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

Conifers For Poorly Drained Soils

Posted by Hugh on December 7th, 2014

Trimmed yew hedge

Before planting conifers in your landscape, it’s absolutely important to know the drainage (percolation rate) of the soil, particularly if it is clay-based. Most conifers prefer well-drained sandy and clay loam soils.

To determine your soil type and rate of drainage, try the “hole test” recommended by Virginia Tech University horticulturists. Dig a hole approximately one foot deep and fill it with water. Time the rate (on an hourly basis) of water drainage out of the hole. If the water drains away at about one inch per hour, you have a desirable, well-drained soil. If drainage is much faster, your soil is probably high in sand, and if much slower, your soil is probably high in clay.

You might try replacing the soil in an extra wide planting hole with coarse sand or pea gravel. To prevent plant losses on soggy wet soils, set conifers on an incline plane or rolling slope so the roots will not drown in the low oxygen soil. A final alternative is to plant the root ball shallow on high soil mounds or berms.

Some conifer species adapt to poorly drained soils such as bald cypresses (Taxodium spp.), dawn redwood (Metasequoia), and arborvitaes (Thuja spp.). Eastern larch (Larix laricina) lives in swamps in the northeast U.S. and Canada, but most Larix species do not like wet feet. Nootka or Alaska cedars (Xanthocyparis nootkatensis) prefer moist soils that must be adequately drained. Coastal populations of Atlantic Whitecedar (Chamaecyparis thyoides) inhabit swampy environs, but many treasured collector cultivars don’t seem to prosper on wet sites.

Yews (Taxus spp.), pine (Pinus spp.), spruce (Picea spp.), and firs (Abies spp.) demand ideal drainage all the time. Plant with good soil with the proper amounts of soil amendments.

Emerald™ Arborvitae

Posted by Hugh on December 4th, 2014

Emerald™ Arborvitae at NC Arboretum in Asheville, NC

Emerald™ or ‘Emerald Green’ arborvitae (Thuja occidentalis ‘Smaragd’) is not new shrub or cultivar. More than 3 generations of gardeners have used this unique form of eastern arborvitae as their “go to” evergreen shrub up and down the eastern coast and through the Midwest (USDA hardiness zones 3-7). Emerald is a semi-dwarf evergreen shrub with a compact, narrowly pyramidal habit.

Emerald arborvitae differs from 12-15 feet high and 4-5 feet wide at maturity. A row of these “cookie cutter” shrubs shows very little variability as a lovely privacy hedge or foundation planting. Leaves are glossy, bright green, and scale-like in flattened sprays. Color rarely bronzes off in a cold winter in east Tennessee (zone 6). Urn-shaped ½ inch long cones turn reddish brown in late autumn.

Eastern arborvitae grows in any well-drained soil in full sun or part shade. Deep watering is highly recommended over long summer dry spells. This conifer struggles on a poorly drained site. Foliage is more open (less tight) when planted on shady sites. Under southeast U.S. heat and humidity Emerald arborvitae excels, far better than the species.

Feed in late winter with a slow release fertilizer specially designed for evergreen shrubs such as Osmocote™, Nutricote™, or Schultz Nursery Plus™. Add to organic mulch in the spring. Prune arborvitaes in late winter before onset of new spring growth. Remove broken branches and inspect hedges for possible bagworm infestations.

The tightly bundled branches may break apart under excessive ice and snow loads. Arborvitaes are rarely troubled by disease or pest problems and are quite tolerant to air pollutants in large urban centers. Bagworms and spider mites are occasional insect pests. Protection against deer browsing is imperative.

Lacebark Pine Is An Arboreal Gem

Posted by Hugh on December 1st, 2014

Lacebark Pine Blooming in mid-May

Lacebark pine (Pinus bungeana) is an arboreal gem which few gardeners are privileged to own (USDA hardiness zones 4-8). Hopefully, this will change. Lacebark is a lovely 3-needle pine with exquisite exfoliating bark which becomes more attractive as it ages. Bark mottling begins after 8-10 years, that’s worth the wait if you’re a young patient gardener.

Lacebark is a 30 to 50 foot tall pine. Frequently, most gardeners start out planting an affordable 2 – 3 foot multi-branched shrub. A young lacebark starts out slow, but growth rate picks up (4-5 inches annually) after 4-5 years on-site. The lovely cinnamon colored candles tip the branches in May, similar to candles decorating a cake. When fully expanded, the 2 – 4 inch long bristly needles are sharp to the touch.

Lacebark requires no special care other than fertilizing in the early spring and mulching until it is established after 2 years. Plant lacebark in full sun and in above-average garden soil that is well-drained. An older tree is moderately drought tolerant. Occasionally, you may want prune off a few side branches to show off the exfoliating bark pattern within. Young tree bark tends to color olive green and gradually bleaches out to an oft-white many years hence.

Most potentially serious disease and insect pests may be avoided through proper siting and care. Select a visible landscape location which is frequently visited, such as near a patio, carport, driveway or a window which looks out at lacebark.

Lacebark pine can be purchased from specialty mail-order nurseries via the internet. Lacebark is a long term investment, an evergreen that you and future generations will cherish for its exquisite patchwork bark.

Patchy bark

List of Zone 6 Hardy Camellias Grows Longer

Posted by Hugh on November 29th, 2014

‘April Tryst’ Camellia

‘April Remembered’ Camellia

If you live and garden in USDA hardiness zone 6, several camellia cultivars are winter hardy. The past decade has seen an increase in the list of hardy cultivars. These same cultivars are also reliable planted in zone 7. Here is a sampling of the best Zone 6 Hardy Camellias:

Fall Bloomers:

Londontowne Blush

Long Island Pink

Snow Flurry

Sweet October

Winter’s Interlude

Winter’s Joy

Winter’s Star

Spring Bloomers:

April Dawn

April Remembered

April Snow

April Tryst

Korean Fire

Pink Icicle

Spring’s Promise

Winter of 2013-14 was the roughest in my 9 years of growing camellias in northeast Tennessee (zone 6). All March-April bloomers lost their flower buds. All camellias in my garden survived the cold and looked great by summer.

Subjecting camellias to direct winter winds and planting them late in the year are two big mistakes. Don’t plantafter October 1st; spread 2-3 inches of an organic mulch around newly planted camellias as a soil heat blanket. October tends to be a dry month in the mid-South region; irrigate new camellias during rainfall deficit. Caveat: do not overwater camellias; November-December rainfall is usually plentiful. One-year old planted camellias acquire good drought tolerance. Irrigate only when summer months are exceptionally dry.

As a holiday promotion local big box stores may sell the camellia cultivar ‘Yuletide’ with bright red blooms and dark green leaves which open around late October. Most flowers will not open as frigid temperatures will arrive shortly. Open flowers are immediately injured and temperatures below 15º F will kill (blast) unopened floral buds. Yuletide may be zone 7b hardy.

Lastly, some zone 7 rated cultivars demonstrates exceptional plant cold hardiness. Their flowers (Sasanqua types) open in early autumn. Their winter foliage bronzes slightly, but shrubs rarely lose a leaf. More about these cultivars at a future blog

Species Tulips Thrive in Tough Spots

Posted by Hugh on November 27th, 2014

Tulipa bakeri ‘Lilac Wonder'(photo from Brent and Becky’s Bulbs, Gloucester, VA)

T. ‘Peppermint Stick’ (photo from Brent and Becky’s Bulbd, Gloucester, VA)

T. clusiana ‘Cynthia’ (photo from Brent and Becky’s Bulb in Gloucester, VA)

Species tulips (mini-tulips) are tough! In the wild they grow in the winter environs and dry soils of Central Asia, the Middle East, and China (USDA hardiness zones 3-7). In gardens they prosper for many years in full to partial sun and in average soil with good drainage.

Over the centuries mini-tulips have been improved. Color choices include red, bright yellow, orangey-red, pink, orchid, white, and bi-colors. Bloom times vary from early thru late spring.

Mini-tulips partner well with low-growing varieties of stonecrops (Sedum), which also thrive in subpar soils and hot, dry sites. Avoid planting in poorly drained or soggy soils. Voles may become a serious pest.

Plant mini-tulips at the same time you’re sowing other spring-blooming bulbs from October thru December when average day temperatures are in low 4oºF range and the ground is not frozen. Bury them just 4-5 inches deep. No fertilizer or soil amending is needed.

To maximize their potential to naturalize, do not trim foliage after flowering ends; allow foliage to die back on its own. New bulblets (offsets) and new bulb should develop underground. Mini-tulips suffer in southern U.S. zones if winter soil temps stay too warm to initiate flowers; plants also may germinate weakly and not bloom.

They’re small… so bunch a handful in pockets in flower borders, in rock gardens, along fences or walks. Tuck some around the base of late leafing deciduous trees.

Mr. Brent Heath, Brent and Becky’s Bulbs in Gloucester, VA, provided the following info:

T. sylvestris – stoloniferous, naturalizes in light shade, yellow, sweet fragrant outwardly facing flowers.

T. clusiana var. chrysantha –high desert mountain type from Iran to northern India is perfect for rock gardens; varieties ‘Lady Jane’ and ‘Cynthia’.

T. whatalei – orange cup-shape flowers in light shade (South) to full sun (North).

T. bakeri – ‘Lilac Wonder’ and ‘Honky Tonk’(soft yellow-pink hybrid) prefer full sun.

T. linifolia – dark red flowers and narrow edged leaves; ideal for sunny rock garden.

Tips On Crape Myrtles In Fall And Winter

Posted by Hugh on November 24th, 2014

Poor Pruning of Crape Myrtles

“Crape Murder” In Early February

Hardy cultivars of crape myrtles are best left alone in the fall. Light pruning to remove a broken branch or the seed capsules is ok, but major pruning should wait until early spring. “Crape murder” is a common practice in the Southeast U.S. and is not recommended any time or place. It involves lopping down tree and shrub crape myrtles to 5-6 feet height. The reason often cited by professional landscapers is that retail merchants want customers to see their signage.

The severe 2013-14 winter caught many landscape companies pruning in January and February. The aftermath was that many crape myrtles died to the ground. Fortunately, most did sucker back up and flower in summer (about 4-6 weeks later than normal). Plants had to be pruned to redevelop their branching habit.

If you must dig one up to transplant, wait until mid-March or later. Fall planting can be risky. Crape myrtles are cheap to replace or to start over. Often a fall or winter transplanted crape myrtle starts off weak, particularly if the previous winter weather has been severe.

Andrew Bunting, plant curator at the Scott Arboretum (campus of Swarthmore College in Swarthmore, PA) lists these cultivars that came through the winter 2013-4 with virtually no damage:

fauriei ‘Fantasy’
fauriei ‘Townhouse’
indica ‘Carolina Beauty’
indica ‘Pink Velour’
‘Acoma’
‘Lipan’
‘Muskogee’
‘Natchez’
‘Osage’
‘Tuscarora’
‘Tuskegee’

In northeastern cities such as Boston, New York, Philadelphia, Wilmington, and Baltimore, crape myrtles are rated as hardy perennials and not woody shrubs or trees. Following a severe winter, expect some to dieback to the ground. Some of the hardiest forms originate from the U.S. National Arboretum. If you desire to trial only 3 or 4 cultivars, ‘Natchez’ and ‘Muskogee’ (tree forms) and ‘Acoma’ and ‘Osage’ (shrub forms) are most reliable.

Dragon Eye – Actually Four Different Pines

Posted by Hugh on November 19th, 2014

Pinus wallichiana ‘Zebrina’ at Richmond Botanical Gardens in VA

Pinus densiflora ‘Oculis Draconis’ at Richmnod Botanical Gardens

In U.S. nursery catalogs, at least four gold striped needle pines are designated “Dragon’s Eye Pine”. They are Japanese red pine (Pinus densiflora ‘Oculus Draconis’), Japanese black pine (P. thunbergi ‘Oculus Draconis’), Variegated Korean pine (P. koraiensis ‘Oculus Draconis’) and Variegated Himalayan pine (P. wallichiana ‘Zebrina’) (USDA hardiness zones 4 to 7). Three of four, designated ‘Oculis Draconis’, are ones that fit into most small to medium sized gardens.

All four Dragon’s eye pines grow tree form, 25 to 35 feet high and 15 to 20 feet wide. All starts off slowly, growing only 6-8 inches per year. Within 3-4 years growth rate doubles to 12 to 16 inches annually. Variegated Himalayan pine grows tallest, 40 to 45 foot tree tall with longer internode lengths between branches. All grow in a well-drained, slightly acidic soil in full sun to partial shade.

The striped needle variegation is present year-round and becomes more intense as summer rolls to fall. The variegation persists through the winter season and actually gets better as the specimen ages. The Japanese red bark form exhibits scaly fissured bark is lovely, ranging in color from gray to rich rusty orange. This is a graceful tree when mature, with an irregular branching habit and tilted trunk. It stands out planted among deep-green conifers or in front of a dark green background. Utilize primarily as a specimen tree in a prominent landscape area such as near a patio or deck.

An unusual and elegant ornament for the winter landscape, the dragon’s eye pine has 3-5 inch long green needles stiff needles with prominent yellow and green bands. Branching open up in later years, and tree become irregular in form. Its bright colored needles become a 4-season asset in the landscape. As red pine ages it develops a nice reddish-orange exfoliating bark on the trunk and main branches.

Dragon-eyed pines are available from on-line specialty nurseries.

Information credit: Michael Balogh, Mountain Meadows Nursery near Asheville, NC assisted in the preparation of this write-up.

Trees And Shrubs That Grow In Poorly Drained Soils

Posted by Hugh on November 17th, 2014

Surface Knees of Bald Cypress Tree at Longwood Gardens, Kennett Square, PA

If a section of your landscape is poorly drained, there are a number of trees and shrubs that will adapt over time to short periods of wet or soggy soils. Plant roots must survive in low oxygen soils. Your choices of plants are not lengthy; few landscape plants will not tolerate root suffocation for even brief intervals of time.

On landscaping sites with poor drainage, start with trees and shrubs that native to wet bottomland areas. They make the best candidates. When planting tolerant trees and shrub species, plants must have a period of time to adapt to the flooded, low oxygen soils. They are likely shallow-rooted and require staking for initial support. Over time, plants will develop physiological and anatomical features to tolerate poor drainage. For example, bald cypress (Taxodium distichum) develops “knees” on the ground surface to capture air.

Plant scientists at North Carolina State University in Raleigh, NC recommend starting with small plants that have been grown on poorly drained sites. It also helps to create raised beds, swales, grassed waterways, and drainage lines that can divert excess water away from planting sites. The following list is not complete, but does include some great plants. Many are excellent choices for inclusion in rain garden sites.

Tree List:

Red Maple (Acer rubrum)

Silver maple (Acer saccharinum)

Pawpaw (Asimina triloba)

River birch (Betula nigra)

Hackberry (Celtis occidentalis)

Green ash (Fraxinus pensylvanica)

Eastern redcedar (Juniperus virginana)

Sweetgum (Liquidambar styraciflua)

Sweetbay magnolia (Magnolia virginiana)

Blackgum, tupelo (Nyssa sylvatica)

Swamp white oak (Quercus bicolor)

Bur Oak (Quercus macrocarpa)

Willow oak (Quercus phellos)

London plantree (Platanus x acerfolia)

Willows (Salix spp.) -tree and shrub forms

Bald cypress (Taxodium distichum)

Eastern arborvitae (Thuja occidentalis)

American Linden (Tilia americana)

Canadian hemlock (Tsuga canadensis)

American elm (Ulmus americana)

Shrub List:
Summersweet, sweet pepper bush (Clethra alnifolia)

Buttonbush (Cephalanthus occidentalis)

Red osier dogwood (Cornus sericea)

Common witchhazel (Hamamelis virginiana)
Possumhaw (Ilex decidua)

Winterberry holly (Ilex verticillata)

Yaupon holly (Ilex vomitoria)

Virginia sweetspire (Itea virginica)

Ninebark (Physocarpus opulifolius)

Dappled willow (Salix integra ‘Hakuro Nishiki’)

American elderberry (Sambucus canadensis)

Snowberry (Symphoricarpos alba)

Coralberry (Symphoricarpos orbiculatus)

Arrowwood (Viburnum dentatum)

Nannyberry (Viburnum lentago)

Better Choices Than Leyland Cypress For Privacy Screen

Posted by Hugh on November 12th, 2014

Cryptomeria Privacy Screen near Chattanooga TN

For homeowners in a rush to establish a tall green privacy screen from the neighbor(s), perhaps a 12-foot tall green fence may be your better option. Among the choices of evergreens to plant, Leyland cypress (x Cupressocyperus leylandii) is fastest growing, but is plagued by any of three serious disease problems. An established leyland cypress planted 12 feet apart completely occupies its place and stands 12 plus feet tall within 10 years if adequately fertilized and irrigated.

Foliage disease problems usually do not infect leyland cypress until 10-12 years after planting. No disease cure-alls (fungicides) are presently available. Pruning off diseased branches on tall ladders is the best cure-all which can be a highly expensive and a dangerous chore for diyers to take on.

In northerly zones (USDA hardiness zone 6 and 7), Japanese cryptomeria (Cryptomeria japonica) and ‘Green Giant’ arborvitae (Thuja plicata x T. standishii) may be the evergreen privacy screen that you’re looking for. Within 1-2 years after planting, their growth rate is moderate, 16-20 inches annually. They may not be as vigorous like leyland cypress, but without the disease threat that may destroy a privacy screen within 20 years. Two-year established arborvitaes and cryptomerias exhibit better drought resistance than Leyland cypresses.

An occasional pest of all three evergreen species are bagworms which can devour new soft spring foliage. Inspect evergreens in late winter and treat with any of a number of pesticides previously listed in my “bagworms” blog. The winter foliage of all three usually bronzes off, but quickly recovers (greens-up) in the early days of spring.

‘Gyokuryu’ Japanese Cedar -Privacy Screen For Small Gardens

Posted by Hugh on November 9th, 2014

Photo credit: Dr. Susan Hamilton, University of Tennessee

Gyokuryu Japanese cedar (Cryptomeria japonica ‘Gyokuryu’) is a dense, broadly pyramidal evergreen shrub (USDA hardiness zones 5-8). It has short stiff needles that tend to be a slightly darker green than other cryptomeria cultivars. Gyokuryu holds its dark green color through most winters in zone 7 and further south. Expect winter bronzing when Gyokuryu is planted on high windy sites. Branches are pliable and release heavy snow to prevent limb breakage.

Spring/summer growth rate is moderate. Gyokuryu starts out as a short ball-shaped shrub, flattened on top. After 3 to 4 years it develops a dominant upright leader and takes on a pyramidal form. Gyokuryu grows 15 to 20 feet high and 5 to 7 feet wide in 20-25 years. Growth rate ranges from 6 to 9 inches per year. Over the years it becomes a handsome stand alone specimen plant, or you can group several together as a hedge or privacy screen.

Cryptomerias are planted in full sun and in an average well-drained, moderately acidic pH soil. One to three year old plants benefit from mulching. Disease and pest problems are minimal when plants are properly sited and not overcrowded. It is best to plant them 5-6 feet apart and allow them to gradually to fill in on their own. Two year established plants exhibit better than average drought tolerance. Supplemental irrigation during prolonged dry spells over 3 or more weeks is recommended for total optimum growth.

Deer generally stay away from cryptomerias. Feed in late winter and repeat in late spring with water soluble fertilizer (Miracle Gro™, Jacks™, or equivalent); or a granular fertilizer such as 10-10-10 or equivalent. Hollytone™ is a reliable evergreen plant fertilizer.