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

Three Beautiful Ornamental Crabapples

Posted by Hugh on April 4th, 2014

'Prairifire' Crabapple

Crabapples (Malus spp.) get a bad rap! Many gardeners associated them with the old diseased and pest prone varieties planted a half-century ago. Modern cultivars make nice small ornamental trees. The new cultivars exhibit exceptional resistance to five serious diseases of crabapples: apple scab, fire blight, cedar-apple rust, leaf spot and powdery mildew. Three of the best cultivars include ‘Prairifire’, Sugar Tyme™ (Malus ‘Sutyzam’), and ‘Louisa’ (Malus ‘Louisa’) crabapples.

Sugar Tyme crabapple has moderate upright branching and forms an oval tree top or canopy. It matures to 20 by 15 feet in height and spread. Pink in bud, flowers open snowy white. The mostly blemish-free dark green summer leaves turn a bronzy to yellow in mid-autumn. The ½-inch diameter ruby red fruit ripen in fall and persist through winter.

Prairifire (listed also as “Prairie Fire”) forms a densely round deciduous tree, 15 by 20 feet in height and spread at maturity. Pinkish-red buds open to lightly fragrant red flowers. A good annual crop of small ½ -inch diameter purplish-red fruits ripen in the fall and persist through the winter.

Louisa is a weeping, pink-flowered crabapple tree that typically matures 15 to 18 feet high and wide. The cascading branches may be lopped off anytime they touch the ground. Reddish floral buds open to fragrant light pink blossoms. Tiny 3/8-inch diameter fruits mature to yellow with a pale rosy blush and persist well into winter.

Crabapples grow in compost-rich, well-drained acidic soil, and in full sun. Prune the tree(s), as needed, after flowering before the end of May (USDA Zones 4–8). All three cultivars produce no messy fruits, most of which are consumed by hungry winter-feeding birds. If you’re tired of the Bradford pear look, plant a crabapple.

Attracting Monarch Butterflies To Your Garden

Posted by Hugh on April 1st, 2014

Monarch Butterfly (Kris Light photo)

From Canada to Mexico, gardeners are called upon to halt the decline of the Monarch butterfly populations across North America. The best way you can help is to fill your garden with Monarch’s favorite flowering nectar plants and milkweeds (Asclepias spp.). Plants should be sited in open full sun and moist well-drained soil. Avoid spraying pesticides within several hundred square feet of the designated butterfly planting.

Nectar plants are a food source for adult butterflies. Butterflies feed on the nectar which also helps to pollinate flowers. Select brightly colored flowers which are native to your area. Common nectar plants for monarchs include blackeyed Susan (Rudbeckia spp.), beebalm (Monarda spp.), anise hyssop (Agastache spp.), cosmos, aster (Symphyotrichum spp.), purple coneflower (Echinacea purpurea), lantana, Mexican sunflower (Tithonia), ironweed (Vernonia lettermannia), butterfly shrub (Buddleia spp.), marigold (Tagetes spp.), tall growing sedums (Sedum spectabile), Joe-Pye (Eupatorium spp.), blazing star (Liatris spp.), and zinnia.

Add larval-host plants to attract more butterflies to your garden. All butterflies need larval-host plants upon which to lay their eggs. In the case of Monarch caterpillars, the only host plants are the milkweeds (Asclepias spp.). Some favorite milkweed species include: common milkweed (A. syriaca) for large acreage gardens and swamp milkweed (A. incarnata) for smaller garden plots. Showy milkweed (A. speciosa), bloodflower (tropical milkweed) (A. curassavica), and butterfly milkweed (A. tuberosa) are some others.

For best results, add a varied number of flowering plants with staggered bloom times to keep butterflies grazing in your garden through the entire growing season. The local garden center may offer additional plants not listed here.

You can help rebuild the monarch population by planting colorful milkweeds and native nectar plants in your garden this spring.

Beautiful Giant Dogwood Has Some Limitations

Posted by Hugh on March 28th, 2014

Variegated Form of Giant Dogwood in Vancouver, BC

Giant dogwood (Cornus controversa) is a medium-sized deciduous tree that grows to 35 to 40 feet high (in the wild to 60 feet) in USDA hardiness zones 5 to 7. This Asian native (China and Japan) is cherished for its distinctive horizontal (tiered) branching habit.

Giant dogwood prefers an acidic, organically rich, moisture, well-drained soil. It succeeds in full sun to part shade, depending where you live. It thrives in cool climates such as the Northeast and Northwest U.S. regions. It languishes in the Southeast U.S. unless planted in a shady nook.

Small, creamy-white flowers appear in flattened 3-6 inches wide cymes (clusters) in late spring (May-June). The individual flowers are small and not bracted like flowering dogwood (C. florida). Giant dogwood is quite attractive in full bloom. Flowers give way to clusters of ½ inch bluish-black drupe fruits that mature in late summer. Scads of birds will inform you when they are ripe.

Leaf arrangement is uniquely alternate, sharing this trait with our native Pagoda dogwood (C. alternifolia). Dark green oval-shaped leaves are 3-6 inches long and light green beneath. Fall color varies region by region across the U.S., and hues are typically faded green to bland yellow. The cultivar ‘Variegata’ is a standout with dark green summer leaves edged with creamy white margins.

Giant dogwood is susceptible to a number of disease and pest problems. Location…location…location plays an important role here. Leaf spot, root rot, and stem canker may be severe in some years, often weather-induced. Scale, leaf miner and borers are occasional pest issues. Generally, deer do not favor dogwood leaves and twigs.

Perhaps, a final limitation is that growth buds tend to break too early in the spring and the new leaves get nipped by frost in northerly areas. Where climate and soils are favorable, this dogwood offers much year-round appeal.

Serviceberry- Favorite Tree of Gardeners And Birdwatchers

Posted by Hugh on March 24th, 2014

'Autumn Brilliance' Serviceberry in Conlon Garden

On an early late winter’s morn, the frosty appearance from a nearby mountainside may actually be from our native serviceberries (Amelanchier spp.) (USDA hardiness zones 4-9). Serviceberry’s small white blooms frequently signals that winter’s end is near. Flowering may last 7-10 days.

Downy serviceberry (A. arborea) and shrubby Allegheny serviceberry (A. laevis) are commonly planted. Amelanchier is regionally called many names, including shadbush, shadblow, sarvisberry, sarvis tree, and Juneberry. The latter refers to the small greenish-blue, ripening red fruits in late May in the Southern Appalachian region (USDA hardiness zones 6 and 7).

Berry hungry birds don’t wait for fruits to ripen before devouring them. A popular favorite among native tree and bird watchers, the average full service garden center stocks very few during their spring sales rush.

Annual growth rate is rapid, 20 to 30 feet tall and 15-20 feet wide. Serviceberry tolerates many types of soil, preferring a moist, acidic, well-drained soil, and partial to full day sun. The tree often develops multi-trunked. Water and mulch a newly planted tree until it is established. Within two years a tree can handle moderately dry spells. If pruning is needed, do so in the spring after flowering.

In most years, serviceberries suffer from few disease and pest issues. In a rare wet summer, severe leaf spotting may force leaves to rain down in August and dash all hopes of fall color. Both Autumn Brilliance™ and Princess Diana™ are popular cultivars with stunning red fall color in most years.

Serviceberry’s multi-trunked branching fashions a wonderful winter silhouette on a dreary snowy day.

Yoshino Flowering Cherry Is Southern Favorite

Posted by Hugh on March 21st, 2014

Street Planting of Yoshino Cherries in Johnson City, TN

In The Southeast U.S. most ornamental flowering cherry trees (Prunus spp.) are challenged by summer heat and humidity. ‘Yoshino Cherry’ (Prunus x yedoensis) continues to be the top performer in the group (USDA hardiness zones 5-8).

In 1912, the Japanese government gifted the United States 3000 Yoshino flowering cherries. In the years that followed, Yoshino became the premier flowering cherry at spring festivals in Washington, DC, Macon, Georgia, and other locales.

Yoshino is native to Japan, Korea and China. The beautiful blossoms cover every twig on the tree. The white to pink flowers are slightly fragrant. The trees flower dependably every spring although late winter freezes may damage some flower buds.

A mature Yoshino reaches 20 feet tall and 15 feet wide. Its compact form makes it a good fit on small residential spaces along with other spring beauties such as crabapples, azaleas, forsythias, and others.

Yoshino should be planted in moist well-drained soil and in full day sun. Properly mulch a young Yoshino until tree becomes well established. Insect borers and stem canker diseases can be serious problems. Growth rate is rapid and disease pressure less when properly sited. Annual pruning within a month after bloom is recommended to remove root suckers, broken branches, and diseased wood.

Several cultivars of Yoshino cherry are available at garden centers exhibiting slightly different traits:
‘Akebono’ (aka ‘Daybreak’) – soft pink double flowers
Cascade Snow™ – snow white flowers, dark green summer foliage turns yellow-orange in fall; highly disease resistant
‘Ivensii’ – fragrant white flowers on weeping branches
‘Pink Shell’ – flower buds open pink and fade to white
‘Yoshino Pink’ – later blooming pink cultivar

‘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.