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

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.

Getting Rid Of Poison Ivy

Posted by Hugh on July 15th, 2015

Some pesticides to manage poison ivy

Poison Ivy Overrunning Rose Bush

Poison ivy (Toxicodendron radicans) is a woody perennial vine or small shrub that is grows wild in fields, woodlands, and home landscapes. As a vine, poison ivy has 3-leaf (trifoliate) compound leaves; leaf margins may be entire or tri-lobed. It is frequently misidentified as Virginia creeper (Parthenocissus quinquefolia), which has compound leaves with five rather than three leaflets. Poison ivy aggressively attaches itself to trees or other structures with hairy, aerial roots borne protruding along stems.

Poison ivy grows rapidly by underground rhizomes and seeds. Seeds are distributed by birds and other animals that eat the small fruits. Poison ivy often becomes entangled in shrubs and groundcovers making it difficult to control without harming desired plants growing nearby.

To eradicate poison ivy from your property, dress protectively. Wear a long-sleeved shirt, long pants and plastic (not cloth) gloves. Launder the clothing separately after spraying and discard the plastic gloves.

A number of chemical herbicides contain the following ingredients: glyphosate, triclopyr, 2,4-D amine, dicamba and mecoprop. Some garden centers sell a 3-way herbicide containing 2,4-D amine, dicamba and mecoprop.

Herbicides are applied to leaves and cut stems and translocated through the rest of the plant, killing entire shoots and roots. Repeated applications are often necessary, up to three times over a 2- month period before you successfully eradicated poison ivy, so be patient.

Herbicides work better when you spray at the right time. Poison ivy is most sensitive in mid-summer after leaves have fully expand and before autumn leaf color starts. Glyphosate (Roundup® or equivalent) offers the best control when mixed as a 2% solution (approx. 2 TBSP per gallon).

In residential lawns, a 3-way herbicide may be applied to tall fescue, bermudagrass, zoysiagrass, St. Augustinegrass and centipedegrass for poison ivy control. Glyphosate, 2,4-D amine, dicamba, mecoprop and triclopyr are translocated through grass blades and cut stems to grass crowns and roots. Repeat spraying as needed.

Always read and follow pesticide labels.

ARS Selects ‘Oso Easy Lemon Zest’ Rose For Award of Excellence

Posted by Hugh on July 13th, 2015

‘Oso Easy Lemon Zest’ Rose From Proven Winners

The American Rose Society (ARS) announced at the 2015 National Conference that Proven Winners received the Award of Excellence for its Oso Easy Lemon Zest shrub rose. To receive this honor, a rose must prove its toughness and beauty in six different no-spray trial locations across the U.S.(USDA hardiness zones 5-9).

“Oso Easy Lemon Zest rose is a healthy-growing, self-cleaning rose that does not fade to white. It’s one of our favorite roses and one of our top sellers,” according to Tim Wood, Product Development, Spring Meadow Nursery.

Oso Easy Lemon Zest rose was developed by Chris Warner, the highly acclaimed rose breeder from Shropshire, England. After years of trials and evaluation, Oso Easy Lemon Zest rose has lived up to the highest standards. This rose exhibits a very high level of disease resistance. Its sunny, canary yellow flowers do not fade to white as they age. It is hardy and free-flowering, self-cleaning with attractive glossy green foliage.

This shrub rose prefers moist, well-drained soils and in full sun. It grows well in containers, or group several together for a landscape show. Its vibrant color makes Oso Easy Lemon Zest a super focal point in a garden or patio setting.

Spraying and pruning is generally not needed, but this shrub rose may be shaped in early spring before leaf out. Fertilize in early spring and again in early summer with any brand of rose foods sold at local garden centers.

Let Gaura Flutter In Your Garden This Summer

Posted by Hugh on July 12th, 2015

White flowering Gaura

Dark Pink Gaura at Biltmore Estates in Asheville, NC

What first catches your eye about perennial gaura (Gaura lindheimeri) is its light airy white (or pink) flowers (USDA hardiness zones 5 -9). Orchid-like blossoms are perched atop long thin stems. A faint breeze makes flowers flutter like a cloud of small butterflies above the dark green foliage. Also called wandflower, this Texas native is exceptionally heat and drought tolerant.

Don’t let its delicate appearance fool you. Many plant shoppers may pass it by at garden centers in the spring. It blooms non-stop all three growing seasons. Gaura is easy to grow and very low maintenance. Use it to edge a perennial or annual flower bed or group 3 or more in a rock garden or a container. Autumn foliage takes on a maroon tint.

New white and pink blooming cultivars continue to arrive at local garden centers. Most (not all) cultivars grow 2 ½ to 4 feet high. Among the best:

‘Whirling Butterflies’ has loose sprays of white flowers, lightly pink tinged.

‘Siskiyou Pink’ is a smaller cultivar; spring flowers start out pale pink and darken later in the summer.

‘Crimson Butterflies’ is a compact cultivar with dark red-pink blooms.

‘Ballerina Blush’ (pale pink blooms) and ‘Ballerina Rose’ (rose pink) grow only 12 – 18 inches tall.

Gaura does not always overwinter reliably. Good soil drainage is a must! Plants do not like soggy ground in winter. Gaura has a long taproot system, so is very drought tolerant. Its fertilizer needs are minimal.

Gaura rarely is troubled by disease or insect problems; leaf spots and powdery mildew may pop up if summer weather is exceptionally wet or plants are over-irrigated.

Colorful Oleanders For Hot Summer Climes

Posted by Hugh on July 9th, 2015

Oleander in North Texas garden

Oleander (Nerium oleander) is an attractive evergreen shrub for warm climates. Indigenous to the Mediterranean region, it is popular in warm regions of the U.S., namely in western, coastal, and southern states (USDA hardiness zones 8-11).

Oleander prefers moist, well-drained soil and a sunny landscape site. Established shrubs withstand dry and windy conditions along coastal areas. Brightly colored flowers, depending on variety, range from red, purple, pink, lilac, salmon, yellow, and white. A few flaunt variegated foliage. Oleander blooms in spurts from late spring to early fall.

Oleanders grow 8-15 feet in height and 5-10 feet in width. Some cultivars can be trained into small trees which may get 20-25 feet tall. Overall floral fragrance differs from one plant to the next.

Plant nursery-grown container plants in spring, summer, or fall. For a hedge space oleanders 6 to 12 feet apart, depending on cultivar size and vigor. Water plants during the summer if weekly rainfall falls below 1- inch.

Prune oleander immediately following its main bloom period to encourage bushier shrubs, more flowers, and to reduce size. Use caution around children and pets, as all parts of oleanders are highly poisonous; plant sap causes skin irritation to some individuals.

Most oleanders are vigorous growers and grow equally well in containers. In northern areas oleander is treated as a winter house plant; repot plant(s) in fresh media (soil) and set into a larger container. Overwinter this frost-tender plant by bringing it indoors when fall temperatures drop below 45°F at night. Some varieties are hardier than others. Prune plant back hard before bringing into a sunny room for the winter.

Aphids and scale are occasional nuisance pests and oleanders are deer resistant.

‘PeeDee Ingot’ Liriope Brightens Dark Areas

Posted by Hugh on July 6th, 2015

Liriope muscari ‘PeeDee Ingot’ (full sun)

Liriope muscari ‘PeeDee Ingot’ (part shade)

If you live in the Southeastern U.S., another variety of liriope probably will not impress you. Here we call it “monkeygrass”. PeeDee Ingot liriope (Liriope muscari ‘PeeDee Ingot’) is no ordinary ground cover (USDA hardiness zones 6-10). ‘Peedee Ingot’ liriope is named after the Peedee River in South Carolina near where it was found.

You might mistake it for Ogon sweetflag (Acorus gramineus ‘Ogon’) for its gold colored foliage. Liriope’s lilac-lavender flower spikes in mid-summer should convince you otherwise. Individual clumps grow a bit more than 18 inches tall and almost twice that in width.

The spikes of lilac-lavender flower provides a wide contrast against the grass-like chartreuse leaf blades. Plant it in average well-drained soils and in partial to full sun for best expression of its gold color. PeeDee Ingot needs some respite in summers south of zone 7. Its gold color will likely fade away or burn leaf tips if sunlight is too bright and the ground too dry.

Annual growth rate is not as rapid as many green leaf liriopes. This long-lived perennial is easy to grow with few disease and pest problems. PeeDee Ingot tolerates heavy shade, but most of its golden hue fades away by late summer. Clumps can be dug and divided almost any time they’re actively growing.

PeeDee Ingot is commonly used as a ground cover, utilized for front bed edging in the garden or container. It serves as a beautiful foil among other nearby plants with green or purple foliage colors.

Like most liriopes, the evergreen foliage maintains its presence through the winter, although abit bedraggled by winter’s end. Now is the time for a drastic crew cut to freshen foliage that will be emerging shortly. Pruning (mowing down) clumps is done at the start of spring.

My Search Continues For A Hardy Gardenia

Posted by Hugh on July 3rd, 2015

Gaardenia As Hedge Plant At Fast Food Restaurant in NC

Gardenia As Hedge At Fast Food Restaurant in NC

Non-hardy Double Flowered Gardenia in Tree Form

The longer you garden, many plant species keep improving, including their winter hardiness. A few years ago, growing gardenias (Gardenia jasminoides) in a U.S. zone 6 garden was a dream. Today, hardy gardenias are a safe bet in zone 7 or in zone 6 in a protected area of the garden, away from wintry winds. Otherwise, gardenias make good houseplants.

Pure white fragrant flowers cover this lovely evergreen shrub in early summer. Single pinwheel shaped flowers are most common, but semi-double and double flowering types are also available. Cultivars vary in flower fragrance from a hint to highly scented.

Gardenias grow 2 – 6 feet tall and 3 – 6 feet wide, depending on cultivar and desired size after pruning. Gardenia care is similar to that of rhododendron or camellia. Provide morning sun and afternoon shade or in full day dappled sunlight. Locate gardenias near a home entry door, patio or deck, where you and your guests may fully enjoy their fragrance.

Whether planted in a container or garden bed, gardenias require moist, well-drained, acidic medium (soil) that contains lots of organic matter. Gardenias need watering when rainfall is less than an inch per week. Fertilize plant(s) every spring with an acidic type fertilizer such as water-soluble Miracle-Gro™ or Espoma Hollytone™.

Yellowing leaves indicates any of three possible problems. If it is the bottom foliage turning yellow, it could be under- or over-watering. If the upper leaves show interveinal chlorosis (yellowing), your gardenia plant needs an iron supplement or the soil is not be acidic enough. Gardenias are subject to a number of pests which can be managed using insecticidal soap.

‘Frost Proof’ and ‘Daisy’ are two that I have trialed in my zone 6 garden. The harsh winter of 2013-14 killed both varieties to the ground. By late June both cultivars had sprung back to life from the crown but did not bloom. A year later both cultivars were dead.