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

‘Shaina’ Japanese Maple

Posted by Hugh on April 23rd, 2013

'Shaina' Japanese Maple at Atlanta Botanical Garden in April

The foliage of ‘Shaina’ Japanese maple (Acer palmatum ‘Shaina’) starts out hot red in early spring. The deeply cut leaves are bunched together for a tufted or layered look. From mid-spring thru summer, the foliage, now maroon red, holds its color.

Shaina grows naturally as a shrub, 8 feet high and 4 to 5 feet wide in 10-12 years. Some nurseries sell it in tree form, but it must be judiciously pruned to maintain this shape. Non-showy reddish flowers appear in May and contribute little in ornamental value.

Japanese maples should be plant in the right location, protected from high winds, and irrigated as needed. They grow in compost-rich, well-drained soil in full sun to partial shade. In more southerly locales, plant them in a full-day, partially shaded garden spot (USDA hardiness zones 6-9).

In general, Japanese maples contract few serious disease or pest problems. Stem canker maladies may arise if improperly sited or environmentally stressed. In northern areas spring foliage may pop out early and be injured by late night frosts. Covering with a cloth tarp is advised when frost warnings are posted in your area.

Shaina is a lovely understory shrub with attractive red foliage and plant form. Plant it as a specimen or a container accent plant near your home patio where guests can take notice.

Cool Blooming Osteospermums

Posted by Hugh on April 11th, 2013

Osteos at UGA Gardens in Athens, GA

Osteospermums (Osteospermum x hybrida ) are members of the daisy (Asteraceae) family, commonly called African Daisy, Blue-eyed Daisy, or Cape Daisy. Osteos are cool season annuals that excel in northern and less so in southern U.S. gardens. Osteos bloom more profusely in full sun, but want some cooling relief during the summers.

Osteos have always been a popular cutflower, but are now becoming a annual bedding plant. They should be planted early with petunias and million bells (Calibrachoa). The heat of summer knocks osteos out of bloom, but they often recover to bloom again in late summer. Keep them adequately watered the first month after planting.

Flat daisy-like petals radiate out in a tubular or spoon shape. Every year new color choices continue to win over gardeners. Plant breeders are improving summer heat-tolerance and introducing more compact growing cultivars. Color choices abound from lavender, pink, white, yellow and bi-color, with more introduced every year. Their dark green foliage may vary with the cultivar from lance- , ovate, and/or lobed- shaped.

They prefer an acidic soil, but perform well between 5.5 to 6.5 pH. Feed osteos on a bi-weekly basis with a water soluble fertilizer such as Miracle-Gro™, Jack’s™, or Schultz™ according to package directions. Although drought tolerant once established, osteos need one inch of water weekly to look their best.

During periods of intense heat and drought, growth slows or plants go dormant. Cut osteos back in late summer to stimulate new stems and leaves. Remove wilted flowers and old worn foliage to induce new flowering.

Osteos are super performers in hanging baskets and window boxes. Cultivar series vary from 12 – 36 inches in height by 12 – 24 inches in spread. Among the popular osteos are the Voltage®, 3D®, and Margarita® series.

Coastal Azalea Copes With Heavy Clay Soils

Posted by Hugh on April 4th, 2013

Rhododendron atlanticum at Duke Gardens in Durham, NC

Coastal Azalea (Rhododendron atlanticum) is a deciduous native azalea that grows along coastal plains of the Mid-Atlantic and Southeast U. S. Their white 1 to 1 ½ inch tubular flowers appear about the time that lilac petals are beginning to fading. Flowers are snowy white with a pinkish blush, and emit a distinctly clove fragrance. Blooms open a few days before the new spring foliage.

Coastal azalea forms a low compact deciduous shrub. It rarely grows taller than 4 feet in height and 4 to 6 feet wide. It should be grown in full sun (in zone 5b -6) and in partial shade (zones 7-8). Coastal azalea grows best in a well- drained acidic soil. It should be watered during prolonged summer dry spells. Its bluish-green foliage remains disease and pest free if plants are not environmentally stressed.

Coastal azaleas are highly stoloniferous, spreading by underground stems and forming small plant colonies around themselves. They tend to sucker a lot less in clay soils. The cultivar R. atlanticum ‘Winterthur’ has an outstanding compact growth habit and tends not to sucker.

R. atlanticum is parent to a number of hybrid deciduous azaleas:

‘Fragrant Star’ (R. canescens x R. atlanticum) – fragrant white flowers (slightly larger than ‘Snowbird’); 4 by 4 foot compact shrub with blue green foliage, introduced by Briggs Nursery in Olympia, WA.

‘Snowbird’ (R. atlanticum x R. canescens) – 4 by 4 foot compact shrub with blue green, mildew resistant foliage; introduced by Biltmore Estates in Asheville, NC.

‘Marydel’ (R. atlanticum x R. periclymenoides)- abundant pinkish-white, fragrant flowers from late April into May; introduced by the late Polly Hill.

‘My Mary’ [R. atlanticum x R. periclymenoides] x R. austrinum – very fragrant yellow flowers in late April.

Fall Color Calendar For Red Maple

Posted by Hugh on March 20th, 2013

'October Glory' red maple in East Tennessee

Red maple (Acer rubrum) is commonly planted as a 40-60 feet tall street or shade tree (USDA hardiness zones 3-9). Tiny red flowers burst open early, often in early March throughout the Southern Appalachian region (USDA hardiness zones 6 and 7). Flowers give way to reddish double winged samaras. Its glossy dark green 3-5 lobed leaves are 3-6 inches across and with deep red petioles. Red Maple’s most identifiable trait is its vibrant autumn leaf colors, which can vary by a month or more depending on cultivar.

Red maple is native to moist well drained soils, preferably in full to partial sunlight. It tolerates wet soils and is unswayed by temporary flooding, such as in rain gardens. In some Midwest states it has earned the nickname “swamp maple”. It is resistant to urban air pollutants.

Red maple may be troubled by insect or disease problems, often when tree is planted on a poor landscape site. Leaf aphids, wood borers and scale insects can be occasional pests. Verticillium wilt disease attacks the vascular system, frequently the result of unusually long dry spells lasting three or more years.

Red maple is sometimes called “soft maple” because high winds and ice storms may break branches. Its notoriously shallow root system may raise adjacent sidewalks or driveways. Pruning is best postponed until the spring and summer months when sap pressure in low. Sap from this species can be used to make maple syrup.

Five popular cultivars (rated by fall leaf color date) in the southeast and mid-Atlantic states include:
Autumn Blaze® (A. x freemanii) – 50 ft. x 40 ft. – earliest deep burgundy red leaf color
Red Sunset® (A. rubrum) – 45 ft. x 35 ft. – early bright red leaf color
‘Autumn Flame’ (A. rubrum) – 35 ft. x 15 ft. – better red color in southeast U.S.
‘Armstrong’ (A. rubrum) – 45 ft x 15 ft. – columnar habit for narrow street plantings and variable fall color
October Glory® (A. rubrum) – 40 ft. x 35 ft. – one of the latest for red fall color

Little Girl Magnolias Avoid Early Spring Frosts

Posted by Hugh on March 17th, 2013

'Susan' Magnolia

The early flowering deciduous magnolias, namely star (Magnolia stellata) and tulip (M. soulangeana) magnolias, are often susceptible to late winter-early spring frosts. In the 1980’s the U.S. National Arboretum released the series of 8 shrub-type cultivars called the “Little Girl Magnolias”. They were crosses between M. liliiflora and M. stellata. Over ten years these deciduous shrubs will grow 10- 20 feet tall and wide.

Little Girl magnolias represent a great leap forward in developing a later flowering forms. Each cultivar blooms 7-10 days later in spring. The large goblet-shaped flowers are long tepals (petals and sepals) which measure 6 to 9 inches in length. ‘Ann’, ‘Betty’, ‘Susan’, and ‘Jane’ have been the popular choices among the eight introduced cultivars.

Flower colors vary by cultivar in pink to purple shades. Little Girl magnolias often surprise with occasional blooms through the spring and summer months. They are commonly large multi-stemmed shrubs, which can be easily trained into small trees. The deciduous leaves are thick and leathery and cope with summer’s heat and dry spells. With proper care and on the right planting site, magnolias are generally long-lived and disease and pest free.

Little Girl magnolias grow in moist, well-drained soils, preferably with a slightly acidic pH, and in full to partial sun (3 – 4 hours minimum sunlight). They do not tolerate flooding or wet feet. Prune spring flowering magnolias soon after the spring flowering flush is over. Prune to remove basal suckers and to maintain the desired shrub or tree form.

Magnolias can be easily started by layering a branch to the ground in the spring. Bend the flexible shoot to the ground and hold down with a heavy rock. By autumn a rooted shoot may be cut away from the main branch, dug up, and moved to its new garden location or gifted to a garden friend.

Growing Pear Trees Too Challenging For Southeast Gardeners?

Posted by Hugh on February 15th, 2013

Pears To Be Harvested in Two Months

For many reasons growing pears in the Southeastern U.S. is very challenging. First, European (Pyrus communis) and Asian (P. pyrifera) pears are susceptible to fireblight (Erwinia amylovora). This bacterial disease is very difficult to manage. Two of the leading European pear varieties, ‘Bartlett’ and ‘Bosc’, are highly susceptible to fireblight. Varieties found to be fire blight resistant include: ‘Warren’, ‘Aires’, and ‘Moonglow’. ‘Shinto’, an Asian pear variety with russet brown fruits, exhibits above average fireblight resistance.

European pear varieties do not ripen on the tree. Fruits are harvested on the scheduled date for the variety and ripened indoors. Unripened pears should be stored in a closed plastic or paper bag (sack) for 7-10 days at room temperature (60-70 °F). Fruits may then be refrigerated to slow down their ripening. As with apples, Asian pears ripen on the tree, and are ready to eat when harvested. Asian pears are picked from late August to early October, depending on the variety grown.

European pear varieties will not pollinate Asian pears. Asian pears tend to bloom several days later than European varieties. Both European and Asian pears require cross-pollination from two or more different varieties which bloom near the same time.

Both European and Asian pears are notorious for “biennial bearing”. A tree may overproduce one year, and yield a small crop the next (the “off” year). Biennial bearing in the “on” year often results in limb breakage and smaller fruits. To prevent or break the biennial bearing cycle, remove excess fruit by hand within 30 days after full bloom in the “on” year. As a rule, 30-40 leaves support one pear fruit.

Finally, pruning pear trees can be a chore. Pears have a strong vertical branching form. Trees often grow tall and narrow, not easily within reach without a tall step ladder. Current pear dwarfing rootstocks have not been reliable, although better types may be available a few years away.

Witchhazels Invent Their Own Season

Posted by Hugh on January 7th, 2013

Hamamelis x intermedia 'Gingerbread' blooming in February

Witchhazels (Hamamelis spp.) are medium to large shrubs which can be shaped into small trees by judicious pruning. In general, all witchhazels grow in full sun but can prosper with moderate amounts of shade. Other than pruning, they require little extra care. Plant in any soil type as long as it is adequately drained and mildly acidic.

Species native to the Eastern United States include American witchhazel (H. virginiana) and vernal witchhazel (H. vernalis). Asian species include Chinese witchhazel (H. mollis), Japanese witchhazel (H. japonica), and hybrid forms (H. x intermedia). The witchhazel flower color palette ranges from pale yellow, deep gold, copper, and purplish red.

In calendar order, first to flower is Vernal witchhazel (USDA hardiness zone 4). Vernal is a densely branched 8 to 12 foot shrub which blooms from early to mid-winter. Usually, flowering follows a short warm period. Small ½ inch wide yellow flowers, flushed red at the base, emit a pleasant witchhazel aroma.

The Asian witchhazels follow from mid-February thru most of March. Flowers of many new cultivars are larger and brighter colored. Among witchhazels the Asian forms present the widest flower color palette and have increased in popularity as a group

American witchhazel is the last to bloom in October and November in Southern Appalachian region (USDA hardiness zones 6 and 7). This witchhazel grows tall and is frequently pruned into an 18-25 foot tree.

All witchhazels turn pale yellow to dark golden foliage colors in autumn.

Blossom End Rot Affecting Your Vegetables?

Posted by Hugh on December 1st, 2012

Blossom End Rot on Tomato (photo credit- Dr. Steven Bost, Univ. of Tennessee Plant Pathologist)

The bottom side of your tomato fruits appears to be rotting? The problem is not a disease, but a calcium disorder called “blossom end rot of tomatoes”. This nutritional malady also affects squash, pepper, eggplant, melon, and cucumber.

There are 3 causes for calcium deficiency: 1.) a deficiency of available calcium in your garden soil, 2.) inadequate soil moisture, or 3.) over-feeding plants with nitrogen fertilizer. One, two, or all three causes may in play at the same time.

Watering during periods of extreme drought will feed more soil calcium to the plant. Irrigate to make up for natural rainfall deficits. up to 1 ½ inches per week. Mulching around vegetable plants with grass clippings, straw, or wood chips also helps. Be certain that lawn clippings have not been sprayed over the past month with herbicides which control dandelions and other broadleaf weeds.

Lime is a good source of calcium, but it takes several weeks for quick forms of lime to breakdown and become easily absorbed by roots. Dolomitic (gray) and hydrated lime may take 3-4 months to activate in a soil and are best applied over the winter months. Test your garden soil in autumn to determine when and how much lime to add. Use the correct amount as lime will raise the soil pH, making it less acidic.

High nitrogen levels may promote rapid vegetative growth, but the plants don’t absorb enough calcium to compensate, resulting in localized calcium deficiency in the fruit (or vegetable).

Finally, plant roots amy become injured from flooded soil or mechanical injury from tillage equipment such as hoes and rototillers. Root loss from poor aeration means the plant is not taking up enough water and nutrients.

Sugar Maple Is A Four Star Autumn Attraction

Posted by Hugh on November 9th, 2012

Sugar maple autumn color

Spring flowering

Sugar maple (Acer saccharum) is a native deciduous tree often planted as a large shade or street tree. It commonly grows 60 to 75 feet (and taller) with a dense rounded foliage canopy. Native to central and eastern North America regions, sugar maple grows best in fertile, mildly acidic, moist well-drained soils and in full sun to part shade.

The 5-lobed deep green leaves of summer takes on yellow, orange and red shades in the autumn. Clusters of yellowish-green flowers appear in mid-spring a week before the leaves emerge. Flowers ripen into clustered pairs of double-winged samaras (or “helicopters”) in late summer. In the winter tree trunks may be tapped for maple syrup (“saccharum” means sugar).

Disease and pest problems are less when properly sited and maintained. Do not plant in dry compacted sites such as in downtown parking lots or as street trees. Poor locations bring on numerous serious diseases and insects, including verticillium and fusarium wilts, leaf spots, cankers, wood borers and scale. Its shallow roots raise up urban sidewalks.There are more than 25 sugar maple cultivars, and here are three exceptional ones.

‘Green Mountain’ has broadly pyramidal tree form. The foliage may struggle in summer heat and dry periods, causing leaf edges to brown (scorch). However, its thick deep green foliage is resistant to leaf hoppers and scorch, making it an ok choice as a street tree.

‘Legacy’ sugar is a more heat and drought resistant, making it a good pick for the southeastern U.S. The tree canopy is densely branched and has glossy thick green leaves. The leaves turn yellow to orange in autumn.

‘Green Column’ (A. saccharum subsp. Nigrum), aka black maple, exhibits better than average heat and drought resistances. Summer foliage is dark green and is thick and leathery to the touch. It develops a yellow fall color that’s two weeks later than other sugar maples.

Fall Blooming ‘Little Suzy’ American witchhazel

Posted by Hugh on November 7th, 2012

Hamamelis virginiana 'Little Suzie' in October '12

Little Suzy American witchhazel (Hamamelis virginiana ‘Little Suzy’) was hybridized and introduced by Harald Neubauer, owner of Hidden Hollow Nursery in Belvidere, TN. This medium sized shrub grows 8-10 feet tall and 10-15 feet wide. It is particularly suited to small urban gardens where standard American witchhazels (20-25 feet in height and width) are too large. Little Suzy’s short compact nature is due to its shorter internode lengths.

Little Suzy blooms freely at a young age. The witchhazel-scented soft yellow blooms appear in October and November in the Southern Appalachian region (USDA hardiness zones 6 and 7). The 4- narrow, strap-shaped yellow petals appear at a time of year when little else is blooming.

New leaves emerge reddish-bronze in early spring and turn dark green. Summer leaves are dark green and remain blemish-free from disease and pest woes. Foliage stays clean and pest-free throughout the growing season. The 3 to 6 inch long coarsely toothed leaves turn clear yellow before falling in late autumn.

American witchhazel is not finicky where it grows, either in full sun to partial shade. It prefers moist, acidic, and well drained soil, but a 2-year established shrub exhibits good heat and drought tolerances. Their “popcorn” like seed capsules can disperse seeds 25 feet or more away.

American witchhazel is utilized as a fall blooming oddity or plant several together for a deciduous hedge or privacy screen. Through judicious pruning a shrub can be shaped into a lovely small tree.

Little Suzy witchhazel is available from specialty plant nurseries on-line.