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

Favorites Among The Rose Of Sharon (Althea) Shrubs

Posted by Hugh on August 15th, 2018

‘White Chiffon’ hibiscus (scene in a shopping mall)

‘Sugar Tip’ hibiscus

Rose of Sharon, aka shrub althea, (Hibiscus syriacus) is a woody hibiscus shrub that is hardy in temperate northern areas of the U.S. (USDA hardiness zones 5-9). This summer flowering shrub is exceptionally easy to grow. At one time, it was a great pass-along shrub that fell out of favor. However, old fashioned varieties frequently reseeded around the garden. New cultivars strut variegated foliage, double flowers, and infertile (sterile) blooms that produce little or no seed.

Rose of Sharons are available in a wide range of flower colors including pink, purple, blue, white, and almost red. Blooms may be single, semi-double, and double and range in size from 2-5 inches across. They grow in average to good garden soils with moderate drainage. For maximum flowering, site plants where they receive 6 or more hours of direct sun and feed annually with a slow-release fertilizer such as Osmocote™ or Nutricote™. Blooms attract numerous bees and butterflies. Japanese beetles may mar the flowers for a few weeks in early summer, but shrubs generally rapidly recover.

After their first year, Rose of Sharons are highly drought tolerant. Shrubs respond well to annual pruning and to severe “rejuvenating” by pruning to a few inches above the ground. Some gardeners opt to grow them as perennials by cutting he plant back every year or two. In late spring the “shortened” plant(s) emerge and only grow a few feet tall with many stems and flowers.

‘Lavender Chiffon’

Top Picks Among Rose of Sharon Cultivars:

Chiffon® series feature anemone-like double blooms for low seed set and long-blooming; color choices: Lavender (purple), Blue, and White; 8-12 feet x 6-10 feet wide.

Sugar Tip® – pure pink double blooms (no seed) and variegated creamy-white / bluish-green foliage; 8-12 feet x 6-8 feet.

Purple Pillar® – slender columnar growth habit (16 feet tall x 3 feet wide), ideal fit for small urban gardens; 4-inch vibrant purple single to semi-double flowers with red centers.

Utilize Rose of Sharon as a specimen shrub or small tree, as a shrub border, or set into a large container.

Growing Castor Bean Plant

Posted by Hugh on August 10th, 2018

Castor Bean (Ricinus communis)

Over the years castor bean (Ricinus communis) plants have been a common sight in public gardens. These tall ornamental annuals are cherished for both their colorful flowers and seed capsules, and bold foliage. The species, a botanical member of the spurge family (Euphorbiaceae), is indigenous to the southeastern Mediterranean region, Eastern Africa, and India. Unlike many spurges, the sap is watery and not milky.

Castor bean is known by a number of colloquial names including mole killer plant and castor oil plant. Each fruit is a spiny capsule containing large, bean-like seeds, with a brownish mottling shells. Despite its name, castor bean is not a true “bean”. Plant stems and spiny seed pods vary in color and are showier than the actual blooms. The male flowers are yellowish-green with creamy white stamens. The female flowers hide within the spiny seed pods, have red stigmas, and are produced in less numbers than the male.

Modern day landscape varieties are selected for leaf and flower color as well as oil production. Growth rate is very rapid and can easily grow 10 feet and more in a single growing season. Its enormous, glossy palmate star-like leaves measure anywhere from 6 to 30 inches across, and leaf lobes, numbering 5 to 11, are deeply cut. Each leaf is attached by a long slender petiole to the main stalk. With some varieties the leaves start off reddish purple, bronze or green, gradually developing darker tones as they mature.

Planting into your landscape, sow the seeds or transplant starts in full day sun and in deep humus-rich soil. In northern areas, where the growing season may be short, start plants from seeds indoors. Shelter plants from strong winds that can damage the large, glossy leaves. Water and fertilize generously for super- sized plants.

In the 16th century, castor oil was utilized as an alternative to lamp oil. In the U.S., castor bean plants were grown for its oil, used in making soaps, linoleum, nylon, paints, et al. In the first half of the 20th century it was also used as a laxative and in skin and hair cosmetic products. Plant roots repel gophers and moles.

Warning: the colorful castor bean “beans” are highly ornamental and highly poisonous. if ingested. If you wish to save the seed from one year to the next, wear rubber gloves to carefully cut apart the seed stalk. Allow the seed pods to dry in a cool dry room; crack open and remove the seeds carefully. Place the seeds in a paper envelope and store inside your refrigerator. Be certain to label “highly poisonous”.

Recommended Varieties:

‘New Zealand Purple’

‘Carmencita Bright Red’, ‘Pink’, ‘Rose’

‘Gibsonii’

‘Red Spire’

Korean Sweetheart Tree

Posted by Hugh on August 1st, 2018

Fruit capsules fill the tree in August

Unique Striated Bark

The late Dr. J. C. Raulston, N.C. State University horticulture professor emeritus, discovered Korean sweetheart tree (Euscaphis japonica) in 1985 on the Korean Peninsula while participating in a U.S. National Arboretum collection expedition (USDA hardiness zones 6-8). Dr. Raulston brought seeds back to the N.C. State Arboretum for assessment and evaluation. The species common name “sweetheart tree” was coined by Tennessee nurseryman Mr. Don Shadow.

Small 9-inch long terminal panicles of yellow flowers appear in late spring, most hidden within the dense foliage and go mostly unseen. Opposite pinnately compound leaves are 6-10 inches long. The compound leaves are comprised of dark green, 2-4 inch long leaflets. The tree’s greatest asset is the showy bountiful clusters of heart-shaped fruit capsules. They gradually ripen from green to pink to finally red in late summer. In early to mid-October the fruit capsules split apart to reveal a tiny, shiny, black seed within. The grayish colored bark has white striations which provide some winter interest.

Sweetheart tree prefers a good loamy well-drained soil and planted in full sun to partial shade. Feed annually with a slow-release fertilizer such as Osmocote® or Nutricote®. Although an older established tree is highly drought tolerant, provide supplemental irrigation to a new 1-3 year old tree if summer rainfall is sparse.

No serious disease and insect problems trouble this small 2o-25 feet tall tree. In the early years corrective pruning is recommended for shaping the young tree. Availability is primarily from on-line plant nurseries.

Native Plumleaf Azalea Blooms In Late July

Posted by Hugh on July 28th, 2018

July-blooming Plumleaf Azalea

Rare Yellow Flowering Form

Plumleaf azalea (Rhododendron prunifolium) is a native deciduous azalea that grows in the Chattahoochee River Valley on the Georgia-Alabama line (USDA hardiness zones 6-9). It is one of the signature plants of Callaway Gardens in Pine Mountain, Georgia.

Their bright orange-red flowers surprise in late July into early Augusta and blooms may last for 2 weeks or more. Spring and summer foliage is medium-green and remains mostly blemish-free. Compared to many other spring blooming native azaleas, flowers are not fragrant. Fall leaf color is also uneventful. Insect and disease problems are rare if the plant is properly sited.

This 5-8 feet tall and wide shrub performs best in morning sunlight and shaded from the harsh afternoon summer sun. It grows in well-drained, compost amended soil. Plumleaf azalea prospers in the calcareous clay soils found in the Appalachian region without pH correction. Plant in full-day light shade in zones 7-9. Set the shrub into a shallow wide dug hole that has been generously amended with compost and/or peat.

Feed in early spring with a slow-release fertilizer such as Osmocote™ or Nutricote™. An alternative nutrition program is to use a water soluble product such as Miracle-Gro™ or Jack’s™ in early spring and again in early summer. Maintain 2-3 inches of a pine-based mulch around the base of the shrub. Irrigate plant(s) the first 2 years of establishment and you will be rewarded for many summers to come.

Plumleaf azaleas are usually available from mail order companies on-line. It is best to purchase and plant them before late spring so that their fine shallow rootsystem can adapt to their new site before winter arrives.

Plumleaf azaleas bloom on new current season’s wood. Prune deciduous azaleas anytime after bloom to maintain a desired height and spread. Plumleaf azalea is primarily available at local native plant nurseries or is offered online.

Very Rare Chinese Emmenopterys Tree

Posted by Hugh on July 25th, 2018

Chinese Emmenopterys (Photo by Dr. Tim McDowell, ETSU Botany Professor)

Emmenopterys flowers (photo by Dr. Tim McDowell)

Chinese Emmenopterys (Emmenopterys henryi) is rare in the wilds of China, and may be even rarer in cultivation (USDA hardiness zones 5-9). Discovered in 1907 by renowned botanist and plant hunter, Ernest H Wilson. He described it as: “…one of the most strikingly beautiful trees of Chinese forests.” It should grow 30 + feet tall, but can reach 80-100 feet in China.

Emmenopterys is widely distributed in south-central China, but is endangered due to agricultural expansion, logging, and poor forest regeneration. A member of the coffee family (Rubiaceae), the tree can grow to over 100 feet, although large specimens are extremely rare. Clusters of fragrant, creamy white, 1-inch, funnel-shaped flowers can be up to 10 inches across and are surrounded by large white “bracts,” similar to those seen on Japanese hydrangea vine (Schizophragma).

According to the China Plant Red Data Book, the species does not flower until 30 years of age and usually sets seed once every 2 to 4 years. A botanist in Johnson City, TN has nurtured a 15-year old specimen in his home garden. It has flowered a few times over the years, but never so fully. He reports that the flowers are very fragrant and are frequently visited by yellow swallowtail butterflies.

At Lewis Ginter Botanical Gardens in Richmond, VA, a nine-year old 25 foot tree was in full bloom on July 12, 2007. The funnel-shaped blooms have a unique form with each cluster surrounded by large white bracts; the blooms are accentuated by red petioles. Flowers are pollinated by a wide variety of insects including beetles and butterflies. Its seeds are winged and are distributed by wind.

At the Stephen F. Austin Gardens in Nacogdoches, TX, Dr. Dave Creech, Director of S.F.A. Gardens, reports that two plants were planted in 1998. “Our two trees have grown vigorously and are quite attractive in foliage. Our largest tree, the first to bloom, is now a full 25 feet tall and perhaps 20 feet wide at this writing (Nov 2009). While apparently quite healthy, the tree has not bloomed since the 2007 event.”

Dr. Creech describe the tree as having the clean, large opposite leaves with attractive red petioles. “Our two trees rest under a high canopy pine forest and in moist well drained soil. Both trees have grown vigorously and sport attractive ridged light-colored bark that is quite striking. White flowers are in panicles about 6 inches high and 8 inches wide with individual flowers less than an inch wide. The flowers are reminiscent of Pinckneya pubens.”

Propagation: Mist vegetative cuttings collected from late spring to early summer.

Source Credit: some information collected from Stephen A Austin Gardens website and Wikipedia

New Angelface Angelonias Produce Larger Flowers

Posted by Hugh on July 20th, 2018

Angelface Blue Improved (PW image)

Closeup of Angelface Improved White (PW image)

Angelonias, aka summer snapdragons, (Angelonia angustifolia) hail from Mexico. Angelonias are top performing summer flowering annuals (USDA zones 9 -11). The AngelFace® series were recently developed by Proven Winners (PW). Plants are covered with snapdragon-like blooms up and down the floral stems, 18-24 inches high and 12-18 inches wide. Angelface series boast slightly larger green leaves and bigger blooms than the Serena™ series.

Angelonias are heat-loving plants that grow vigorously and bloom best from early summer into fall. Plants should be sited in full sun or light shade and moist, well-drained soil. Before planting amend the garden soil with lots of compost to boost plant vigor and bloom numbers. Set out bedding plants in spring, 2-3 weeks after the threat of frost temps has past. Angelonias do tolerate temporary soggy soil and moderate drought.

Space individual plants 12 -14 inches apart in cool Northern climates and 18 to 24 inches apart in warm Southern regions. When the young plants reach 6 inches tall, pinch out the tips of the main stems to encourage branching and bushiness. Fertilize at planting time with a slow release product such as Osmocote™ or Nutricote™. Feed the bed or container in mid-summer with a water soluble fertilizer such as Miracle-Gro™ or Jacks™. Mulching with wood chips or yard compost will help conserve soil moisture. No floral deadheading is necessary.

Angelonias are mostly disease and pest-free as well as deer resistant. Plant them in garden borders or in mixed containers or window boxes. Flowers, according to PW, emit a distinct grape soda-like fragrance. Cut flowers are long lasting.

Angelface_’Cascade Pink’ (PW image)

Angelface Super Angelonia™ is a new series from PW, produce even larger plants and flowers. Under ideal growing conditions, plants grow 20 to 24 inches tall and 1-inch flowers on upright stems. “Supers” differ from the original Angelface series the taller plants and larger flowers are better suited for consumer use as cut flowers with a more upright habit.

Colorful ‘Sugar Tip’ Althea ( Rose Of Sharon)

Posted by Hugh on July 15th, 2018

Hibiscus syriacus ‘Sugar Tip’ In mid-June in UT Gardens, Knoxville, TN

Lightly variegated foliage

Rose of Sharon or shrub althea (Hibiscus syriacus) is a vigorous, upright, multi-branched, deciduous shrub that generally grows 8-12 feet tall and 4-6 feet wide. Althea is native from eastern to central Asia (USDA hardiness zones 5-8).

Sugar Tip® is a patented variety that features variegated creamy-white and blue-green foliage and soft pink double flowers. Leaf variegation is its unique trait. It produces smallish pale-colored double flowers that do not garner as much notice as the large single flowered varieties.

The 5-petaled double flowers, up to 3 inches across, appear over a long, early-summer to fall bloom period. The pink double flowers have prominent floral stamens in center. Flowers are mostly sterile, resulting in no weedy seedlings to pop up around your property.

Altheas tend to leaf out in late spring. The 3-4 inch long, 3-lobed, medium green leaves are palmately-veined. The blemish-free variegated foliage remains attractive from late spring through mid-autumn. Fall foliage color is inconsequential.

Flowers

Altheas are easily grown in average, moist, well-drained, moderately acidic soils and in full to partial sun. Under partial shade altheas bloom less and can become weak wooded, and more prone to disease issues. Best flowering occurs in full sun. This shrub is highly summer heat and humidity tolerant. Altheas are frequently seen planted in downtown urban congested areas.

Altheas bloom on new wood, so pruning is performed in late winter or spring. Heavy pruning results in less blooms which are much larger in size. Altheas are easily propagated by softwood stem cuttings collected in late spring. Sugar Tip may be trained as a small tree or espaliered.

No serious insect or disease problems trouble this tough hardy shrub. Occasionally, leaf spots, blights, rusts and cankers may appear if site location is poor. Japanese beetles, whiteflies and aphids are occasional insect feeders. In some years Japanese beetles may severely damage foliage when left unchecked.

As with most shrub altheas, they serve as superior summer flowering shrubs. Plant single specimen shrub or tree; mass several together as foundation or border shrubs, or as a deciduous privacy hedge or screen.

Fill Summer Flower Beds With Annual Rudbeckias

Posted by Hugh on July 10th, 2018

Rudbeckia hirta ‘Tiger Eyes’ at NC Arboretum in Asheville

‘Indian Summer’ rudbeckia in Pittsburgh, PA

Black-eyed Susan (Rudbeckia hirta) is a native wildflower. Annual or biennial forms are also called gloriosa daisy and brown-eyed Susan. In recent years public urban gardens are growing annual types. From summer into early autumn, brown-eyed Susans produce showy daisy-like blossoms up to 3-inches across with light or deep yellow rays and brownish-purple centers (“buttons”). Their cut flowers will decorate households.

This coarse weedy plant has undergone a breeding improvements. Today’s varieties bloom most of the summer and with disease-resistant leaves. Colorful ray flowers are available in shades of red, yellow, bronze, orange and bi-colors. They bloom non-stop through the summer atop sturdy upright stems. Plant heights vary by cultivar from 1-3 feet high. Rough, hairy, lance-shaped leaves are 3-7 inches long.

This biennial or short-lived perennial is winter hardy to USDA Zones 3-7. It blooms the first year from seed set out in early spring. It grows in average, moist, well-drained soils and in full sun. Brown-eyed Susan is at its finest in moist, compost-rich soils. For maximum bloom time, start seed indoors in late February or the beginning of March. Garden centers sell them in cell/six packs. Set out seedlings or purchased plants after the last frost date has passed. At planting time feed the flower bed with a granulated fertilizer such as 10-10-10 or or equivalent plus a secondary feeding in early summer. Deadhead spend flowers to encourage lateral branching and additional bloom. Removing old spent flowers also prevents self-seeding.

Most disease and pest problems may be avoided if properly sited and care for. In some years aphids, rust, powdery mildew, and septoria leaf spots may trouble these annuals. Watch for slugs and snails on young plants.

At Atlanta Botanical Gardens

Five popular annual rudbeckia cultivars

Cherry Brandy – cherry-red ray flowers

Prairie Sun – orange to lemon yellow petal with green button cone

Rustic Dwarfs – shorter form in a mix of flowers from yellow to rich mahogany

Tiger Eyes – golden yellow ray flowers; improved powdery mildew resistance

Toto – dwarf, compact plants and golden-yellow blooms

Heat Loving Annuals For Containers

Posted by Hugh on July 6th, 2018

Angelface’Blue Iimproved’ (photo from PW)

Ipomoea batatas ‘Cameo’

Not all annuals grow well in containers. An aggressively growing annual may not be a suitable companion plant in containers. Small containers dry out quickly. Large containers, a minimum of 16 inches across, should be your beginner size. For an eye-catching container garden, utilize plants that require the same care but differ in colors, heights, and textures.

I’ve selected a dozen annuals (list below) that beat the heat. They must stay hydrated (watered) and container size is of importance here. Group a variety of annuals that are compatible with one another. One does not outgrow another and they like to same diet that includes water plus fertilizer. Usually in spring, give them a drink every other day. Your container will likely need watering everyday or 3-4 days a week. To know for sure, poke a finger an inch or two into the soil (potting media).

If you rely on rain to water your plants, much of the precipitation will repel off the leaves and fall away, rather than moisten the soil. Don’t trust that rain is supply your plants during the growing season. Hand watering with a hose will do a better job.

To ensure that your annuals bloom all season, deadhead spent blooms that look wilted or dead. Provide a clean fresh appearance of new blooms all summer long. Fertilize at planting time using a slow release product such as Osmocote™ or Nutricote™ according to the label directions. By mid-summer plant nutrition is exhausted. Apply water soluble fertilizers such as Miracle-Gro™, Schultz™, or Peters™.

A Dozen Summer Heat And Humidity Tolerant Annuals

Globe amaranth at NC Arboretum

Persian Shield (Strobilantes)

Globe amaranth (Gomphrena)

Egyptian star flowers (Pentas)

Fanflower (Scaevola)

Marigold (Tagetes)

Mexican sunflower (Tithonia)

Summer snapdragon (Angelonia)

Setcreasa pallida ‘Purple Heart’

Lantana

Dichondra

Euphorbia

Ornamental Sweet Potato (Ipomoea batatas)

Smaller Alternatives To Limelight® Panicle Hydrangea

Posted by Hugh on July 2nd, 2018

‘Limelight’ hydrangea at the NC Arboretum in Asheville, NC

‘Little Quick Fire’ hydrangea

Beautiful panicle hydrangeas (Hydrangea paniculata) are among the best hydrangea choices for the summer garden (USDA hardiness zones 3 to 8). Flowers of some cultivars age gracefully with floral heads turning lightly pink. They are perfect for use in containers or in groupings or masses, shrub borders, hedges, and screens. Panicle hydrangeas are suitable as fresh cut or dried flowers.

Limelight® hydrangea is the current standard-bearer among panicle hydrangeas with huge 6 – 8 (some to 12) inches chartreuse (off white) flower heads. Limelight grows more compact compared to the species @ 6 to 8 feet tall and wide. Its yellow fall leaf color generally does not stand out.

Plants grow from 3 – 10 feet high depending on the variety chosen. For best flowering grow panicle hydrangeas in full sun to light shade and in moist well-drained soil. Feed hydrangeas in early spring with a slow release fertilizer such as Osmocote™ or Nutrikote™. Keep hydrangeas mulched during the hot dry portion of spring and summer. Shrubs bloom on new wood in summer, and are pruned to desired size and shape in early spring.

For smaller landscapes, choose from any of these smaller cultivars:

Bobo® hydrangea – fluffy, creamy floral spikes, that turn to deep pink with red highlights, on sturdy red stems. Earlier blooming Bobo opens 1-2 weeks before many H. paniculata varieties start blooming. Bobo grow 3–5 feet tall, and is a good option in small gardens and growing in large containers.

Little Lime® hydrangea – dwarf version of Limelight® grows 5-6 feet tall and wide and boasts creamy florets that age to rosy pink.

Little Quick Fire® hydrangea – smaller version of Quick Fire® @ 3-5 feet tall and to 2-4 feet wide. It blooms early in upright panicles. Panicles emerge white, change to pink, and mature reddish-purple by late summer.

Little Lamb® hydrangea – downsized version of H. paniculata ‘Grandiflora’ @ 6-8 feet tall and wide. Dense, cone-shaped panicles of mostly sterile, small white flowers. Panicles stand upright on stiff sturdy stems. Smaller, fluffy, fertile florets lie beneath showier sterile florets.