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

‘Miss Kim’ Lilac Tackles Southeast U.S. Heat and Humidity

Posted by Hugh on April 17th, 2014

'Miss Kim' Lilac

When northerners move south, they insist on growing lilacs (Syringa spp.). Southern U.S. heat and humidity often take their toll on these lovely fragrant and colorful spring flowering shrubs (USDA hardiness zones 3-8).

One very popular and exceptionally reliable lilac is ‘Miss Kim’ lilac (S. pubescens ssp. patula ‘Miss Kim’). A cultivar of Manchurian lilac, it develops into a compact, upright branched, 5 to 7 foot deciduous shrub. The sweetly fragrant lavender (in bud), ice blue single flowers form in dense panicles or clusters. Flower panicles average 3 inches in length and cover the shrub in early May.
Prompt removal of faded flower panicles before seed set will increase bloom count next spring.

The rounded (ovate) 4-5 inch dark green leaves develop a burgundy look before dropping in the autumn. Miss Kim does not sucker like some lilac cultivars. It has no serious insect or disease problems. Miss Kim lilac exhibits high resistance to powdery mildew. Deer don’t seem to bother lilacs unless favorite food sources are depleted. Lilac blooms attract numerous hummingbirds and butterflies.

Lilacs are not fussy growers, and thrive in average, mildly acidic to neutral pH, well-drained soils. They tolerate light shade, but flowering and overall performance are best in full sun. Avoid overcrowding for good air circulation to prevent or reduce mildew disease.

‘Miss Kim has been the top performing lilac in the Southern Appalachian region (USDA hardiness zones 6 and 7). Cutflowers decorate dining table when Miss Kim is in bloom.

Mighty Rodgersias For Your Shade Garden

Posted by Hugh on April 14th, 2014

Rodgersia In Vancouver Botanical Garden, BC, Canada

In a shade garden the large palmately compound foliage of rodgersias (Rodgersia spp.) make a bold statement (USDA hardiness zones 4-9). In recent years rodgersias are becoming more available at garden centers in the U.S. Three of five species are listed below. Hybrid forms are also available.

Rodgersias thrive in moist, organically rich soils. They want either half-day direct morning sun or partial shade all day long. They also prefer a cool location. Shoots emerge slowly in late spring. The edge of a bog garden, pond, or in a damp meadow are good places to grow rodgersias, along with other moisture loving plants as ferns, toad lilies (Tricytris spp.), sweet flags (Acorus gramineus), ligularias, astilbes, and hostas.

Give rodgersia three years to bulk up. Their size and leaf texture will make them a focal point in your shade garden. Plants grow 3 to 6 feet tall depending on species, soil quality, nutritional level, plant age, and soil moisture. In late spring/early summer, white flowers rise high above the foliage and the old floral heads age gracefully. Rodgersias exhibit few disease or pest problems.

Fingerleaf rodgersia (Rodgersia aesculifolia) is the most available in the U.S. Native to China it grows 3 to 5 feet tall and wide and features thick blackened rhizomes (USDA hardiness zones 5-9). The attractive non- petalled (apetulous) flowers are fragrant and the flower stalks, stems and leaf margins are covered with brown hairs. Flowers stand well above the foliage. The large, crinkled, coarsely-toothed, palmate, dark green, basal leaves span 12 inches across with seven (vary from 6-9) leaflets. The foliage of cultivar ‘Chocolate Wings’ remains dark bronze all season long.

Featherleaf rodgersia (Rodgersia pinnata) grows 3 to 4 feet tall and wide. Leaves arranged in pairs. Clusters of apetulous, white, creamy-pink, or rose-red flowers arise high above the foliage. Each of the 6-9 palmate leaflets range from 6-8 inches in length. By late summer foliage has turned reddish-bronze. ‘Superba’ is a popular cultivar with bronze-tinted foliage all season and bright pink flowers.

Bronze-leaf rodgersia (Rodgersia podophylla) exhibit 5 large, jagged palmate leaflets that emerge bronze-green in the spring, green in summer, and rust red in the fall (5-8). It grows 3 to 6 feet high and wide. The creamy white foot long flowers tower above the foliage.

Join The Brunnera Revolution

Posted by Hugh on April 10th, 2014

'King's Ransom' Brunnera

Over the past decade heartleaf brunnera (Brunnera macrophylla), aka Siberian Bugloss and Alkanet, has become a popular spring flowering perennial in U.S. and Canadian gardens (USDA plant hardiness zones 3 – 8). Native to Russia brunnera need little care when properly sited. Sprays of tiny blue-petalled /yellow centered forget-me-not flowers explode into a blue haze in mid-spring.

Brunneras continue to get better and better with several sensational cultivars recently introduced. The old-fashioned green leaf species from your grandmother’s garden have been transformed into gorgeous foliage creations.

Plants grow low and wide. Medium green leafy mounds stand 10 to 12 inches high and 18 to 24 inches wide. Bottom leaves on 1-2 year old plants may size 3–4 inches in diameter, and even broader on older plants under optimum growing conditions.

In the warmer Southern zones (6 – 8), shelter brunneras in partial to full shade and in moist compost-rich soils to avoid summer leaf scorch. Two-year old established brunneras will tolerate moderate drought. Plant foliage is highly disease and pest resistant, but may become marred by nematodes in late summer. Mulching proves to be highly beneficial in preventing this malady.

Brunneras make great shade garden companions with foam flower (Tiarella spp.), coralbells (Heuchera spp.), barrenworts (Epimedium spp.), Solomon seal (Polygonatum spp.), small-leaved hostas (Hosta spp.), and many others. Popular cultivars include:

‘Jack Frost’ – green-veined circular leaves with matted silver coating (sport of ‘Langtrees’).
‘Looking Glass’ – glossy silver leaf surface (sport of ‘Jack Frost’)
‘King’s Ransom’ – frosty coated leaf surface and creamy white margins
‘Langtrees’(aka ‘Aluminum Spot’) – dark green leaves with prominent silver flecks at leaf center which radiate out.
‘Sea Heart’ – pink-budded, opening blue flowers; thick silvery leaves with prominent dark green venation; heat and humidity tolerant.
‘Silver Heart’ – large thick pure silver foliage, netted with light green veins; heat and humidity tolerant.

Pest Alert: Kudzu Bug- Plant Pest And Home Invader

Posted by Hugh on April 7th, 2014

Kudzu bug (photo supplied by John Rochelle, Plant Inspector, TN Dept. Of Agriculture

Kudzu bug was first seen in Atlanta, Georgia in 2009. Currently, this plant pest and home invader has spread rapidly through the southern U.S. (to Texas) and as far north as eastern Maryland and southern Delaware. Kudzu bug belongs to the shield bug family (Plataspidae), but does emit a strong odor. It secretes a noxious chemical that can cause eye and skin irritation.

The bug prefers to feed on legume plants in the legume family such as redbud, yellowwood, black locust and wisteria and crop plants like soybeans and lespedeza. It will devour an entire hillside of kudzu where it likes to overwinter. In North Carolina adults emerge in May and produce two generations per year.

In the spring adults emerge from protected overwintering sites in search of kudzu and to mate and lay eggs. A second generation moves into soybean or other bean fields later in the summer. In the fall, the bugs return to kudzu or protected areas such as plant debris, tree bark, homes or other structures. Kudzu bugs are drawn to light colors, and can become a major home invader.

Since kudzu bug is a recent pest in the U.S., management options are currently being worked out. Pyrethroid insecticides appears to be effective against kudzu bugs. Young nymphs seem to be the most susceptible stage. In the fall pyrethroids can also be sprayed on exteriors of houses where kudzu bugs are congregating. Use any insecticide according to labeled directions for the crop. Removal of kudzu in areas adjacent to fields is recommended when possible since this is the first host plant the insect seeks after emerging from its overwintering location.

Special thanks: Mr. John Rochelle and Adam Blalock for information contained in this blog.

‘Thailand Giant’ Elephant Ear Fun Novelty

Posted by Hugh on April 6th, 2014

Enormous Foliage of 'Thailand Giant' Elephant Ears

‘Thailand Giant’ elephant ear (Colocasia gigantea) is rated as an annual (USDA hardiness zone 8-10), where the growing season may last 300 days and longer. Thailand Giant develops into a massive 9- foot tall plant with attractive grey-green foliage species. In the Southern Appalachian and Middle Atlantic regions they may reach 5 – 6 feet before autumn freezes killed this non-hardy tropical elephant ear. Its gigantic leaves and tropical appearance catches your eye.

Thailand Giant can be planted safely outdoors in a large heavy container or a garden bed in mid-May in the Southern Appalachian region (USDA hardiness zones 6 and 7). Heat, humidity, and soil moisture are key factors for success. It grows best in partial (6-hours minimum) to full sunlight and in a rich loamy well-drained soil. Deeply water Thailand Giant frequently during long rainless intervals, 2 inches or more weekly.

Clusters of large fragrant white flowers form at an early age, but most are hidden under the enormous sized foliage. It blooms all summer long. Individual leaves may grow in excess of 3-5 feet long and 2-3 feet in width when luxuriantly watered and fertilized on a regularly. Feed with a water-soluble fertilizer such as Miracle-Gro™ or Daniels™, applied every two weeks through late August.

In the fall before first frost, cut back the foliage, dig up the plant, cut off stems and leaves, and transplant into a large container filled with moist soil (or potting media). Store in a cool place (40-45 °F), such as an unheated garage, over the winter. Keep the potting media moderately (not totally) dry. The whole crown (minus leaves and petioles) should remain intact and dormant through the winter. Begin to re-watered in early spring as the frost threat has subsided.

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