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

Winter Planting –Why Not!

Posted by Hugh on September 27th, 2017

Needle scorched Arborvitae after cold dry winter

Healthy Mix of Evergreens

For those who live in northern regions where winters are cold and snowy (USDA hardiness zones 3-6), many (not all) gardeners can still plant many kinds of trees, shrubs and perennials in late fall and winter if the ground is not frozen. Deciduous plants are in their natural period of rest or dormancy. This does not include evergreen trees and shrubs.

Deciduous vs Evergreens

Fall planting of deciduous trees works better because their need for water is a lot less in winter. Evergreens retain their leaves/needles all winter. Leaf metabolism is a lot less than in summer. Once the ground freezes, roots have trouble foraging for water, and by late winter, leaves/needles may become scorched along the edges, turn brown or die. Fall planting can be more difficult for broad-leaved evergreens like rhododendrons or hollies (Ilex). Mulch around evergreens before the ground freezes to trap in soil warmth and stimulate root growth.

Soil -Water Availability

Across the U.S., winter weather is very different. In the upper Midwest, the fall season is short, and winter is usually long and frigidly cold. The ground freezes early and stays through early spring in most years. Here, spring planting is more reliable with plentiful rainfall.

Along the Pacific coast (Washington, Oregon, and California), fall-winter planting makes sense. Summers are hot and very dry. Fall and winter are long cool periods with lots of rainfall that is ideal for root growth. The ground rarely freezes along the coastal areas.

Plant availability is a significant concern. Generally, garden centers and nurseries do not holdover huge inventories of trees and shrubs. Finally, in regions where winters are cold, magnolia, dogwood, tulip tree, sweet gum, red maple, birch, hawthorn, tulip poplars, cherries, plum and many oak species are more susceptible to winter injury (Purdue University study).

Sizing Up Crape Myrtles (Including Most Recent Introductions)

Posted by Hugh on September 24th, 2017

Delta™ Jazz crape myrtle at UNiv. of Tennessee Gardens, Knoxville

Delta™ Flame crape myrtle

Hybrid crape myrtles (Lagerstroemia fauriei x indica) have undergone significant makeovers over the past quarter century. Several new cultivar series continue to arrive garden centers, including: Black Diamond™ series, Enduring Summer™, Delta™ series, and Magic™ series.

In landscape terms size is very important and gardeners often make a serious error when not calculating the size of crape myrtle for the planting space. Crape myrtles fall into four size categories. Included here are a sampling of the major cultivars based on popularity in the mid-South region (Northern Atlanta thru Eastern Maryland):

Four Height Groups and Flower Color

Dwarf (less than 5 feet)
‘Pocomoke’ – rose pink
‘Berry Dazzle’ – fuchsia
‘Cherry Dazzle’ – vibrant red

Semi-dwarf (5 to 12 feet)
‘Acoma’ – pure white
‘Dwarf Centennial’ – lavender
‘Hopi’ – light pink
‘Tonto’ – fuchsia (red)
‘Zuni’ – medium lavender

Intermediate (13 to 20 feet)
‘Apalachee’ – light lavender
‘Dynamite’ – cherry red
‘Lipan’ – medium lavender
‘Osage’ – light pink
‘Sioux’ – dark pink

Tree type (23 feet and higher)
‘Carolina Beauty’ – dark pink
‘Muskogee’ – light lavender
‘Natchez’ – white
‘Tuscarora’ – dark coral pink
‘Tuskegee’ – dark pink, almost red

New crape myrtle series:

Black Diamond™ Series – 10 to 12 feet high and 8 feet spread with almost black foliage. Currently there are 9 cultivars ranging from red shades, pink shades, white, purple, and lavender.

Magic Series™ from First Editions® is a selection of intermediate size crape myrtles with glossy disease-free foliage; they bloom all summer into fall and hold their leaves until late. Currently there are 8 cultivars in the series of various sizes and color range.

Delta Series™ are part of the Southern Living Plant Collection (USDA hardiness zones 7-9); there are currently four cultivars in four colors: white, red, lavender, and light pink; foliage- unique burgundy, cupped leaves; grow between 6-10 foot tall.

Enduring Summer™ are part of the Garden Debut Plant Collection (USDA hardiness zones 7-9); there are 6 cultivars and grow 4-5 feet tall and wide

Eliminating Messy Fruits From Large Landscape Trees

Posted by Hugh on September 21st, 2017

Ginkgo fruits littering area

Walnut cleanup at Chanticleer Gardens, Wayne PA.

Messy fruit from yard trees are dreaded by property owners as well as park and city employees. Some notorious culprits are sweetgums, sycamores (planetrees), oaks, mulberries, persimmons, and (female) ginkgoes. Fruits include hundreds of hard nuts or pulpy, smelly, and potentially hazardous covering sidewalks, driveways, and parking lots.

Foliar sprays are available to reduce or eliminate undesirable fruits from developing on trees. Timing of application(s) are critical and environmental factors make absolute control impossible. Results also vary by each chemical labelled to retard or eradicate fruit development.

For example, preventing acorns on your oak tree is to chemically burn male catkin and female flowers. No registered product is effective for all plants. Florel® is only growth regulator labeled to reduce acorn formation. Application time can often be pure guess work and may be successful less than 50% of the time. Multiple applications may be needed. Spraying your tree can be costly and time-consuming. Hand-removing flowers or small fruits may work on a small tree, but is impractical for large shade trees and for large properties.

Fruits numbers can vary from one year to the next. A mature walnut or oak tree may produce a heavy crop one year and a light one the following 1-2 years. Diseases, pests, and spring weather factors may injure flowers and reduce fruit production.

For large trees you should hire a licensed pesticide applicator or tree professional to achieve adequate results.

Timing of application: Spraying before or after flowers results in wasted time and money and time of application should be between 60 and 95°F. Follow label directions closely.

Chemicals are available to reduce or eliminate fruit set on ornamental trees and shrubs. Follow specific label directions for application rates and safety information.

Florel® Fruit Eliminator (ethephon)

Fruitone® (Naphthalene acid (NAA))

Sevin™ (Carbaryl) – warning: harmful to bees and other pollinators

One final option is to plant landscape plants that are not messy. Yes, lots of beneficial trees produce fruits, but birds and other wildlife usually consume most of them. Male cultivars of large landscape tree include honeylocust (Gleditsia), ash (Fraxinus), fringetree (Chionanthus), redbud (Cercis), and others. Avoid planting hollies and other fruit producing plants adjacent to walkways.

Pest Alert – Emerald Ash Borer Update

Posted by Hugh on September 18th, 2017

Fringetree- Potential host for EAB

EAB Diagram (from Dr. Frank Hale, Univ. of TN Extension Entomologist, Nashville)

Recent news about Emerald Ash Borer continues not to be good. Almost weekly, state officials report the spread of this pest in their state. Emerald ash borer (EAB) is an invasive metallic wood boring or flat-headed wood boring beetle that is killing all species of North American ash trees (Fraxinus spp.). Since 2002, EAB has killed tens of millions of ash trees.

In the botanical world, European olive (Olea europea) and native fringe (Chionanthus virginicus) trees are ash relatives. White fringetree is native to the United States and grows wild from New Jersey south to Florida and west to Oklahoma and Texas. It is also a popular landscape tree in other parts of the country. Some fringe trees in the Midwestern U.S.have been found EAB infested.

Scientists at Wright University in Dayton, OH report the innate potential of EAB to use European olive trees as an alternate host under laboratory conditions. In the field conditions, EAB has not been found in olive trees—at least not in North America. Also,numbers of EAB infested fringetrees in the Midwest and Northeast are still low.

Community readiness is the key. EAB continues to expand its range across the U.S. In preparation for the arrival of EAB, the location of newly infested ash trees is first determined and the trees protected with systemic insecticides. Bio-control efforts are ongoing, and parasites may be released in attempts to reduce numbers of emerald ash borers. Ash trees in poor health are quickly removed and destroyed.

Quarantine procedures should be followed. In particular, potentially infested firewood should not be transported outside of quarantine areas.

Information and Photo Credits: Louisiana State University Ag Center in Hammonds and University of Tennessee Plant Diagnostic Lab in Nashville.

Robb’s Spurge (Euphorbia)

Posted by Hugh on September 15th, 2017

E.-amygdaloides-robbiae at Atlanta Botanical Garden

E. amygdaloides robbiae spring bloom at Atlanta Botanical Garden

Robb’s wood spurge at Virginia Tech’s Haun Garden, Blacksburg, VA

I always been a fan of spurges, but some have not perform well in my garden. One that does not disappoint is Robb’s spurge (Euphorbia amygdaloides var. robbiae), aka “Mrs. Robb’s Bonnet”. This evergreen spurge grows equally well in either sun or shade, including dry shade (USDA hardiness zones 6-8).

This carefree slowly spreading groundcover displays shiny, dark green, leathery leaves. The vegetative clump grows 12-18 inches high. Robb’s spurge looks fantastic in either a pot and in the garden. In its northern range, it should be planted in a wind protected location for best winter foliage.

In very early spring the chartreuse flowers of Robb’s spurge unfurl in dramatic fashion, presenting 18-inch tall stalks of flowers last for months. By mid-spring the yellow green “flowers” are glorious. They are actually colored bracts which arise independently from the base of the plant in clusters. Bracts remain colorful long after the flowers have passed. Pruning cuts reveals the milky sap, which is usually poisonous. Deer and rabbits stay away, but you should also keep way from small children.

Euphorbias make up of one of the largest and most diverse plant families in the world. The milky sap of many herbaceous Euphorbia species have traditionally been used as a purgative or a laxative, hence the common name “spurge”.

Robb’s spurge is a carefree plant, almost too easy to grow. However, beware of what you ask for. Over time the clump spreads via rhizomes which is “containable”. It spreads quicker if the soil is moist and loose with organic matter. It tolerates more shade than most other Euphorbias.

Robb’s spurge is easily propagated by division or cuttings. Useful as a dry shade ground cover or along wooded paths interwoven with more ephemeral plants.

‘Sunshine’ Privet: A Great Accent Shrub and It’s Not Invasive

Posted by Hugh on September 12th, 2017

‘Sunshine’ Privet (photo credit: Ball Horticulture)

‘Sunshine’ privet in Kingwood Center in Mansfield, OH

For generations ligustrum (privet) had been a landscape plant in East Coast and Southern gardens. However, in several states, privets have become declared as an notoriously invasive species . Unfortunately, you should never brand all privet cultivars the same way.

Sunshine privet (Ligustrum sinensis ‘Sunshine’) is likely to change your mind (USDA hardiness zones 6-10). This privet is sterile, e.g. this privet produces no viable flowers or fruits.

It is a long-lived evergreen shrub exhibiting 4-season interest. Its compact nature makes it an ideal choice in small urban gardens. Its golden foliage also tolerates foul city air. Along coastal areas, Sunshine privet is also salt tolerant.

Sunshine privet is a terrific accent plant. Its foliage is strikingly golden year-round. Utilize it in containers, set some out for low hedging, or mass several around as edging along walkways. Again, it will not re-seed into other areas of your landscape.

Unpruned mature plants reach 3-6 feet high and 3-4 feet wide in 10 years. For best color, the golden foliage shines in full sun; it grows in average soil that is adequately drained. Feed in early spring with a slow release fertilizer such as Osmocote® or Nutrikote® at package directions. This shrub is also highly drought tolerant after its first season. Freshly installed dark colored mulch makes the Sunshine privet planting a standout.

If you are handy with a hedge trimmer, Sunshine privet can be maintained as a short formal hedge, as low as 1 foot tall. I’ve seen it utilized in a garden railroad scene where it was clipped every 2-3 weeks. How about including it in a formal knot or quilt garden.

Sunshine Privet is not troubled by disease and insect problems. In general, privets are not a favorite food of deer, but they will damage plants where population are high.

Burning Bush (Euonymus)

Posted by Hugh on September 9th, 2017

Hedge of Euonymus alata ‘Compactus’

Euonymus alata ‘Compactus’ in late summer

Burning bush (Euonymus alatus ) is a large shrub, one that reaches heights between 15 and 20 feet. It originated from Korea, China, Eastern Russia and Japan (USDA hardiness zones 4-8). It is often called winged spindle tree or winged burning bush because of raised ridges along stems.

During the autumn, the deep green leaves turn brightly crimson red or “burning”. Flowers are mostly inconspicuous. Burning bush is a self-seeder and red berries are fertile. It appears on the invasive species list in 21 states.

Burning bush grows in average soil as long as it is well drained. It will not tolerate wet, poorly-drained soil. For best fall leaf color, site shrub(s) in full sun. Feed with a slow release fertilizer such as Osmocote® or Nutrikote® in early spring. Mulch the planting for weed prevention and to reduce irrigation needs. Pruning is rarely practiced on this compact-growing shrub. Young plants display a root suckering tendency.

Rudy Haag (E. alatus ‘Rudy Haag’) is a slow growing burning bush variety that reaches heights of only 4 to 5 feet, a lot smaller than dwarf burning bush. This nearly seedless plant defies the burning bush’s invasive nature. Flowers on Rudy Haag are mostly sterile and therefore do not produce fruits.

Little Moses® is a slow growing, extremely compact form, only 2-3 feet tall and wide. Seeds are fertile.

The good news is that several universities and laboratories in the U.S. are working to develop triploid or sterile forms. As sterile cultivars are identified, I’ll let you know.

All parts of burning bush, including the berries, are poisonous. Keep away from farm livestock, pets and children.

Multi-Purpose Lavender Spur Flowers Sparkle In The Cool Fall Air

Posted by Hugh on September 6th, 2017

Plectrantus ‘Velvet Elvis’ at Longwood Gardens in Kennett Square, PA

Lavender Spur Flower (Plectranthus Mona Lavender™) is a fast growing flowering annuial that is full of lavender blue flowers from late summer to autumn frost (USDA hardiness zones 9-11). Flowers can usually cope with light frosts of 25 – 30° F in early autumn. Plants grow 2 to 2.5 feet tall and wide forming a round dense plant.

Lavender Spur Flower is best sited in light shade or partial day sunlight, preferably in the morning. In full sun this flowering annual tend to grow more compact and the foliage becomes darker green with a more intense purple hue on the underside. Plant in fairly well-drained soil enriched with humus and water regularly. To encourage compactness and better branching, pinch plants every 2 weeks from planting time to mid-summer. Feed plants every 2-3 weeks with water soluble fertilizers such as Miracle-Gro™ or Nature’s Source™.

Two cultivars are available in U.S. garden centers:

Mona Lavender™ is the current best selling cultivar withlavender purple flowers and dark green foliage with deep purple underside and stems.

‘Velvet Elvis’ is a new introduction touted to produce larger and deeper lavender blue flower trusses than Mona Lavender. Foliage is deep green and deep purple beneath; plant habit is more compact.

Lavender Spur Flower are best planted enmasse in a front garden border or plant in containers by itself or with other annuals and perennials. Flower spikes attract butterflies and hummingbirds and plants are generally deer resistant.

Lavender Spur Flower belongs in the same plant genus (Plectranthus) as Swedish Ivy (P. australis). Some may grow it as a houseplant but it will need very bright light to keep blooming indoors.

Suggestion from a blog reader: grow it outside in a hanging basket and overwinter the plant in a greenhouse or sun room.

Plant Late For Fall Pollinators

Posted by Hugh on September 3rd, 2017

Fall sunflowers at Chanticleer Gardens, Wayne, PA

Late flowering coreopsis

Don’t give up gardening in the fall. Many beneficial insects depend on the terrific job that you are doing. The following is a sample listing of annuals and perennials that can employ to support pollinators in the fall. Included are many fall-blooming annuals and perennials.

When designing a pollinator-friendly landscapes, include an adequate number of these fall-blooming plants in your garden designs.

Here are 15 showy native perennials known for their late-season flowering.

Asters (Symphyotrichum spp. and Eurybia spp.)
Fall blooming asters t Chanticleer Gardens in Wayne, PA
False aster (Boltonia spp.)
Fall mums (Chrysanthemum spp.)
Goldenrods (Solidago spp.)
Ironweed (Vernonia spp.)
Joe-Pye (Eutrochium fistulosum)
Fall anemone (Anemone spp.)
Sneezeweed (Helenium autumnale)
Stonecrop sedums (Hylotelephium spectabilis)
Fall sunflowers (Helianthus spp.)
Turtlehead (Chelone obliqua)
Pineapple sage (Salvia elegans)
Mexican sage (Salvia leucantha)
Blanket flower (Gaillardia x)
Stonecrop sedums (Hylotelephium spectabilis)

Don’t leave out summer annuals, many of which are still in glorious bloom in the cool days of autumn. The short list include cosmos, several kinds of salvias, globe amaranth (Gomphrena), and dahlias

Avid fall gardeners living in zones 6 and 7 replant many favorite annuals in late summer and fall as a “shoulder season”. They start out new bedding plants in late August and they will carry through in glorious color into mid-November in many areas of the U.S. The list includes cosmos, marigolds, petunias, calibrachoas, cupheas, celosias, and diascias.

Several other perennials have extended bloom times and may still be flowering in the early days of autumn. These plants can also be grown and installed into the landscape specifically to provide a source of nectar for the pollinators, as well as to boost the amount of color in the fall gardens. Some great options include agastache, coreopsis, coneflowers (Echinacea purpurea), fleabane (Erigeron), and black eyed Susan (Rudbeckia hirta), and salvias (Salvia spp.). Finally, butterfly (Buddleia x davidii) and bluebeard (Caryopteris x clandonensis) shrubs, frequently maintained as perennials by gardeners, continue to bloom way into the fall season.

Crown Of Thorns Is A Versatile Plant

Posted by Hugh on August 30th, 2017

Crown of Thorns (Euphorbia milii)

Crown of Thorns plant (Euphorbia milii) is a thorny slow growing succulent native to Madagascar (USDA hardiness zones 9-11). In colder regions of the U.S., it is an easy- care flowering houseplant that seems to thrive on neglect. It blooms almost year-round. Outside, in a garden setting, it blooms nonstop from spring thru mid-fall here in the Mid-South (Zone 6-7).

Container grown Crown of Thorns at Biltmore Estates, Asheville, NC.

Plant may reach 3 feet in height and 2 feet in width. Sharp spines about 1 inch long cover the stems. Clusters of narrow bright green leaves are sparsely arranged and last only a few months. The thick stems store water, making the plant exceptionally drought-resistant.

The cactus -like plant blooms from spring into late summer, producing tiny, true flowers held in two brightly colored fused bracts that surround small flowers. Floral colors range from red , pink, salmon, yellow, and creamy white. Crown of thorns is easy to propagate from softwood stem cuttings.

Crown of thorns grows in the poorest soil provided it is well-drained It prefers a location in full sun but will tolerate some shade for a portion of the day. It is resistant to salt spray. As an indoor houseplant, set in a south- or west-facing window. Water thoroughly and sparingly. Feed every 2-3 months with fertilizers such as Miracle-Gro® or Schultz®. Lightly prune the plant for shaping. Remove some older, leafless branches to stimulate new growth in spring.

Crown of thorns is deer-resistant. These plants are considered poisonous and should be kept away from pets and children.

Cultivars: Newer cultivars feature fuller plants, brighter colors, bigger leaves and flowers than the old-fashioned varieties.

‘American Beauty’- showy, scarlet-red bracts; also orange, pink, white or yellow bracted cvs.

‘Short and Sweet’ – red-flowered, dwarf variety that only reaches a height of 12 to 18 inches.

“California Hybrids” exhibit unusually stout stems and larger colorful floral bracts.These “giant crown of thorns” include cultivars: ‘Rosalie’, ‘Vulcanus’ and ‘Saturnus’.

“Thai Hybrids” – large leaves and flowers on small 2-3 foot high plants; Karolla struts glossy bright green leaves, brilliant red blooms; Karolla and small types only 1 to 2 feet tall.

According to legend, a Crown of Thorns Plant got its nickname after it was associated with the Crown of Thorns worn by Jesus. Under ideal conditions, a Crown of Thorns. Like a Poinsettia, it is a member of Euphorbia family. It has bracted flowers and milky sap.