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

Cool Plant Combos For Containers

Posted by Hugh on March 10th, 2017

Phormium, 'Phantom' etunia and An Aggressive Sweet Potato Vine

Phormium, ‘Phantom’ petunia, and too aggressive Sweet Potato Vine

Mix of Begonia, Calibrachoa, Pennisetum, Bracteantha

As more and more urban gardeners are growing in small spaces, including decks and patio of condos and town houses, container gardens are becoming more significant. They’re creating large mixed containers that include miniature trees and shrubs rather than their big cousins.

For design containers may include thrillers (tall or spiky), fillers, and spillers (weepers). They contain splashes of color or many color contrasts.

Here is a few design ideas that blend shrubs/trees, perennials, and annuals together for great effect:

Container size is of key important. Large, wide (broad base) containers are the best to avoid tipover from high winds. Halved wine barrels or large concrete planters are good choices for a permanent fixture, as their weight ensures that they won’t get blown over easily. Containers must have one or more drainage holes or a 3-4 inch reservoir containing coarse pea gravel.
Use a miniature tree or shrub as the tallest feature in the planter. Include woody landscape trees and shrubs such as: dwarf columnar conifers, Japanese maple (Acer), camellias, buddleia, hydrangeas, or crapemytle (Lagerstroemia).
Use annuals to add bold color(s) to the display. Great selections to handle the summer heat include: begonias, calibrachoas, impatiens, annual vincas (Catharanthus roseus), scaevolas, and Mexican heather (Cuphea hyssopifolia).
Include perennials to fill in spaces and that add their own lovely color and contrast. Some of the best perennials for this role are: coral bells (Heuchera), miniature and small leaved hostas, sedges (Carex), sweet flag (Acorus), monkeygrass (Liriope), and assorted ferns.
Use plants with similar growing conditions, e.g. in partial to full sun or shade or moist or dry potting soil.
Use a mixture of early-, mid-, and late-season blooming plants to ensure a colorful display all season long.
Check plant hardiness of woody plants in your area to add to container.

Growing Tips: woody landscape trees and shrubs and some perennials need to be transplanted every 2-3 years in late winter. Replace the soil (media) and root and shoot old plants before adding new soil (media). Feed with a slow release fertilizer such as Osmocote™, Scotts™, and Nutricote™.

‘Crippsi’ False Cypress, petunia, and dichondra

Autumn Ferns Offer Lush Tropical Touch

Posted by Hugh on March 7th, 2017

Autumn fern in mid-spring

‘Brilliance’ in a June Garden

Ferns are fine textured lacey-leaf groundcovers. Many kinds of ferns add a tropical accent to the shade garden. Autumn fern (Dryopteris erythrosora), aka Japanese wood fern, has evergreen or semi-evergreen arching foliage, depending how cold winter is (USDA hardiness zones 5 to 8).

Its common name is misleading. Best fronds color is in spring; fronds unfurl with a coppery-red tint and gradually fade to medium to dark green after 4-6 weeks. In late summer, bright-red spore clusters (sori) appear on the frond’s underside. In fall, fronds develop more of a russet tone.

Once established, autumn ferns grow happily beneath large shade trees or in dry soils. Initially, start them off with plenty of water, compost, and mulch to get root system established. They prefer an evenly moist soil, and mildly acidic soil pH between 5.5 and 7.0. Established plants are moderately drought tolerant.

In early spring emerging fiddleheads (fronds) unfurl to form a vase-shaped clump, 18-30 inches tall and wide depending on age. Clumps spread slowly by underground roots. At planting, space 16-18 inches apart for dense coverage. Indifferent to heat, humidity, and cold, this moderate shade lover excels in full morning sun in zone 5 and 6, but wants more shade in southerly climes.

From then on, autumn fern performs season after season with little additional care. It has no serious pest or disease problems and soil nutritional needs are minimal. Applying 2-3 inches of leaf mold is almost equivalent to feeding with slow release fertilizer.

The cultivar ‘Brilliance’ grows 2 feet high and wide and offers long seasonal impact. Its frond’s color is exceptional, that is, the upper surface has a deep coppery tint and high gloss, rich green color through most of the summer, and returns to a russet color in autumn.

Enjoy The Double Soft Pink Flowers of Kwanzan Cherry

Posted by Hugh on March 4th, 2017

‘Kwanzan’ Cherry Tree

Soft pink double flowers

Kwanzan cherry (Prunus serrulata ‘Kwanzan’) is a commonly planted Oriental cherry in the U.S. (USDA hardiness zones 5 – 8). It’s most often utilized as a small 25 to 35 foot tall flowering deciduous tree in an open lawn, patio. and deck setting for its cool summer shade. It is a 4-season specimen and should be located where it can be viewed year-round.

Kwanzan cherry is in glorious flower in mid-spring and is frequently planted along with Yoshino Cherry (P. x yedoense) in Washington, D.C. and Macon, Georgia for their annual Cherry Blossom Festivals. Yoshino cherry produces abundant single pale pink cherry blossoms a full week or two before Kwanzan. The later blooming Kwanzan is less prone to late spring frosts, which is so important to festival planners.

The 2-inch diameter powder-puff pink flowers are comprised of 24 – 28 petals, with no sexual floral parts. Therefore tree will rarely produce fruits. Flower clusters of 3-5 blossoms develop at each node. New spring leaves are bronze colored at the start and turn to a medium green within a few days. In autumn leaves turn yellow, orange, or copper colored. A unique way to identify Kwanzan is the pair of large distinctive glands at the base of each leaf blade.

Site selection is very important in growing Kwanzan cherry. It performs best in full sun and in a well-drained fertile soil. Hot, dry summers can shorten a tree’s life span. Annual pruning is absolutely essential and should be performed immediately after flowering. Remove dead, weak, or sickly branches, including those that may be infested with scales and other serious insect pests.

Kwanzan cherries are prone to a long list of insect and disease problems, including cankers, black knot, leaf spot, die back, leaf curl, powdery mildew, root rot and fireblight. Potential insects include aphids, scales, borers, leaf hoppers, caterpillars, tent caterpillars, Japanese beetles and spider mites. Canker, borers and virus can be particularly troublesome under high stress environmental conditions such as hot droughty sites.

Native Red Buckeye Tree Delights in Landscape

Posted by Hugh on March 1st, 2017

Red buckeye at Biltmore Estates, Asheville, NC

Red tubular flowers and palmate foliage

Red buckeye (Aesculus pavia) is a southeastern U. S. native that has become more recognized as a wonderful small landscape tree (USDA hardiness zones 4-8). In its native habitat it is an understory large shrub or small tree frequently surrounded by taller trees or structures. A mature specimen may grow 20-25 feet high and wide in 30 years.

Showy, erect, 4-10 inch long panicles of red to orange-red flowers appear in spring. Many 5- to 9- inch long tubular flowers stand erect on branch tips as decorative candles in late April and May in zone 6. Flowers open at the same time the palmate leaves emerge. Flower tint may vary from dark pink to deep red on individual buckeyes growing next to one another. A rare yellow flower form, listed as A. pavia var. flavescens, is offered by a few specialty plant nurseries. Hummingbirds and butterflies pollinate individual flowers.

Red buckeye grows in average, moist, well-drained soil, and in full morning/afternoon shade or in all-day partial sunlight. The tree holds up to lots of shade although flower numbers are less. Spring feeding with granular 10-10-10 or equivalent fertilizer plus the addition of 2-3 inches of a fresh organic mulch are highly recommended. Soil moisture is of key importance. Summer foliage tends to scorch and declines sooner in dry warm conditions. In southern climes all-afternoon shade is the rule!

Attractive glossy, dark green, palmately compound leaves are attractive in spring and early summer. Disease and pest problems prove to be of little consequence, except that scorched and disease spotted foliage have dropped by September 1st and branches are mostly bare.

Smooth orange-brown seed husks contain 1-3 shiny seeds (1-2 inch long nutlets). Seeds are called “buckeyes” and ripen by early fall. New plants can be grown from seeds. They should be planted immediately and not allow to dry out prior to sowing. Seedlings often flower 3-4 years later. Seeds are poisonous and are rejected by most wildlife.

Getting A Sourwood Tree Going

Posted by Hugh on February 26th, 2017

Wild tree at NC Arboretum in Asheville, NC in October

Young Sourwood Tree

Sourwood (Oxydendrum arboreum) is one of our most beautiful U.S. native trees. Trees often grow multi-stemmed or shrub-like to 20-30 feet or in tree form to 35-40 feet high and narrow in spread. Trying to establish a new tree can be challenging.

In the wild sourwoods are often found growing in shallow soils on steep craggy mountainsides. They are a pioneering species. Tiny dehiscent seeds are dispersed into the wind and blown, like dust, from established trees over many acres of land. Tens of thousands of seedlings may germinate but few may survive. In Tennessee I have seen new seedlings prospering on cleared reclamation sites where soils are poor.

For a home gardener the challenge is to get this finicky species to survive its initial two years. Site them in the type of soil and environmental conditions which rhododendrons and mountain laurels enjoy. Newly-planted sourwoods tend to prioritize by establishing its root system first. New shoot growth may be slow.

Sourwood should be planted in late winter to early spring before leaf out. Plant in a well-drained moderately acidic (5.5 to 6.5 pH) soil. Prune back the new tree to 1 – 2 feet from the ground at planting. Essentially, you are starting over with 100% root system and 10-15% top growth. Within 2 months one or more root suckers may sprout and this will be your new sourwood. Select 1-3 of the most vigorous shhots and eliminate all others. Feed with 10-10-10 or equivalent granular fertilizer and irrigate during long dry periods.

In nature sourwoods seem to prefer the eastern facing slope in an open woodland area where they receive midday sun. Young transplants respond to fertilizing; older well-established trees do not. Sourwoods need some pruning, mostly to develop the tree’s framework. They have few serious insect or disease problems. Purple spotting on leaves is common in early autumn, but causes little injury.

Finding a nursery grown tree for sale is rare and many sellers will not guarantee them. Some on-line nurseries do list them.

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.