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

‘Blackout’ Heuchera Exceptionally Vigorous Type

Posted by Hugh on March 18th, 2014

Heuchera x 'Blackout' And 'All Gold' Hakone Grass In Container

A floral bouquet full of tiny flowers stand tall above the high gloss ebony foliage of Blackout coralbells (Heuchera x ‘Blackout’) (USDA hardiness zones 4 to 8). The foliage holds its color and sheen most of the summer. The foliage is evergreen through the winter in zones 6 thru 8. Airy spikes of cream colored bell-like flowers open in mid-June. Many weeks later, the light tan colored seed heads continue to stand high above the dark foliage.

Blackout is part of the tough Heuchera villosa breeding lines. It is grows vigorously, 12-18 inches tall and 18-24 inches wide by its second year in a garden or a container. Blackout exhibits good summer heat tolerance under moderate sun or partial shade. Full direct morning sunlight seems to bolster the darken foliage. Direct afternoon sun may scorch foliage unless under daily irrigation.

Blackout should be planted in rich well-drained soil. It is moderately drought tolerant and mulching aids in soil moisture retention. For a neater appearance remove old floral heads. The dark evergreen foliage pales out during the winter offering only minimal ornamental interest. Remove all or most of the previous year’s foliage in late winter to over fresh.

In general, heucheras have no serious insect or disease problems and are deer and rabbit proof. They’re fertilized in the spring as new growth begins to emerge. Feed with slow-release fertilizer such as 14-14-14 Osmocote™, 13-13-13 Nutricote™, or equivalent.

Hypearls® St. John’s Wort Worth The Hype

Posted by Hugh on March 15th, 2014

Hypericum 'Hypearls Renu' at University of Tennessee Gardens, Knoxville

St. John’s Wort’s (Hypericum spp.) are terrific landscape shrubs and ground covers with bright yellow flowers in late spring and colorful berry fruits starting in late summer (USDA hardiness zones 5-9). Bees and birds are attracted to flowers and fruits respectively.

Hypearls® are a new series of hypericums. Cultivars are available in four compact growing sizes, ranging in height from 24-36 inches. The yellow cup-shaped flowers contain numerous stamens; they bloom reliably from July thru September. Attractive berry fruits follow, in colors from cream to red, depending on cultivar. Cut shoots are long lasting and make attractive additions to floral arrangements.

Hypearls hypericums should be planted in full to partial sunlight for heaviest flowering. They grow in average soil as long as it well-drained soil to prevent root rot, a major malady of hypericums. Newly-planted hypericums may initially suffer from leaf burn but quickly recover. Once established, they are heat-lovers. Prune in early spring if you wish to control shrub size or shape.

Hypearls are well-branched with robust foliage, flowering and fruit set. Bright one-inch yellow/gold flowers in July give way to showy cream, red, salmon or pink berries in August.

• ‘Hypearls Jacqueline’ grows 28 inches tall and the berries start out yellow-orange and mature to deep red.
• ‘Hypearls Jessica’ grows 25 inches with round cream-colored berries.
• ‘Hypearls Olivia’ is the tallest at 36 inches, and newly-formed yellow berries mature to a striking salmon color.
• ‘Hypearls Renu’ reaches 30 inches in height and the round cream berries finish bright pink. New foliage has a reddish tint.

Start Spring Out with Easy To Grow Japanese Pieris

Posted by Hugh on March 12th, 2014

Japanese Pieris in Conlon Garden

Japanese pieris (Pieris japonica) offers a year-round show in a garden with evergreen foliage and showy bell-shaped blooms (USDA hardiness zones 5- 8). New spring foliage starts out bronze-colored and matures to dark green. Attractive, pendulous branches if ivory white flower appears in early spring. Remnants of the old seed heads generally persist into the following winter.

Japanese pieris grows best in part sun to light shade. It requires more shade in southern locations and will tolerate almost full day sunlight in northern climes. Do not crowd plants as pieris must have good air movement to ward off potential mildew and leaf spot ailments.

Pieris grows 4-5 feet high and 3 feet wide depending on the cultivar planted. Growth rate is moderate to fast, depending on the level of care provided. Offer pieris irrigation over a long summer dry spell. It thrives in compost rich well drained acidic soil. A soil pH between 5.5 and 6.0 is ideal.

Numerous cultivars abound. Good cultivar selection is key to long term survival. Some of my favorites include ‘Mountain Fire’ (fire-red new foliage), ‘Little Heath’ (gold-edged foliage on slow-growing plant), ‘Dorothy Wyckoff’ (compact growth habit), and ‘Cavatine’ (cold hardy dwarf form perfect in rock gardens). New in the Southern Living Plant Collection™ is Mountain Snow™, rated as more heat tolerant than other pieris cultivars.

Japanese pieris is a low maintenance shrub that either stands alone as a specimen, plant several enmasse, or grow in large 15 gallon or larger wide containers in zone 6 and warmer climes. Pruning needs are minimal, usually following the spring bloom cycle.

Re-starting Summer Flowering Shrubs After Winter Injury

Posted by Hugh on March 9th, 2014

Chaste tree (Vitex agnus-castus)

Some non-hardy shrubs can be treated as hardy perennials. Crape myrtles (Lagerstroemia indica) and chastetree (Vitex agnus-castus) may emerge in poor condition after an unusually cold winter. Shrubs like butterfly bush (Buddleia spp.), and blue mist (Caryopteris spp.) often emerge in a ragged state, but recover quicker if cutback near the ground several weeks before spring bud break.

All examples are summer bloomers on current season’s wood. Renewal pruning is easy to understand, essentially cutting a shrub back to 3-6 inches above the ground. There is no advanced waiting required before grabbing a lopping shears or chain saw to perform this task.

After pruning follow-up by feeding the cutback shrubs. Each shrub or tree should receive a heaping handful of 10-10-10 or equivalent granular fertilizer. Fertilizer should be spread 12-18 inches away for the crown (base) of the tree or shrub. One caveat: the shrub should be healthy before renewal pruning is tried. A weak plant is unlikely to survive this technique, but will likely grow and bloom poorly if you had not acted.

By mid-spring, many shoots are likely to grow around the shrub base. A follow-up pruning may be needed if you desire a taller shrub. Leaving many multiple shoots will reduce plant height. Also, the amount of sunlight penetrating the plant will be inadequate, resulting in poor summer flowering.

Plant Native Allegheny Spurge More

Posted by Hugh on March 6th, 2014

Young Spring Green Leaves of Allegheny spurge

Japanese pachysandra (Pachysandra terminalis) is a popular ground cover for partly shaded landscape areas. Our native pachsandra, called Allegheny spurge (P. procumbens), is less known and utilized.

The glossy dark evergreen leaves are wider than Japanese pachysandra. Clusters of white bottlebrush flowers emerge 2-4 inches high in early spring; flowers mature pale pink as new mid-spring foliage emerges. Leaves take on a mottled, matted green look in late summer. The foliage mats down to retard soil erosion on slopes and to crowd out competing weeds.

Individual plants tend to clump or mound and grow 50% slower than their Asian kin. Japanese pachysandra is winter hardier (USDA hardiness zone 4) compared to Allegheny spurge (zone 5). Both grow well under shade trees, particularly where ornamental grasses tend not to prosper.

Allegheny spurge likes a slightly acidic (pH 5.6 – 6.6), moist, well-drained soil. In USDA zone 6 and further south, full day sunlight tends to burn the foliage. Before planting amend the ground with generous amounts of sphagnum peat or compost. Apply a slow-release 10-10-10 fertilizer once in early spring; or use a water-soluble fertilizer designated for acid-loving plants and apply 2-3 times over the season, but no later than late August.

Over its initial two years, irrigate native spurge to get a good start. Leaf spot diseases are rarely problematic unless plants are frequently watered overhead. It mixes well with other shade perennials such as bleeding hearts (Dicentra), lungworts (Pulmonaria), dwarf Solomon seals (Polygonatum), brunneras, and assorted ferns.

Fall Look Of Allegheny Spurge

Early Spring Flowering Okame Cherry

Posted by Hugh on March 3rd, 2014

Mid- March Flowering Okame Cherry

‘Okame’ Cherry is a hybrid between Taiwan Cherry (Prunus campanulata) and Fuji Cherry (P. incisa) (USDA hardiness zones 6-8). Okame is the first ornamental cherry to bloom in the Southern Appalachian Region (USDA hardiness zones 6 and 7).

In the midst of a mild winter, Okame often starts blooming a few days after Valentine’s Day (February 14). Most years their lovely fuchsia pink flowers appear in mid-March and survive overnight temperatures in the upper twenties °F.

Following petal fall the dark red calyxes stay on for another 2-3 weeks. In early summer dark red ovoid drupe fruits ripen and are consumed by numerous species of birds.

Spring leaves start out bronze tinted and turn dark green and glossy through spring and summer. Foliage turn bronze-red before dropping in mid-autumn. Okame’s polished reddish-brown bark is marked with gray horizontal lines called “lenticels”.

Okame matures into a small tree, 20 to 30 feet in height and 10 to 15 feet wide. The tree’s upright branch form makes it an ideal candidate as a street tree. Don’t neglect summer watering its first two years after planting.

Okame is best planted in well-drained loamy soil and in open full sun. The tree tolerates light shade, but blooms heaviest in full sun. As a rule, ornamental cherries are susceptible to several diseases and pests, but Okame cherry is more resistant than most. In early summer inspect tree(s) for Japanese beetles, scale and spider mites and treat accordingly. Prune annually to remove dead, diseased or pest ridden branches, if any. Good air movement around tree also helps.

‘First Lady’ and ‘Dream Catcher’ are 2003 and 1999 U.S. National Arboretum releases respectively. Both are rated as improved hybrid forms of Okame cherry. Both cultivars typically grow 20-30 feet tall with upright branching. Branch tips are weep slightly, and are blanketed with single, dark rose-pink flowers in late March to early April.

Sweetbox – Excellent Evergreen Shrub For Shady Areas

Posted by Hugh on February 28th, 2014

Late Winter View of Sweetbox

Few evergreen shrubs grow in the shade. Sweetbox (Sarcococca hookeriana var. humilis) is a compact dwarf evergreen shrub or ground cover which is easy to grow (USDA hardiness zone 5-b to 8). Foliage remains lustrous dark green year-round.

Sweetbox grows in partial to full shade, 1 to 2 feet tall and 6 to 8 feet in spread. Fragrant white flowers appear in mid-to late winter which your nose may sense before your eyes. Blue-black berry-like fruits ripen in fall and winter and are quickly consumed by birds.

Sweetbox grows best in mildly acidic, well-drained, compost-rich soil. If two or more, space plants 5-6 feet apart. Feed with a 6-month rated slow-release fertilizer yearly or fertilize with a water-soluble fertilizer for acid-loving plants. Irrigate during the summer months when weekly rainfall amounts are infrequent. Two-year established plants exhibit good drought tolerance.

Sweetbox, a member of the boxwood family (Buxaceae), provides a dark green backdrop for spring-flowering bulbs and shade-loving perennials. It forms a long-lived ground cover beneath deciduous trees. Its evergreen foliage is utilized in making fall-winter wreaths and other holiday displays.

Rake tree debris, e.g. twigs and leaves, away from the planting to keep sweetbox looking neat. Disease and pest problems are rare. Foliage is resistant to many air pollutants. Scale may occasionally become a serious pest.

Sweetbox is rarely sold at local garden centers, but is easily purchased on-line. Because sweetbox is slow-growing, it does cost a bit more, but is a worthwhile long-term investment.

Challenging Sourwood Worth A Try

Posted by Hugh on February 25th, 2014

Beautiful July Flowering Sourwood Tree

Sourwood (Oxydendrum arboreum), aka lily of the valley tree, is one of the most beautiful U.S. native flowering trees (USDA hardiness zones 5-9). However, attempting to establish one in your landscape may prove challenging.

The tree grows in sparse populations from eastern Tennessee, western North Carolina, and Georgia Piedmont. It grows naturally to 20-30 feet tall shrub and 35-40 feet tall tree. Most trees grow in a narrow pyramidal form, less than 15 to 20 feet wide.

Sourwood offers four seasons of landscape beauty. Delicate-looking white fragrant flowers (racemes) open in early July and may bloom 3 to 4 weeks. The pendulous 10 to 16 inch long creamy bell-shaped floral sprays drape from the growing tips of branches. The seed capsules turn gray in late fall and persist through the winter.

Sourwood‘s spectacular fall leaf color is an array of burgundy, scarlet, and purple lasting over 2 to 3 weeks. Its deeply fissured bark is similar to persimmon, and easier to view after autumnal leaf drop.

Sourwood prefers well-drained acidic soil and sited in full or partial sunlight. A tree in heavy shade does not bloom as well or provide a spectacular fall foliage as one in mostly full sunlight.

Few cultivars are available. Reasons to nurture a sourwood tree in your landscape: July flowering time, lily of the valley floral sprays, awesome red fall color, major winter food source (seed) for birds and wildlife, and delicious sourwood honey. Flowers attract numerous bees and butterflies.

See also blog titled: “Tips For Growing Sourwood”

Tips On Growing Sourwood Trees

Posted by Hugh on February 22nd, 2014

Awesome Fall Color Of Sourwood In Western North Carolina

Sourwood (Oxydendrum arboreum) is one of the most beautiful flowering trees in the U.S. Trying to establish one in your landscape can prove quite challenging. In the wild sourwood grows in shallow soils on steep craggy or rocky ground. Dry ground seems to be the rule. It grows either multi-stemmed (shrub-like) to 20-30 feet or tree form to 35-40 feet and half that in width.

Sourwood is a pioneering species. Tiny dehiscent seeds are dispersed into the wind and blown like dust over many acres of land. Tens of thousands of seedlings germinate each spring on new ground that may have been previously clear cut for reclamation. If available, supply water intermittently over dry periods the first two summers. Established trees tend to better cope with heat and dry soils.

For a home gardener the challenge seems to be getting one established. Site them in the type of soil and environmental conditions which rhododendrons and mountain laurels enjoy. They prefer a loose, gravelly, acidic soil containing some organic matter and excellent drainage. A newly-planted sourwood prioritizes by establishing its root system first.

Purchase primarily nursery container-grown trees, if you can find them. Plant in well-drained soil and prune the new tree or shrub back to 6-12 inches from the ground in early spring. Essentially, you are starting over with 100% root system and 10-15% top (shoot). What comes up is your new tree, more vigorous than one not pruned.

In nature sourwood seem to prefer the eastern facing slope of the woodland where they receive midday sun. Young transplants respond to fertilizing; older well-established trees do not. Sourwood requires little pruning and has few serious insect or disease problems.

Prune to Rejuvenate Old Foundation Shrubs

Posted by Hugh on February 18th, 2014

Old fashion Nandina in Desperate Need of Pruning

Eventually, old foundation shrubs around your home grow too tall and spindly and need to be started over. Rather than digging them up, most deciduous and a few broadleaf shrubs respond to rejuvenation pruning. Sorry, evergreen conifers do not respond to this form of pruning.

Get started with a sharp pair of pruning loppers or tree saw for the large cuts and hand pruners for smaller cuts. February and March are good times to rejuvenate old shrubs.

Before getting started with pruning, understand what you’re about to do. You desire a low, dense-growing multi-stemmed shrub. Pruning reduces shrub size and redirects new growth from surface roots and above-ground shoots.

Remove the tallest and thickest woody shoots to the ground. Cutback pencil-thick shoots to 12-18 inches from the ground. Remove all weak or dead stems flush to the ground.

After pruning, feed the shrubs, applying 1-2 handfuls of 10-10-10 (or equivalent) granular fertilizer in a 1-2 feet wide circle around each shrub. Disperse no fertilizer closer than 6 inches from the shrub base.

Rejuvenated shrubs should vigorously re-grow in the spring and summer months. Summer flowering shrubs likely will not bloom the first year after pruning.

Caveat: pruned shrubs must be in good health before attempting to rejuvenate them. If they have not re-grown by late May, a trip to the garden center to purchase new plants is in order.