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

Bloomerang™ Lilac For Non-Stop Flowering

Posted by Hugh on April 8th, 2012

Young 'Boomerang' Lilac in mid-April Garden

In most Northeast and Midwestern states, lilacs (Syringa spp.) are the classic spring-flowering shrub, treasured for their beautiful and fragrant flowers. Lilacs are vigorously growing shrubs and are utilized in the landscape as single specimens or as multiple hedging shrubs for privacy. Further south, in the warmer Southern Appalachian region (USDA zones 6 and 7), most lilac cultivars tend to disappoint because of low flower numbers and their susceptibility to foliar powdery mildew in late summer.

Bloomerang™ is a hybrid cross of four lilac species (Syringa patula x S. macrophylla x S. meyeri x S. juliana). It grows bushy and compact at 5 feet tall and 6 feet wide. Boomerang grows vigorously, fits into small garden spaces, and forms a lovely low growing hedge.

Clusters of sweet-scented flowers open deep purple that densely cover the branches in April and bloom off and on until October frost. Flower clusters fade to pink and fall without any need for deadheading. Although the long re-blooming trait is never showy, you and your gardening friends will likely take notice.

Boomerang is best pruned immediately following spring bloom, to form a dense shrub with more branches and flowers. This lilac is deer resistant and its small dark green leafy foliage is moderately resistant to powdery mildew.

Lilacs grow in full to partial sunny locations and in a low acidic to slightly alkaline soil pH. Lilacs benefit from annual feeding containing minor nutrients such as Miracle-Gro™, Miracid™, Hollytone™ or Schultz® fertilizers. Follow package label directions.

Re-blooming Iris For Twice (and More) Flowering

Posted by Hugh on April 6th, 2012

Re-bloomer Iris germanica 'Sugar Blues'

Gardeners who desire more flowering from garden iris (Iris spp.) should be planting re-blooming types. Some cultivars may re-bloom up to three times in one growing season. The re-blooming trait is found both in bearded and beardless irises (I. germanica).

Re-bloomers need to be well established for one year, sometimes two, to bloom multi-seasonly. Some re-bloomers are sporadic, and a short list of dependable varieties is included below.

Information on growing tall bearded iris is found in an earlier blog (April 1, 2012). Re-bloomers multiply faster than one-time bloomers, and need to be divided every two to three years to avoid overcrowding. Some cultivars need to be well established before they re-bloom; lift and divide only part of the clump and leave the remaining portion undisturbed to re-bloom. Also, clipping off the foliage too early in late summer reduces re-bloom potential.

Re-bloomers are heavy feeders and benefit from two feedings, once in the spring, nearing the end of the regular flowering period, and a second time in mid- August, the start of the 2nd or 3 rd re-blooming period. Fertilize with a low nitrogen analysis, such as 5-10-5. Re-blooming cultivars need frequent irrigation during dry summer periods compared to standard irises.

A baker’s dozen cultivars include: Best Bet, Bountiful Harvest, Clarence, Hemstiched, Immortality, Jennifer Rebecca, Mother Earth, Pagan Goddess, Pagan Dance, Autumn Tryst, Champagne Elegance, Orange Harvest, Rosalie Figge.

Complete Care of Tall Bearded Iris

Posted by Hugh on April 4th, 2012

Tall bearded Iris-- Queen of the Perennial Garden

Most gardeners plant tall bearded iris from late August through October to insure good root development before winter sets in. Spring planting is another option as iris may be purchased in containers. Bare root rhizomes need to soak overnight in water before planting. Bearded irises prefer a sunny location and a slightly acidic well-drained soil. Work in plenty of compost into the garden soil prior to planting and lightly mulch iris 1-2 inches after planting. Irrigate the bed every 5-7 days if natural precipitation is light; once the first new center leaves appear, iris rhizome(s) have rooted.

Remove the bloom stalks after flowering and cut the foliage down to 3-4 inches in late fall. Irises need dividing every 3-4 years to prevent overcrowding. Right after Labor Day is a fine time to divide and/or transplant in the Southern Appalachian region (USDA zones 6 and 7). Avoid the stressful hot days of summer. Plant each rhizome shallow, barely beneath the surface of the soil.

Irises grow best in raised beds, particularly if the garden soil is heavy clay. Add superphosphate (0-45-0) to the soil before planting. A good low-nitrogen fertilizer such as 6-12-12 can be used early in the spring. Do not mulch or overwater.

Tall bearded rises are susceptible to a number of disease and pest issues. Remove and discard (do not compost) all dead leaves and bloom stalks by late fall so not to overwinter various diseases and pests.

In the spring treat leaf spot diseases with Daconil™ fungicide. To manage iris borers, aphids and beetle grubs, choose a systemic insecticide like Merit™ (imidacloprid).

Katsura Tree Comes Home To America

Posted by Hugh on April 1st, 2012

Katsura Tree at Chanticleer Garden near Philadelphia, PA

Katsura tree (Cercidophyllum japonicum) is a large 50-60 feet tall tree from Japan and China. Katsura became extinct in North America during the Pleistocene Age and was re-introduced in 1862 by botanist Thomas Hogg. It is truly a beautiful tree, yet is still rarely planted.

Katsura is hardy in zones 4-8. It prefers a moist well-drained, compost-rich soil in a full sun to partial shade setting. Katsura’s annual growth rate is medium to fast, and develops either single or multi-trunked.

Spring foliage is unique, 2-4 inch wide circular leaves edged with tiny round -edged teeth. New leaves emerge reddish purple, quickly turns matted green, then to blue green in summer, and muted yellow-orange in autumn. On a cool late September morn the maturing Katsura foliage fills the autumn air with a cinnamon-like fragrance. Katsura is dioecious, an individual tree either male or female. The latter forms tubular seed capsules which disperse thin circular winged seeds on a windy October day.

Nursery stock is predominantly balled and burlapped (b&b), but container grown trees are becoming more available. Most full service garden centers can order it for you or purchase one on-line.

Katsura requires ample space such as in large residential lots, public parks, golf courses, and commercial properties. Foliage stays pest free.

Katsura cultivars abound starting with ‘Amazing Grace’, an exquisite weeping form with exceptional blue-green foliage.

Piedmont Azalea

Posted by Hugh on March 30th, 2012

: Piedmont Azalea (R. canescens) at Callaway Gardens

Early flowering Piedmont azalea (Rhododendron canescens) is one of the most common native deciduous azaleas in the southeastern U.S. It is frequently confused for pinxterbloom azalea (R. periclymenoides) which blooms 3-4 weeks later. Piedmont azalea is hardy in USDA hardiness zones 6 to 9.

Piedmont azalea reaches a mature height between 6 to 15 feet, about one-third higher than wide. There is great variability within this species. Flower colors may vary from white to deep pink, depending on the seed parentage in the geographic area. The fragrant blossoms appear in early spring before the leaves emerge. Floral stamens protrude outward two to three times beyond the length of the tubular petals. The lightly fragrant flowers invite numerous butterflies, hummingbirds, and bees into the early spring garden.

It is found in deciduous woodlands where it receives ample sunlight in early spring, and stays mostly shaded through the summer months. It prefers a moist, organically rich, well-drained, and acidic soil. Fertilize shrub(s) lightly and add pine straw or pine bark mulch to conserve soil moisture.

Piedmont azalea has a shallow stoloniferous rootsystem, and a shrub may form plant colonies around itself. Prune upright growing Piedmont azalea immediately after flowering to increase shrub density and width. Piedmont azalea is susceptible to a number of eating or chewing pests.

Evergreen Kousa Dogwood? – Depends on Where You Garden

Posted by Hugh on March 28th, 2012

Chinese dogwood in flower

Chinese (kousa) dogwood (Cornus kousa) is a small spring flowering dogwood. Kousa blooms about 2 – 3 weeks after our native flowering dogwood (C. florida) has finished. Lustrous dark green leaves begin to emerge a week or two before the lovely pointed 3- inch white bracted flowers. Fall leaf color is purplish red and not quite as vibrant as C. florida. Its patchy exfoliating bark is a winter asset which gets better as the tree ages. The fleshy raspberry fruits are not a popular food source with birds and four legged critters in the fall.

Evergreen kousa dogwood (Cornus kousa var. angustata) is a variant also listed as Cornus angustata. Angustata forms a shorter tree with narrow pale green evergreen foliage is reliably evergreen in USDA zones 7-b and 8, and takes-on a purple wintry tint in zones 6-b and 7-a. The tree is deciduous in zone 6-a and further north. Protection from winter winds may retain the autumn foliage longer. Angustata mature tree height averages 20-25% smaller than the species.

Plant in part shade and in well-drained compost rich soil in southerly climes of zones 7-b and 8 and in full sun further north. Angustata is only moderately tolerant of summer heat and humidity and should be irrigated during periods of extreme drought.

Two evergreen cultivars are:

Empress of China®, introduced by John Elsley, flowers abundantly in mid to late May.
‘First Choice’, a selection from JC Raulston Arboretum in Raleigh, NC. has good flowering and growth rate.

Very Tall Stake For A Weeping Blue Atlas Cedar

Posted by Hugh on March 26th, 2012

Weeping Blue Atlas on Poor Site

Weeping Blue Atlas Cedar (Cedrus atlantica ‘Glauca Pendula’) is “gravity prone”. This strongly weeping tree just doesn’t happen without staking in its formative years. At planting position a sturdy 12-16 foot metal or plastic stake or rod close to the trunk at planting time.

The staking and tying procedure is neither complicated nor time consuming. When the spring growth flush has finished and while the leader is still soft enough (flexible), bend the leader upward and tie to the stake or trellis. Use soft jute or cotton twine, and not wire twist-ems® or plastic ties. After 6-8 months, loosen the ties so they won’t girdle the tender main shoot (leader).

The new shoots emerge in mid to late April. The needles have fully elongated by late May. Staking is best performed anytime from late June thru mid July in the Southern Appalachian region (USDA hardiness zones 6 and 7). The shoots should be slightly hardened but still flexible. If too stiff, the main shoot (leader) may not bend to straighten up vertically and leave a crook.

How many years you continue to stake ‘Pendula’ depends on the mature height desired. Most gardeners train to 5-8 feet, but I encourage you to set a higher goal between 12-16 feet.

Another idea is to train Blue Atlas cedar to an arbor or trellis at a garden entry (see photo below).

Staking when young provides an early foundation for a well-shaped mature tree. Plants can be alot like people. Youngsters left to their own devices become unruly adults.

Cedrus atlantica 'Pendula' on Trellis

Contorted Filbert Offers Great Fall And Winter Interest

Posted by Hugh on March 23rd, 2012

Catkins of Harry Lauder's Walking Stick

Contorted filbert (Corylus avellana ‘Contorta’), aka Harry Lauder’s walking stick, is an 8-10 foot tall shrub. It grows in average well-drained acidic or mildly alkaline soil and thrives either in full or partial (6 hours) sunlight. Contorted filbert is usually sold in a grafted form.

It is also called corkscrew hazelnut because most branches, twigs and leaves display a twisting or spiraling nature. Showy yellowish brown male catkin flowers grow to 2-3 inches in length in late winter and early spring. Tiny female catkins are barely visible. Contorted filbert does not bear fruits (nuts).

The light green almost circular leaves (2-3 inches in diameter) are double-toothed along the leaf margin. The foliage turns a drab yellow in the fall. Following leaf abscission, the curlicue branching provides considerable autumn and winter interest.

Contorted filbert has no serious insect or disease problems. Susceptibility to crown gall is often associated with a poorly drained site. Occasional scale insect infestations may be eradicated with 1-2 applications of dormant oil in the winter months before new leaves emerge. Root suckering may become a maintenance nuisance. These straight growing (not twisted) suckers tend to eventually dominate the entire shrub and should be removed.

‘Red Majestic’ is a new contorted filbert. The new spring growth emerges with burgundy red tint which bleaches out to a dark green foliage by late May.

Evaluating The Weeping Redbuds

Posted by Hugh on March 21st, 2012

Weeping Redbud (Cercis)

There are so many fine redbuds (Cercis spp.) which are hardy in the Southern Appalachian region (USDA zones 6 and 7) and elsewhere. Through research and breeding efforts at the JC Raulston Arboretum in Raleigh, NC, Southeast U.S. gardeners can grow several more cultivars of our native Eastern redbud (C. canadensis and subspecies texensis) and chinese redbud (C. chinensis). There are two popular and one new weeping form.

Traveller Weeping Redbud (C. canadensis ssp. texensis ‘Traveller’) produces deep rose pink flowers in early spring. Leaves are dark green with high gloss over its upper surface. Traveller has graceful arching branches. The tree’s overall form is mound-like and grows taller and wider over time. Its rootsystem is strong and vigorous.

Lavender Twist redbud (C. canadensis Lavender Twist™ or ‘Covey’) is more winter hardy (USDA zones zones 5-9) than Traveller (USDA zones 6-9). It demands staking to straighten up (for height) the main leader. Without staking, Lavender Twist’s strong weeping nature will turn it into a low trailing shrub. Staking also helps to better anchor the tree’s less vigorous root system.

Lastly, there is the new Ruby Falls™, described as a 4-6 feet tall and 6-8 feet wide weeping Lavender Twist with purple ‘Forest Pansy’ redbud foliage. Ruby Falls is a 2010 introduction from NC State University and is available in very low numbers worldwide. It is rated as winter hardy in USDA zone 6

All three weeping redbuds fit in a small garden, and all should be utilized as a small accent tree in ready view from the garden patio deck and from inside the home.

Protect Fruit Trees and Bee Population

Posted by Hugh on March 19th, 2012

: Cedar rust infection spot

Warm weather in early spring means scab, cedar apple rust and powdery mildew diseases are upon the new leaves as they start to emerge. Preventative spraying for leaf diseases will result in management of additional fungi diseases through the growing season.

Fungicides are protectants and not cure-alls. A light rain shower (as little as ¼ inch of precipitation) will wash off the “water soluble” spray and it must be re-applied as soon as possible. Timely spraying helps to break the disease cycle.

Beginning in late March, across most areas of the Southern Appalachian region (USDA zones 6 and 7), spray only fungicides in early spring as not to injure our fragile bee populations which are pollinating flowers. Most insect pest problems on fruit trees do not start until after petal fall.

Cedar-apple rust and powdery mildew are primarily threats in the wet cool spring period. Cedar apple rust infections decline by late May. Keep in mind that some apple varieties are more susceptible than others to disease pressures.

Begin spraying when flower buds are in the tight cluster to pink stages. Several products are labeled including Mancozeb (also sold as Dithane), metiram (Polyram), Captan and Ziram. Consult your state/county Extension agent for specific rcommendations where you garden.