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

Past Winners of the Perennial Plant of The Year Award

Posted by Hugh on January 1st, 2014

'Karl Foerster' Feather Reed Grass

Arkansas Blue Star

Each year PPA members choose a Perennial Plant of the Year™. Since 1990 24 great plants have been selected. Some of the selection criteria include:
• Suitable to a wide range of climatic conditions
• Low Maintenance
• Pest and disease resistant
• Availability at garden centers
• Multiple seasons of color (beauty)

The list of Perennial Plant of the Year winners:
1990 Creeping phlox (Phlox stolonifera)
1991 Palace Purple coralbells (Heuchera micrantha ‘Palace Purple’)
1992 Moonbeam coreopsis (Coreopsis verticillata ‘Moonbeam’)
1993 Sunny Border Blue veronica (Veronica ‘Sunny Border Blue’)
1994 Sprite astilbe (Astilbe ‘Sprite’)
1995 Russian sage (Perovskia atriplicifolia)
1996 Husker Red penstemon (Penstemon digitalis ‘Husker Red’)
1997 May Night salvia (Salvia ‘May Night’ (‘Mainacht’))
1998 Magnus purple coneflower (Echinacea purpurea ‘Magnus’
1999 Goldsturm blackeyed Susan (Rudbeckia fulgida var. sullivantii ‘Goldsturm’)
2000 Butterfly Blue scabiosa (Scabiosa columbaria ‘Butterfly Blue’)
2001 Karl Foerster feather reed grass ( Calamagrostis x acutiflora ‘Karl Foerster’)
2002 David summer phlox (Phlox ‘David’)
2003 Shasta daisy (Leucanthemum ‘Becky’)
2004 Japanese painted fern (Athyrium niponicum ‘Pictum’)
2005 Lenten rose (Helleborus x hybridus)
2006 Firewitch dianthus (Dianthus gratianoplitanus ‘Feuerhexe’)
2007 Walker’s Low catmint (Nepeta ‘Walker’s Low’)
2008 Rozanne cranesbill (Geranium ‘Rozanne’)
2009 Aureola Japanese forest grass (Hakonechloa macra ‘Aureola’)
2010 Wild indigo (Baptisia australis)
2011 Arkansas bluestar (Amsonia hubrichtii)
2012 Jack Frost brunnera (Brunnera macrophylla ‘Jack Frost’)
2013 Variegated Solomon Seal (Polygonatum odoratum ‘Variegatum’)

For a complete description of each plant, log onto the Perennial Plant Association Website.

Leyland Cypress – Alternative Christmas Tree For The South

Posted by Hugh on December 25th, 2013

x Cupressocyparis leylandii

If you grew up with a spruce or a fir Christmas tree, Leyland Cypress (x Cupressocyparis leylandii) could be a big change. This conifer species thrives in the southern U.S. (USDA hardiness zones 7-b to 9). Leyland is a good choice for a live cut or transplanted holiday tree as firs (Abies spp.) and spruces (Picea spp.) fail in the southern U.S. heat and humidity. It also grows well in a landscape container.

The scale-like foliage holds its natural green color much better and does not shed compared to the popular Fraser or balsam firs. If it does not, the tree is likely bone dry and a potential fire hazard.

Don’t purchase a leyland that has been cut more than two weeks and laying in a tree sale lot. It is better to visit a Choose and Cut grower. A fresh cut leyland from a tree lot generally does not need to be re-cut when setting the butt into the stand. Leyland can hold heavy ornaments if it has been properly sheared at the tree farm.

Once set up in the home, keep the cut tree away from heating vents and water as needed. Similarly, a live balled and burlapped (b&b) or container tree should be treated the same. Inside a warm home too long, it may break dormancy and be susceptible to the frigid winter weather when transplanted outdoors. Limit its time inside the home to two weeks.

Leyland continues to increase in popularity as a Southern Christmas tree. It is ready to sell as a Christmas tree in 4 to 5 years compare to 7 to 8 years for firs, pines and spruces.

Credit: Dr. Ken Tilt, retired professor of Horticulture from Auburn University, provided much of the information written here.

‘Ogon’ Dawn Redwood Offers 4-Seasons Interest

Posted by Hugh on December 9th, 2013

Summer Foliage of 'Ogon' Metasequoia

Dawn redwood (Metasequoia glyptostroboides ‘Ogon’ (aka ‘Gold Rush’) is a stunning foliage color variant (USDA hardiness zones 5 to 8). Metasequoia was thought to be extinct until the mid-1940’s when rediscovered in China. Its leaves were commonly found imprinted in fossil rocks.

When developing your landscape plan, place Ogon where it will become a focal point on the property. New foliage emerges clear yellow in the spring and turns a steadfast chartreuse color through in spring and summer months. In the fall the soft feathery leaves finish burnt orange and blanket the ground surface. After several years thin peeling strips of mahogany-colored winter bark and vertical silhouette make Ogon a four-season delight.

Dawn redwood prefers a moist well-drained soil and is tolerant of wet sites for short intervals lasting a few weeks. Full sun and adequate soil moisture are necessary to retain foliage color longest. Dawn redwood exhibits no serious disease or pest problems. New foliage may scorch, often indicating need for additional watering when tree(s) are young.

An Ogon tree grows one-third less than the species @ 50 to 60 feet high and 30 feet wide. Utilize as a specimen or park tree on medium to large properties. Align several together in an allee΄ design such as seen at Juniper Level Botanical Garden at Plants Delight Nursery in Raleigh, NC.

Mexican Feather Grass

Posted by Hugh on November 21st, 2013

Mexican Feather Grass In University of Tennessee Gardens, Knoxville in December

The ultra-fine soft foliage of Mexican feather grass (Nassella tenuissima) will grab your interest. Just a slight breeze will create wave movement in your garden (USDA hardiness zones 7 to 10). It grows 1½ feet high (2 feet tall in flower) and 1½ to 2 feet in width.

Mexican Feather Grass is a cool season grass native to dry rocky slopes and open grasslands from south central U.S. to Argentina. Established feather grass is highly drought tolerant. It thrives in full sun and average is well-drained soil. It grows poorly in either water-logged ground and in moderate shade.

Spring’s fine-textured foliage is lime-green followed by silvery-gold inflorescences in late spring. Summer’s heat and humidity causes this cool-season species to go dormant. Inflorescences age to a wheat-straw or blonde color. As temperatures cool down in the fall, Mexican feather grass goes through a second growth flush.

In the winter the foliage turns straw-colored, and plant form, texture and flowing habit all remain attractive. Cut back Mexican Feather Grass in late winter before spring’s growth flush begins. Mexican feather grass may re-seed, but is not difficult to manage.

Mexican feather grass performs well in rock gardens and xeric landscapes. It thrives planted in containers if not allowed to dry out. Its wispy threadlike foliage is attractive spilling over walls, boulders, or the edge of a container. Over time this vigorous grass tends to overwhelm most other perennials and annuals in mixed garden beds or containers.

Renewal Pruning Is An Easy Technique To Learn

Posted by Hugh on November 16th, 2013

Healthy Rhododendron Is Easy To Coppice

Renewal pruning is the practice of severely cutting back selected shrubs and trees. The task is simple. There are no books to read. Select a day from mid-February to early April (USDA hardiness zones 5-7). Cutback the entire shrub(s), leaving 3-5 inch tall cut stems or stubble. The cut stems will bud out in the spring along with adventitious buds below the soil line.

Renewal pruning can eliminate weather-damaged, diseased, and insect-riddled wood, particularly scale insects, without resorting to heavy pesticide use. All diseased and pest-ridden prunings should be removed from the property or burned. Healthy pruning wood can be ground up for mulch that is spread after 6 months or more composting.

Renewal pruning invigorates old shrubs, brightens foliage color, and increases fruit size and quality. Pruning tools needed: hand clippers, loppers, hand pruning saw, or chain saw. Do not use string trimmers (“weed-eaters”).

Renewal pruning may not the ideal practice for all shrubs.
• Summer flowering shrubs often recover and bloom the same year. Some spring flowering shrubs may not re-bloom for 1-2 years.
• Overgrown rhododendrons, hollies, pieris and mountain laurels respond better to a practice called “coppicing” in late September or early October in USDA hardiness zones 5-7.
• Plant health must be good. Weak, sickly shrubs may likely die when drastically cutback.
• Shrubs must be well-established for 3 to 4 years before renewal cutback.
• Don’t cutback grafted or budded plants in fear of losing the cultivar (above-ground portion) The root system may gain dominance.

Partial list of shrubs which respond to renewal pruning:

Glossy abelia (Abelia x grandifolia)
Butterfly bush (Buddleia davidii)
Beautyberry (Callicarpa spp.)
Blue mist shrub (Caryopteris x clandonensis)
Smoke tree (Cotinus coggygria)
Forsythia (Forsythia spp.)
Fothergilla (Fothergilla spp.)
Rose of Sharon (Hibiscus syriacus)
Smooth hydrangea (Hydrangea arborescens)
Pee Gee hydrangea (Hydrangea paniculata ‘Grandifolia’)
Oakleaf hydrangea (Hydrangea quercifolia)
Crape myrtle (Lagerstroemia indica x L. faurei)
Trumpet honeysuckle (Lonicera sempervirens)
Firethorn (Pyracantha spp.)
Sumac (Rhus spp.)
Rugosa rose (Rosa rugosa)
Pussy willow (Salix spp.)
Corkscrew willow (Salix matsudana)
Elderberry (Sambucus canadensis)
‘Hancock’ coralberry (Symphoricarpus orbiculatus ‘Hancock’)
Chaste tree (Vitex agnus-castus)
Weigela (Weigela florida)

Invite These “Bells” To Next Spring’s Garden Ball

Posted by Hugh on October 30th, 2013

Spanish Bluebells and Microbiota in Conlon Garden

Fall planting of many kinds of bulbs is a worthwhile long term investment of your time. Many bulbs (and corms) like daffodils and crocuses will naturalize where you plant them. They also bloom for long periods from late winter into spring. Bulbs bloom nice their first spring; flower heavier the second year; and multiply each succeeding year.

Two bulbs that are underplanted are Spanish bluebells (Hyacinthoides hispanica) and summer snowflakes (Leucojum aestivum). They naturalize and thrive in compost rich moist soil. In zone 6 and further north, sow them in full sun; plant them where they receive afternoon shade in the hot Southeastern U.S.

Spanish bluebells (USDA hardiness zones 4 through 10) bloom in the late spring in full sun or partial shade. Their dainty bluebell flowers are supported on sturdy stems and are excellent as cut flowers. The cultivar ‘Excelsior’ is a rich darker blue than other cultivars, and stand slightly higher to 12 inches.

According to Becky Heath, co-owner of Brent and Becky’s Bulbs in Gloucester, VA, the popularity of summer snowflakes (USDA zones 4-8) have increased over the past 20 years. ‘Gravetye Giant’ is one of her favorites; they are exceptionally vigorous and naturalize rapidly. Their white lily of the valley blooms are large and showy in April / May garden. Plants grow 2 feet or more in full sun or part shade. The fragrant nodding white bells are tipped with light green dots.

Fall Is Spring Bulb Planting Time

Posted by Hugh on October 18th, 2013

Mix of Tulips and Pansies at Callaway Gardens

If you love spring flowering tulips, daffodils and other spring-flowering bulbs, some planning and planting chores should be set into motion this fall. Spring flower bulbs should be planted when cool soil temperatures (below 55 °F) return. For gardeners living in the Southern Appalachian region (USDA hardiness zones 6 and 7), bulb planting begins in early October and ends when the ground freezes or around the first of the New Year.

Bulbs and corms (ex. crocus) should spend the winter in the cold moist ground. They may also be potted in moist soil-less media and stored in a refrigerator for 90 days or more. This mimics the outdoor garden environment. Refrigerated bulb pots can be forced to bloom indoors in February and March. Cover the pots with shrink wrap or in plastic bags to prevent the potting media from drying out or foul smelling your refrigerator.

If you have lots of bulbs to plant in the garden, invest in a power drill and an augur. Most garden centers sell augur bits. This tool makes bulb planting alot easier physically. A recommended depth chart should be available where you purchased the bulbs. Mark the proper depth on the augur with tape. After 5-6 holes, you’ll become a planting pro.

If the bulbs are planted before October 15th, consider inter-planting with winter hardy pansies and violas. Pansies will guarantee a blast of color from fall into late spring while you’re waiting for bulbs to poke through in late winter.

If you can’t plant bulbs right away, store them in a cool, dry place with good air circulation. If you purchased bulbs earlier and found them partially sprouted in the garage, plant them immediately, even if you need to use a pick axe in an icy soil. Most should come up and bloom feebly the first year.

Popular Landscape Trees Deer Don’t Like

Posted by Hugh on October 15th, 2013

Red Buckeye

Flowering Dogwood

This title is somewhat misleading. Deer will eat or sample (nibble) on any landscape plant, particularly if they are hungry enough. Deer also do not read lists of plants they’re suppose to leave alone.

The following list of deer resistant plants is a sampling from reports across the U.S. It does not include every tree reported. Deer species and numbers vary across this big country. A deer’s food palate may also differ from one region to another. It also depends on how hungry the numbers of deer in an area may be.

Some native trees such as American beech, buckeyes, green ash, persimmon, hophornbeam, and flowering dogwood are important food resources for deer and other wildlife. But, they do little significant damage to their host tree(s). If you are trying to introduce young host trees into a landscape, you should fence them off for 3-5 years until they become larger and better established. Finally, prune up low branches out of reach of deer feeding.

Abnormally high deer populations starved for a lack of their favorite foods (mast) will eat or browse on almost any plant. This is a survival reaction. To truly protect plants from deer when deer numbers are unusually high, a tall fence or reinforced netting may be your best options.

Deer Resistant Tree List:

Paperbark Maple (Acer griseum)
Japanese Maple (Acer palmatum)
Striped maple (Acer pensylvanicum)
Norway Maple (Acer platanoides)
Red Maple (Acer rubrum)
Sugar Maple (Acer saccharum)
Ohio Buckeye (Aesculus octandra)
Red Buckeye (Aesculus pavia)
Mimosa (Albizia julibrissin)
Downy Serviceberry (Amelanchier arborea)
Shadblow (Amelanchier canadensis)
Allegheny Serviceberry (Amelanchier laevis)
Pawpaw (Asimina triloba)
Himalayan Birch (Betula jacquemontii)
Yellow Birch (Betula lutea)
River Birch (Betula nigra)
Paper Birch (Betula papyrifera)
European White Birch (Betula pendula)
European Hornbeam (Carpinus betulus)
Deodar Cedar (Cedrus deodara)
Katsura Tree (Cercidiphyllum japonicum)
Chinese Fringe Tree (Chionanthus retusus)
Flowering Dogwood (Cornus florida)
Chinese (Kousa) Dogwood (Cornus kousa)
Winter King Hawthorn (Crataegus viridis ‘Winter King’)
Japanese Cedar (Cryptomeria japonica)
Leyland Cypress (Cupressocyparis x leylandii)
Persimmon (Diospyros virginiana)
American Beech (Fagus grandifolia)
European Beech (Fagus sylvatica)
Green Ash (Fraxinus pennsylvanica)
Ginkgo (Ginkgo biloba)
Honey Locust (Gleditsia triacanthos)
Carolina Silverbell (Halesia diptera)
American Holly (Ilex opaca)
Eastern Red Cedar (Juniperus virginiana)
Goldenrain Tree (Koelreuteria paniculata)
Tulip or Yellow Poplar (Liriodendron tulipifera)
Southern Magnolia (Magnolia grandiflora)
Dawn Redwood (Metasequoia glyptostroboides)
Eastern Hophornbeam (Ostrya virginiana)
Sourwood (Oxydendrum arboreum)
Spruces (Picea spp.)
Japanese Red Pine (Pinus densiflora)
Limber Pine (Pinus flexilis)
Eastern White Pine (Pinus strobus)
Flowering Cherry (Prunus serrulata)
Douglas Fir (Pseudotsuga menziesii)
Sassafras Tree (Sassafras albidum)
Bald Cypress (Taxodium distichum)

Timing Fall Leaf Color Of Red Maple Cultivars

Posted by Hugh on October 7th, 2013

'October Glory' Red Maple in Mid-November in Tennessee

Red maple (Acer rubrum) is one of the most popular large street and shade tree in the Southern Appalachian region (USDA hardiness zones 6 and 7). Most cultivars average 40-60 feet tall in height.

Tiny red flowers burst open early, often before the official first day of spring. Flowers give way to reddish double winged samaras. Its glossy dark green 3-5 lobed leaves are 3-6 inches across with deep red petioles. Many red maple cultivars strut their vibrant red foliage on a specific week in October or November.

Red maple is native to moist well drained soils, preferably in full to partial sunlight. It tolerates wet soils and is unswayed by temporary flooding such as in rain garden zones. In some Midwest states it has earned the nickname “swamp maple”.

Red maple is also cataloged as “soft maple” because high winds and ice may break brittle branches. Its notoriously shallow root system may lift up adjacent sidewalks or driveways.

Red maple may be troubled by insect or disease problems, often when the tree(s) is planted on the wrong landscape site. Leaf aphids, wood borers and scale insects can be occasional pests. Verticillium wilt disease attacks the vascular system, frequently the result of unusually long dry spells extending three or more years. It is resistant to most common urban air pollutants.

Five popular cultivars planted in the southeast and mid-Atlantic states include:
Autumn Blaze® (A. x freemanii) – 50 ft. x 40 ft. – early deep burgundy red leaf color
Red Sunset® (A. rubrum) – 45 ft. x 35 ft. – early bright red leaf color
‘Autumn Flame’ (A. rubrum) – 35 ft. x 15 ft. – better red color in southeast U.S.
‘Armstrong’ (A. rubrum) – 45 ft x 15 ft. – columnar habit for narrow street plantings
October Glory® (A. rubrum) – 40 ft. x 35 ft. – one of the latest for red color

Pruning is best performed in the spring and summer months when sap pressure in low. Sap from this tree can be used to make maple syrup during the winter months.

Too Early Fall Color A Telltale Signal Of Tree In Trouble

Posted by Hugh on October 6th, 2013

'Red Sunset' Maples Coloring In Late September in Tennessee (photo by Ken Soergel)

Early leaf color or premature leaf drop often tells a property owner that their tree(s) may not be healthy. Photo above, taken in front of a new subdivision, says alot. Large red maples show leaf color weeks ahead of their natural timeline. Notice the narrow median where the trees are planted.

The cause of early foliage change may be weather-related, a foliar or root disease, an earlier insect infestation, or a site with one or more environmental factors. Extremes of either a dry or a wet summer (flooding) may lead to premature leaf drop or early fall leaf color. Urban air pollutants can be blamed.

In this landscape situation (photo), red maples were the wrong tree choice for the site. Red maple is nicknamed “swamp maple”; you find the species naturally growing along streams, and near lakes and ponds. Red maple has a notoriously shallow root system, a network of surface roots that destroy a home lawn or lift sidewalks.

In this example, on an obvious dry soil site, crape myrtle (Lagerstroemia spp.), sweetgum (Liquidambar styraciflua), elms (Ulmus spp.), Chanticleer pear (Pyrus calleryana), hornbeams (Carpinus spp.), or yellowwood (Cladrastis kentukea) would have been better tree choices.

A professional landscaper should have known that the tree choice was wrong. Unfortunately, mistakes like this are all too common.