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

Mapleleaf Viburnum For Woodland Areas

Posted by Hugh on September 27th, 2016

U.S. Native Mapleleaf Viburnum (V. acerifolium)

Cyme flowers of Mapleleaf viburnum

The genus Viburnum is a rich source of over 150 species of great flowering shrubs worldwide. Many viburnums are native to North America including mapleleaf viburnum (Viburnum acerifolium). This totally underutilized deciduous viburnum is a great choice to plant in shrub borders, foundation, or hedging, as well as to naturalize in an open woodland area (zone 3-8).

Shrub grows 4 – 6 feet tall and 3 – 4 feet wide. In late winter before spring bud break, swelling flower buds turn distinctively pale purple. Creamy white 1 to 3 inch wide flowers (cymes) appear in early to mid-May. Flowers give way to pea-sized fruits that ripen to bluish-black in late summer, and persist through most of winter. Shrub may form basal suckers and form colonies over many years.

Mapleleaf viburnum is a relatively small, rounded, suckering, deciduous, woodland shrub. Leaves are generally 3-lobed, 2-5 inches long, and very maple-like; juvenile foliage on seedling plants may not always develop side lobes. Leaves are opposite, ovate to rounded, coarsely toothed. Fall color is variable from one year to the next. When best, it is hard to beat, leaves turning purple to magenta in the fall.

Mapleleaf viburnum is easy to grow in average, medium moist, well-drained soil and in full sun to part shade. This viburnum is an exceptional grower in dry, shady woodland locales. Prune as needed immediately after spring flowering. Lightly feed with a granular fertilizer such as 10-10-10 or equivalent. It appears to be pH insensitive. Mulch to maintain a weed-free planting. Mapleleaf viburnum has no serious insect or disease problems and damage from deer feeding is minimal.

Mapleleaf viburnum is sold primarily by nurseries that specialize in selling native plants on-line.

Five Landscape Plants On The Gardeners’ Taboo List

Posted by Hugh on September 24th, 2016

Lonicera nitida ‘Briloni’ is highly desirable

Avoid planting Red-tip photinia

To many people, maintaining a garden or landscape means a lot of hard work. Sometimes the weeds outgrow what you have planted. Some landscape plants promise a lot of beauty but deliver nothing but problems. Some trees are weak wooded, prone to pests or diseases, and outgrow their space. Some produce smelly odorous flowers. I urge you to avoid these five plants.

Callery Pears (Pyrus calleryana) grow 35 to 50 feet high. They’re labeled ‘Bradford’ or Cleveland Select’. Their weak branches make them highly prone to storm damage. The odor from spring flowers can be stifling. Older trees produce thousands of tiny pear fruit that give rise to multitudes of thorny seedlings that invade woodlands and vacant lots.

Red-tip Photinias (Photinia x fraseri) are beautiful shrubs. Their lustrous burgundy red leaves and snow white flowers will lure you into purchasing them. A small 3-4 foot plant in a #3 container may become 15 feet high and wide in less than 8 years. Bright red new leaves turn green in 4-6 weeks. By mid-summer leaves are attacked by a defacing fungus disease called Entomosporium leaf spot. Unless you spray often with a fungicide, the disease eventually kills the shrub.

Russian Olive (Eleaegnus angustifolius) is a large deciduous shrub or small tree, up to 25 feet tall. The tree forms a dense canopy with distinctive silver-gray, lance-shaped foliage. Yellow spicy odor flowers appear in late spring and hundreds of silver olive-like fruits laden down branches in late summer. A related species, autumn olive (E. umbellata) produces thousands of bright red fruits in the fall. Both species are rated as highly invasive. Sharp thorns form of twiggy branches and becomes a nightmare to prune.

Leyland Cypress (x Cupressus leylandii) gets more than 70 feet tall and up to 15 feet wide over 30 years. It is highly susceptible to Seridium canker and two other destructive pathogens. Fungicides are available to prevent or lessen disease severity, but this evergreen reaches monstrous sizes to treat all the problems. Drought stress also favors disease.

Honeysuckles (Lonicera spp.) originating from east Asia, many shrub and vine types, are invasive nuisances, particularly in the Eastern and Southern U.S. Their attractive trumpet-shaped, sweetly scented flowers make them attractive purchases. Three recommended exceptions: Winter Honeysuckle (L. fragrantissima), Boxleaf Honeysuckle (L. nitida), and native Coral Honeysuckle Vine (L. sempervirens) do not invade.

Starting Oak Trees From Acorns

Posted by Hugh on September 21st, 2016

Acorns Germinating Under Tree In February

Red oak acorns on tree

Acorns begin ripening and falling from oak trees (Quercus spp.) anytime from late August until mid-November. Ripening dates vary from one year to the next. Harvest the healthy plump acorns, either off the tree or from the ground. Remove and dispose of the cap. If you have collected several kinds, identify and label the oak species.

Plant all white oak species group, including white, bur, chestnut and swamp white oaks, immediately in the fall. Red oak species (pin, red, willow, shingle, sawtooth, et al) acorns may be planted in early spring or in late autumn.

White Vs Black Oaks: White oak acorns mature in one year and will often sprout on the ground outdoors in warm autumn weather. White oak acorns do not exhibit seed dormancy and will start germinating after falling to the ground. Red oak acorns mature in two years. Members of the red oak group possess seed dormancy and generally will not germinate until the following spring; they require a minimum chilling of 42 days chilling period. If stored properly and kept damp, red oak acorns can be held in cold storage for planting in late April through early summer.

If spring planting is desired, store acorns into a polyethylene plastic bag, designated “freezer bag”. Fill with lightly moistened peat mix or sawdust. Inspect acorns through the winter and keep mix slightly, but not sopping wet. Do not freeze acorns. Plant pre-chilled acorns of the red oak species group in early to late April in the ground or into containers.

Direct Sowing In Containers: Select the healthiest looking acorns (plump and healthy) and place 1-2 acorns to a 1 inch depth into loose potting soil in one-gallon pots (#1 size) with drainage holes on the bottom. The tap root will grow quickly to the bottom of containers. Keep the soil (media) moist.

Uniquely Different Chinese Flame Tree

Posted by Hugh on September 18th, 2016

Chinese Flame tree in Bristol, VA in early October

Pink lantern capsules

Chinese flame tree, aka bougainvillea goldenrain tree (K. bipinnata), is another tree option in U.S. southern landscapes (USDA hardiness zones 7-10). It is closely related to the more widely planted goldenrain tree (Koelruteria paniculata). This fast growing tree develops into a nice 20-40 feet tall medium-size tree with an irregular canopy.

Chinese flame tree is highly drought tolerant (after one year established). It grows in average soil, and leaves holds up in urban air pollution. No serious disease or pests trouble the tree and deer leave it alone. Showy long panicles of fragrant yellow flowers appear in summer, one of a very few trees that do so. By mid-September attractive rose-colored seed capsules, mimicking bougainvillea flowers, have matured. They’re often added in dry flower arrangements.

Flame tree is easily distinguished from more popular Golden raintree (K. paniculata) since the former is more upright branched and has 2x pinnately compound leaves, compared to the single pinnate compound leaves of goldenrain tree Leaves hold late into autumn and turn a blah golden color before abscising. The bark on Chinese Flame tree is smooth and light brown when young, and becomes ridged and furrowed as it ages.

In deep South landscapes, flame tree is more multi-stemmed and reaches a height of 40 feet and higher as a specimen lawn tree. It is frequently seen planted in parking lots and highway plantings because of its landscape versatility.

Beware that seedlings from both Koelreuteria spp. will appear anywhere and everywhere in your landscape and all your neighbors’ yards. Pods and stems will fall over the winter. Flametree are for sale at on-line specialty nurseries

Fritillarias – Very Different Spring Flowering Bulb

Posted by Hugh on September 15th, 2016

Red Fritillarias Interplanted with other bulbs

Yellow variety ‘Lutea’ at Keukenhof, Netherlands

Crown imperial (Fritillaria imperialis), aka fritillaria, is an impressive spring flowering bulb that is native of Southwestern Asia to the Himalayas (USDA hardiness zones 5-8). In late April to May, large drooping orange, red, or yellow bell-shaped flowers are topped by a small pineapple-like tufts of leaf-like bracts. The leafy fringe on top resembles a crown, hence the common name “Crown Imperial”. All parts of the plant emit a skunk-like odor.

Individual bulbs grow 3-5 feet tall and 1 to 1½ feet wide. Some gardeners will inter-plant multi-rows of mid- to late-season tulips, daffodils, et al. with the taller growing fritillarias. Each bulb produces flowers on top of a thick, stout, upright flowering stem. Lance-shaped green leaves (to 6 inches long) have wavy margins and appear in whorls around the lower one-half of stem.

Fritillarias are at their best in full sun. Plant bulbs 6-8 inches deep in compost-rich, moist, very well-drained, high pH soils. Space bulbs 12 or more inches apart in autumn for adequate winter chilling in the winter soil. Protect from high wind or be prepared to stake stems.

According to Brent Heath, from Brent and Becky’s Bulbs in Gloucester, VA, “if you garden in most areas of the Eastern or Midwestern U.S., fritillarias are very challenging to grow. Gardeners in the Southwestern U.S. have the best luck with growing fritillaries”. They suffer in heavy clay soils which tend to stay very wet during summer and winter months, resulting in bulbs to rot in the ground.

Foliage dies back by early summer as the bulbs go dormant. Bulbs are large but fragile and are best left undisturbed once planted. Bulbs are best mulched with medium to coarse bark mulch to provide winter protection. Fritillarias resent highly moist soils, particularly in the summer and winter months which leads to bulb rot. Plants are also susceptible to leaf spot, rust and mosaic virus. Most critters like voles, squirrels and deer leave fritillarias alone.

Tip: Excellent soil drainage is the key. Plant on a bed of gravel or coarse sand. Set each bulb on its side to keep water from collecting in the depression at the top of the bulb to prevent or reduce bulb rotting.

To create a spectacular display, plant 6-12 bulbs in the rear of a spring flower border where they can be clearly viewed but their unpleasant flower and foliage fragrance will not picked up.

House Plant Basic Care Tips

Posted by Hugh on September 12th, 2016

Collection of House Plants at Biltmore Estates, Asheville, NC

Two varieties of Bromeliads In Summer Shade

Tropical house plants decorate homes, restaurants, shopping malls, and work environments (USDA hardiness zones 8 through 11). Many will grow in medium to low light areas of your home, work, and where flowering plants do not perform. Here are some basic house plant tips:

They languish in areas where temperatures are below 55 °F. Dry room air often results in brown leaf edges. Room humidity can be raised by setting a plant on a tray of wet gravel (but not sitting in standing water), or close by a room humidifier. Simply grouping several plants close together will raise the humidity.

Spring, summer, and fall feed plants every 2 – 3 weeks with a water soluble “house plant fertilizer” at one-half package directions. Winter feeding is usually unnecessary or performed once monthly. Once monthly, flush the soil with water to leach out excess fertilizer salts.

Plants may be moved outdoors in summer and placed under a large shade tree in filtered or indirect light and temperatures between 55 – 90 °F.

Occasionally rinse large leafy foliage plants with a garden hose or bath shower to remove dust and pollen. Turn large foliage plants regularly to supply adequate light to all sides of plant(s) and prevent it from reaching outward toward light source.

Over time bottom leaves will brown and die out. This is natural. Snip them off to keep the plant tidy.

Water thoroughly and as needed. Never overwater your houseplants. Irrigate with non-fluoridated, room temperature water to avoid burning the foliage.

Repot annually. Choose a container 2 inches larger than the existing one. Shake old soil away from roots and replace with a well-drained potting mix.

Disease and insect problems are rare, but occasionally happen. Inspect plants every few weeks for scale, mealy bugs, mites and aphids. Their feeding symptoms cause leaf curl, speckling, or bronzing of the foliage. In particular, inspect underside of leaves for webbing. Spray with insecticidal soap or neem oil every one to two weeks until pest has been managed.

Caution: The leaves of some house plants are toxic and should not be ingested. While most are not poisonous and cause death, some may cause temporary swelling of the tongue and throat, leading to a temporary loss of speech or stomach aches. Some common examples are dumbcane (Dieffenbachia), Chinese Evergreen (Aglaonema). Sap from Crown of Thorns (Euphorbia) may result in skin irritation. Keep such plants away from children or pets that might be tempted to taste it.

Some Zone 7 Camellias Survive In Zone 6 As Well

Posted by Hugh on September 10th, 2016

Mid-November blooming ‘Shishigashira’ camellia in my zone 6 garden

Camellia sasangua ‘Kanjiro’

A short list of early blooming Sasanqua camellias possess the ability to do grow well in zone 6 areas. In my opinion, the zone 7 cultivar ‘Shishigashira’ steps to the head of the class. It is a November bloomer that has proven to be exceptionally cold hardy dwarf variety.

The good folks at Cam Too, a camellia wholesale nursery in Greensboro, NC, highly recommends these hardy cultivars: ‘Kanjiro’, ‘Hiryu’, ‘Yoi Machi’, ‘Crimson Candles’ and ‘Korean Fire’. All are (Camellia sasanqua) bloodline except Korean Fire (C. japonica) .

Their vegetative and floral hardiness is excellent–even following nights in the low 20’s, the open flowers still held their color. Plants exhibit upright branching and will be full in good light exposure. all would be cold hardy to zone 6-b and would flower for you.

Shishigashira – hot pink semi-double flowers; low and wide spreading habit.

Kanjiro – pink semi-double bloom edged in red with golden stamens and a slight fragrance; dense semi-weeping habit; glossy, dark green foliage.

Hiryu – deep crimson red, rose-form, double flowers in early fall; compact shrub, and more sun-loving than most camellias.

Yoi Machi – vigorous grower with white petalled flowers with pale pink margins; it blooms from late fall into spring.

Crimson Candles – vigorous grower and disease resistant; small bright rose-red single flowers in early fall; new foliage is bronze-red.

Korean Fire – single red flowers which start opening in late February thru April; reportedly survived -23 °F in southeast Pennsylvania, unusual for C. japonica.

Simple growing tips: camellia culture is similar to that of rhododendrons or azaleas. They prefer a mildly acidic well-drained, compost rich soil. Grow them in full morning sunlight in zone 6 and 7-a and in partial all day sun in zone 7b and points further south. Protect camellias against prevailing winds, particularly in the winter months. Irrigate new plants in their first year, but do not overwater. Mulch with an acidic type leaf mold from oak leaves or pine bark chips or nuggets; mulch feeds and protect roots from drastic heat and droughty soils.

Avoiding Slug Problems On Hostas

Posted by Hugh on September 6th, 2016

Slug injury on hosta

Finding slug resistance among hosta varieties is relative. By late summer, you will find some holes in leaves in almost every variety, some a lot worst than others. There are ways to reduce slug injury in your host plantings.

Weather is a key factor. Wet summers means higher slug and snail populations. Dry summers is the opposite. They hide and multiply in a moist environment containing plenty of dead or decaying leaf and twig debris on the ground.

Good garden sanitation is important in reducing slug damage. Keep hosta beds free of weeds, fallen leaves and other wastes. Mulches and decaying foliage make an ideal slug haven. Cut your hostas back to ground level when foliage dies back late in autumn. Compost plant wastes away from hosta plantings..

During extended dry periods, irrigate hostas deeply but not frequently. Excess watering causes attracts snails and slugs. If you’re not watering sufficiently, plant leaf edges and tips will turn brown.

Hand-pick slugs from your hostas and nearby plants. Slugs are nocturnal feeders. Deposit them in a “kill jar” containing isopropyl alcohol or soapy water.

Make your own slug trap. Set shallow containers such as empty margarine and cream cheese containers are perfect. Filled containers with beer at dusk. Sorry, but fresh beer does attract more slugs than stale beer. Space traps 4-6 feet apart around hostas and other susceptible plants. Slugs will crawl into the bowls overnight and drown.

Hosta varieties with heavier and textured leaves are generally more slug resistant. Some examples include:

‘Abiqua Drinking Gourd’

‘Big Daddy’

‘Blue Mammoth’

‘Blue Plate Special’

‘Blue Shadows’

‘Blue Umbrellas’

‘Bright Lights’

‘Camelot’

‘Frances Williams’

‘Halcyon’

‘Krossa Regal’

‘June’

‘Love Pat’

‘Regal Splendor’

‘Sagae’

‘Spilt Milk’

‘Sum and Substance’

‘Tokudama’

The bottom line: Plant hosta varieties with thick or heavily textured leaves. Be ready to use slug bait or create your own bait trap. Slug baits are readily available from garden centers. Non-chemical alternatives are also effective. Most bait products contain metaldehyde. It is highly toxic by inhalation, moderately toxic by ingestion and may cause skin and eye irritation. It is poisonous on birds and other wildlife, including household pets.

Leaf Retention In Landscape Trees

Posted by Hugh on September 2nd, 2016

Leaf retention of American Beech

Beech in Tennessee Woodlands

Most deciduous landscape trees drop their leaves sometime in autumn. The physiology of autumn leaf drop is primarily stimulated by changes in photoperiod or shorter daylength. Autumn colors develop and the leaf petioles form an abscission layer. Black gum (Nyssa sylvatica), for example, start to color up in early September.

Winter leaf retention by deciduous trees is termed “marcescence”. Some hardwood trees, particularly Beech (Fagus spp.) and oak (Quercus spp.) trees, retain their leaves through the winter months in Northeastern U.S. Oaks and beeches are in the Fagaceae family. Additional species include witch hazel (Hamamelis spp.), hornbeam (Carpinus spp.), and hophornbeam (Ostrya virginina).

Most (not all) oaks and beeches begin shedding old leaves the latter days of February. Plant scientists speculate that retained leaves may deter browsing animals such as deer. The dried leaves may help to protect dormant buds or make them difficult to nibble on. Dried leaves are likely less nutritious.

Most years Japanese maple (Acer palmatum) have shed their leaves by late November. Some cultivars may be slow to shed their foliage, and are caught in an early hard frost. Leaves turn brown and hang on for several weeks, sometimes for months. Dissected leaf varieties are more affected compared to palmate types. Fine textured dissected-leaf cultivars, like ‘Tamukeyama’ and ‘Waterfall’, often retain their brown withered foliage until early March.

Young and newly planted landscape trees tend to retain leaves their first year after planting. Fruit trees, specifically apple and pear trees, are in a juvenile stage.

But not to worry. High winds, snow loads, and rains in winter, in addition to swelling of vegetative buds in the spring causes marcescent leaves to fall to the ground.

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).