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

Pest Alert: Viburnum Leaf Beetle May Be Invading

Posted by Hugh on August 30th, 2016

Arrowwood viburnum (V. dentatum) Is Highly Susceptible

Viburnum-leaf-beetle (photo from Michigan State University)

Viburnum Leaf Beetle is gradually coming to the Southeastern U.S. It was first found in upstate New York in 1996. This pest has been on the move, eating its way through native viburnums from upstate New York to northern Pennsylvania to western Maryland.

It feeds only on viburnum species. Preferred species include native arrowwood viburnum (V. dentatum), European cranberrybush viburnum (V. opulus), American cranberrybush viburnum (V. trilobum), and Rafinesque viburnum (V. rafinesquianum). Other viburnums that also serve as hosts include Sargent viburnum (V. sargentii), wayfaringtree viburnum (V. lantana), nannyberry viburnum (V. lentago), and blackhaw viburnum (V. prunifolium).

This insect overwinters as clusters of eggs inside pencil-sized twigs, essentially killing these small twigs on edge of branches. Affected shrubs leaf out from lower buds and infest new pencil-sized shoots in spring. The larvae skeletonize the leaves and can completely defoliate plants by mid-June. Larvae drop off the shrubs, pupate and emerge as adults.

From July through September the adults do minor feeding, lay eggs and repeat the cycle. Each year viburnums decline from repeated infestations and die after 3 to 5 years of defoliation and egg-laying damage. Viburnum beetle is pretty easy to kill with insecticides containing either pyrethroid, carbaryl, or acephate (Orthene®), targeting larvae and adult stages. Unfortunately, spray applications of pesticides do not protect shrubs from egg-laying adults that may fly in from untreated areas during July through September.

Another treatment approach is to inject or drench the soil around the susceptible shrub with imidacloprid (Merit® or Bayer Advanced Garden Insecticide®) in late fall. This will protect shrubs from the larval feeding in the spring.

According to Research Entomologists at Michigan State University, these viburnum species are highly resistant: Koreanspice viburnum (V. carlesii), Burkwood viburnum (V. burkwoodii), doublefile viburnum (V. plicatum var. tomentosum), Judd viburnum (V. x juddii), lantanaphyllum viburnum (V. x rhytidiphylloides), and leatherleaf viburnum (V. rhytidiphyllum).

‘Furman’s Red’ Sage For Long Blooming Period

Posted by Hugh on August 28th, 2016

Salvia ‘Furman’s Red’

Texas sage (Salvia greggii) is a low bushy native perennial or woody shrub. It is native to Texas south to Mexico and varieties come in white, red and purple. It has proven to be exceptionally cold hardy (USDA hardiness zones 5b-9).

Furman’s Red sage is a superior cultivar here in the Southern Appalachian region.Flowering is best in spring, less so in summer, and finishes with a superb show in the fall.

Furman’s Red salvia demands sunlight (6 hours minimum) and a well drained garden soil. It tolerates a wide range of soils, wanting only good drainage. Feed a slow release fertilizer such as Osmocote® or Nutricote® at planting time or in early spring. An alternative fertilizing plan is to apply Miracle-Gro®, or Schultz® every 4-6 weeks according to package directions.

Plants grow upwards of 3 feet tall and 2 feet wide. From late spring, summer and early fall, this long-flowering salvia is topped with bright red two-lipped flowers. Leaves are soft green. Foliage is mostly deciduous, but foliage remains green over mild winters in zone 6 Tennessee.

Tidy up old plants in early spring and cut back in summer to stimulate a second flush of flowers. Follow a regular watering schedule in the first growing season to develop a deep, extensive root system. Added irrigation encourages repeat blooming in hot dry summers.

The minty fragrance of the flowers attracts hummingbirds, butterflies and bees. Texas sage is deer and rabbit resistant.

Furman’s Red salvia is a 2005 Plant Select Winner. Available is limited to on-line native plant nurseries such as High Country Gardens in New Mexico (mailing address 2438 Shelburne Road Suite 1, Shelburne, VT 05482).

Late Summer Bulbous Beauties – Spider Lily and Fall Crocus

Posted by Hugh on August 26th, 2016

Spider Lily Pops Up in Weedy Lawn

Colchicum (fall crocus)

Spider lilies (Lycoris radiata) go by a number of colloquial names including resurrection flower, surprise lily, and naked ladies. Naked 1-2 foot tall flower scapes bear 4-6 bright coral-red flowers. Each 2- inch long flower exhibit reflexed tepals and long protruding stamens resembling spider legs (common name “spider lilies”).

Almost overnight, the leafless flower spikes arise in late summer. Several weeks later, strap-like gray-green leaves arise where the floral stalks had been and have now disappeared. Foliage stays evergreen through the winter to feed the below ground bulbs before dying back in spring.

Plant bulbs 9 -12 inches apart in late spring or early fall. Plant them shallow with the neck of the bulb just peaking through the ground. Plants will naturalize by bulb-offsets and form small colonies over time in the southeastern U. S. (USDA hardiness zones 6-10).

Autumn crocus (Colchicum autumnale) is native to Great Britain and Ireland (USDA hardiness zones 4-7). Colchicums bloom in the earliest days of fall often coming up in late August. In late spring, plants send up 4-6 dark green lance-shaped leaves, some which 10- 14 inches long. The foliage yellows and dies down by summer into dormancy. Flower stems with no leaves emerge from the ground to 4-6 inches tall in late summer to early fall bearing goblet-shaped 3 inch long flowers. Flower colors vary from purple to pink to lilac. Weak flower stems tend to flop.

Plant corms 3 inches deep and 6 inches apart in August for bloom that occurs in the same year and many years following. To move or expand an existing planting, mid- to late-summer in the best time.

Both Lycoris and Colchicum grow in organically rich, medium moisture, well-drained soils in full to partial sunlight. Plants respond negatively to soil moisture, preferring dry soils during the summer dormant season and moderate soil moisture during bloom period in late summer. Provide a minimum of 4-5 hours of sunlight for high flower count.

Colchicums (autumn crocus) are not be confused with the true autumn crocus or saffron crocus (Crocus sativus) that also bloom around the same time. The latter are edible and closely related to the spring-flowering crocuses. All plant parts of colchicum are highly poisonous

Neither lycoris or colchicums have serious insect or disease problems. In a wet summer slugs and snails may become significant troublesome pests.

“Plant It Pink” Planting Program

Posted by Hugh on August 23rd, 2016

Invincibelle Spirit ll Hydrangea

Invincibelle Spirit ll (photo provided by Proven Winners)

To build awareness and show support for those affected by breast cancer, over 40 volunteers filled public gardens and surrounding areas with pink plants in downtown Haslett, a suburb of Lansing, MI. The Invincibelle® Spirit II hydrangeas are a beautiful reminder that we are not alone in our hopes and prayers for a cure.

With one in eight women facing a breast cancer diagnosis in their lifetime, Proven Winners® ColorChoice® supports the Breast Cancer Research Foundation (BCRF). BCRF is the highest rated breast cancer organization in the U.S. and provides critical funding for cancer research worldwide to fuel advances in tumor biology, genetics, prevention, treatment, metastasis and survivorship. Since 2009, over $903,000 has been raised for BCRF through plant sales and Pink Day fundraisers hosted by independent garden centers across the United States and Canada.

This donation effort continues the legacy of giving one dollar($) from each plant sold to BCRF. Invincibelle® Spirit II (Hydrangea arborescens ‘Invincibelle Spirit ll’) is a 2015 introduction. It is an improvement upon the original Invincibelle® Spirit, from the breeding work of Dr. Tom Ranney at the North Carolina Research and Extension Center at Mills River, NC. Invincibelle Spirit ll hydrangea has brighter flower color, stronger stems, and superior container presentation. It is also a reliable re-bloomer that sparkles in gardens from Manitoba to Mobile.

Simple Growing Information: Smooth hydrangea (H. arborescens) is a loosely branched deciduous shrub that grows to 3 – 6 feet tall and wide (USDA hardiness zones 3-9). This native species is easy to grow in average, moisture, well-drained soil in partial sun to shade. Invincibelle® Spirit hydrangea series grows more compact at 3 – 4 feet in height and width. It flowers on new wood from late spring thru early summer. Prune this hydrangea after the main flowering period has finished. Irrigate shrub(s) during dry periods to keep summer foliage looking fresh.

Credit: sales data on Invincibelle Spirit II hydrangea provided by Mark Osgerby, Spring Meadow Nursery, Inc. in Grand Haven, Michigan. Photos provided by Proven Winners.

Seeding Shady Areas Of Your Property

Posted by Hugh on August 21st, 2016

Shady Patch of Lawn

How many times have you been told: “you can’t grow lawn grass in shady areas”. Most lawn grasses perform best in full sunlight. Red or chewings fescues (Festuca rubra) perform under as little as 2-3 hours of direct or dappled sunlight.

Shade fescues are relatively easy to maintain. Mowing height should be 2 inches high in spring and fall and 2 ½ inches in summer. They do not require much fertilizer. Red fescues tolerate winter cold temperatures, but are less drought and heat tolerant than tall fescues. They also resent heavy foot traffic.

Fertilize shade fescue lawns at least twice annually – March or April and again in September or October. When starting a new seeding, use 3-4 lbs. seed/1000 sq. ft. rate.

Preparing new ground: rototill to a depth of 4-6 inches. Have a soil test performed at least 4-6 weeks prior to seeding to accurately determine how much lime (or gypsum) and fertilizer to apply. If the soil has not been tested in 3 or more years, apply a complete lawn fertilizer (contains N, P, and K) according to recommended rate on the package. Evenly rake fertilizer and organic amendments into soil and eliminate soil ruts.

Evenly disburse (sow) grass seed according to recommended package seeding rates. Lightly rake the seed into the soil ⅛ inch deep. Keep the area watered daily (if no rainfall) until seeds have germinated (usually in 10-14 days) and the seedlings have grown sufficiently to establish a lawn.

Extra step prior to seeding: if the site is excessively weedy, mow the area and apply a non-selective herbicide such as glyphosate (Roundup™).

Covering Bare Spots: Mow lawn closely, rake up cut grass, leaves, stones, sticks and other debris. Sow seed in bare areas by hand, fertilize and add soil amendments as needed. Seeding rate is 1-2 lbs per 1000 square feet.

Flowering Cabbage and Kale For Autumn Gardens

Posted by Hugh on August 18th, 2016

Collection of Flowering Kale at Dallas Arboretum

Flowering Kale in Container

Creating both edible and ornamentally pleasing vegetables has been a goal of plant breeders. Flowering cabbage and kale (Brassica oleracea) are a new landscaping niche in the autumn garden. Plants develop huge leafy rosettes and eventually form heads. Color patterns on leaves include white, cream, red and purple shades. The younger center leaves of the heads are mostly edible.

Grow ornamental types like you would their edible cousins in garden beds or in containers. Plants are cold hardy and make it through winter without injury in zones 7 and 8. Further north in zones 5 and 6, winter treats the foliage more harshly and plants start to decline around Thanksgiving. A touch of frost brings out the blues and purples of leaf color.

In most growing regions growing ornamental kales and cabbages in full sun is preferred. Further south, take into account the intense sun in south Florida, Texas, and California; light afternoon shade is the rule for heads to reach maximum size. Mature plants may measure 1 to 1½ feet across.

In late summer transplants are set out and should be watered, fertilized, and sprayed for insects. Set plants about 1½ feet apart in a garden (or containers) when summer heat begins to moderate and cool nights have returned. Lightly fertilize plants monthly with water soluble fertilizers such as Miracle Gro®, Daniels®, or Nature’s Source®.

If white cabbage or sulfur butterflies are still fluttering around, spray with a biological insecticide such as Bacillus thuringiensis (BT) or other pesticides sold at most independent garden centers. An alternative to spraying pesticides is to cover plants with a row tunnel or finely spun fabric netting in late summer while caterpillar activity is still high. Choose a different planting spot each year so that soil-borne diseases do not build up in the soil.

Broadleaf Weed Control Starts In Late Summer

Posted by Hugh on August 15th, 2016

Thistles difficult to manage

Winter annual weeds in fall garden

Broadleaf weed control takes center stage for chores to tackle in home lawns and gardens in late summer. Many winter annuals like henbit and chickweed, common inhabitants in the early spring garden start to germinate on the early days of autumn. Perennial dandelions are poking their heads up after summer dormancy. Spring and early summer herbicide applications may not provide as good of control as in fall.

In the spring there is the danger of pesticide drift onto nearby good landscape plants. In the fall deciduous shrubs and trees are shedding their leaves and become less susceptible to the spray drift from Roundup and phenoxy herbicides (active ingredients: 2,4-D, dicamba and MCPP). Be careful not to overapply dicamba in ground around trees and shrubs you want to keep.

Weedy trees, shrubs and vines are also tough to eliminate. Examples are poison ivy, English ivy, Virginia creeper, tree of Heaven (Ailanthus), and thorny brambles. These are best managed starting in mid- to late-summer. Some broadleaf weeds such as thistles, knotweeds and spurge do not give up easily and multiple applications are the rule. Heavy weed invasion in lawns represents poor mowing practices, low soil fertility, or all the above.

Thoroughly read, understand, and follow all information on herbicide labels. Again, never spray on windy days; avoid hot days (over 85 °F) and herbicide volatility. Don’t spray weeds when they are drought stressed. Do not spray if rainfall is forecast within 24 hours following application. Don’t mow for 2-3 days before or after application. Wait a minimum of 30 days before seeding an area treated with broadleaf herbicides.

Important rule on fall spraying: Outside temperatures should be 60 °F and warmer over a 6 hour interval for the foliar herbicide spray to be absorbed inside the target weeds.

Japanese Asters (Kalimeris) Are Summer-blooming Gems

Posted by Hugh on August 12th, 2016

Japanese aster (Kalimeris)

Double Japanese asters (Kalimeris pinnatifida) are not true asters. They bloom in summer unlike the more popular fall blooming asters (Symphyotrichum spp.). Essentially, the genus Kalimeris (from Asia) and Boltonia (U.S. native) are closely related and used interchangeably.

‘Pinnatifida’ is without question the best known cultivar. In August the plant is smothered with 1-inch diameter semi-double white daisy flowers with buttery yellow centers. Blossoms mimic miniature mums. It forms an upright, bushy 2 to 3 feet tall plant. Small basal leaves form a rosette, each 2-3 inch long, narrow, and deeply cut lobes (pinnate); even smaller 1 inch long lance-shaped medium green leaves form around flowers.

Semi-double flowers do not reseed; over time a single plant will sucker and colonize around itself, and are not invasive. Kalimeris may be divide in spring to maintain overall vigor and to form new starts in your garden or friend’s. Fertilize in early sping with a slow release fertilizer such as Osmocote™, Nutrikote™ or Nature’s Source™. Foliage and flowers are not trouble by disease or pest issues.

Kalimeris is easily grown in moist, well-drained soil in full to partial sun (USDA hardiness zones 6-9). Mulching aids to reduce mid-summer drought stress and induce flower power. In hot southeast U.S. partial afternoon shade keeps plants blooming longer.

In shady spots plants may take on a wild rambling look; either cut-back them by half in early summer to develop a dense shrubby habit or remove surrounding vegetation. Utilize kalimeris for floral color in a perennial border, wild garden or meadow.

Japanese aster was a favorite of the late Elizabeth Lawrence, a wonderful southern garden writer.

New PG Hydrangeas Excel In Performance

Posted by Hugh on August 10th, 2016

H. paniculata ‘Little Lime’

Hydrangea ‘Quick Fire’

Panicle, PeeGee or PG hydrangeas (Hydrangea panculata) brighten up the July and August garden landscape. They’re native to China and Japan.

They grow and bloom almost anywhere in the U.S. (USDA hardiness zones 3 – 8). Unlike mophead hydrangeas (H. macrophylla), that often fail in full day sun, PGs excel in 6 hours or more of sun.

PG hydrangeas are vigorous growers with upright branching and coarse textured deciduous foliage. Depending on variety, shrubs grow 3-15 feet (some to 25 feet) tall. Multi-branched shoots are clothe with dark green, oval shaped leaves and are topped with upright, sharply-pointed, conical, 6-8 inch long terminal flower panicles. Flowers may be a mix of both fertile and sterile florets and bloom from mid-summer into fall. PG hydrangeas are pruned any time from late fall to mid-spring. They may also be trained into a tree form.

Most gardeners today know PGs by the best selling cultivar ‘Limelight’ which has become the standard for excellence. It grows 6-10 feet tall (depending on amount of annual pruning provided); heavy with 6-8 inch, conical shaped, terminal flower panicles; branching is very upright.

‘Limelight’ at NC Arboretum, Asheville, NC

Three of “new” best paniculatas are:

‘Little Lime’ – grows 5-7 feet tall; large, tightly packed, lime-white flowers that turn shades of pink where summers are cool.

‘Quickfire’ – grow 6-8 feet tall and equally wide; blooms are white, become pink after a few weeks, and finish rosy-pink.

Bobo™ – this Belgium introduction is a very compact size that is ideal size-wise in small gardens and patio containers; large white loose blooms midsummer to fall.

Bacterial wilt, leaf spot, rust, and mildew diseases and aphids and mites are occasional disease and insect problems. Poor site selection often enhances problems with diseases and pests.

Garden Phlox – Select Mildew Resistant Varieties

Posted by Hugh on August 7th, 2016

Garden phlox (bicolor)

Phlox ‘David’

Garden phlox (Phlox paniculata), aka summer phlox, is native from New York to Iowa south to Georgia, Mississippi and Arkansas (USDA hardiness zones 4 to 8(9)). They are valued for their long beautiful floral display and fragrance. In the wild phlox grow it in moist, rich open woodlands, alluvial soils along streams and rich garden soils.

The right location is an absolute when growing garden phlox. Phlox prefer an compost-rich, moist, moderately acidic, well-drained soil. Best flowering on sturdy healthy plants is in full sun. Space plants adequately for good air circulation to prevent or reduce powdery mildew problems. Phlox are intolerant of dry soils and summer dry spells. Avoid overhead watering and trickle irrigation; mulching helps to cool soil and maintain soil moisture. Remove faded flower panicles to prolong bloom period and to prevent unwanted self-seeding (cultivars generally do not come true from seed).

Garden phlox are clump growers and grow 2-4 feet tall and 2-3 feet wide on sturdy stems. The dark green lance-shaped leaves are 4-6 inches long and prominently veined. Dome shaped flower clusters are densely packed with a hundred or more 1 inch wide tubular florets. Each individual floret has a long corolla tube and five flat petal-like lobes. Color choices include white, lavender, pink, rose, red and bi-colors. Butterflies and hummingbirds swarm around the fragrant flowers; deer usually stay away.

Divide clumps every 3-4 years to maintain plant vigor.

Phlox is not always an easy plant to grow. Powdery mildew and occasional spider mites can be troublesome, particularly in the southeastern U.S. Do your homework when selecting the cultivars to plant in your garden. Check for trial garden evaluations at state agricultural university. A cultivar rated as resistant in powdery mildew in Chicago may not be in Philadelphia, Atlanta, or Dallas. In a 1999-2001 North Carolina State University Trial in Mills River, no varieties proved to be completely powdery mildew resistant. However, these cultivars exhibit a high degree of disease resistance: ‘David,’ ‘Delta Snow,’ ‘ Natascha,’ ‘Robert Poore,’ ‘Speed Limit 45’ and the species Phlox caroliniana.

Some comments from Mt. Cuba phlox trials (2015-17) in Delaware have been added. This garden blog will be updated in future.

Powdery mildew resistant cultivars to try:

‘David’ – pure white tubular florets; 3-4 feet tall and 2-3 feet wide; floral display not impressive in Mt. Cuba trial.

‘Delta Snow’ – snowy white tubular / purple eye florets; 2-3 feet tall and wide; plants became floppy in midsummer in Mt. Cuba trial.

Flame™ Pink – fuchsia pink /darker pink eye florets; compact 15-18 inches tall and wide; some leaf spotting in late summer.

‘Katherine’ – dense, blue-lilac / white center florets; 2-3 feet tall and wide; spider mites problem in Mt. Cuba trial.

‘Minnie Pearl’ – white florets; 20 inch tall and wide; repeat blooming; floppy plant habit in late summer.

‘Robert Poore’ – rich lavender purple florets; 4-5 feet tall and 2-3 feet wide; spider mites problem in Mt. Cuba trial..

‘Shortwood’ – pink / dark pink eye florets; 42-48 inches tall and 24-30 inches wide.

‘Volcano Purple’ – lavender/purple / white eye florets; very compact 12-20 inches tall and 18-24 inches wide.

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