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

Dieback Shrubs

Posted by Hugh on November 5th, 2018

Buddleia

Dieback shrubs are a group of hardy landscape shrubs that emerge and grow vigorously from mid-spring through early summer. They bloom reliably from late summer into early fall. Plants are near the edge of their hardiness range, and often die back to the ground in the winter. They act more like herbaceous perennials. The above-ground shoots are not dependably winter hardy.

Stated another way, a dieback shrub is a woody deciduous species that grows one full plant zone lower (colder) as a perennial. A zone 7 hardy woody shrub performs more like a herbaceous perennial in zone 6. It dies back to the ground in winter and re-grows and blooms the following year. Prune the shrub back in early spring before the bud break. Their colorful flowers attract bees, butterflies, and other pollinators, and are mostly deer resistant.

Four Reliable Dieback Shrubs:

Butterfly bush (Buddleia x davidii) is cold hardy to zone 5 which makes it suitable for most gardeners in the United States. These shrubs generally grow 2-3 feet tall, usually as wide and tall. They’re tough plants that can tolerate lean and alkaline soils. Plants perform at their best in average well-drained soil with a pH range of 5.5 to 8.5.
Bluebeard shrub (Caryopteris spp.), also called blue mist or blue spirea, produces gray-green foliage and bright blue flowers in early summer through fall (USDA hardiness zones 5-9). Leading varieties include Petit Bleu® (rich blue blooms), ‘Worcester Gold’, and ‘Longwood Blue’.
Chaste tree (Vitex agnus-castus) include short growing varieties like Blue Puffball™ (3-4 feet tall and wide in zones 6-9) and Blue Diddley® (3-6 feet tall in zones 5-9).
Crape myrtle thrives in the southeast U.S. (zones 6-10), but are at risk in colder northern areas. Grow them as perennials in full sun and average well-drained soils. Select the hardiest forms from the U.S. National Arboretum. I recommend these 4 varieties such as ‘Natchez’, ‘Muskogee’, ‘Acoma’, and ‘Osage’ to try in zones 5b -6a as herbaceous perennials.

Fall – Winter Pruning Dos and Don’ts

Posted by Hugh on October 30th, 2018

Bad cuts (sap leakage in winter)

Hand tools for pruning

Pruning is a chore that you don’t need to put off until spring. Many trees and shrubs may be pruned this autumn. However, NOT all landscape trees and shrubs are pruned. Here are some pruning guidelines to follow:

WAIT to prune spring flowering deciduous shrubs such as Forsythia, Lilac, Bridal Wreath & Vanhoutte Spireas, Quince, Viburnums, Fothergilla, Weigela, Deutzias, and some others. Add some evergreen flowering shrubs including all azaleas (both evergreen and deciduous) and rhododendrons, Japanese andromeda (Pieris japonica), Mountain laurel (Kalmia), Daphne, and Mahonia. Wait 3-4 weeks after spring flowering to prune all the above shrubs plus a few others not listed.

DO PRUNE NOW: Summer flower shrubs should be pruned now while they are dormant to manage size, shape, balance, and uniformity prior to spring growth. These include Summer Spireas, Panicle hydrangeas (H. paniculata) & Smooth hydrangeas (H. arborescens), Rose of Sharon (Hibiscus syriacus), Bluemist (Caryopteris), Butterfly bush (Buddleia), Potentilla (cinquefoil), Summersweet (Clethra). and others.

Hold off pruning Big Leaf Hydrangeas (H. macrophylla). They bloom both on old last year’s wood and on new wood. Wait until spring to determine if winter climes have injured the old wood. After harsh winters Big Leaf hydrangeas may be cutback to 3-5 feet and will bloom mostly on new wood later in summer.

ROSES: Pruning varies according to the species of roses. Hybrid Tea, Grandiflora and Floribunda types can be lightly prune back by 25 to 30%. In the early days of spring, prune to the desired height and width, remove diseased or broken canes, and thin out the interior of the bush. Shrub roses including Knock Out™, Home Run™, and Carefree™ series are pruned down to 18-36″ in height. Shorter types like OsoEasy™ and Flower Carpet™ are pruned to 12-18 inches in height.

Don’t Prune Crape myrtles until late winter

CRAPE MYRTLES: Predicting winter cold is foolhardy, so hold off until spring. In general, crape myrtles need for little annual pruning other than removing dead, diseased, weak wood, and the old seed heads.

DECIDUOUS SHADE TREES: Prune them now before or after leaf drop. For young, newly developing trees, thin out excess branches, remove lower limb, and shape of the tree’s upper crown.

SPRING FLOWERING TREES: Wait 3-4 weeks until after spring flowering to prune, mostly for appearance. Remove dead, diseased, and weak branches and twigs.

Special note: Maples (Acer spp.), Birches (Betula spp.), Yellowwood (Cladrastus), and Dogwoods (Cornus) exhibit a high sap pressure and often bleed when pruned in late winter and early spring. If you prune them now, they will “bleed” sap.

Stoloniferous Dogwoods Jazz Up The Winter Landscape

Posted by Hugh on October 25th, 2018

Redtwig Dogwood Brightens Up The Winter Garden

White fruits in September

Red osier dogwood (Cornus sericea) is a medium-sized, deciduous shrub native to much of the Northern and Western United States (USDA hardiness zones 2-7). Without question these shrubs standout in winter by their colorful stems (see pruning recommendations below). Cut branches are an added plus for indoor arrangements. The yellow-twig form (C. sericea ‘Flaviramea’) is also available.

Leaves are oblong-lanceolate (up to 5 inches long), oppositely arranged with 5-7 pairs of lateral veins, and entire margins. Species may grow up to 10 feet tall and spread voraciously by underground stolons to form large clumps. One landscape idea is to mix red and yellow–twig dogwoods together for a winter color blast. Osier dogwoods grow well in very large containers, but quickly outgrow their pot space in 2-3 years.

These stoloniferous dogwoods bloom in mid-spring (in Tennessee). The terminal creamy white (cyme) flowers measure 1.5 to 2.0 inches across and white berries follow in late summer.

Plant shrubs in full sun (in northern areas) and in partial shade (in zone 7) and average soil. Fertilize in early spring before buds break and irrigate during long dry summer spells. Shrubs establish quickly and are very drought tolerant after one year. Many cultivars are available, and are highly variable in leaf and stem color. This shrub dogwood may be confused with C. amomum which has a similar red bark, but C. amomum has blue fruits and brown pith.

Arctic Fire® is a non-suckering compact form with dark red winter stems. It grows 4-5 feet tall and 4-5 feet wide. It puts on a spectacular show in the wintert. Most varieties of stoloniferous dogwoods grow 8 to 10 feet, making Arctic Fire a great breakthrough for smaller gardens or residential landscapes.

Stoloniferous dogwoods are disease and insect resistant and deer generally overlook them. They make great landscape additions; utilize them in perennial or shrub borders, masses and groupings, container gardens and winter gardens.

Pruning tip: cut 2-3 year old shoots back to the ground each spring immediately after flowering to ensure a good display of the winter branches.

“No Dig” Planting Of Tulips

Posted by Hugh on October 20th, 2018

Mixed planting of Daffodils and Tulips

‘Pink Perfection’ tulips planted by “No Dig” method

Digging lots of holes to plant 25 0r 50 tulip bulbs is a backbreaking chore. It doesn’t have to be that way. More than a decade ago, plant researchers at Cornell University in Ithaca, N.Y., developed a planting method called “top-planting”. It eliminates all the digging and the tulips come back and bloom well for several years.

Top-planting, also called “drop and cover,” requires a lot less effort. I call it “No Dig Bulb Planting” and is a lot simpler:

Till the planting area 3 to 4 inches deep with a roto-tiller.
Plant in a site with full sun and good soil drainage.
Spread bulb fertilizer and lightly till in the fertilizer (optional).
Set the bulbs on top of the tilled area (no need to press the bulb into the ground).
Cover with 2 to 4 inches of composted mulch or aged compost.
No Dig works as well for daffodils as tulips.

Do not over-mulch. Adding more mulch may result in less blooms. Any good garden compost or double ground bark mulch should work. Brent Heath, co-owner of Brent and Becky’s Bulbs in Gloucester, VA recommends adding two inches of mulch in the fall.

Bulb Spacing: Tulip (or daffodil) bulbs that measure 2 inch wide bulbs should be spaced 3 times the bulb size or 6 inches apart. That’s 4 bulbs per square foot.

Tulip varieties that perennialize well are recommended, “particularly Darwin hybrids” according to Brent Heath. Bulbs will re-grow and re-bloom for several years after planting. Many gardeners may opt to inter-plant bulb plantings with summer flowering annuals, perennials, and vegetables.

Caveat: dormant tulips and daffodils like to spend their summers in dry soil. Too much irrigation during the summer months may rot the sleeping bulbs.

Gardeners can enjoy masses of tulips without digging a hole for each bulb.

Overwintering Caladium Tubers

Posted by Hugh on October 15th, 2018

Dr. Mary Lewnes Albrecht, retired dean of the Herbert College of Agriculture at the University of Tennessee, offers her recipe for overwintering caladiums. For many years Dr. Albrecht has been saving several heirloom varieties by this procedure:

Caladium plants dug and in trays ready for trimming

#1. Plants start to go dormant in late September through October (zone 7a Tennessee) and earlier if summer weather has been dry. Signs of dormancy: foliage begins to fade, fewer new leaves emerge, and planting looks thinner. It’s time to dig.

# 2. Dig and knock as much soil off the tubers as possible. Trim the roots to about an inch in length and clip back shoots to about 3 to 4 inches in

Single tuber pre-trimming the roots

length. Collect caladium tubers in cardboard, wooden or plastic trays. Tubers are cured when the roots and leaf bases easily come off, leaving the dormant buds behind on the tubers (usually after a week or two).

Alternative method: spread the dug tubers out on a tarp on the garage floor and let them cure.

# 3. After curing, sort tubers by size which may vary from one year to the next. Lots of consistent rainfall and hot temperatures will yield large tubers. Caladiums are tropical and thrive in summer heat and soil moisture.

Caladiums – single layer of tubers curing

# 4. Store dry tubers in open low trays. Do not stack them in deep layers. Allow good air movement around the tubers for dryness. A well-insulated garage in the 40 to 50 °F range is ideal.

Credit: photos provided by Mary L. Albrecht

Umbrella Pine—A Conifer Collector’s Dream Plant

Posted by Hugh on October 10th, 2018

Umbrella Pine at NC Arboretum in Asheville, NC

Golden Needle Form

Japanese Umbrella Pine (Sciadopitys verticillata) is an evergreen (USDA hardiness zones 5b -9). It is not actually a pine. Historically, umbrella pines date back to the dinosaur age. This mid-sized landscape tree displays several fine attributes: shiny leaves are arranged in whorls like the spokes of an umbrella; peeling, reddish brown bark and a conical habit.

To conifer collectors, umbrella pine is the ultimate prize to add to a private collection. A young nursery produced tree may require training to develop a central leader. Dwarf cultivars (see below) grow slowly, only 4-5 inches yearly.

Umbrella Pine prefers a moist, organically rich, well-drained, moderately acidic soil. Feed with a slow release organic fertilizer in early spring. Maintain a 2-3 inches layer of an organic mulch around the tree base. In the mid-South (zones 6 -7), the tree prefers one-half to full-day sunlight. Further south, morning sunlight is preferred. Pruning needs are rare, mostly to maintain the tree’s pyramidal form and to remove a broken limb or two in late winter. Disease and insect problems are rare.

In its early years, umbrella pine is a slow grower. Eventually, it reaches 30 to 40 ft. in height and 20 ft. in spread. Historic tree specimens may attain 70 or more feet in height. This unique conifer possesses stiff needles arranged in whorls resembling an upside-down umbrella. Branches can withstand heavy snow and ice loads.

The Umbrella Pine is an evergreen prized for its striking foliage and superior pyramidal form. Needles rarely go off color in winter. Select forms are available at specialty conifer nurseries.

‘Gruene Kugel’ – compact form from Germany. Rounded in shape when young, developing slowly into a small compact tree with glossy deep green foliage year-round.

‘Joe Kozey’ grows tall and exceptionally narrow at 20 feet high and only 6 feet wide; slow-growing, spire-like habit.

‘Picola’ – broad growing, 2 inch long dark green needles; ultra-dwarf selection 16- 20 inches tall after 10 years; rock garden plant.

‘Mitsch Select’ – a dense multi-stemmed shrub form with loose pyramidal habit and forest green needles.

‘Picola’– exceptional slow growing pyramidal form with dark-green foliage.

Fall/Winter Water Garden Maintenance

Posted by Hugh on October 6th, 2018

Healthy Water Garden

Water Lilies And Lotus Plants

In the spring and summer seasons, a water garden is a tranquil and refreshing respite in the home landscape. However, in the fall, lots of leaves and debris fall into the pond. Here are a few tips to prepare your water garden for the winter season.

Some water gardens are designed so that the waterfalls and streams run continuously through the fall-winter season. Heaters keep the water surface from icing over. It maintains a small area open to permit harmful decomposition gases from accumulating.

At first frost floating tropical water plants like water hyacinths and lettuce are killed and and should be removed from the water garden. Marginal plants, such as Elephant Ears, Cannas, Papyrus, and tropical water lilies, may be overwintered in a cool 40°F garage in a dormant state or grown in a greenhouse or sunroom. Hardy water plants such as water lilies & lotus occupy the pond’s deeper depths and shallow aquatic plants around the pond’s perimeter.

Use pond netting to protect the water surface from leaves and other debris. If you can not use netting, utilize a skimmer net to remove heavy amounts litter. Inspect pumps and filters for any debris blockages. If pumps, filters and UV lights will not be running during the winter, remove them, drain the water, and store equipment indoors.

Pond hardy fish such as koi & various types of goldfish acclimate very well to cold water conditions. They do not require feeding once water temps dip below 60°F. In areas where the pond will not freeze, switch over to a winter food that is more easily digested.

Ten Native Shrubs Possessing Great Fall Leaf Color

Posted by Hugh on October 1st, 2018

Fothergilla gardenii

Bottlebrush buckeye fall color

Some native U.S. landscape shrubs are not only great spring/summer flowering shrubs, but their fall foliage color(s) are an added attraction. Here are ten of my favorites listed alphabetically by genus:

Bottlebrush Buckeye (Aesculus parvifolia) – foliage of this summer flowering shrub turns bright yellow in fall. (zones 4-8)

Red Chokeberry (Aronia arbutifolia) – under-planted native shrub that grows 6 – 10 feet high. White flowers appear in early spring; recommend compact cultivar ‘Brilliantissima’ with attractive glossy red berries and red fall foliage color. (zones 4-9)

Fothergilla (Fothergilla gardenii) or (F. x ‘Mt. Airy’) – both selections are among the finest spring flowering shrubs along with red fall leaf color. (zones 5-8)

Oakleaf Hydrangea (Hydrangea quercifolia) – is a highly variable flowering shrub, available in a range of sizes from 3-25 feet. Some varieties exhibit exceptional red or bronze foliage in autumn. (zones 5-9)

Virginia Sweetspire (Itea virginica) – blanketed with fragrant blooms in May and dependable red-purplish leaf color in autumn (zones 4-8)

Blueberry (Vaccinium corymbosum) – grow 2-6 feet tall (depending on variety planted). Plant two or more different varieties for more berries. Blueberries require a highly acidic soil pH around 5.0-5.5. Its bluish-green summer foliage turns bright red in autumn. (zones 5-8)

Arrowwood Viburnum (Viburnum dentatum) – an under- planted native viburnum that blooms in May. Fall foliage turns yellow to red to burgundy along with dark blue fruits. (zones 3-8)

Arrowwood (V. dentatum) fall color

Witherod viburnum (Viburnum nudum ‘Winterthur’) –white flowers in late spring are followed by bluish black fruits and red to reddish-purple fall foliage. (zone 5-9)

American cranberry bush (Viburnum trilobum) – tall 12 feet high shrub deep burgundy-red fall leaf color and bright red drupes often persist through winter. (zones 3-7)

Blackhaw viburnum (Viburnum prunifolium) – flat white cymes (flowers) with numerous yellow stamens and purple-red fall foliage color. (zones 3-8)

Toadlilies In The Autumn Garden

Posted by Hugh on September 25th, 2018

Toadlilies -fall flowering

Tricyrtis ‘Sinonome’

Toadlilies (Tricyrtis spp.) are late season flowering perennials in the shade garden. Most perennials have finished blooming as their flower buds are forming. They’re native to moist woodsy environs of India, China and Japan and are Botanical members of the lily (Lilaceae) family (USDA hardiness zones 4-9). When properly sited, toadlilies are long-lived and require little care.

The plant name – “toad lily” – refers to the speckled flower colors. Flowers are borne in the axils of the leaves. Depending on species, plants grow 1 ½ to 3 feet high. Funnel shaped orchid-like flowers come in an array of spotted colors and are either star or bell shaped.

Toadlilies prefer part to full shade, and moist compost-rich garden soil. Under ideal conditions plants need little or no fertilizing. Plants should be protected from the wind particularly in hotter areas of the U.S. Otherwise, feed plants lightly once or twice during the summer with water soluble fertilizers such as Miracle-Gro™, Jack’s™, or Nature’s Source™. Mulching keeps the soil moist and suppresses weeds. Divide roots of the toadlilies in early spring and space new plants 18-24 inches apart.

Toadlilies live mostly untroubled by disease or pests. Anthracnose leaf spotting may pop up in wet summers. If so, clean up all leaf debris and discard in late winter. Deer may or not eat toad lilies? Rabbits can also be troublesome. Varieties with hairy foliage tend to repel critters.

Two species of toad lilies, T. hirta and T. formosana are currently most popular, Two species of toad lilies, T. hirta and T. formosana are currently most popular; they produce abundant purple-and-white blooms on 36 – 40 inch stems. Many new hybrid forms are finding their way into garden centers. ‘Miyazaki’ hybrids are known for their superior flowering, vigorous growth, hardiness, and disease resistance. T. hirta ‘Miyazaki Gold’ has gold-edged green leaves and ‘Moonlight’ has entirely golden leaves. T. macropoda ‘Sinonome’ and ‘Tojen’ has dark green foliage and lavender and white flowers; ‘Lightning Strike’ displays green and gold leaves and speckled flowers on arching stems.

Osage Orange As A Landscape Tree

Posted by Hugh on September 20th, 2018

“Hedge Apples”

Sturdy wood of osage orange

Osage orange (Maclura pomifera) has been declawed and neutered (USDA Zones 5-9). A member of the mulberry family (Moraceae), this tough prairie tree species is native to east Texas, Oklahoma and Arkansas. It grows fast @ 2 ½ to 3 feet per year. It is also called Bois D’Arc (pronounced “bow-dark”).

Osage orange is a dioecious species. Female trees are generally not recommended for landscape use because the fruits pose a considerable litter problem. The “hedge apples” are large 4-6 inch wide yellowish green fruits. Each may weigh 2 to 3 pounds and fall from the tree in October to become a maintenance headache. Female trees need a male tree pollinator in order to produce fruit.

Fierce ½- inch long thorns, hidden within the dense branches, can do lots of harm, even puncture a vehicle tire. The bark on mature trees is deeply fissured, with an orange-brown inner wood peeking through. The wood is hard, does not split or rot, and makes great fence posts. A century ago, in lieu of fences, farmers in the South Central states planted thousands of miles of hedgerows of osage orange. The tree suckers freely and becomes a quagmire of vicious thorns.

Osage orange is easily grown in adequately drained soils in full sun to part shade. The tree grows almost anywhere, in poor infertile, acid or alkaline soils, and dry or wet fields. It also tolerates drought, heat, cold and wind. Disease and pest problems are practically non-existent. Its foliage is tolerant of urban air pollutants.

‘White Shield’ (photo courtesy of J F Schmidt Nursery)

‘Wichita’ and ‘White Shield’ are fruitless and thornless (male) selections. Both cultivars are attractive landscape trees with deep green shiny foliage that turns a beautiful fall pale to golden yellow in fall. ‘Wichita’ grows slightly taller than ‘White Shield’, and its branching tends to be slightly more upright. ‘White Shield’ forms a rounded canopy, averaging 35 feet in height and spread. Trees bloom in late spring with tiny (mostly inconspicuous) green flower clusters.

Either cultivar is a good choice for large residential or commercial properties, city parks, and golf courses. Plant the tree under power lines or utilize as a deciduous windbreak.