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

Purple Heart Tradescantia

Posted by Hugh on August 15th, 2015

‘Purple Heart’ Setcreasia at Ohio State University Gardens

Cobweb spiderwort (T. sillamontana ) at Dallas Arboretum

Purple Heart tradescantia (Setcreasea pallida ‘Purple Heart’), formerly Tradescantia purpurea), is an annual trailing groundcover with purple stems and violet-purple foliage. This flowering vine is primarily grown for its vibrant foliage. Purple Heart is utilized in garden beds, large containers or hanging baskets. By summer’s end individual plants may grow 8-12 inches tall and spreading 16 inches wide.

Purple Heart grows best in full sun to light shade. Its foliage color is darkest in bright sunlight and purple hue diminshes under lower light levels. Colorful leaves may reach 7 inches in length, most often 3-5 inches.

Over the first 4-6 weeks pinch growing tips to encourage better branching and bushier plant habit. Note: pinched cuttings root easily. Small 3-petalled, pale pink flowers appear in late summer. Cut back flowering stems in late summer after blooming to improve plant density. Water frequently and fertilize to establish plant(s). Feed monthly with water soluble fertilize such as Miracle-Gro™, Nature’s Source™ or Schultz™. Plants become very drought tolerant in late summer.

Purple Heart is easily propagated from vegetative cuttings. Stick 3- to 5-inch long tip cuttings in a loose, airy soil mix of medium grade perlite, or gritty sand, or water. Cuttings root quickly, usually within 2-3 weeks. Pot them up to start other container(s) or add to existing garden bed in spring and summer.

Viruses, aphids, spider mites may be occasional problems. Discard virus infected plants immediately.

In mid-autumn frugal gardeners collect cuttings and grow Purple Heart indoors over winter. New cuttings can be started in spring and moved into back to the garden in mid- to late spring.

Others spiderworts to consider:

‘Cobweb’ spiderwort (T. sillamontana) is a wonderful plant collector’s oddity. Native to the mountains of northern Mexico (zones 7b – 10), it remains evergreen in zone 8b and further south. Gray-green leaves and thick stems are covered with white hairs (“cobwebs”). It sports deep pink three petal flowers.

S. pallida ‘Blue Sue’ is a passalong plant sold by Plant Delights Nursery in Raleigh, NC (zones 7b – 10). The 2-inch wide x 5 inch long bluish gray leaves clasp upright dark purple stems; forms an 18 inches tall x 5 feet wide patch over 10 years. Small diurnal lavender flowers appear in late June (NC). Tony Avent recommends it as a groundcover around open branched shrubs, including roses.

Rebloomers Need Your Help

Posted by Hugh on August 12th, 2015

Rebloomer daylily (Hemerocallis ‘Stella D’Oro’)

Iris ‘Immortality’ at NC Arboretum in Asheville, NC

Re-bloomers are specific cultivars that bring on a repeat floral show – two and sometimes three in one season. In my garden re-blooming iris and re-blooming daylilies return for another round of bloom in late summer and fall. Also, deadheading some perennials will cause them to flower again.

You, the gardener, must supply needed soil moisture and nutrition (primarily nitrogen) as these plants should not struggle through an environmentally stressful summer. Plant vigor gets recharged by frequent irrigation and adequate fertilizing. In some situations you may need to monitor and treat disease and insect problems.

As plants finish blooming in “prime time”, remove all spent flower heads to prevent seed formation. For iris prune off old flowers in late May, daylilies in late June and July.

Deadheading: some perennials re-bloom a second and third time when old spent flowers are promptly removed, and plants are properly nurtured. Here are a dozen of easy to re-bloomers: yarrow (Achillea), blanket flowers (Gaillardia x grandiflora), perennial salvia (Salvia x nemorosa), tickseed (Coreopsis verticillata), coneflower (Echinacea purpurea), redhot poker (Kniphofia), gayfeather (Liatris spicata), summer phlox (Phlox paniculata), Shasta daisy (Leucanthemum x superbum), blackeyed Susan (Rudbeckia fulgida), Stokes aster (Stokesia) and speedwell (Veronica spp.).

Note: not all daylily and iris varieties are re-bloomers.

Blackberry Lily

Posted by Hugh on August 9th, 2015

Orange spotted flowers

Blackberry (Belamcanda chinensis) at Yewdell Gardens, Louisville, KY

Blackberry lily (Belamcanda chinensis), aka leopard lily, is native to Central Asia, China, Japan and India (USDA hardiness zones 5-9). It derives its name from clusters of shiny black seeds clearly in view as individual seed capsules split apart as they ripen. Its common name is misleading as it is not a lily, but instead a member of the Iris family (Iridaceae).

The sword-shaped leaves mimic those of gladiolus, also members of the Iris family. The medium green leaves measure up to 10 inches length. Plants grow 2 to 3 feet tall and bloom in mid to late summer (depending where you live). Flowers average 2 inches across, comprised of 6 orange colored petals splashed with red dots. Floral sprays stand on wiry, naked stems, typically 2-3 feet above the flat fan foliage. Heavy rains tend to topple floral stems which do not pick themselves back up.

Two species of blackberry lilies: 1. orange-colored flowers (B. chinensis) are most common; 2. unspotted yellow flowers of B. flabellata (‘Hello Yellow’). Latter species wants for more shade and water. Individual flowers last only a day. Decorative seed capsules are utilized in dried floral arrangements in fall.

Blackberry lilies thrive in average moist well-drained soils and light exposures from partial (4-5 hours) to full day sunlight. Plants may be started from seed or from rhizome divisions. In late summer or fall, before capsules fully open, collect seed and sow in a prepared bed about ½ inch deep. Seedlings emerge in late spring and usually bloom the first year. Blackberry lilies fail planted in poorly drained ground.

Clumps slowly expand via creeping rhizomes and usually not long-lived. They tend to seed-in readily, rarely becoming invasive.

Blackberry lily requires little maintenance. Few potential diseases and pests are troublesome. Iris borers may attack plant rhizomes. Some plant parts are poisonous, if ingested; keep away from young children or pets.

Beware! Yellow Jackets

Posted by Hugh on August 6th, 2015

Paper wasp (photo by Dr. Frank Hale, University of Tennessee Entomologist

Most humans fear and hate yellow jackets. They are actually wasps and important predators of several harmful insects. They’re easily identified by their distinctive markings along their abdomen. They tend to dart about rapidly, in a side-to-side flight pattern. Female yellow jackets are the ones capable of stinging.

Wasps (Vespula spp.) are not bees; they’re brightly colored “cousins” of ground bees. In late summer, while most ground nesting bees are storing up food for the winter, wasps begin to emerge. They had constructed their nests in cool spots such as old rodent burrows, ground holes, under roof eaves, and in mortar cracks between bricks of buildings.

Yellow jackets are social insects. They are not pollinators, but do prey on other pollinating insects and nectar. They scavenge on animal wastes and foods high in protein or sugar. Wasps are highly aggressive and are easily provoked by humans. Favorite places to forage include waste receptacles, soda cans, and picnic foods which they carry back to their nest.

The aggressive behavior of yellow jackets, coupled with their tendency to attack as a group, makes them formidable pests to deal with. When outdoors follow these few wasp avoiding tips. Keep all liquids covered. Don’t swat or crush yellow jackets as this may incite other yellow jackets to attack. If you get too near a nest, backoff slowly. Do not wear bright colored clothes or heavy perfumes.

Call a professional exterminator who has the knowledge, safety clothing, and proper pesticides to find and destroy nests close by your home or patio. Otherwise, leave these mostly beneficial insects alone.

List Of Conifer Reference Gardens In Southeastern U.S.

Posted by Hugh on August 1st, 2015

American Conifer Society Reference Gardens in the Southeastern Region

March 2015

Platycladus orientalis ‘Franky Boy’ at UT Gardens, Knoxville, TN

Pinus wallichiana ‘Zebrinus’ on ETSU Campus in Johnson City, TN

Want to learn about which evergreen and deciduous conifers grow well in your area. The American Conifer Society (ACS) has established a reference garden network across the U.S. If you are developing dwarf conifer collection and want to know their growth rates, visit a reference near you. These public arboretums and botanical gardens are also wonderful vacation destinations.

At this writing eleven (11) gardens have been designated in the Southeastern U.S. Here is the current list:

Gardens of the Big BendUniversity of Florida

155 Research Road

Quincy, Florida

University of Tennessee – JacksonWest TN Research and Education Center Gardens

605 Airways Drive

Jackson, Tennessee

Atlanta Botanical Garden1345 Piedmont Avenue NE

Atlanta, Georgia

University of Tennessee GardensUniversity of Tennessee

2431 Joe Johnson Drive

Knoxville, Tennessee

Lockerly Arboretum1534 Irwinton Road

Milledgeville, Georgia

Al Gardner Memorial Conifer GardenJ. Sargeant Reynolds Community College

1851 Dickinson Road

Goochland, Virginia

Smith Gilbert Gardens2382 Pine Mountain Road NW

Kennesaw, Georgia

Lewis Ginter Botanical Garden1800 Lakeside Avenue

Richmond, Virginia

State Botanical Garden of Georgia2450 S. Milledge Avenue

Athens, Georgia

Norfolk Botanic Garden6700 Azalea Garden Road

Norfolk, Virginia

Hatcher Garden and Woodland Preserve820 John B. White, Sr. Blvd.

Spartanburg, South Carolina

State Arboretum of Virginia400 Blandy Farm Lane

Boyce, Virginia

South Carolina Botanical GardenClemson University

150 Discovery Lane

Clemson, South Carolina

Baker Arboretum4801 Morganton Road

Bowling Green, Kentucky

East Tennessee State University ArboretumEast Tennessee State University

Johnson City, Tennessee

JC Raulston Arboretum4415 Beryl Road

Raleigh, North Carolina

Memphis Botanic Garden750 Cherry Road

Memphis, Tennessee

All About Thistles

Posted by Hugh on July 30th, 2015

Weedy Thistle In Flower Garden

Weedy Thistle flowers

Some weeds are very nasty and on top of my list are the dreadful thistles. Learn the lifecycles of those in your region and the proper method to eliminate them.

Canada thistle (Cirsium arvense) is a perennial species found in many areas of the eastern U.S. Other thistles in my region are bull and Russian thistles that are biennials. Male and female flowers of Canada thistle are found on separate plants, while flowers of other thistles are on the same plant.

Thistles often get their start in abandoned city lots and in uncultivated farm fields. When ready, ripe seed pods may release hundreds of windblown seeds that land in your garden or mine. One Russian thistle (Salsola tragus) plant may produce over 200,000 seeds. In residential areas it usually is an uncaring neighbor or absentee landowner who allows thistles to spread.

If you do not catch them early on, it may take years to get rid of them. Here are four methods of managing thistle infestations:.

Method #1: Never Let Them Seed. Prevent thistles from forming flowers. Cut them off with a mower, hoe, or weed whacker. Frequent mowing prevents mature seed heads from forming. This is particularly effective against biennial species.

Method #2: Dig out the root. If only a few thistle plants, dig up the entire root system which may extend deep into the soil. Broken secondary roots can produce new plants. This method is impractical for large infestations.

Method #3: Herbicides. Apply a non-selective broadleaf herbicide to the entire area. Warning: all vegetation (good and bad) will die. This method is most effective against large infestations.

Apply herbicides when thistles are actively growing, when outdoor temperatures are between 65 and 85º F.
Phenoxy herbicides include these ingredients: MSMA, dicamba, MCPA, and 2,4-D. Tradename products like WeedB-Gone™ and Trimec™, containing 2 or 3 ingredients, work best with multiple applications every 2-3 weeks.
Glyphosate (Roundup™) may be applied to individual thistle plants by swabbing with a paint brush or sponge.

Method #4: Pasture Management. Let horses, goats and sheep to graze on certain thistle species.

Additional notes: Some thistle species are listed as invasive in parts of the U.S.. Canada thistle is a valued nectar food source for larvae (caterpillars) of the Painted Lady butterfly.

Long Blooming Tennessee Coneflower

Posted by Hugh on July 27th, 2015

Tennessee Coneflowers at Butterfly Arboretum in Jonesborough, TN

Individual flowers of TN coneflower

Dependable Tennessee coneflowers (Echinacea tennesseensis) bloom almost all summer (USDA hardiness zones 4-8). That’s three months long. Plants are covered with pale pink, flat ray flowers; blooms measure 2 to 3 inch across with greenish-brown centers or cones. It is a great addition to hot dry sites, including shallow rocky soils, conditions that would challenge other coneflower species. Group several together in a perennial border, meadow, or wildflower garden. New compact forms grow well in containers.

This Echinacea species grows 18 to 30 inches tall. It thrives in full sun and in moist, well-drained soils. After the first year, plants tolerate dry soil conditions. Plants tend to be floppy in partial shade and need staking. From mid-June into September TN coneflower blooms non-stop. The petals extend out or up and seem to follow the sun. The pale pink petals do not reflex backwards like popular purple coneflowers (E. purpurea).

TN coneflowers have no serious insect or disease problems. Japanese beetles, powdery mildew and leaf spot are occasional problems. They do not benefit from high soil fertility, which tends to weaken stems. Flowers attract many species of butterflies and birds (particularly finches). Deer generally do not bother coneflowers. Every 4 to 5 years divide clumps when the garden bed becomes overcrowded. Plants usually re-bloom without deadheading; periodic removal of spent flowers does improves overall bed appearance.

Hybrid cultivars:

‘Rocky Top’ is a compact grower with pastel pink on 2 to 3 feet tall and 1 foot wide plants.

Pixie Meadowbrite™ is a dwarf form (18 inches tall and 20 to 24 inches wide) with medium pink flowers.

At one time Tennessee coneflower was listed as endangered; it is easy to find in commerce today.

Sensuous Begonia boliviensis

Posted by Hugh on July 24th, 2015

Container Floral Mix with ‘Bonfire’ Begonia and Petunias

New cultivar ‘Santa Cruz’

Bolivian begonias (Begonia boliviensis) are tuberous rooted types indigenous to the Andes Mountains in Bolivia and Argentina (USDA hardiness zones 9 to 11). Plants grow rapidly and bloom non-stop from late spring to early fall. No deadheading of spent flowers is necessary. Bright red to orange flowers feature four long curved petals and lush medium-green pointed angel-wing foliage which cascades over the edge of the container. Additional floral color shades are becoming available.

They’re at their best planted in urns, window boxes or hanging basket as “spillers”. Plants arrive at area garden centers and greenhouses in mid- to late-spring. The 2-inch long tubular red-orange flowers form at the end of growing tips. Hummingbirds are attracted to the brightly colored flowers.

Bolivian begonias thrive in brightly lit areas ranging from full to partial sun and light shade. Potting media must be well-drained and monthly feeding and moderate moisture promotes greater flower numbers. Feed regularly with water-soluble fertilizers such as Miracle-Gro™, Daniels™ or Jacks™. Begonias do not tolerate overwatering and poor drainage leads to root rot problems.

In areas with mild winters (zone 7b and further south), plant(s) may be stored in an unheated garage in a semi-dormant state. Cut the plant back to within 2-3 inches of the soil line in late fall. Re-pot older plants into new soilless media. In northern zones, move container(s) into a greenhouse or sunroom over winter. To spur new growth, move plant(s) outside and begin watering and feeding.

Leading cultivars are orange flowering ‘Bonfire’ (vegetatively produced) and red-orange ‘Santa Cruz’ (from seed). Other available B. boliviensis series include Copacabana® and Sparkle®.

In late fall you may opt to start new plants to grow in a heated hobby greenhouse. Vegetative cuttings of Begonia boliviensis root easily.

New Compact Russian Sages Arriving

Posted by Hugh on July 21st, 2015

Russian Sage ‘Little Spire’ at Morris Arboretum in Philadelphia, PA

Russian sage (Perovskia atriplicifolia) is a long-lived easy care summer flowering perennial or sub-shrub. It grows in dry to medium moist, well-drained soil and, first and foremost, in full sun. It holds up to summer’s heat, drought, and humidity (USDA hardiness zones 5-9). The Perennial Plant Association designated Russian Sage as the Perennial Plant of the Year in 1995.

Russian sage (species) typically grows 4 to 5 feet tall and 3 to 4 feet wide when not pruned. Terminal panicles of light blue tubular flowers are perched on upright square stems. It blooms consistently from early July to October in the Southern Appalachian region (USDA hardiness zones 6 and 7).

The principal appeal of Russian sages are their cool blue to lavender colored flowers in mid-summer and loose open growth habit. A member of the mint family, they emit a sage-like odor when leaves are crushed. Russian sages add structure and grayish color to a winter landscape. This tough perennial has no disease or pest problems. Deer and rabbits leave them alone and its grayish-green foliage copes with urban air pollutants.

For neatness, prune back plants to 3-6 inches from the ground in early spring as new growth begins. Full size Russian sages, compact cultivars less so, tend to flop or take on a droopy appearance in late summer. Deadheading old flower stalks and some late summer tidy-up pruning spur new growth and re-blooming. Fertilize with 10-10-10 or equivalent once in early spring; or feed in spring and again in early summer with water-soluble fertilizer such as Miracle-Gro™, Jacks™, or Daniels™.

These five compact cultivars make a better fit in a small urban garden:

‘Filigran’ – 3 – 4 feet tall and wide, light blue flowers and lacey silvery foliage on upright branches.
‘Lacey Blue’ – 1 – 1 ½ feet high by 2-3 feet wide, compact British introduction with dense large lavender-blue flower panicles that are thick stemmed for less “flopping”.
‘Little Spire’- 2 – 3 feet high and wide; masses of small, violet-blue flowers and dense silvery-green foliage.
‘Longin’ – 3 – 4 feet high and wide; deep blue flowers on stiff, upright stems.

‘Rocketman’ – new 2 ½ – 4 feet tall with strong stems and upright branching.

Enjoy Summer Fragrance Of Oriental Lilies

Posted by Hugh on July 18th, 2015

Oriental lily

‘Stargazer’ lily is popular choice

Oriental lilies (Lilium x orientale) grace summer gardens with brightly colored fragrant blooms (USDA hardiness zones 4-9). Long tubular (trumpet) flowers measure 6-8 inches across and come in a limited color choices. From one year to the next, flower numbers increase.

Oriental lilies prefer a compost-rich, well-drained soil where they will delight over several summers and in full to partial sun (5 hours minimum). Maintain 2-3 inches of mulch around plants to keep soil and roots cool and moist.

To create a showy display, plant bulbs 6-10 inches deep in fall or in early spring, preferably in groups of 3 or more. Further, add a few cultivars of Asiatic lilies, that tend to bloom a few weeks to a month earlier. Space bulbs 12-15 inches apart and supply adequate moisture year-round. Fertilize with 10-10-10 or equivalent in early spring.

Lily bulbs are sold for fall planting and pre-chilled bulbs are set in early spring, particularly in southern climes. Potted flowering lilies of all kinds are also sold at garden centers and may be set directly in the garden. Remove spent flowers to prevent seeds from forming. Leave stems and leaves to gradually die back. Gradually, your lily bed will become crowded, and bloom numbers start to decline. By late August, leaves have yellowed; dig up bulbs and divide them. Store the bulbs in a cool, dry place for planting later in the fall.

Usually trouble and pest free, potential diseases include: (1) lily mosaic virus; (2) bulb rot (usually wet, poorly-drained soils); and (3) botrytis. Plants may need staking if grown in shade (weaken stems) or in areas with strong winds.

Mix oriental lilies with other sunloving perennials and annuals. Plant some around a patio or deck to fully catch their fragrance on balmy summer evenings. They may also be grown in containers, but stems and flowers tend to be smaller and may need staking. Lilies are also long lasting cut flowers.

Brent Heath with Brent and Becky’s Bulbs recommends planting these 3 Oriental Lily Cultivars:

‘Casa Blanca’ features pure white flowers that are 8-10 inches in diameter with reddish-brown anthers. Blooms sit on sturdy 3-4 feet tall stems.
‘Stargazer’ is a popular early blooming cultivar with strong 3-4 feet tall stems. Each stem bears 4-12 pink, red and white flowers with reflexed tips and showy orange anthers.
‘Tom Pouce’ (in Dutch means “dessert”) grows 18-36 inch tall with fragrant pink flowers with prominent yellow streaking.