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

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.

Mussaenda: A Stunning Tropical For Summer Gardens

Posted by Hugh on August 27th, 2017

Mussaenda red hybrid at Biltmore Estates in Asheville, NC

Mussaenda ‘Queen Sirikit’

Mussaenda (Mussaenda spp.) is a small tropical tree or large shrub. It’s a spectacular bloomer that grows to 10-15 feet tall in tropical zones (USDA zones 10-12). It is sometimes called “tropical dogwood” or “Buddah’s lamp”. In large containers it will reach 1-3 feet tall. Mussaenda blooms from late spring to mid-fall in mild-winter areas. Bloom colors range from yellow, red or creamy white with red, white or pink bracts or sepals surrounding the flowers. The spectacular blooms attract butterflies, bees and birds.

Plant into a well-drained potting mix or humus-rich, mildly acidic soil and keep media moderately moist. Mussaenda grows robustly in direct sunlight, preferably 6 hours or more daily in cool regions of the U.S. Further south (zones 7b -11), expose to morning or late afternoon sun only and keep mostly shaded during the hot midday period for best summer flowering. The plant establishes quickly, within 6 weeks after initial planting. Prime flowering season is from late spring to very early fall (in zones 6 and 7).

Feed with a slow-release fertilizer granules such as Osmocote® or Nutrikote® at package directions. Cuttings should be collected in late summer. Flowering and growth slows down or stops once temps fall into the low 50°Fs. Overwinter in a greenhouse or a sun room. Prune back plant(s) hard before bring it indoors for overwintering. Mussaendas are relatively insect and disease free, although scale, mealybugs and mites are sometimes problems.

Swallowtail on flowers

Cultivars:

Five different species are in cultivation and along with hybrid cultivars, ranging in height from 2 feet to 15 feet tall.

M. erythrophylla ‘Queen Sirikit’ grows very shrub-like with pale yellow to white flowers with red centers and peach colored bracts. Their pendant flowers often appear floppy ‘flowers’ and in urgent need of water.

Tropical Beauty Of African Rose Mallow

Posted by Hugh on August 24th, 2017

Hibiscus acetosella ‘Cranberry’ in Baltimore, MD

Hibiscus ‘Red Shield’

African Rose Mallow (Hibiscus acetosella), aka Red-leaf Hibiscus and false Roselle, is grown in most of the U.S. as a colorful annual, although it is rated as a perennial shrub for USDA Zones 9-11. It is native to Africa and, as expected, thrives in hot tropical environment such as in the deep South or Southern California and Arizona where the growing season is a lot longer. Many U.S. gardeners grow rose mallow for their tropical foliage in summer and not for their flowers.

Rose mallow starts blooming in very late summer when daylength becomes shorter. Bloom continues through the winter until frost, or in tropical climates until daylength increases. Individual blooms measure 3.75 inches (9.5 cm.) and last one day.

If grown under full sun and adequate soil moisture, plants become deeply rooted and do not require staking. Foliage color is more intense and blooms fully in open sunny sites. Leaf hues are not as intense in partial sun and plants may need staking. They’re fast growing, up to 5 to 7 feet, along with a narrow single main stem. To promote a better branched, shrubbier habit, pinch off the apical growing tip several times during the summer to develop a stocky 3- to 6-foot tall plant.

Plant it in any well-drained garden soil or in a rapidly draining potting mix when grown in large containers. To repeat this tropical hibiscus flourishes in areas with high summer heat and humidity. Leaves also tolerate salty air along coastal areas.

‘Red Shield’, ‘Cranbury’, and ‘Maple Sugar’ are popular cultivars (possibly the same variety?). Their glossy purplish-red multi-lobed foliage looks similar to Japanese maples.

The brightly colored flowers attract numerous insect pollinators and birds and hummingbirds. Usually deer stay away. Leaves are edible, the crunch of leaf lettuce, but with a slightly bitter taste (in my opinion). Please pass the salad dressing.

Prairie Dropseed (Sporobolus) – A Durable Ornamental Grass

Posted by Hugh on August 20th, 2017

Sporobolus at NC Arboretum

Prairie Dropseed at NC Arboretum in Asheville

Prairie dropseed (Sporobolus heterolepsis) is one of the finest warm season grasses native to the Western U.S. (USDA hardiness zones 3 to 9). Initially, this clump-forming perennial grass grows at a slow to medium rate. By early summer its fine textured deep green leaves form an arching fountain habit. Prairie dropseed inhabits prairies, meadows, open ground, and along railroads.

Clump develops into a mound an average of 2-3 feet tall and wide. By late summer, loose, airy, tan colored inflorescences emerge on 2-3 feet tall spikes along with its unique fragrance. Some report that it smells like coriander, cilantro, or popcorn. By late October the foliage turns russet color and in winter to light bronze.

Prairie dropseed excels in hot, dry conditions where it can really soak up the sun. This grass is exceptionally drought tolerant and is tolerant of soils with low fertility. Initially slow to establish, new plants may be started from seed, although it does not freely self-seed in a garden.

No serious insect or disease problems trouble this native grass. Deer generally leave it alone. Its deep fibrous rootsystem provides exceptional soil erosion control and it resistant to air pollution.

‘Tara’ is a dwarf selection from Roy Diblik. Tara grows slower than the species and has a more upright v-shape habit; leaf blades take on a golden to pumpkin orange color in fall. Utilize it to edge front of beds and borders and in rock gardens. It is beautiful in mass plantings such as meadows. In fall, foliage turns a rust-red color, and seeds provide food for birds.

Landscape use: grow it for its architectural form or as a tall groundcover, or in rock, prairie, meadow, and rain gardens. Annual maintenance is minimal. Cut back old clumps and you may opt to fertilize lightly with 10-10-10 or equivalent in early spring.

Blonde Ambition® Blue Grama Grass

Posted by Hugh on August 17th, 2017

‘Blonde Ambition’ Blue Grama Grass near Fort Collins, Colorado

Seed heads

Looking for something a little different, plant Blonde Ambition® blue grama grass (Bouteloua gracilis ‘Blonde Ambition’). It was discovered and introduced by David Salman of High Country Gardens. This prairie species is native from Manitoba Canada, south through the Rocky Mountains, Great Plains, and Midwestern states, to Mexico. It is exceptionally heat and cold hardy and recovers rapidly following a heavy snow cover (USDA hardiness zones 3 – 9).

The fine-textured gray-green leaf blades (to 1/4 inch wide) typically form a dense clump growing 18 to 24 inches tall. Foliage turns golden brown in late autumn, at times taking on an orange and reddish hues.

Blonde Ambition is unlike any other ornamental grass in cultivation. In early summer its unique eyelash-like chartreuse flowers stand like tiny horizontal flags on stems that rise a foot or more above the foliage. The chartreuse flower color ages to blond, so different compared to the dark purplish flowers of the species. The long lasting blonde seed heads stay fastened to wiry blue-green stems and poke through after a heavy snow.

Plant in full sun in most any soil, acidic or alkaline, as long as it is well-drained. Initially, irrigate a new plants so it fills in faster. It tolerates poor soil and is highly drought resistant. Lightly fertilize with 10-10-10 or equivalent in early spring, although this tough grass will cope with low fertility. Start off by mowing off the planting in the early days of spring. Diseases or pests are non-existent and deer and most other four-legged browsers of vegetation stay away.

Blonde Ambition was a 2011 Plant Select winner. It is primarily available from e-commerce native plant nurseries.

Avoid Dreaded Tulip Fire Disease

Posted by Hugh on August 14th, 2017

Tulip Fire (Photo by Chuck Gleaves, Horticultural Director at Kingwood Center in Mansfield, Ohio)

Tulip mix

For over a one-half century Kingwood Center in Mansfield, Ohio has been widely known for their fabulous tulip displays every spring. Over the past few years Kingwood’s garden staff had noted a decline in bloom because of a disease identified as “Tulip Fire” (Botrytis tulipae).

This fungal botrytis disease tends to accumulate in the soil in wait of an ideal environmental weather pattern. In previous years the staff had treated tulip beds with appropriate fungicides, but spring 2017 was the year of “the perfect storm”. Most of the tulips in six large beds were lost to this botrytis disease. Combined with an unprecedented attack from rodents, garden staff had to pull out the tulips and posted signs of the “crop failure”.

“The problem has been accumulating for 62 years”, says Chuck Gleaves, garden director, “and no immediate solution is expected”. Most gardeners have learned to adopt principles of crop rotation. Pesticide applications will not work here. All the tulips were removed from the six affected beds. This fall garden staff plan to plant hyacinths. No tulips will be planted in the affected beds for a minimum of two years. Planting costs will increase because hyacinths are considerably more expensive over tulips.

Gleaves promises that Kingwood will continue to grow lots of tulips, but in different areas and rotate hyacinths with tulips in selected beds. Over time, they hope to reduce the accumulated inoculum of Botrytis.

Additional Notes:

Non-chemical control

Check bulbs carefully and discard any with signs of the small black sclerotia in the outer scales, or with any signs of decay
Remove infected bulbs promptly to avoid contaminating the soil with sclerotia
Do not plant tulips for at least 3 years in sites where tulip fire has occurred
If a contaminated site must be replanted, dig the ground deeply to try and bury the contaminated upper layers deep enough to be below planting depth
Rotate tulips to new garden areas each year to avoid fungal scerotia buildup in soil.
Treat tulips as annuals and remove them after flowering.

Chemical control: Integrate chemical tactics with cultural controls. Alternate or tank-mix fungicides (not use same fungicide all the time):

Chipco 26019
Daconil
Cleary’s 3336 EG or OHP 6672 (Thiophanate methyl).

Sun Or Shade –These Six Shrubs Don’t Care

Posted by Hugh on August 10th, 2017

Mountain laurel at I-26 Rest Area, Asheville, NC

Daphne odora ‘Aureomarginata’ at Biltmore Estates, Asheville, NC

A surprising number of flowering shrubs perform beautifully in either sun or shade, making them quite versatile where planning a landscape. All can be utilize around outdoor living areas such as decks and patios. Several good candidates are these six:

Japanese pieris, aka lily of the valley shrub (Pieris japonica) is a versatile shrub for sun to part shade (USDA hardiness zones 5 to 8). This broadleaf evergreen shrub grows to 8-12 feet tall and up to 8 to 10 feet wide; most cultivated cultivars are generally smaller in size. New spring foliage emerges with a bright, rich orangey or bronze tint, which matures to dark, glossy green in summer. Leaf size ranges from 1 to 3.5 inches long.
Winter daphne (Daphne odora) is a broadleaf evergreen best grown in warmer climates (zones 7 to 9). It blooms from late-winter into early spring;. Soft pink to white flowers are sweetly fragrant. Leaves may scorch in full sun. Winter Daphne grows 3 to 4 feet tall with a spread of 2 to 4 feet.. Foliage is glossy and leathery; each obovate, 4-inch-long leaf is a rich, deep green. Several cultivars are available with ‘Aureomarginata’ (creamy or golden leaf edges are popular.
Oakleaf hydrangea (Hydrangea quercifolia) is among the largest of the six shrubs, reaching 6 to 8 feet tall and wide provided you select the correct cultivars. Species oakleafs easily grow 2-3 times larger. Shrub blooms on old wood; if pruning is necessary, wait until after flowering (zones 5 to 9).
Japanese kerria (Kerria japonica) is frequently mistaken for forsythia as both bear bright yellow flowers in spring and display a low-growing, arching shrub habit. Its flowers are single, five-petaled, yellow to golden yellow, rose-like blooms. Kerria grows to 3-6 feet tall and to 6-8 feet wide on slender, green stems that retain their color in winter. It is both deer and drought tolerant (zones 4 to 9).
Mountain laurel (Kalmia latifolia), related to Japanese Pieris, are at home in 1-2 hours of dappled or filtered sunlight. This evergreen shrub grows 5-7 feet tall and wide with glossy green 4-5 inch long leaves. Select from over 40 colorful cultivars, ranging from white, pink, pink-rose flowers which open in May (zones 5-9).
Leatherleaf mahonia (Mahonia bealei) is native to the forested areas of the far western U.S., reliably hardy in zones 5 to 8 and copes with considerable shade. It’s a broadleaf evergreen with a spreading to upright habit, usually reaching 4 – 6 feet tall by 4 – 5 feet wide, although if sited close to a wall or fence, it can be trained to grow taller.

All shrubs prefer moist, rich, well-drained soils and some amounts of morning sunlight. They are moderately drought tolerant after the first year. Flowers attract bees; fruit attracts birds deer resistant, birds love the berries. Prune within 4-6 weeks after spring bloom has ended.