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

Four Very Different Annuals You Should Try

Posted by Hugh on February 23rd, 2017

Plectranthus ‘Velvet Elvis’

I asked three regional horticulturists to identify an under-planted drought tolerant annual. Here are four (4) that they recommended:

Drumstick flower or “Billy Buttons” (Craspedia globosa) produces a golden-yellow display of spherical flowers that often reach the size of golf balls (USDA plant hardiness zones 8-11). The silvery-gray foliage reaches about 2 feet tall and wide, and blooms almost all year long where winters are mild. They’re nearly carefree, tolerate most types of soil, and ask for an occasional watering. Drumstick flower aren’t susceptible to disease or pest problems. (suggested by June Jolly @ NC Arboretum in Asheville, NC.)

Evolvulus Blue My Mind™ (Evolvulus spp.) is a heat and sun loving, a drought tolerant ground cover with the silvery-green foliage; it is covered with petite, true blue flowers from spring to fall. With a mounding/trailing habit, it grows 6-12 inches high and 12-18 inches spread. It is also an excellent addition to containers. (suggested by Kaylee Decker @ Dallas Arboretum in Dallas, TX)

Plectranthus ‘Velvet Elvis’ has larger deep lavender blue flowers, a more compact habit (compared to most other varieties), and dark green leaves. It is an excellent addition to combination containers or a color spot in front of the border (zones 9-11). Blooming is most prolific from late summer to frost when daylength is shorter. Plant grows 2 feet tall and 2-3 feet wide. (suggested by Susan C. Morgan @ thehorticulturallink.com)

Salvia ‘Amistad’ is a strong growing variety with stunningly beautiful deep purple flowers. This floriferous Salvia guaranitica hybrid grows 3 ½ feet tall x 7 feet wide clump in long season gardens in the Southern U.S. (zones 8-11). Otherwise, it grows 2 feet tall and 3-4 feet wide annual in northern gardens. Deadheading enhances repeat blooming. Ideal for pots or summer borders. Deep purple tubular flowers attract lots of bees, butterflies and an occasional hummingbird or two. (suggested by Susan C. Morgan @ thehorticulturallink.com)

Exceptionally Hardy ‘Margarita’ Carolina Yellow Jessamine

Posted by Hugh on February 21st, 2017

Jessmine (Gelsemium sempervirens)

At Daniel Stowe Botanical Garden in Gastonia, NC

Carolina yellow jessamine (Gelsemium sempervirens) is a lovely ignored native vine. It is native from Virginia to Texas to Florida, easily spotted growing in a sunny location growing on trees (USDA zones 6-9). It is the state flower of South Carolina. Grow it as a trellised vine or as a low shrub-like mound (ground cover).

Flowers often serve as an early call that winter is coming to an end. Carolina jessamine is prized for its spectacular display of fragrant, bright yellow flowers. At the Atlanta Botanical Gardens, where the vine is evergreen, it starts blooming in late March. This well-mannered vine climbs beautifully on a trellis, arbor or over fences and walls without smothering surrounding trees and shrubs. It is also useful as a mounding semi-evergreen ground cover.

Is there a reliable zone 6 jessamine? YES! ‘Margarita’ is a superior seedling selected by Don Jacobs of Eco Gardens in Decatur, Georgia. It has survived winters to -25 ºF in Pennsylvania. ‘Margarita’ has earned a Gold Medal Award winner from the Pennsylvania Horticulture Society. Expect partial shoot dieback following a harsh winter.

For best results, plant it in a compost-rich, moist, well-drained, moderately acidic soil. A 1- year old established vine is able to tolerate periods of drought . ‘Margarita’ produces standout clear yellow trumpet flowers in early summer with some repeat bloom in fall. Its mild vanilla-like fragrance attracts a variety of pollinators.

A well-established vine may grow 20 feet or more when grown on a trellis. It benefits from pruning immediately after flowering.

Note: flowers, leaves, and roots contain poisonous strychnine-related alkaloids and may be lethal to humans and livestock. The floral nectar is reported to be toxic to honeybees if too much is consumed.

Blue Star Amsonia Is A Solid Performer

Posted by Hugh on February 17th, 2017

Blue Star in Fort Worth TX Garden

Blue Star amsonia in flower

Blue Star (Amsonia tabernaemontana) is native to the central U.S. (USDA hardiness zones 3-9). This herbaceous perennial is frequently seen growing in open woodlands in the midwest and south to Florida and Texas.

In mid-spring (in Tennessee), plants are filled with clusters of soft light blue star-like flowers, each nearly ¾ inches across. This clump-forming perennial stands erect 2-3 feet tall and wide. Dull green willow-like leaves turn bright yellow in autumn although this is not an every year occurrence.

Blue star grows in any average, moderately moist, well-drained soil and in full to partial sun. It prefers moist, loamy soils, but it tolerates heavy clay soils. After its first year planted, it is summer dry tolerant. When grown in full sun, plants require no pruning or staking. When grown in some shade and/or in rich soils, however, blue star tends to become more open and floppy and often requires some staking or pruning. For a neater appearance, cut back stems by one-third to one-half after flowering to develop a dense mound plant form.

This easy-to-grow long-lived perennial requires very little extra maintenance. Blue star is not troubled by insect or disease problems. Occasionally, rust disease may become problematic in wet summers. Deer usually leave the foliage alone. Mass several plants together in rain gardens, in open woodland areas, and containers. Showy blooms may be used in cut arrangements.

‘Blue Ice’ is a selection from White Flower Farm with periwinkle blue flowers. Flowers are larger than the species. The bright green foliage forms 12-16 inches tall, compact spreading plant. Leaves turn an above average yellow color in fall.

‘Short Stack’ is another seedling selection from a batch of seedlings of the var. montana. It’s a dwarf version, barely half the size of species at 10 inches tall x 18 inches wide. Clean dark green foliage contrasts nicely with the medium sky-blue flowers atop the plant.

Controlling Rabbits In Your Garden

Posted by Hugh on February 14th, 2017

Pesky Rabbit (photo from unknown source)

Rabbits make their homes in brushy areas such as along fence rows or untended areas between neighboring yards. They frequent nearby yards and gardens, perhaps your own, in search of vegetation to eat. Most people, particularly young children, adore them but a cute bunny can cause lots of damage in a flower /vegetable garden or a newly planted fruit orchard.

Rabbits gnaw down newly planted tree and shrub seedlings and the bark of young fruit trees. They also puncture trickle irrigation tubing. The most effective method for keeping rabbits out of gardens is fencing. A 2-foot-tall fence made of chicken wire is very effective. The wire should be tightly fastened down to the ground or buried a few inches below the surface.

An electric fence composed of 2-3 strands of wire 4 or 5 inches apart with the bottom strand about 3 inches above ground is an excellent rabbit deterrent. Little harm comes to the rabbits as they quickly learn to stay away. This kind of fencing can be relatively expensive and needs to be maintained. All vegetation beneath the live wire must be kept closely clipped with a string weed wacker. Another option is to spray a vegetation killer such as glyphosate (Roundup®) 2-3 times over the growing season.

Rabbits damage woody plants by clipping or gnawing the bark off stems, branches and buds. Seedlings can be protected by wrapping hardware cloth around the lower stems or by using “tree shelters” available at garden and farm supply stores. Taste repellents sprayed directly on the vegetation can be used with varying success, but need to be frequently reapplied.

Although few rabbits live longer than one year, their populations can multiply rapidly. A pair of rabbits can produce up to six litters per year with 2-3 young per litter. In many rural areas, sportsmen like to hunt rabbits, but this is not an option in populated areas. Trapping rabbits is legal in many areas, but first check with local wildlife officers. Live traps are generally most effective used along with several baits.

Curing Winter Blues… A Trip To The Philadelphia Flower Show

Posted by Hugh on February 11th, 2017

2016 Philadelphia Flower Show Display

2016 “Liberty Bell” Display at Phil. Flw. Show

Since 1827, the Philadelphia Flower Show has been the world’s longest-running and largest indoor flower show. This 8 days flower show, from 11 March 2017 (Saturday) to 19 March 2017 (Sunday), is organized by Pennsylvania Horticultural Society (PHS). The 8- day event features incredible large-scale floral displays, elaborate gardens, and creative floral arrangements.

Over ¼ quarter million visitors are expected to attend this year’s flower show. They will be treated to fabulous design, live entertainment, culinary demonstrations, gardening how-to workshops, and lectures by experts. The show also hosts a variety of special events including live entertainment, demonstrations, gardening workshops, parties, and lots more.

This year’s theme, “Flowering the World,” will celebrate the beauty and ingenuity of Dutch culture. No other country is as well known for its flower industry as the Netherlands, which fills our world with color. You will view landscapes filled with tulips, hyacinths, fritillarias, daffodils, anemones and lots of cut-flower and bulb markets that have shaped Dutch history.

Explore Holland’s unique landscape, from windmills – one of the earliest uses of natural energy – to 21st-century eco-domes and the Dutch Wave movement, which takes a natural and sustainable approach to landscape design.

Displays will include bridges, windmills, canals and water gardens in a sea of 30,000 flowers — with 6,000 more blooms suspended in a giant floral canopy. Guests can also pass under a brick bridge inspired by the Amsterdam cityscape and adorned with Delft tile patterns, overflowing flower boxes, and hanging baskets. The surrounding garden will be planted with cherry trees, sycamores, and drifts of floral color.

In the Garden Market leading exhibitors will showcase indoor and outdoor ornamental plants, Mediterranean plants, seasonal ornamental plants, plants in containers, cut flowers, starting plants from seeds or bulbs, and seed, soil, peat and perlite, packaging materials, garden accessories, tools, decorations, garden plants and arranging, plant care products and protective chemicals, decoration materials, exotic and miniature trees, fertilizer and chemicals, landscaping and garden architecture, pots and baskets, greenhouses, greenhouse related materials, greenhouse heating & ventilation materials, watering and sprinkler technologies, decorative pools.

The Pennsylvania Convention Center is located at 12th and Arch Streets. Tickets cost $35. Around large metropolitan areas local travel agencies in New York, Delaware, Baltimore, Washington DC and points in between will be offering.

‘Ascot Rainbow’ Variegated Spurge

Posted by Hugh on February 10th, 2017

Euphorbia ‘Ascot Rainbow’

May flowering

‘Ascot Rainbow’ Spurge (Euphorbia x martinii) is an herbaceous evergreen perennial which has shown to be remarkably winter hardy (USDA hardiness zones 5b-9). This spurge is a relatively low maintenance perennial. This plant has both distinctive variegated flowers and foliage. Plant several spurges together for an awesome visual show.

Ascot Rainbow Spurge struts attractive bluish-green narrow foliage with distinctive yellow leaf edges. The foliage often develops a pinkish tinge in late fall. In spring beautiful clusters of showy chartreuse bracts that surround relatively insignificant true flowers, sit atop tall stems.

This spurge grows about 15-18 inches tall (up to 30 inches in flower) and a spread of 18 -24 inches across. Generally, old bloom stalks are removed as new vegetative growth begins in mid-spring. Fruits formed after flowering, but have no aesthetic significance. Its foliage tends to remain dense right to the ground. Plants grow at a medium rate and, under ideal conditions, can prosper in its garden spot for 5 or more years. Extreme winter weather, abnormal for an area, can mar the showy foliage. Heavy wet snow can also break or splay the fleshy stems and foliage.

Spurges perform best in full sun to partial shade in either dry and moist soils as long as they’re well-drained. Feed at planting time and annually each spring with a slow release fertilizer such as Osmocote™ or Nutrikote™. Established plants are highly drought-tolerant, and are a excellent choice for xerophytic (dry) gardens in sandy soils. Spurges tolerate urban environs well. Utilize one or more in garden beds, containers, or rock gardens. Deer don’t particularly care for this plant and will usually leave it alone in favor of tastier treats. Do not plant it around children and pets as the milky sap of spurge is toxic.

Transform These Three Shrubs Into Trees

Posted by Hugh on February 9th, 2017

‘Diabolo’ Ninebark as young tree

Foliage of Viburnum sieboldii

Some large shrubs can be trained into lovely small flowering trees. These three flowering shrubs may be trained into small 15-25 feet tall, single or multi- trunk trees:

Siebold viburnum (Viburnum sieboldii) is a tall upright branched deciduous shrub (USDA hardiness zones 4-7). This native from Japan grows to 15-20 feet tall and 10-15 feet wide within 10-12 years.

In mid to late May, showy white flat-topped flowers appear in abundance, measuring 3-4 inches across. Flower heads are composed of small sterile center flowers surrounded by larger white fertile flowers. Flowers give way to ½ inch wide red berry-like fruits (drupes) on showy red fruiting stems in late summer; they ripen to black in fall and attract winter feeding birds. The 3-inch long, medium to dark green leaves has no memorable fall color.

Panicle hydrangea (Hydrangea paniculata) also originates from Japan and China and is exceptionally cold hardy (USDA hardiness zones 3-8). Depending on cultivar, this vigorous grower reaches 8-15 feet tall as a shrub and to 25 feet tall as a lovely patio tree. From mid-summer into fall, huge 6-8 inch long, creamy white terminal flower panicles contain both fertile and sterile flowers. Its dark green, blemish-free ovate foliage is coarse textured. Select tall growing cultivars like ‘Limelight’ or ‘Grandiflora’ to transform into trees.

Diabolo ninebark (Physocarpus opulifolius var. Diabolo) is an upright, spreading, deciduous, shrub (Zone: 3 to 7). ‘Diabolo’ is a purple-leaved cultivar that grows 6-8 feet as a shrub and 12-15 feet tall in tree form. It is easily identified for its exfoliating bark on older branch and trunk wood which peels off in thin strips to reveal the reddish to light brown inner bark. This heightens its winter interest. Small pink or white flower heads, resembling flowering spireas (they’re related), appear in late spring. Flowers give way to drooping clusters of reddish seed capsules. The 3-5 lobed, 4-inch long ovate leaves start out dark purple and bleach out to dark green in the heat of summer, and turn a blah yellow in fall.

All three landscape shrubs grow well in average, mildly acidic (pH 5.5 to 7.0), moderately moist, well-drained soils and in full to partial sun. All three are relatively drought tolerant after their first year. Prune siebold viburnum and ninebark immediately after spring flowering. Wait until late winter to prune panicle hydrangea. No serious insect or disease problems are attributed to these shrubs when they are properly sited in the landscape.

Butterfly Weed Named 2017 Perennial Plant Of The Year

Posted by Hugh on February 4th, 2017

Fall seed pods of Asclepias tuberosa

Milkweed (Asclepias tuberosa), aka butterfly weed, is a long-lived tuberous rooted perennial indigenous to the southeastern U.S and mid-western U.S. and Canada (USDA hardiness zones 3 to 9). It grows in dry/rocky open woodlands, prairies, farm fields, and along roadsides. Individual plants typically grow as a clump to 2- 3 feet high and 1 -2 feet wide. Unlike many of the other milkweeds the sap is not milky.

For almost six weeks, from late spring into summer, clusters of vibrant orange to yellow-orange flowers (umbels) cover the plant canopy. The narrow, lance-shaped leaves are attached to hairy stems. Flowers are an important nectar source for many butterfly species and leaves are an important larvae food for monarch butterflies.

Butterfly weed freely self-seeds in the landscape. Prominent 3 – 6 inch long spindle-shaped seed pods break open when ripe and release multitudes of silky-tailed seeds which may carry a long way by wind. Seed pods may be utilized in dried flower arrangements.

Butterfly weed is a perfect choice meadow or prairie garden for full sun. It grows in average, dry to medium, well-drained soils in full sun. It does well in poor, dry soils, and established plants are highly drought tolerant. Shoots emerge late in the spring and grow rapidly. It frequently included in butterfly gardens, meadows, prairies, or other plantings.

Plants are easily started from seed, but may take 2 – 3 years before flowering. Do not try to dig up wild plants as they rarely survive transplanting because of their deep taproot system. Young seedlings are best left undisturbed for two years to become established.

Few disease and insect problems trouble butterfly weed if grown in the proper site. Wet poorly-drained soil usually results in rot rot diseases. Leaves are susceptible to rust and leaf spots, often in overcrowded plantings. In medical circles the plant is commonly called “pleurisy root”, and once used to treat wheezing and coughing.

Their bright orange flower clusters are among our showiest native wildflowers and picked for floral arrangements.

‘Hello Yellow’ is a yellow flowering cultivar.

Pest Alert: Update On Emerald Ash Borer

Posted by Hugh on January 31st, 2017

Green ash tree (F. pennsylvanica)

EAB exit holes (photo by Dr. Frank Hale, Univ of Tenn Extension Entomologist)

Across the U.S. and Canada, ash trees are dying from infestations of Emerald Ash Borer (EAB), an Asian insect pest. In many U.S. cities, ash (Fraxinus) is a major urban tree genus. Since 2002 EAB has become a serious pest that has killed more than 40 million ash trees in 18 states.

This hardwood tree is important to the timber industry. The wood is used in the manufacture of furniture, flooring, ship building, etal. All native species of ash are susceptible, including American ash (F. americana) and green ash (F. pennsylvanica).

Early detection of the pest in special traps can slow its spread and minimize the impact. Some tree and landscape companies can perform trunk injections and soil treatments. In many states tree injections are done by ISA Certified professionals. In many cities property owners must decide to treat, remove or retain infested trees.

This invasive beetle lays eggs on the tree bark. The hatched larvae tunnel underneath the bark and will kill the tree within three years or less. Here are some guidelines to slow the rate of EAB infestation:

Don’t transport firewood from place to place, even within the state where you live. Don’t bring firewood along for camping. Instead, buy the wood from a local source.
Don’t buy or move firewood from outside the state. If someone comes to your door selling firewood, inquire about the source.
Watch for signs of infestation. If you suspect that your ash tree may be infested, visit your state website online or call a certified arborist, one certified by the International Society of Arboriculture (ISA).

Stop The “Crape Murder”

Posted by Hugh on January 28th, 2017

Beautiful structure of multi-year old crape myrtle

Remove old seed heads in March (this photo taken 5 months later in August)

In Tennessee (where I live) and in the Southeastern U.S., bad crape myrtle (Lagerstroemia x) pruning continues to be done by professional landscapers and homeowners (USDA hardiness zones 6-9). This practice, also called “topping”, reduces tree (or shrub) height. Over 25 years, Southern Living magazine called this “crape murder”.

Crape murder is not going away. More crape myrtles are improperly pruned than correctly pruned. Usually, the practice will not kill the tree, but it can result in less flowering and shorter tree life. Wood decays frequently occur.

If a crape myrtle becomes too large for a certain location, either it was planted in the wrong spot to begin with or the wrong variety was purchased. Before you plant, select crape myrtle varieties that will fit their location at maturity. That information is printed on the plant tag.

Never top crape myrtles! Generally, crape myrtles require very little annual pruning and are best pruned in late winter once the worse of the winter weather is over. Most branches only need thinning, e.g., removal of last summer’s spent flowers and seed heads. Remove any branches that cross or rub against one another. Eliminate suckers around the base of the tree and water sprouts (vigorous upright growth) inside the tree canopy.

According to Dr. Allen Owings at the LSU AgCenter, Hammond Research Station, Hammond LA, properly pruned crape myrtles exhibit:

Stronger Branch Wood
More Flowers
Larger Flowers
More Pollinating Insects
Better Bark Features
Fewer Water Sprouts
Fewer Suckers
More Birds Nesting
Less Fungal Decay in Wood
Fewer Insects and Sooty Mold
Less Leaf Spot
Better Air Circulation

Encourage friends and neighbors to prune crape myrtles properly. When allowed to grow and mature, they become beautiful majestic trees. If you do not know how to prune crape myrtles, hire a certified tree arborist where you live. Consult the International Society of Arboriculture (ISA) website for a list of certified arborists in your area.