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

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.

Bagworms Can Devastate Evergreens

Posted by Hugh on June 8th, 2011

Bagworm on conifer- photo by Alan Windham

Bagworms feed on more than 128 species of plants, including junipers, cedars, arborvitae and white pine. More than one year of severe defoliation will kill a formerly healthy specimen. Bagworms have one generation per year. Eggs usually hatch in mid to late May across the Southern Appalachian region (USDA zones 6 and 7).

Upon hatching, the young larvae crawl out of the bottom of the bag and begin eating plant foliage. Maturing larvae can do considerable defoliation during early summer. As the worms age, they construct a silken shelter over their body and are more difficult they are to kill.

Bagworms’ carrot-shaped bag is constructed of bits of material from the plant upon which it’s feeding and expands as the bagworm grows. The bag is carried wherever the worm goes. When disturbed, the bagworm merely pulls its head back into its bag for protection.

Insecticides should be applied when the bagworms are small, but after all have hatched by early June. After mid-June pesticide control is too late. Complete spray coverage is essential. Carbaryl (Sevin), Bt (Dipel), Malathion, acephate (Orthene), and pyrethroids like bifenthrin (Talstar), cyfluthrin, and permethrin), and spinosad (Conserve SC) are highly recommended. Spinosad controls the hard to kill older bagworms.

Stewartia- A Tree for All Seasons

Posted by Hugh on June 1st, 2011

Lovely Japanese stewartia at Biltmore Estate in Asheville, NC

June flowering stewartia

Japanese stewartia (Stewartia pseudocamellia) is a truly beautiful 20-30 foot small tree or multi-trunked shrub. Stewartia may be finicky to grow, but a great plant nonetheless. Although rarely seen in U.S. gardens, Japanese stewartia is the most commonly grown of the six stewartia species. All are winter hardy in the Southern Appalachian region (USDA zones 6 and 7).

Visually, stewartia provides four seasons of ornamental beauty. Lovely 2 to 2 ½ inch camellia-like white flowers appear in early June and are in bloom for 2 – 3 weeks. The 3 – 4 inch blemish-free green summer foliage turns yellow and/or crimson red in mid- autumn, depending on its location. Its patchwork mottled bark becomes more attractive with age.

The trick to growing stewartia is selecting a proper site. Stewartia may flourish for many years if the soil drainage and sunlight exposure are near perfect. Japanese stewartia grows similar to flowering dogwood (Cornus florida), requiring a compost rich, acidic pH and almost perfectly drained soil.

Filtered all-day sunlight or six hours of morning /early afternoon sunlight is ideal. Prolonged periods of scorching summer heat and low rainfall may be fatal to Japanese stewartia. Irrigate to cool and refresh the tree(s) and keep adequately mulched.

Does Mulch Attract Termites?

Posted by Hugh on May 29th, 2011

Recently mulched shrubs

Mulching, in itself, does not attract termites to your home. That’s the conclusion of two university studies. Soil moisture appears to be the key factor that attracts termites to the home. The subterranean termites found in scattered, localized areas are routinely found in wood chip mulch.

While landscape mulches are good for woody and herbaceous plants, they’re admittedly favorable for termites and other insects as well. Soil moisture favors termite exploration, tunneling and feeding.

University of Maryland entomologists found that termite populations were detected beneath many kinds of mulches, including eucalyptus, hardwood, pine bark, and pea gravel. However, termite activity was significantly higher beneath the gravel mulch. Scientists concluded that termite activity is more about a suitable habitat.

A University of Florida study reported that termites can be found in mulch, but their survival is poor. Why? – because the ability of termites to survive the chipping process that manufactures mulch is not good. Mulch-fed termites suffer significantly lower survivorship.

Overall recommendations: Keep mulch 12-18 inches away from the house foundation. Termites do need a cellulose materials like mulch to feed on. Always watch for signs of termites and their location (activity) around your home.

Is Paulownia Invasive?

Posted by Hugh on May 24th, 2011

Paulownia uninvited!!

Paulownia or Empress tree (Paulownia tomentosa) is a medium to large 30-50 foot tree. It is extremely fast growing, brittle wooded tree, as much as 4 feet per year. Across the Southern Appalachian region (USDA zones 6 and 7), the large pale violet flowers of paulownia are easily visible in May, perched on branch tips.

Its enormous 10-12 inch large medium green leaves are pushing out at the same time. The leaves dump considerable litter beneath the tree in the fall. Fall foliage color is of little importance.

Paulownia is an exotic from China which many plant experts have labelled “invasive”. A large paulownia tree produces many thousands of viable seeds which are dispersed by wind. The seeds are very susceptible to damping off disease (Pythium) and many do not survive. Seeds do germinate on “sterile” soil such as recently cleared ground and burned areas.

Paulownia is rarely seen in open fields already containing vegetation, compared to other serious invasives such as tree-of-heaven, privet, honeysuckle, et.al. It may grow on the edge of forests, but does not survive or compete in woodland shade.

Paulownia wood is highly prized by the Japanese for furniture, cooking utensils, owls, etc. There are several growers in the Southeastern U.S. who grow the fast growing paulownia wood for its export value.

Yellowwood Not Every Year Bloomer

Posted by Hugh on May 22nd, 2011

Yellowwood's gray beech-like bark

American yellowwood (Cladrastis kentukea) is a medium-sized flowering tree. In the month of May, a beautiful yellowwood tree is in bloom somewhere in the Southern Appalachian region (USDA zone 6 and 7). The 1- 1 1/2 inch white pea blossoms comprise the 8-14 inch long wisteria-like panicles which drape from branch and twig tips.

Yellowwood may bloom 2 to 3 consecutive years and not flower again for 1 to 2 years. The triggering mechanism for flowering is not clearly understood. A complex of environmental and physiological factors may be involved.

Over the past two decades the weather across the Southern Appalachian region can only be described as “extreme”, unusually dry, hot summers and unseasonably mild winters. A physiological condition called “biennial bearing” may be in play here. If a tree sets an unusually heavy seed load one summer, few to no flowers are initiated the following spring.

Whether it flowers or not, yellowwood makes a fine landscape shade tree for any sized landscape. Plant in well drained, slightly acidic soil in full sunlight. Its dark green compound leaves remain pest free from spring until early autumn. Yellowwood’s bright yellow fall color arrives at a time when many trees have already defoliated. Its smooth gray colored bark is very beech-like and has multi-seasonal interest.

Summer Wine™: The Taming of The Ninebark

Posted by Hugh on May 19th, 2011

Physocarpus 'Summer Wine'

Over the past 25 years our native Eastern ninebark (Physocarpus opulifolius) has been reborn. Its overly vigorous nature has been tamed. Latest up is Summer Wine™ ninebark with small, deeply cut, wine burgundy leaves, quite different from the medium green foliage of old-fashioned ninebarks. Summer Wine is a more compact (5-6 feet in height and width) grower.

Grow ninebark in full sun to retain its reddish leaf color longer. Ninebark grows in any soil type, tolerates wet soggy ground, and is pH insensitive. It demonstrates exceptional heat and drought tolerance after one year in the garden. Annual pruning, right after spring flowers have faded, further limits growth and presents many design choices.

Summer Wine fits a multiple of landscape uses: grouped enmasse as a dense growing deciduous hedge, screen or border, or grown by itself as a landscape specimen or in a patio container. Ninebark grown in outdoor containers is winter hardy here in the Southern Appalachian region (USDA zones 6 and 7).

White spirea-like flower clusters, 1 ½ – 2 inch wide, open in May. White blossoms and dark foliage playoff each other. The reddish leaf tint has bled out by mid-summer, now dark green and usually blemish-free. Autumn leaf color is of no consequence.

Select Hollies for Privacy

Posted by Hugh on May 16th, 2011

: Ilex opaca ‘Greenleaf’

I continue to witness the overplanting of Leyland cypress (Cupressocyparis x leylandii) across the Southern Appalachian region (USDA zones 6 and 7). This is followed by Japanese cedar (Cryptomeria japonica) and western arborvitae (Thuja x plicata). These three evergreen species have a rapid growth rate and eventually attain heights of 40-60 feet, sometimes in less than 20 years. Ask yourself the question: “do you really need a huge green barrier around your property?”

Hollies offer the benefits of lustrous green foliage and colorful fruit. The following evergreen species create a dependable privacy screen: Dwarf Burford holly (I. cornuta ‘Dwarf Burford’), Inkberry (I. glabra), American holly (I. opaca), Foster #2 holly (I. x attenuata), and Nellie R. Stevens holly (I. x ‘Nellie R. Stevens’).

A few simple tips about growing hollies:

Hollies prefer a slightly acidic, well-drained, and organically rich soil.
Hollies prefer full to partial sun location.
Established hollies demonstrate good drought tolerance.
Space plants a minimum of 12 feet apart.
Hollies should be properly mated. Fruit are produced on female cultivars and a matching male pollinator should be planted.

Growing Azaleas in Outdoor Containers Year-Around

Posted by Hugh on May 10th, 2011

'Elsie Lee' azalea (photo by Sam Kinsey)

In the Southern Appalachian region (USDA zones 6 and 7), if you desire to grow azaleas in above ground containers year around, you must select winter hardy cultivars. Two of the best for containers are ‘Elsie Lee’ (2½- inch wide semi-double light lavender blooms) and ‘Herbert’ (1 ¾- inch wide bright purple with dark blotch). ‘Elsie Lee’ boasts a neat, compact shrub form while ‘Herbert’ has a dense, slightly more spreading habit.

Both exhibit exceptionally long flower period. Spring – summer leaves are medium green, changing to bright yellow, orange, and/or red shades in the autumn. They’re mid-season bloomers and vigorous growers, attaining 3-4 feet in height and width in 10 years.

Grow azaleas to keep roots cool inside the lightly colored (not black) containers. Follow a regular watering and nutrient feeding schedule to establish a deep, extensive root system. Pot in a well drained peat and bark based potting soil or medium with a 2-3” surface layer of mulch. Feed with an acid-based liquid fertilizer like Miracle-Gro™ or Miracid™. Prune azaleas as needed to shape plants and to eliminate dead or diseased twigs.

‘Elsie Lee’ is a Tony Shammarello hybrid from Ohio. ‘Herbert’ azalea (R. yedoense var. poukhanense x R. ‘Hexe’) is a fabulous David Gable hybrid from Pennsylvania. Bred more than 50 years ago, they’re winter hardy to -15 degrees F (USDA Zones 5-9).

Stop Ignoring Enkianthus

Posted by Hugh on May 7th, 2011

'Red Bells' enkianthus

From the photo, looks like a pieris? No, it’s redveined enkianthus (Enkianthus campanulatus) and its brightly colored bell-shaped flowers are attention getters in the early May garden. Lovely cream yellow to orangy red bell shaped flowers are faintly red veined. The bell shaped blooms exude a slight scent, one that you may like or not.

From the start, growth rate is slow, but once established, shrubs mature to 8 to 12 feet in height and about the same in spread. Culture is similar to azaleas, pieris and rhododendrons which they are related to. Enkianthus grows well in full sun to light shade. They are not as fussy regarding pH and moisture needs, provided the soil is well drained. Enkianthus becomes well established within two years, and are rated as moderately drought tolerant. Do provide supplemental irrigation during the driest periods of summer.

Over twenty cultivars are listed, varying in flower colors from near white (pale cream), pink and red. Fall color is quite variable among vcultivars and growing site from yellow, orange or red. Enkianthus has no serious disease or insect problems.