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

Vanilla Strawberry™ Hydrangea

Posted by Hugh on June 18th, 2015

‘Vanilla Strawberry’ Hydrangeas at Biltmore Estates, Asheville, NC

Vanilla Strawberry™ hydrangea (Hydrangea paniculata) is a new peegee hydrangea selection introduced from France and it is really catching on with U.S. gardeners (USDA hardiness zones 4-9). This exceptionally cold hardy hydrangea blooms from late June thru early September. Blooms are enormous and stand upright. Following a heavy summer shower, saturated floral trusses temporarily bow down under their sheer weight, but gradually recover.

Flower color varies with age: new blooms open green, turn creamy white, to blushing pink, and finish rosy pink! New blooms are produced over 3 months. Cut flowers make great additions to fresh and dried floral arrangements.

Vanilla Strawberry is a vigorous grower and low-maintenance. Shrub is a well-branched and reaches 6 to 7 feet high and 4 to 5 feet wide in only 2-3 years. Grow panicle (“peegee”) hydrangeas in full sun in zones 6 and further north; in southerly climes, provide full morning sunlight and moderate afternoon shade. Hydrangeas thrives in moist, well-drained soil. Feed hydrangeas in early spring with a season-long slow-release fertilizer. Apply 2-3 inches of an organic mulch in the spring to conserve soil moisture. Irrigate during long summer dry spells.

Peegee hydrangeas look great as a deciduous hedge, or scattered in an open woodland garden, or as an individual specimen shrub. It can also be trained as a single trunk tree. They are troubled by few disease or pest problems. Since they bloom on current season’s wood, prune in late winter to reduce plant height and spread and to remove weak thin branches. Hydrangeas attract several kinds of butterflies.

Lots Of Stokes Asters To Pick

Posted by Hugh on June 15th, 2015

Stokesia ‘Peachie’s Pick’

Stokes aster (Stokesia laevis) is an underutilized herbaceous perennial. It is indigenous to the southeastern United States (USDA hardiness zones 5-9 and AHS heat zones 4-11). Many attractive cultivars are now available (see below). Most stokes asters produce mostly blue and purple colored floral cultivars, but violet, yellow, white, and blended color forms are also available.

Stokes aster prospers in full sun but does tolerate very light shade. A well-drained soil is absolutely essential; it tolerates a wide range of soil types. A one year-old established clump is moderately drought tolerance. Soppy winter soil is the usual cause of losing Stokes aster; few garden diseases and pests trouble this perennial.

It bears large showy flowers from late spring through summer. Blooms are attached to short stalks and sit slightly above the foliage canopy. Most cultivars produce two and more flushes of flowers if deadheaded immediately and irrigated over dry periods. Fertilize at planting time or in early spring with a slow-release product such as Osmocote™, Nutricote™, or Nursery Special™.

Cultivars:

White flowering – ‘Alba’ and ‘Silver Moon’

Blue-flowering – ‘Blue Danube’, ‘Blue Moon’, ‘Blue Star’, ‘Klaus Jelitto’, and ‘Wyoming’.

Yellow flowering – ‘Mary Gregory’ (large 3-4 inch wide lemon yellow).

Deep purple flowering – ‘Honeysong Purple from Wayside Gardens of Hodges, SC; the tint deepens as the flower ages, contrasting with white stamens and red overtones.

Lavender-blue flowering – ‘Omega Skyrocket’ bears on long stalks, a trait that endears it with cutflower enthusiasts. A white selection is also available.

‘Peachie’s’, often listed as ‘Peachie’s Pick’ in nursery catalogs, is the cultivar that gets the most buzz. It was selected by Peachy Saxton in Meridian, MS. It bears large lavender-blue flowers that stand tall above the plant foliage. It blooms repeatedly from mid-June to frost.

It has large 2- inch diameter lavender-blue flowers on erect 18-inch stems from mid-summer onward. Peachie’s Pick forms a tidy 10-12 inches tall and 18-20 inches wide mound of deep green foliage; foliage is evergreen during most winters in zones 7-9.

Swamp Azalea Deserves More Garden Space

Posted by Hugh on June 12th, 2015

‘Lemon Drop’ Swamp Azalea (Photo by Jay Jackson)

‘Miss Lindy’ -pink selection from Jay Jackson (his photo)

Swamp Azalea (Rhododendron viscosum, formerly R. serrulatum) is very different among deciduous azaleas. Most rhododendrons (azaleas) do not care for soppy, poorly drained soils. This U.S. native is an exception, indigenous to swamps, bogs, stream edges and wet lowlands from southern Maine to northeastern Ohio south to Florida and Alabama. Add that it is also exceptionally winter hardy (USDA hardiness zones 4-9). If your property has a stream, pond, or leach field, this species is a good choice.

Swamp azalea grows 8-10 feet tall and 6-8 feet wide. It is an early summer bloomer with abundant long tubular flowers that some might confuse as wild honeysuckle (Lonicera spp.). Its spicy, clove-scent fills the late June-July garden air and attracts butterflies and hummingbirds. The 1 to 2 inches long white flowers are sticky to the touch. Pale pink and lemon yellow forms can be observed in the wild.

Two-year old established plants are highly drought tolerant. The glossy green summer foliage is highly disease and pest resistant; some wild forms emerge with bluish green leaves in the spring. All plant parts are poisonous and deer usually keep their distance. Among the native deciduous azaleas, swamp azalea’s flame red foliage color is exceptional. Pruning is best after flowering to manage plant height and spread.

Swamp azalea is best grown in acidic (pH range between 5.0 – 6.0), compost-rich, well-drained soil and under partial shade. Full morning sunlight in northerly zones (zones 4-7) is adequate. Some seaside selections are very salt tolerant, and is best sited away from strong winter winds.

Roots are fibrous and grow near the soil surface. They benefit from annual mulching (wood chips or pine bark or needles). Plants slowly naturalize from root suckers.

Cultivar list includes ‘Lemon Drop’ , ‘Parade’, ‘Pink Mist’ , ‘Pink Rocket’ among others.

Japanese Hydrangea Vine Worth The Wait

Posted by Hugh on June 10th, 2015

Flower/foliage of cultivar ‘Moonlight’

5 year old Schizophragma hydrangeoides

Japanese hydrangea vine (Schizophragma hydrangoides) ‘Moonlight’ is a deciduous woody vine (USDA hardiness zone 5 to 8). It is closely related to climbing hydrangea vine (Hydrangea anomala ‘Petiolaris’).

This ornate climbing vine is valued for its silvery, silvery-green, heart-shaped foliage and large, flat-topped, lace cap hydrangea-like clusters (8-10 inches across) of creamy white flowers. Initially, it starts out slowly, but will cover a 5 square foot area on a wall and puts on a fabulous flowering show after 5 years.

The 8-10 inch wide creamy -white panicled blooms are comprised of numerous fertile florets surrounded by sterile outer flowers that each have only one spade-shaped petal. They appear in late June into July in Tennessee bloom for 6 to 8 weeks. Flowers are lightly fragrant up close. Leaves measure 3-5 inches across with good yellow fall color.

This woody grows against a wall, fence, or large tree. Fine adhesive rootlets emerge from young stems and attach to the mortar or brick surface. Reddish-brown stems provide a little winter interest. The silver-green leaves have long petioles with deep-green veining.

Japanese hydrangea vine is planted in part sun to partial shade for best flowering and foliage. Grow it in rich, medium moisture, well-drained soil. Fertilize lightly in early spring, but do not over stimulate. Prune in late winter to early spring to remove any winter injured stems and to contain growth. A single plant will eventually grow 20 to 30 feet or more wide. Space multiple plants 6-9 feet apart along any long wall to be covered. Insect or disease problems are rare.

Vine growth rate: over the first two years growth rate is slow, but gains speed in subsequent years. Plants begins blooming within 3 years which is a lot better that hydrangea vine. It is not as pH sensitive as hydrangea vine.

Managing Leaf Spot Infections

Posted by Hugh on June 8th, 2015

Leaf spotting on Hosta

There are nearly 1,000 fungal pathogens that cause leaf spot diseases on garden plants. Fungal leaf spots vary in size—from the size of a pinpoint to lesions that consume the entire leaf. Many leaf spots are tan to dark brown in color and may be circular, angular or irregular in shape.

Some of the common leaf spot-causing fungi are Alternaria, Ascochyta, Cercospora, Colletotrichum, Fusarium, Gloeosporium, Helminthosporium, Phyllosticta, Ramularia and Septoria. Generally, they do not kill plants but mar their attractiveness.

Most leaf spot diseases require cool conditions, wet foliage, high humidity and little air movement. Crowded plants often lead to leaf spot infections. Long intervals of wet weather in spring and summer or overirrigating enhances infection outbreaks.

The first rule is to keep foliage as dry as possible. Water at times of the day when the foliage will quickly dry out; avoid late night irrigation. Secondly, increase air movement around plants.

Learn to properly identify leaf spots by the symptoms and adopt the best control strategies. Leaf samples may be sent to a diagnostic clinic at your state’s university lab or local Extension office.

A number of fungicides are labeled for controlling a wide range of leaf spot diseases. Some of the most effective for leaf spots include Pageant (pyraclostrobin + boscalid), Medallion (fludioxonil), Eagle/Systhane (myclobutanil), Chipco 26 GT (iprodione) and Daconil (chlorothalonil).

Remember that fungicides are protectants and not cure-alls. Applied the fungicide before symptoms (leaf spotting) is detected. These products can prevent fungal leaf spots from spreading. Good cultural practices and irrigation timing, along with proper preventative or control strategies will greatly reduce leaf spot severity.

Credit: Thank you to Paul Pilon, Ball Horticulture, Chicago for information in this blog.

Sunset Cutie® Gaillardia

Posted by Hugh on June 5th, 2015

‘Sunset Cutie’ Gaillardia (photo by Paul Pilon)

New from PlantHaven is a new 15-inch gaillardia (Gaillardia x grandiflora) called Sunset Cutie® with red-bronze flowers edged in creamy yellow. It will leave a bright fiesta feel to our home landscape.

Sunset Cutie has a compact mounding plant habit. It will bloom nonstop on your patio this summer or in your perennial flower bed. It is hardy to Zone 5 to 9.

Grow gaillardias in full sun and well-drained soil or container media. Soil (media) drainage is an absolute key to plant and flowering longevity. Keep plant(s) adequately watered and fertilized. Feed container grown plants monthly with a water soluble fertilizer such as Miracle-Gro™, Schultz™, or Nature’s Source™.

Gaillarida or “blanket flower” is seldom bothered by deer. Deadheading keeps plant(s) blooming from late spring to autumn’s first frost.

Winter Damage On Crape Myrtles

Posted by Hugh on June 2nd, 2015

Crape myrtles suckering from base

Winter damaged crape myrtle

Extremely cold winters of 2013-14 and 2014-15 have damaged many cultivars of crape myrtles (Lagerstroemia x indica). Don’t assume that new crape myrtles are hardy; many are rated hardy only to zone 7. Several of the U.S. National Arboretum cultivars are hardy in zone 6. Gardeners living in the Mid-Atlantic or the lower Midwest states, where crape myrtles are iffy, frequently start over by cutting them back near the ground in spring and fertilizing.

Is your crape myrtle dead? First, determine if the tree (shrub) is alive? Nick the bark with your fingernail or a knife to determine if the wood is still green (living). Use a chain saw, pruning saw or loppers to cut the trunk(s) close to the ground. Within a few weeks green shoots will begin sprouting around the base. Choose 3 – 5 well-spaced shoots to become the new main trunk(s) and cut off the rest. Large specimens can sucker back and even bloom in late summer and the early days of autumn.

Fertilize every 6 – 8 weeks with a high-nitrogen fertilizer until mid-August and no more through the end of the year. Maintain 2 – 3 inches of mulch and keep soil and mulch away from the shrub/tree base. Irrigate crape myrtles bi-monthly in the absence of rainfall.

When replanting, set crape myrtles in the ground shallow and never deep in the planting hole. Stop the practice of hat-racking, commonly called “crape murder”, as it places a tree under stress and more susceptible to winter freeze damage. Do not prune crape myrtles in the winter months (early March in most areas).

Finally, select exceptionally cold-hardy cultivars, such as ‘Natchez’ (tree form, white blooms), ‘Hopi’ (shrub, medium pink), ‘Acoma’ (shrub, white).

Modern Day Clematis Bloom Freely

Posted by Hugh on May 29th, 2015

Late Summer Blooming C. viticella 'Emily Plater'

Late Summer Blooming C. viticella ‘Emilia Plater’

Free-flowering ‘Rooguchi’ clematis

The old-fashioned clematis(es) in grandma’s garden bloomed one time in spring or summer and bore huge showy flowers (USDA hardiness zones 3-7). Vines took up lots of space in the garden. Old cultivars grew 8-9 feet tall; many bore one single large flower at the end of each growing stem. They bloomed at one time and, even today, are stunningly beautiful and still sold at many garden centers.

Today’s gardens are smaller in size. Clematis plants need to be more compact, free-flowering, and produce more flower power over several months in smaller spaces. Modern day clematis are fibrous rooted to withstand colder winters and have better mildew disease resistance. Many are double flowering, offer more color choices that do not fade and are easier to prune. Early flowering types are also available that bloom profusely on either old wood or new growth.

Many shorter types can be grown in pots and containers instead of walls and trellises. Some are “free-flowering” types produce a lot of flowers up along their stems. Some develop 5 to 7 leaf nodes that form multiple flowers buds over several months.

Many gardeners have a difficult time understanding how to prune clematis. Modern cultivars are a lot easier to prune. In early spring simply removed all but 6 to 9 inches of old vine wood above soil level. After pruning and fertilizing in early spring, vines and compact shrubby types grow rapidly and bloom over several months.

I highly recommend Raymond Evison 2007 book “Clematis for Small Spaces,” which details 150 of the best clematis cultivars for patios and decks.

Flame Azalea Favorite Among Native Azaleas

Posted by Hugh on May 26th, 2015

Young 4-year old Flame azalea (select seedling)

Flame azalea (R. calendulaceum) is a spectacular sight when it flowers in early May through June (depending on location). The mountainsides across the Appalachian region seem to be afire with their yellow, orange or red flowers (USDA hardiness zones 5 thru 8). Its native habitat is in open, dry sites in woods, on the hillsides, and on mountaintop open areas (“balds”) from 600 to 5,000 feet in altitude.

Flowers tend to be larger than other native azalea species. Each flower truss contains 3 to 10 flowers, which open before or when leaves are present. Funnel-shaped corolla is about 2 inches long and up to 3 inches wide. Long stamens protrude out from the corolla. The upper petal (lobe) on each bloom exhibits a prominent orange or pinkish blotch. Flowers tend not to be fragrant.

Flame azalea forms an upright branched shrub 5 to 12 feet high with an open spreading canopy. The medium green leaves take on yellow, bronze, and red hues in fall before abscising. Leaves are deciduous, about 1-3 inches long, medium to dark green above, and tiny hairs beneath. Both leaves and branches often develop in whorls.

Flame azaleas are difficult to propagate from cuttings, but are easily started from seeds collected in the fall. The tiny seeds are sprinkled on a fine peat /bark soil-less medium, lightly covered, and frequently misted with water daily. Seeds germinate over 2 – 3 weeks. It may take 3 or more years for seedlings to bloom for the first time.

In the garden flame azalea grows best in morning sun and afternoon shade. Soil drainage must be well drained and supplied with adequate moisture. Mulch around shrub with pine needles or nuggets. Avoid soppy soils! Feed lightly once or twice during the late spring during its growing period with an acidic water-base fertilizer such as Miracle-Gro™, Schultz™, or Natures Source™. Prune primarily to control shrub height and spread.

Flame azaleas are the “asked-for” native azaleas by gardeners, yet are rarely sold at garden centers. Find them at e-commerce nurseries on-line.

Red Abyssinian Banana For Tropical Looking Landscapes

Posted by Hugh on May 24th, 2015

Red Abyssinian Banana in container

Ensete banana

Red Abyssinian banana (Ensete maurelii ‘Red Abyssinian’) is a tropical banana from high in the mountains of Ethiopia in eastern Africa. Its enormous reddish to purplish foliage and red – burgundy trunk adds a tropical presence to any garden. Compared to hardier banana genus Musa, Ensete does not produce root suckers (pups) nor is it a clump grower. All foliage originates from one trunk. By late September plant may grow 8 – 10 feet tall and 6 – 7 feet wide in temperate gardens and double that size in tropical regions.

Individual leaves expand to 10 feet or more in length. The green leaves orient upright and are splashed with vivid burgundy splotches over the new stems and foliage. Foliage color is more vivid if grown in full sun. Red Abyssinian can be planted in large containers or troughs and set on your deck or patio.

Red Abyssinian holds its foliage very upright on a burgundy colored pseudo-trunk. Spring/summer growth is extremely vigorous. This tropical banana excels in hot, humid, wet summers and rich fertile soils and fails when soil moisture and nitrogen fertilizer are lacking.

At the garden center your initial purchase may be a 18-inch starter plant from tissue culture, and in only 4 – 5 months it develops into a 6 – 8 foot giant. Beautiful flowers form only in tropical climates with a much longer hot weather to permit uninterrupted growth.

Select a large container greater than 24 inches in diameter at the base and weighted down to support what will be an enormous plant by late summer. Maintain your banana on the luxury diet with sun, water and liquid fertilizer.

Choose flowering bedding plants, large leaf hostas, vining ground covers, and/or ferns to complement Ensete banana in a container. In zone 8 and further south combine tropical gingers, spiky-leaved phormiums, and various palms.