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

Arrowwood Viburnum Very Tough U.S. Native Shrub

Posted by Hugh on August 22nd, 2013

Viburnum dentatum in Reading PA

Lustrous dark green foliage

Arrowwood Viburnum (Viburnum dentatum) is an easy to grow deciduous shrub that handles most landscape conditions, including soil types (USDA hardiness zones 5 to 8). It grows best in full sun and in a well-drained soil.

Clusters of tiny, creamy-white flat-topped flowers appear from late spring into summer. A bountiful crop of dark blue berries follows in the fall, a favorite of many birds and 4-legged wildlife. The lustrous dark green summer leaves turn a mix of yellow, red, and purple in the fall.

Depending on cultivar selected, arrowwood grows 5 to 15 feet high and wide. Arrowwood exhibits vigorous growth which demands annual pruning to keep its suckering habit in check. Most suckers are formed around the trunk base. Cutting off branches in late winter will reduce bloom numbers; pruning can be put off until mid to late June (after flowering). Remove any and all suckers anytime.

Like some baseball players, arrowwood is a “utility” shrub. It plays into a multiple landscape strategies: 6-8 foot deciduous hedge or screen, an important wildlife attractant, or a beautiful specimen plant. Arrrowwood is mostly disease resistant , although it is highly susceptible to viburnum beetle from late April into early May.

Top Cultivar Choices:
Blue Muffin™ is dwarf, densely branched, 4-5 feet tall and wide shrub; creamy-white blooms cover the branches followed by a heavy crop of dark blue fruits; excellent choice for a small garden.
‘Emerald Lustre’ is a Southeastern U.S. (particularly zones 7 and 8); flaunts dark green glossy foliage, lots of purple-black fruits, and yellow-bronze fall foliage color.
Northern Burgundy® is a late June blooming form which bears huge crops of blue-black fruits and deep burgundy fall color annually; grows 12 feet high and wide.
Autumn Jazz® is a Midwestern selection that grows 10 to 12 feet tall and 8 to 10 feet wide; upright, vase-shaped branching and fall leaf color a blend of yellow, red and purple.
Pathfinder™ is dwarf form (6 feet tall and 4 feet wide) with glossy dark green summer foliage. Flower and fruit traits similar to species.
Chicago Lustre® grows 8 to 10 feet tall and wide with lustrous dark green glossy summer foliage; reddish purple fall color and cold hardy (zone 5).

Divide Irises In Late Summer

Posted by Hugh on August 17th, 2013

Reblooming Iris germanica 'Immortlity'

Irises (Iris spp.) are beloved spring flowering perennials. Perhaps some fans and clumps flowered poorly this spring. There are several reasons for this, including: old clumps in need of dividing, weather issues, poorly drained soil, inadequate nutrition, too much nitrogen fertilizer, heavy shade, and pest and disease problems.

Irises do not compete well for space with other plants, including weeds. Heavy amounts of grassy weeds, including nutsedge, can quickly overtake iris fans and clumps. Plants become starved of nutrients resulting in poor growth and flowering.

As a rule, irises are dug up and divided every 4-5 years. Rhizomatous type irises (bearded, median, and Japanese) and clumping (Japanese roof, Siberian, flag) irises should be divided starting in late summer (August 15 to October 1) in USDA hardiness zones 5 to 7. In northerly areas, do not transplant iris after mid-October as they may heave out of the soil during the winter.

Prepare a new planting area and mix lots of rotted compost into a well-drained soil. The site should receive three-quarter to full day direct sunlight. Cut all fan leaves back to 4-6 inches. Irises are spaced 18 to 24 inches apart.

Select fans with plenty of white roots. Discard all old woody and gnarly fans with insect and disease symptoms and withered or dead foliage. Dispose with the household trash and not add to garden compost pile.

Do not fertilize new or reworked beds in the fall. Wait until spring. Feed with a slow release fertilizer such as Osmocote 14-14-14, Nutricote 13-13-13, or equivalent product. Irrigate newly planted irises until fall showers are plentiful.

Recommended Tall Fescue Cultivars

Posted by Hugh on August 15th, 2013

Beautiful Lawn In Front of Biltmore Estate, Asheville, NC

Tall fescue is considered one of the best cool season lawn grasses around homes and on public and commercial lands in the eastern and midwestern U.S. (USDA hardiness zones 5 thru 7). The cultivar K-31 is still an old standby, but so many better performing cultivars have now within reach. They feature improved color, plant density, and finer leaf texture. New cultivars also offer better disease resistance.

Between 2007 – 2011 over 100 varieties have been evaluated (AR, KS, KY, MD, MO, NC, TN, and VA). The recommended varieties include: LS 1200, BULLSEYE, RHAMBLER SRP, SHENANDOAH III, TURBO, FAITH, CATALYST, FALCON V, FIRECRACKER LS, SHENANDOAH ELITE, BRAVEHEART, COCHISE IV, WOLFPACK II, SPYDER LS, SIDEWINDER, RK 5, TRAVERSE SRP, TALLADEGA, 3RD MILLENNIUM SRP, MONET, SPEEDWAY, and MUSTANG 4.

Tall fescue should be mowed at a cutting height of 3 to 3.5 inches, fertilized with 1-2 lbs of nitrogen per 1,000 sq. ft. in early spring and again in late summer. An established lawn of tall fescue is moderately drought tolerance and does not require summer irrigation and feeding. During exceptionally hot dry summers, tall fescue may naturally turn brown, but greens up when adequate natural rainfall returns.

When purchasing seed containing several tall fescue varieties, the grass mix does not need to contain only the varieties mentioned above. It’s more important to utilize the strengths that two or more varieties contribute jointly.

Fungus In A Lawn A Natural Phenomena

Posted by Hugh on August 11th, 2013

Unidentified Lawn Fungus

White or brown colored mushrooms are the visible reproductive (fruiting) structures of some types of fungi. An umbrella-shaped fruiting body is the most common form, but mushrooms come in many shapes, sizes, and colors. Most people call them mushrooms, toadstools, or puffballs. Mushrooms are the reproductive stage of fungi and their spores are “seed”, the next generation. Their key objective is to produce and release spores.

Most fungi in lawns are beneficial. Fungi serve as nature’s decomposers, feeding off the soil’s organic matter and releasing nutrients that become available to plant roots. Many fungi, including those that cause lawn diseases, produce small fruiting bodies that are scarcely noticeable. They’re not the typical mushrooms that panic most homeowners.

Microscopic fungal spores are carried by wind and water to new areas. When spores reach a favorable place, they germinate (like seeds), sending out long thin filaments called “hyphae”. These hyphae form a network of mycelium that decomposes wood, fallen leaves, mulch, dead insect and worms, etc. The organic matter serves as food for the fungi.

Mushrooms are produced when weather and soil conditions are optimal. Fungal mycelium generally survive in the soil many years. Picking and/or raking up mushrooms doesn’t kill the underground mycelium from which they are growing. Rapid removal may prevent their spores from spreading to new sites. Likewise, the spores from neighboring properties may come to your lawn. Removing mushrooms from lawns principally serve to keep them away from children and pets and to improve a lawn’s appearance.

Finally, unless an accurate lawn disease diagnosis has been made, blind applications of fungicides to “kill mushrooms” is often a wasteful and costly practice. Observing mushrooms growing on the ground is a natural phenomena.

Pest Alert: Inspect All Garden Roses For Rose Rosette

Posted by Hugh on August 9th, 2013

Abnormal Growth on Knockout Rose in Bristol, TN

Rose rosette is a serious virus disease of roses (Rosa spp.). Over the past 3 years ago gardeners have experienced losses of popular shrub roses. The disease continues to gain ground across the U.S. Rose nurseries are working feverishly to find a solution.

Landscapers and gardeners should inspect all garden roses, including hybrid tea, grandiflora, floribunda, polyantha, and the popular shrub roses such as Knockout™, Home Run™, Carefree™, Drift™, etal. The virus disease is spread by an eriophyid mite while feeding from infected to healthy roses. This tiny mite is a very common plant pest over a large geographic area and is often missed by landscapers and gardeners.

Inspecting your roses weekly and removing all suspicious growth are the best measures for managing rose rosette. Pruning includes complete removal of infected rose canes (shoots) to the main trunk or close to the ground. Deposit all prunings in the household trash. Do not throw diseased canes in a rubbish or compost pile.

Apparently, the disease has no soil borne activity. If you have lost roses to the disease, dig out and properly dispose of the shrub. You can replant another rose in the same planting hole.

Managing eriophyid mite populations requires biweekly spraying with any of the following insecticides and miticides: Cygon 2-E™ (dimethoate), bifenthrin, carbaryl (Sevin), and Avid™ (abamectin).

Continue to review updates about rose rosette disease.

New ‘Big’ Begonias Showier Alternative To Wax Begonias

Posted by Hugh on August 6th, 2013

‘Big™ bronze-leaf begonias with sun coleus in Johnson City, TN

Wax begonias (Begonia x semperflorens) continue to be dependable a summer flowering annual for gardens and container use. They also hold up to summer’s heat, humidity, and dry spells and foliage remains mostly pest and disease free. Begonia benariensis are a relatively new introduction by the Benary Seed Co. and are trademarked as Big™ begonias at garden centers. They boast larger showy flowers than traditional wax begonias.

Big™ begonias bloom non-stop for almost six months (mid-May thru October) in the Southern Appalachian region (USDA hardiness zones 6 and 7). Big begonias are available in bronze-leaf (full sun) and green leaf (part sun) forms. Currently, flower colors are limited to bright red (Big™ Red Bronze-leaf and Big™ Red Green-leaf), and rose colored (Big™ Rose bronze).

Flower sizes vary from 2 to 3 inches in diameter. The brightly colored blooms are visited by many kinds of butterflies thru the spring and summer months. Flowers are self-cleaning and do not require deadheading. Plants grow compact and well-branched at 18 to 24 inches high and wide. At planting Big™ begonias can be minimally spaced 12-14 inches apart in garden beds or in containers.

Big™ begonias, particularly bronze-leaf grow best in full sun, and green leaf cultivars thrive in partial shade. Choose a site with well-drained soil and with lots of well-rotted compost added. Green leaf types tend to scorch in zones 7-b and further south in intense sunlight.

Big™ begonias perform best with moderate fertility and are not heavy feeders. Add 2 to 3 inches of mulch to improve soil organic matter and to conserve soil moisture. Irrigate during extreme dry spells to maintain health, vigor, and flower numbers. At spring planting, feed with a slow-release fertilizer such as Osmocote™ 14-14-14 or Nutricote™ 13-13-13. One additional feeding in mid-summer with a water-soluble fertilizer (such as Miracle-Gro®, Schultz®, or Jacks®) is often needed in southern climates (zones 7-9).

Wax and Big™ begonias are used for front bed edging, look awesome planted in front of evergreen shrubs.

‘Sun King’ Golden Aralia Brightens Up Any Garden Spot

Posted by Hugh on August 3rd, 2013

Aralia cordata 'Sun King' in Vancouver, BC, Canada

Plants with golden foliage can brighten up a drab green garden patch. Sun King golden aralia (Aralia cordata ‘Sun King’) is no exception, hardy in USDA hardiness zones 3-9. The golden compound foliage emerges in mid-spring and retains its bright color throughout the summer.

This herbaceous perennial grows 4 to 6 feet high and 3 to 4 feet wide. Growth rate is rapid and dies back to the ground in late autumn. In mid-summer numerous small clusters of tiny white flowers shoot up, borne on 2 feet tall racemes, with lustrous purplish-black berries that follow in the fall.

Sun King makes a bold almost tropical statement in a semi-shade garden. Grow it in a compost-rich moist soil and in ½ day sunlight (morning hours preferred). It is suited to a wide soil pH range. The foliage will definitely burn in full day sun. In USDA zones 8 and 9, grow only in dappled sunlight to avoid foliage burn. Golden aralia should be kept mulched and irrigated over long summer dry spells.

Sun King aralia mixes well in containers planted with green and other brightly colored foliage plants. It combines with variegated Solomon seal, hostas, brunnera (Brunnera macrophylla), lungworts (Pulmonaria spp.), coral bells (Heuchera spp.), and astilbes. Golden aralia is deer resistant and its tiny white flowers attract numerous honeybees.

A native of Japan, Korea, and China, ‘Sun King’ aralia was introduced to the U.S. by Barry Yinger.

Small (Dwarf) Crape Myrtles Becoming The Vogue

Posted by Hugh on July 27th, 2013

: ‘Tightwad Red’ Crape Myrtle

Over the past quarter century crape myrtles (Lagerstroemia spp.) have become the quintessential flowering shrubs of summer along with hydrangeas (Hydrangea spp.), altheas (Hibiscus syriacus), and chaste tree (Vitex agnus-castus).

Crape myrtles are grouped into four distinct size categories: trees, large shrubs, medium shrubs and dwarf sizes. A spate of new dwarf cultivars have raised the bar. All dwarf cultivars listed below are rated for zone 7 or higher, but have performed well in zone 6-b (where I garden).

Treat dwarf crapemyrtles like perennials. Pruning and fertilizing bring them back to life. Wait until mid-April to revive them. Remove the old seed heads and assess the extent of winter dieback. It involves mostly small pruning cuts. From this point, dwarf crape myrtles remain mostly trouble-free the rest of the year.

Cherry Dazzle™ produces cherry red blooms from summer into fall. Shrubs grow 3-5 feet in height.

‘Centennial’ – sister seedling to ‘Victor’; 5 to 6 feet in height, but easily maintained at 3 to 5 feet height and spread/ bright lavender flowers/ leaf mildew resistance/ orange fall color/ reddish-brown mature bark.

‘Pink Ruffles’ – ruffled, pink blossoms/ orange – red fall leaf color/ grayish brown bark.

‘Pokomoke’ – 3 to 4 feet height and width /dense glossy green foliage/deep rose pink flowers.

Tightwad Red ® (L. indica ‘Whit V’) – dark red sterile flowers (no seed pods) / purplish-green foliage that’s highly leaf mildew resistant.

‘Victor’ – 5 to 6 feet height and 3 to 4 feet wide/ red flowers/green summer foliage/ red fall color.

Crape myrtles grow best in full sun and in moist fertile soil. They tolerate hot dry sites once shrubs become established after their first year. They grow well in limited planting spaces such as urban parking lots and in small pavement cutouts if limited irrigation is supplied. They tolerate clay and alkaline soils.

Add dwarf crape myrtles when planning a new garden bed.

Many Cool Choices of Japanese Forest Grass

Posted by Hugh on July 24th, 2013

Hakonechloa macra 'Aureola'

Japanese Forest Grass (Hakonechloa macra) is the shade-loving grass utilized for accent – to brighten a dark patch in the garden (USDA hardiness zones 5-9). Forest grass grows best in a moist, compost-rich, well-drained soil. Soil moisture and light exposure a key factors to prevent foliage from scorching or discoloring. Too much or too little of either is never a good thing.

Partially shaded areas are preferred, but it can handle direct morning sunlight in (U.S. hardiness zones 5 and 6). Cultivars with variegated foliage are affected by the degree of sun exposure. In warmer climes gold hues may change to lime green.

Clumps of forest grass are rhizomatous and slow growers, particularly their first year after planting. Old foliage dies to the ground in late winter and new shoots emerge in mid-spring. Disease and pest problems are rare if environmental factors are proper.

‘Aureola’ is the most popular cultivar and was selected 2009 Perennial Plant of the Year by the Perennial Plant Association. It features golden variegated foliage, graceful arching habit, and an initial slow growth rate. It grows 14 to 18 inches high in a shady garden bed or mixed with other plants in containers. Grass blades take on a pinkish tinge in the cool autumn weather.

‘All Gold’ is similar to Aureola with ribbon-like gold leaf blades. All Gold is slightly a more vigorous grower and matures to 14 to 20 inches in height.

‘Fubuki’ exhibits white and green striping along the leaf blades, quite different than other forest grasses. Fall foliage takes on a pinkish tinge. Fubuki appears to tolerate more sunlight and exhibits slightly better heat and drought tolerance. “Fubuki” means snowstorm in Japanese.

‘Naomi’ grows 10-14 inches tall with creamy white and yellow-green variegated foliage in the spring and turning purple-red in the fall. Its growth rate is more vigorous than other forest grasses.

‘Nicolas’ grows 10-14 inches tall with bright green summer foliage and turns deep red in the autumn.

Russian Sage More Shrub-like Than Perennial

Posted by Hugh on July 21st, 2013

Russian sage cultivar at Morris Arboretum

Russian sage (Perovskia atriplicifolia) is low maintenance woody-based perennial. It grows in a dry to medium moist average soil and, first and foremost, in full sun. It’s a long-lived perennial which stands up to summer’s heat and humidity (USDA hardiness zones 5-9). Branches tend to flop or take on a droopy appearance in late summer. The Perennial Plant Association named Plant of the Year in 1995.

Russian sage (species) typically grows 4 to 5 feet tall and 3 to 4 feet wide if left unpruned for multiple years. Terminal panicles of light blue tubular flowers are perched on upright square stems. It blooms consistently from early July to October in the Southern Appalachian region (USDA hardiness zones 6 and 7).

The principal appeal of Russian sage is its cool blue flowers and the openness of its plant form. This member of the mint family emits a sage-like odor when the leaves are crushed. Russian sage adds structure and grayish color to the winter landscape. This tough perennial has no disease or pest problems. Deer and rabbits leave it alone and its gray-green foliage copes with urban air pollutants.

For neatness, prune back plants 3-6 inches to the ground in early spring as the new growth begins. Fertilize with 10-10-10 or equivalent in early spring or feed in spring and early summer water-soluble fertilizer such as Miracle-Gro™, Jacks™, or Daniels™.

These four compact cultivars are a better fit in a small urban garden:
‘Filigran’ – 3-4 feet tall and wide, light blue flowers and lacey silvery foliage on upright branches.
‘Lacey Blue’ – 1-1 ½ feet high by 2-3 feet wide, compact British introduction with thick stems with less “flopping”. Upright silver stems bear dense panicles of large lavender-blue flowers.
‘Little Spire’- 2-3 feet high and wide; masses of small, violet-blue flowers and dense silvery-green foliage.
‘Longin’ – 3-4 feet high and wide; deep blue flowers on stiff, upright stems.