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

Summer Blooming Oyama Magnolia

Posted by Hugh on July 10th, 2011

A friend on vacation sent me the attached photo from Wooster, Ohio. When I told him that it was Oyama magnolia (Magnolia sieboldii), he asked why gardeners are not growing it. Good question!

Oyama magnolia is a 10-15 feet tall (and equal spread) deciduous tree or large shrub from eastern Asia. It prefers to grow in partial sunlight and in moist, well drained loamy soil (USDA zones 6 -8). Oyama is an ideal tree/shrub magnolia for a small garden. Spring bloom is in May, avoiding the threat of frost injuring the flower buds of this later blooming magnolia.

The 3-6 inch long medium green foliage is first to appear in April, coated with a silvery pubescence. White nodding egg-shaped flower buds appear in late June, and blooms appear intermittently thru most of the summer. The 1-3 inch wide saucer shaped flowers are white, centered by crimson stamens within. Oyama begins to flower at an early age.

Leaves turn pale yellow before abscising in mid-autumn. Small pink fruits appear in late summer, and split open to reveal orange-red seeds in late September. Branch bark wood is light gray.

Feed magnolias with a slow release fertilizer in early spring. They benefit from annual mulching. Pruning shrub to desired shape and size, and to remove dead or broken branches.

Oyama magnolia is available from a few on-line specialty nurseries.

Invite Sonata Cosmos Into Flower Beds

Posted by Hugh on July 7th, 2011

'Sonata Pink' Cosmos at BuGa Show, Koblenz, Germany

Over the past few years a flower bed containing cosmos (Cosmos bipinnatus) has become a rare sight across the Southern Appalachian region (USDA zones 6 and 7). Not so, at the recently visited BuGa National Gardening Show 2011 in Koblenz, Germany.

Called by some “Mexican asters”, cosmos produces big 3- inch wide red, white, pink or purple blooms. Their lacy or fern-like foliage lends a different textural feel to a flower garden.

Cosmos blooms from the late spring thru summer. The 18 – 24 inch tall ‘Sonata’ series are personal favorites. These dwarf cosmos look super planted in front of garden beds and in containers. Add a fresh bouquet of cut cosmos flowers to your dining room table this summer.

Cosmos grows in any soil type and flourishes without special soil enrichment and heavy feeding. Overwatering tends to reduce overall plant vigor and flowering. Cosmos are sun lovers and do irrigate over exceptionally long summer dry spells.

Deadheading promotes renewed flowering and reduces the dread of self-sowing in the garden. Tall growing (3 feet or more) cosmos may require staking, whereas the shorter Sonatas do not.

Species cosmos are popular in wildflower and meadow gardens where they attract butterflies and honeybees.

Tough And Reliable Chinese Astilbes

Posted by Hugh on July 4th, 2011

Astilbe chinensis at Kingwood Center, Mansfield, Ohio

Astilbes (also called “false spireas”) are favorite late spring flowering perennials. The Astilbe x arendsii hybrids from Germany are most popular and available at local garden centers. Astilbes are very hardy in the Southern Appalachian region (USDA zones 6 and 7).

If low maintenance is your goal, try Chinese astilbe (Astilbe chinensis var tacquetii). Their care is less demanding than the Arendsii hybrids. Chinese astilbes bloom nearly two weeks later. Group many together for mass effect of plume flowers and dense compound foliage.

The ‘Visions’ series are personal favorites. The original ‘Visions’ bears raspberry plume flowers. Later cultivars, ‘Visions in Red’ and ‘Visions in Pink’, are also nice. Plants form a 9- inch tall mound with bronze-green leaves and dense panicles of raspberry colored flowers on 12-15” tall stems.

‘Pumila’ forms a thick ground cover with 8-12 inch tall lavender purple flowers in mid- summer. ‘Superba’ is a taller flowering form and more available in nursery commerce.

Chinese astilbes grow in moist, well drained soils and partial sunlight. Two –year old established plants are exceptionally drought tolerant, have no serious disease or pest problems, and are generally not a favorite of deer.

Goldenrain Tree – A Golden Shower of Bloom

Posted by Hugh on July 1st, 2011

Golden Raintree in Urban Parking Lot

Goldenrain tree (Koelreuteria paniculata) is a medium sized landscape tree maturing to 30-40 feet in height and spread with rounded canopy. A native of China, Japan, and Korea, the tree is winter hardy in the Southern Appalachian region (USDA zones 6 and 7). Large panicles of dark yellow flowers set off a golden fireworks for your 4th of July celebration.

Individual flowers barely measure a 1/2″ wide, but the multi-branched floral panicles measure 10-15 ” across. The bipinnately compound leaves are also large at 8 to 14 inches in spread. The medium green colored spring/summer foliage turns pale green in autumn before dropping.

Yellow-green triangular 1 to 2 inches long seed capsules soon follow after flowering. The papery seed capsules are often called “Chinese lanterns” and are a significant ornamental feature. Each lantern may contain 1-3 hard black globular seeds. By early fall the capsules have turned dark brown. Bark of old trees is ridged with shallow reddish brown furrows.

Goldenrain tree grows in a wide range of soils, including high pH soils. It’s rarely bothered by pests and demonstrates exceptional heat and drought tolerances. It excels as a specimen yard tree, or utilize planted along wide avenues or in parking lots with their lower branches limbed high.

Seed viability may potentially be an invasive plant issue in some Southeastern states.

Looking ahead: see also blog on Chinese flametree to be published 7-15-11

Biltmore Estate and Gardens

Posted by Hugh on June 30th, 2011

Biltmore House

I have visited the Biltmore Estate on several occasions, but my May visit this year was special. I had the opportunity to interview Parker Andes, Biltmore’s Director of Horticulture, and Bill Alexander, Landscape and Forest Historian.

Few properties match the overall grandeur of Biltmore Estate and Gardens in Asheville, North Carolina. Biltmore is a historical perspective of America over a century ago. The property was designed by Fredrick Law Olmstead, Sr., deigned the father of American Landscape Architecture. Famed botanist and horticulturist Chauncey Beadle maintained the grounds nearly 60 years.

Olmstead took on over 1000 acres, an area some 50 times larger than another of his grand projects – New York’s Central Park. The 3- mile entry driveway winds through dense woodlands to the estate home and gardens of tycoon George Vanderbilt. Along the drive are native rhododendrons and azaleas (Rhododendron spp.), mountain laurels (Kalmia spp.), hemlocks (Tsuga spp.), pines (Pinus spp.) and thick stands of bamboo (Bambusa spp.).

Espanade of Replanted Tulip Poplars

A double lined esplanade of 2^nd generation tulip poplars (Liriodendron tulipifera) frame the entrance to Biltmore House. The four-acre Walled Garden and the 16th-century Italian garden are adjacent to the house.

The Spring Gardens Festival had just ended, and newly-planted summer annuals replaced thousands of tulips, hyacinths, etal. The adjacent rose garden was fully in bloom. According to Bill Alexander, the garden staff is launching a multi-year rose trial of varieties gathered worldwide.

Rose Garden at Biltmore

Many mature specimen trees and shrubs are found on the property: one of the first dawn redwoods (Metasequoia glyptostroboides) brought to the U.S. from China in the early 1940’s; a century-old Persian ironwood (Parrotia persica) with its mosaic patterned bark, and a mature Katsura tree (Cercidophyllum japonicum). The enormous size and majesty of the Olmstead- planted beeches and oaks is always breathtaking.

Growing Berries at Antler Hill Farm

I concluded the delightfully full day with a trek through the new Antler Hill area, where the Winery and Creamery (not the original) are situated. Close by is the Historical Farm, which includes the livery, coppersmith, and woodworking shops. Visitors have the opportunity to play games popular in the 19^th and early 20th centuries. An antique farm equipment museum was recently added near the fruit, vegetable and herb gardens.

Magnificent Mountain Laurels (Kalmia)

Bringing Biltmore Gardens home to your garden is no longer wishful thinking. The horticultural team has partnered with several nurseries around the world to reproduce many of the fabulous plants which have grown on the grounds for over a century. Periodically, I plan to feature these horticultural treasures in my blog: whatgrowsthere

July Lawn Care

Posted by Hugh on June 28th, 2011

Beautiful Home Lawn in mid-June

Around July 4th it’s time for a second (and last) application of crabgrass preventative. The herbicide which you applied in late winter is likely worn off. The basic herbicide preventative product tradenames (and active ingredients) are: Barricade® (prodiamine), Dimension® (dithiopyr), Echelon® (prodiamine + sulfentrazone), Pendulum® (pendimethalin), and Ronstar® (oxadiazon). Irrigate (1/2 inch water or 1 1/2 hours watering with an oscillating sprinkler) within a few days after application to activate the herbicide.

Cutting (mowing) of cool season grasses (tall fescue, bluegrass, red fescue, ryegrass) needs to be raised to 3- inch height over the summer months. Fertilizing a cool season lawn is not recommended unless it is kept irrigated over the summer months. Warm season lawns (burmuda, zoysia, centipede) likely need additional nitrogen applied.

July is Japanese beetle assessment time. What is the level of beetle feeding activity on shrub flowers and foliage? This will determine grub levels in the soil feeding on lawn roots this fall. Will you need to begin an insecticide program this fall?

Looking ahead: Has bad weather, diseases, insects, and/or weeds devastated your lawn? You should assess the need for fall renovation in late summer (early September thru mid-October). Tackling this task now in the middle of summer rarely works out. Allow the cooler autumn weather to work in your favor.

Rosebay Rhododendron for Cool Shady Landscapes

Posted by Hugh on June 24th, 2011

Rosebay rhododendron in Tennessee Mountains

Rosebay Rhododendron (Rhododendron maximum) grows in dense woodland shade along cool mountain streams and on moist, rocky slopes. This Southern Appalachian native is extremely winter hardy to -15° to -20° F. It is a late-season bloomer reaching its peak around late June.

Rosebay grows large, 15 to 20 feet in height. On some sites it is not unusual to see tree-like rosebay rhododendrons to 40 feet. The plant habit is spreading, broader than tall. Leaves are large, 4 to 12 inches long, glossy dark green. The new growth feels sticky to the touch.

The inflorescence (truss) of 15 – 30 funnel-shaped flowers. Each 5-lobed flower is approximately 1 inch long, white to pale pink (occasionally deep pink to rose red). The flower trusses lack fragrance.

Rhododendrons prefer a moist, compost rich, acidic soil which drains well. Organic based acidic mulches, such as pine bark or pine needles, will cool and conserve soil moisture.

Many hybrids, using Rosebay as a parent, includes a personal favorite ‘Maxecat’ which blooms in early June from eastern Pennsylvania south to northeast Tennessee. Blooms open light pink and fade to white.

Where Can I Buy That?

Posted by Hugh on June 20th, 2011

Let’s face it – rare and unusual plants are not likely for sale at your local garden center. Full service garden centers located in large metropolitan areas may sell one or two.The internet has become the best plant finding source. Some on-line purveyors may carry a rare item, but not sell it in large quantities. High sticker shock may chase you away. If the plant (tree, shrub, vine, perennial, tropical) is new or very rare, the nursery may price it higher. The principle of “supply & demand” applies here.

Several months back, a reader of “What Grows There” asked where she could purchase pink flowering forms of Chinese dogwood (Cornus kousa) for a friend living in northern Ohio. A pink cultivar (listed under 3 cultivar names: ‘Miss Satomi’, ‘Rosabella’ and ‘Heart Throb’) was cited at four rare plant nurseries. Radiant Rose® (maybe ‘Miss Satomi’) was also listed.

Another reader was interested in purchasing one of the hybrid yellow flowering magnolias (Magnolia x). Here are four on-line nurseries where I founded both plants listed:

Fairweather Gardens P.O. Box 330, Greenwich, NJ 08323

Forest Farms, 990 Tetherow Rd., Williams, OR 97544

Gossler Farms Nursery 1200 Weaver Rd, Springfield OR 97478

RareFind Nursery, 957 Patterson Road, Jackson, NJ 08527

Flaming ‘Fireball’ Hibiscus Quite A Summer Show

Posted by Hugh on June 18th, 2011

Hibiscus 'Fireball' photo by North Creek Nurseries

‘Fireball’ hibiscus (Hibiscus x moscheutos ‘Fireball’) is a vigorous hardy perennial with burgundy tinted cutleaf foliage and huge 10-12 inch clear red flowers from mid-summer to late summer.

Plant height is 4 – 5 feet and 2 – 3 feet in width. A strikingly beautiful plant, ‘Fireball’ thrives on heat and humidity. It wants full sun and a moist well drained soil to reach its full flowering potential. Expect hundreds of blooms on 3-4 years old established plants grown in a richly amended composted soil and kept irrigated.

Flowers are both huge and showy. Blooms are the size of dinner plates. A prominent pistil and stamen is in the center of each flower. Each bloom lasts but one day, but ‘Fireball’ blooms almost nonstop from July to early September.

Hardy hibiscus demands heat, moisture and long days. They are late to emerge from the soil, many years after May 15th in the Southern Appalachian region (USDA zones 6 and 7). Feed them regularly with a water soluble 20-10-20 fertilizer (or equivalent). Hibiscus sawfly, mites, and aphids may be serious nemeses.

This late flowering habit makes hardy hibiscus ideal companion plants to interplant with spring blooming bulbs like daffodils and tulips.

Fireball™ is one of several hardy hibiscus bred by the Fleming Brothers in Lincoln, Nebraska. It was their favorite perennial.

Summer Pruning of Oakleaf and Bigleaf Hydrangeas

Posted by Hugh on June 15th, 2011

Oakleaf hydrangea

Bigleaf or “mophead” hydrangeas (Hydrangea macrophylla) tend to get tall and leggy, and outgrow their garden space. Our native oakleaf hydrangeas (Hydrangea quercifolia) are pruned as blooms quality declines. Remove or “deadhead” all withered or faded flowers. Main pruning time for these two species is from mid-June thru mid-August. Mopheads may rebloom if they had been deadheads by mid-summer, again in September.

These two hydrangea species set their flower buds for next spring on old or current season’s growth on the terminal bud. Pruning in the fall or winter may remove flower buds or stimulate soft late shoots which die over the winter. Make all cuts 1/4 inch above the last set of leaves or cutback flush to a main branch.

Pruning improves the health of the plant, increasing vegetative growth. On older 4-5 year old hydrangeas, remove larger, thicker canes and prune them at the base of the stem. Remove one-quarter to one-third of these older branches. In 3-4 years the hydrangea will be completely rejuvenated.

Dead, dying, diseased stems and flowers can be removed at any time of year.