub

Dependable Conifer Trees For Southeast U.S. Landscapes

Posted by Hugh on February 21st, 2020

Arizona cypress (Cupressus arizonica var. glabra) is a southwestern U.S. conifer tree that is often underplanted. Soil drainage is an absolute must! Growth rate is moderate (15 feet high after 10 years) and eventually will reach 30-50 feet at maturity. (zones 7-9). I have seen multi-year specimens thriving in zone 6b.

‘Crater Blue’ deodar is a highly desirable shrub form

Deodar cedar (Cedrus deodara) is a medium-growing tree that typically grows to 40-50 feet high within its first 25 years. Shrub forms are also available. In its native Central Asia habitat, these cedars reportedly grow much taller. Young deodars start out pyramidal, maturing to flat-topped trees with broad-spreading horizontal branching. Deodar cedars prefer locations that are warm and humid in summers and protected from harsh drying winter winds (zones 6b -8).

Atlas cedar (C. atlantica) grow exceptionally well in the Southeast. Blue needle forms (var. ‘Glauca’) are most popular. Give trees lots of room as young cedars start out pyramidal, but develop wide-spreading horizontal branches as the age (zones 6-9).

Weeping Blue Atlas Cedar (*Cedrus atlantica* ‘Glauca Pendula’)

Few pines (Pinus spp.) perform well in the southern U.S. Notable exceptions are loblolly pine (P. taeda), longleaf pine (P. palustris), and Eastern white pine (P. strobus) (Zones 3-8). Site selection and spacing are of key importance. Pines are susceptible to numerous pests including bark beetles, shoot borers, Zimmerman moth larvae, pine sawfly, scale, among others.

Two deciduous conifers thrive in the Southeastern U.S. Bald cypress (Taxodium distchum) is native to the swamps of Georgia and South Carolina (USDA hardiness zones 4-9), yet is hardy from Florida north to central Michigan. Dawn redwood (Metasequoia glyptostroboides), native to China, also performs equally well (USDA hardiness zones 4-8). Both mature into large 60-80 foot landscape trees, but several dwarf tree and shrub forms are available.

Japanese cedar (Cryptomeria japonica) excels in the southeastern U.S. with few disease or insect problems are available (USDA hardiness zones 5-9). Tree cultivars grow 40-50 feet tall; dwarf tree and shrub forms are also available.

Additional conifers that have been proven reliable include false cypress (Chamaecyparis pisifera), hinoki cypress (Chamaecyparis obtusa), Alaskan cedar (Xanthocyparis nootkatensis), Korean fir (Abies koreana), Western arborvitae (Thuja plicata), Golden larch (Pseudolarix amabilis), and China fir (Cunninghamia lanceolata).