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

Don’t Shy Away From Annual Vincas (Periwinkles)

Posted by Hugh on April 23rd, 2014

Annual vinca or periwinkle (Catharanthus roseus) is a summer flowering annual popular in Southern and Midwest gardens (USDA hardiness zones 9-11). When summer’s heat and humidity soars, vincas look their best and bloom the heaviest. Vincas sparkle in containers, in flower beds, or in front borders around building foundations.

Transplants are set out in mid-spring after soils have warmed up and all threats of frost have passed. Vincas grow best in well-drained, organically rich, loamy soil and in full or part sun. Fertilize at planting with a second application in late July. Vincas enjoy occasional watering during prolonged dry spells but avoid sprinkling overhead. Established plants (after 4 to 5 weeks) are rated moderately drought tolerant.

Most modern day cultivars grow short and compact. They vary from 6 to 18 inches in height and spread. An individual flower is composed of five flattened petals attached to a tubular base. A wide range of flower colors include lavender, red, rose, salmon, several shades of pink, and white. Some cultivars exhibit a center eye in the flowers. Old blooms are self-cleaning and never messy. The 1-2 inch long leaves are dark green and glossy.

Most new cultivars contract few, if any, serious insect or disease problems. Plant vincas on an open site with good air circulation to prevent stem and root rot diseases (phytophtora) and bacterial leaf spots. Slugs and snails can occasionally become pesky in wet summers.

Popular vinca series at garden centers are Aztec, Cooler, Cora, Pacifica and Viper. Vincas often self-seed and re-appear in garden beds several years hence.

Growing Sunflowers Fun Family Activity

Posted by Hugh on April 20th, 2014

Sunflowers Growing In Front Of Home

Growing sunflowers (Helianthus annuus) are the current rage. Sunflowers are native to Central America and have been cultivated for thousands of years. Sunflowers are classified as annuals, living one growing season, and often returning the following spring from seeds dropped the previous fall. Some gardeners put out large beds to feed the birds.

Sunflowers come in many varieties, some 3-5 feet tall with yellow, cream, or red flowers; others 10 feet and more tall giants with sturdy stems and blooms nearly a foot across. Most varieties mature in 70 to 90 days or more. Read the seed package for plant heights and harvest time (ripening).

Sunflowers are easy to start from seed. Sow seeds 4-6 inches apart and cover them with plastic mesh or screen until several have poked their heads up (germinated). Otherwise, birds and animals may dig the seeds up. You can also start seeds in a small protected seedbed, seed flat, or pot and transplant each individually when they’re a few inches tall. For a head start on spring, you may opt to begin 2 to 3 weeks earlier indoors in individual peat pots. Sow 1 to 2 seeds per pot, and thin to one before planting outdoors after the spring frost period.

Sunflower plants grow well in average to rich soil. They grow best in full sun, but do tolerate light shade. They perform better in deep soil for roots to become firmly anchored to withstand strong winds and dry spells.

They do benefit from heavy feeding with 10-10-10 or an equivalent fertilizer at planting time and again 8-10 weeks later. Nitrogen (N) promotes plant growth and sturdiness. Adequate phosphorus (P) and potassium (K) in the soil increases flower bud numbers and bigger blooms.

Tall sunflowers serve as good companions interplanted with ground trailing cucumbers, melons, pumpkins, or squashes. Plant only 5-6 sunflowers per 100 square feet, so not to shade the vines below.

Insects and diseases are seldom problems, particularly on new ground. The birds and squirrels are primary invaders of a sunflower crop, all coming to feast on the delicious oily seeds.

Western North Carolina Highway Planting of Sunflowers Near Asheville, NC

‘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.