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

Perennials With Great Autumn Leaf Color

Posted by Hugh on October 27th, 2021

Arkansas bluestar (*Amsonia hubrichtii*) fall color

In addition to foliage changes seen in landscape trees and shrubs, a select number of perennials contribute to the autumnal leaf colors. Here is a select list of popular perennials endeared for their autumnal foliage hues.

Arkansas bluestar (Amsonia hubrichtii) – stunning golden foliage beginning in late September.

Bloody cranesbill (Geranium sanguineum) – geranium ground cover with reddish purple foliage color in October; Geranium x ‘Rozanne’ foliage develops a bronze-red tint; G. macrorrhizum ‘Ingwersen’s Variety’ – mixed foliage turns an attractive red color in fall.

Jacob’s ladder (Polemonium ‘Bressingham Purple’) turns royal purple foliage in spring and fall; summer foliage is vibrantly green.

Ferns (selected ferns) – Autumn fern (Dryopteris erythrosora), Royal fern (Osmunda regalis); Sensitive fern (Onclea)

Selected forms of sedums (Sedum spp.) develop yellow and orange shades in fall. example: S. rupestre ‘Angelina’

Bronze-leaf rodgersia (Rodgersia podophylla) takes on coppery red and yellows shades in the fall; annual fall color is highly variable.

Dwarf Variegated Solomon seal (Polygonatum odoratum ‘Variegatum’) is rarely recognized by gardeners.

Leadwort (Ceratastigma plumbaginoides) – low mounding groundcover awakens very late in spring. Deep green leaves develop splashes of red in fall. Blue, starry flowers bloom in late summer into fall.

Herbaceous Peony (Paenonia lactiflora) – fall color is iffy among peony varieties; some may turn rusty orange lasting a week or more.

Golden aralia (Aralia cordata ‘Sun King’) – golden foliage hangs on through October.

Ornamental grasses (Miscanthus sinensis); Japanese bloodgrass (Imperata cylindrica); pink muhly grass (Muhlenbergeri capillaris) or white M. capillaris ‘White Cloud’ inflorescences; foliage of assorted sedges (Carex spp).

Several forms of switchgrass (Panicum virgatum) – ‘Northwind’ (autumnal yellow leaf blades), ‘Shenandoah’ (reddish tones 0n leaf blades), ‘Cheyenne Sky’ (dark maroon leaf tips)

Bellwort, merrybells (Uvularia perfoliata) – yellow fall leaf color lasts 7-10 days.

Tips On Overwintering Outdoor Containers

Posted by Hugh on October 21st, 2021

Containers filled with shrubs and perennials, doesn’t necessarily ensure their winter survival. Without adequate cold protection plants may succumb to cold injury—turning them into dead annuals.

Heath (*Erica x darleyensis*) enjoys cool winters (zones 6-8)

To over-winter perennials in containers, you need to know their root and shoot temperature hardiness. Often, plant hardiness ratings is listed on the label.

Roots and shoots of several landscape plants have different hardiness levels. For example, above ground potted landscape species such as hollies, azaleas, and boxwoods may be winter hardy at 5-10 °F, yet their roots are injured below 18-20 °F. Day to day air temps may fluctuate wildly and the plant crowns and roots are much more sensitive to temperature swings than their above ground branches.

Here are several helpful pointers to improve the survival of containerized plants during the winter months:

Taxus (yew) hedge may be injured by late fall pruning

Grow Two Zones Colder. When growing perennials in containers, select those that are rated two plant zones hardier than your own.
Transplant Into Larger containers. Large containers contain more soil and offer greater winter protection to roots than smaller pots can provide. Also, line pots with styrofoam insulation
Huddle for warmth. Group multiple containers tightly together and move them in a wind protective corner of the garden. In some climates, they may also be beneficial to cover them with loose leafy mulch to added temperature protection as well as fluctuation.
Dig Pots In. Container roots can be protected from cold if you trench pots into the ground. Dig a hole or pit in the ground and take advantage of the heat and insulation that the earth provides.
Bring Them Inside. Set the containers inside a shed or an unheated garage to protect temperamental perennials, such as elephant ears, cannas, crinums, blue mist shrub and butterfly bush (Buddleia x davidii) (USDA Zones 5–9).
Delay pruning back some tender shrubs in the fall. Buddleias, crape myrtles, and bluemist shrub (Caryopteris) are examples.
Late fall clipping of hedges, such as hollies, yews, boxwoods, or privets, may be injured if winter temps turn out to be unusually severe in your region.

Forms of Western Arborvitae

Posted by Hugh on October 16th, 2021

Here is a partial listing of cultivars of Western arborvitae (Thuja plicata), as found in the U.S. nursery industry. Several are good choices for dwarf conifer collectors, in rock gardens, and in large containers. Winter hardiness of some cultivars is variable. Note: some are dwarf forms of ‘Green Giant’ arborvitae (Thuja standishii x plicata) which is a hybrid form.

‘Can-Can’ – semi-dwarf, dense, upright tree habit, 8 feet high and 5 feet wide in 10 years; dark green foliage with golden-white tips. (zones 6-9).

‘Excelsa’ – up to 35 feet tall with 20 feet spread; bright green fan-like foliage rated as fragrant. (zones 7-10).

‘Grune Kugel’ – ultra-dwarf slow growing dense mound 12 – 18 inches tall, 18 – 30 inches wide. (zones 5-8).

‘Hogan’ – medium-size columnar grower (40 feet x 20 feet) with dense narrow habit (sometimes mislabeled ‘Fastigiata’). (zones 5-7).

‘Junior Giant’ – about 40% to 50% the size of Thuja ‘Green Giant’ (about 20 to 25 feet tall and 10 feet wide). Branches seem to be held more horizontally. (zones 4-8/9).

‘Pygmaea’ – irregular upright branching; 2-3 feet shrub in 10 years. dense, blue-green foliage, tips may turn bronze in winter. (zones 5-8).

‘Rogers Aurea’ – reaches 4 – 5 feet high and wide with an oval to globose growth habit; decidedly smaller compared to the standard ‘Aurea’ with a broad pyramidal habit; bright golden yellow foliage outwardly, greenish on inner wood. Needles turn gold/orange-ish/bronze color in winter (depending on severity). (zones 5-9).

‘Stoneham Gold’ – dwarf form to 7 feet tall, compact, upright habit; branch tips are golden-yellow. (zone 7).

‘Sunshine’ (also may be ‘Canadian Gold’) – 40 – 70 feet tall, with bright gold needles that reportedly turn off bronze in winter. (zones 5-9)

‘Virescens’– slightly narrower habit, 20-30 feet tall and 9-12 feet wide. Glossy, dark green foliage holds its green year round without winter bronzing.

‘Whipcord’ – shrubby, slow-growing, dwarf form with pendulous whipcord-like green foliage; 2-3 feet tall and wide in 10 years, ages to 4-5 feet; scale-like leaves may turn coppery-bronze in fall. (zones 5-9)

‘Zabrina’ – large tree form, 40 feet at maturity, with broad, pyramidal habit; variegated foliage, specially for its bands of green and golden-yellow. (zones 5-7).

Possum Haw Holly

Posted by Hugh on October 11th, 2021

Possum haw (Ilex decidua) is a deciduous holly, grown as a large shrub or small tree. Its colorful winter berries brighten woodlands along creeks and rivers in the Midwest and Southeastern U.S. (USDA hardiness zones 5 -9). It is known by a number of common names, including bearberry, winterberry, deciduous holly, among others. Its popular name “possum haw” comes from the fact that opossums feed on its fruits.

As a shrub possum haw grows 8 feet to 15 feet high and 8 feet to 10 feet wide. Tree forms grow 18-25 feet tall, depending on cultivar. It may be utilized it as a single fruit-bearing female specimen plant if a male pollinator shrub is nearby. Or plant several for a deciduous privacy hedge or screen.

Small white flowers open in late April in Tennessee and Virginia (USDA hardiness zones 6 -7). Based on the cultivar grown, colorful berries may be crimson, scarlet, orange, gold or yellow.

Plant the appropriate male pollinating variety among many fruit bearing females to insure a bountiful crop of colorful berries from mid-autumn thru the winter months which attract wildlife (see below).

White flowers open in late April in the Southern Appalachian region. Possum haw has an attractive branching habit and gray bark. The 1½- to 3-inch long oval leaves are glossy dark green in summer and transition to a rich yellow fall color before abscising.

Various forms – from weeping to upright – and with other fruit colors are being developed and introduced. Florists are utilizing heavily fruited branches in decorating; the fruits persist for many weeks. Few serious disease and pest problems trouble this shrub.

Possumhaw can be found on limestone glades and bluffs, along streams in wet woods, and in lowland valleys, sloughs and swamps. It is an upright shrub or small tree with a spreading, rounded crown. Its bark is gray-brown and smooth with occasional warts. Birds, deer and a variety of small mammals (including opossums as the common name suggests) are attracted to the fruit. Prune to shape in early spring just before new growth begins.

‘Council Fire’ is a female plant and needs a male pollinator (e.g., male Ilex decidua or Ilex opaca ‘Jersey Knight’) for berry production. One male plant is usually adequate to pollinating 9-10 female plants.

‘Raritan Chief’ – a male clone used to pollinate many deciduous holly hybrids, as it flowers over a long period. It may reach 12 feet tall and features attractive glossy, light green foliage.

Additional Varieties:

‘Byer’s Golden’ – 8-10 feet shrub; gold fruits
‘Council Fire’ – 15 feet high; persistent orange-red fruits
‘Red Escort’ – 18 feet high; male pollinator
‘Pocahontas’ – 7 feet; bright red berries
‘Sentry’ – 18-20 feet high; red berries
‘Sundance’ – 7 feet tall; orange-red berries
‘Warren’s Red’ – 12-18 feet tall; bright red

Coral honeysuckle

Posted by Hugh on October 6th, 2021

Coral honeysuckle (Lonicera sempervirens), aka trumpet honeysuckle, is a vigorous twining flowering vine that is primarily native to the southeastern U.S. (USDA hardiness zones 4 -8). Cultivars are available in shades of red, orange. and yellow. The colorful flowers appear in spring and summer, and colorful berries decorate in late summer and autumn. Invite hummingbirds to your patio via a decorative trellis or pergola.

Coral honeysuckle prefers partial to full sun, and is best grown in fertile, humus-rich, moist, well-drained soil. In early spring, fertilize with a general-purpose granular fertilizer such as 10-10-10 or 19-19-19. Too much fertilizer stimulates lush foliage and less flowers. Coral honeysuckle is a drought-tolerant vine. Moisture stress may decrease blooming. Mulch annually around the plant to conserve soil moisture.

Coral honeysuckle is a twining vine that needs a sturdy climbing support such as a trellis, arbor, or fence. Flowers originate on new growth, so most pruning activity should be postponed until fall or winter seasons.

Prune this vigorous vine annually to rein-in its vegetative vigor and maximize its flower power. Unpruned vines eventually decline in growth and blooms are fewer and many are deformed. Remove one-third of the vine’s old growth annually, cutting the vines back to the main stem. Pruning is best done in late winter. You may rejuvenate an overgrown unproductive vine by cutting it clear to the ground. When new growth returns, regular pruning will keep it looking healthy and tidy.

Pest or disease problems are a rarity, although powdery mildew and leaf spots may pop up in a hot humid summer. Inspect for honeysuckle aphids, particularly during cool, wet spring periods.

Cultivars: Favorites are ‘Major Wheeler’ (non-stop showy clusters of orange-red flowers, ‘Dropmore Scarlet’ (hybrid form with red flowers), ‘John Clayton’ (yellow-flowered, rebloomer), ‘Sulphurea’ (yellow-flowered). Yellow-flowered L. flava is native to the Ozarks.

Bald Cypress For A Small Landscape

Posted by Hugh on October 1st, 2021

Bald Cypress (Taxodium distichum) is well-known as a deciduous conifer native to the southeastern U.S. (USDA hardiness zones 5-9). Pyramidal in form, bald cypress towers over 70 feet tall with a spread up to 50 feet.

Bald cypress is naturally found in southeast U.S. swamps, marshlands, lakes, ponds, and other wetlands. On marshy ground, you may spot their basal “knees” or mounds growing around the tree base. Knees are woody growths that project several inches to a foot above the ground, and are thought to function as aerial roots.

Soft, needle-like feathery leaves emerge in spring. Bald cypress sheds its leaves in autumn, hence its common name, bald cypress. In fall this foliage turns a gorgeous bronze tint in mid-October and early November. The leaves slowly fall from the tree over several weeks, depositing several inches of soft leaf mulch around the tree. Adult trees exhibit a herringbone branching silhouette in the winter landscape. Its exfoliating reddish-brown bark is an added plus.

Bald cypress thrives in full sun and prefers moist, acidic, sandy loam soils. However, but tolerates a wide range of soil conditions ranging from average moist soils and in standing water.

No serious insects or diseases trouble bald cypress. Chlorosis (leaf yellowing) frequently occurs in alkaline soils. Twig blights, bagworms, and various mites are occasional problems.

Varieties for smaller landscapes: ‘Shawnee Brave™ – narrowly pyramidal tree form, 50 feet high and 20 feet wide. ‘Peve Minaret’ – a dwarf tree form growing 10-15 feet high and 6 to 10 feet wide. ‘Cascade Falls’ – a weeping form that must be staked to desired height (8 to 20 feet high). ‘Falling Waters’ – grows 20 feet tall and 15 feet wide with graceful arching form.

The water-resilient wood of this tree is used in the manufacture of landscape timbers, outdoor garden furniture, flooring, shingles, flower boxes, and landscape mulch.

Fuzzy Bolivian Sage

Posted by Hugh on September 27th, 2021

The large and bright fuzzy blossoms of Bolivian Spearhead Sage (Salvia oxyphora), aka Fuzzy Bolivian Sage, should catch your eye in late summer and early autumn. Equally attractive is the plant’s lush tropical-like glossy green foliage.

Fuzzy Bolivian Salvia (*Salvia oxyphora*) at Longwood Gardens

This sage inhabits the edges of moist forests in the foothills of the Andes. It is grown as an annual in full sun in Northern climes during the summer. If grown in containers, you may opt to bring plant(s) indoors over the winter. It prefers midday shade in the hot summer climes in the southern U.S.

This vigorous growing salvia can reach 4 feet high by summer’s end along with deep green tropical-like foliage. Numerous velvety hairs, almost invisible, cover the foliage. Fuzzy deep pink tubular flowers emerge from short dense spikes atop the verdant foliage starting in late-spring.

Fuzzy Bolivian sage prefers a well-drained, rich loamy, mildly acidic pH soil, and in full to partial sun. Cut back stems once in late spring to develop better branched plants. If sown from seeds, start them indoors 6-8 weeks before last spring frost date. Plants are not commonly available for purchase at U.S. garden centers. Fertilize plants at planting time and once again in mid-summer.

Salvias are rarely troubled by very few serious disease and insect pests. Plants may be susceptible to downy and powdery mildew if the planting is crowded or poorly sunlit.

Salvia’s attractive tubular flowers are valued by hummingbirds, bees and butterflies for their pollen and nectar. If salvias appear tired in late summer, shear the plants lightly, including the removal of the spent flowering spikes in order to encourage new growth and flowering.

In the northern portions of its hardiness range (Zone 8), cover crowns (plant bases) with a loose (non-packing) winter mulch such as pine straw.

‘Goshiki’ Holly Tea Olive

Posted by Hugh on September 21st, 2021

Holly Tea Osmanthus, also called holly tea olive and false-holly (Osmanthus heterophyllus) is a large (15 feet tall), dense, upright, oval-rounded evergreen shrub. The species blooms in late fall and the tiny inconspicuous white flowers are sweetly fragrant. Small numbers of fruits ripen the following year, and often go unnoticed.

Osmanthus heterophyllus ‘Goshiki’ is a smaller compact, mound-forming evergreen variety that reaches up to 4-5 feet tall and 3-5 feet wide. It is a perfect choice in a small garden. Goshiki osmanthus flowers open in late September into October and their sweet fragrance fills the air from several feet away. The small (about ¼ inches across) white flowers are borne in clusters of 4 or 5 at the base of the leaf axils.

‘Goshiki’ stands out for its bright leaf variegation dotted with creamy white flecks against the dark green holly-like foliage. It can be utilized as a low hedge or front border evergreen shrub. Blue-black drupe fruits, only 3/8 to 1/2″ in size, are rarely seen in cultivation. Goshiki is not invasive and deer stay away. It was introduced from Japan by Barry Yinger.

Plant in full sun or a partially shaded area and in a humus-rich well-drained soil; it tolerates pH soil between 5.5 to 7.5. Hardy in zones 6-9, site in partial shade in southerly zones 8-9. New spring growth starts out pinkish bronze; the spiny mature leaves display a mix of green, gold, and cream. Relatively pest-free.

Landscape Use: Great plant for low borders and hedges. Slow growing by nature, makes Goshiki a wonderful addition to a dwarf shrub collection, in a rock garden, or in a large container.

Clump Type Ornamental Grasses Excel In Autumn

Posted by Hugh on September 16th, 2021

City gardeners want low maintenance. These ornamental grasses are what you’re looking for. They achieve their intended growth heights in summer, and produce flowers (inflorescence). Foliage of some change color as temps start cooling in late summer.

Five of six listed grass species are winter hardy and overwinter outside in large containers or tubs in most regions (USDA hardiness zones 4-9). Muhly grass is the exception in hardiness (zones 6-10). All six tolerate a wide range of soils and deer leave them alone.

Short List (6) of Ornamental Grasses:

Maiden grass, Eulalia grass (Miscanthus sinensis) are beautiful in the early autumn landscape. Several cultivars are very invasive in U.S. landscapes. My Fair Maiden™ (6 – 8 ft. tall x 4 ft. wide), ‘Rigoletto’, ‘Morning Light’, ‘Strictus, and ‘Zebrinus’ (Variegata’) produce very low amounts of sterile seed and are rated less invasive.

Switchgrass (Panicum virgatum) is a U.S. native prairie grass that is an exceptional performer. ‘Northwind’ switch grass grows 4 -5 ft. tall and 2.5 ft. wide and is tightly constricted at its base; airy panicles of feathery flowers in late summer. ‘Shenandoah’ forms a small 3 feet tall clump; summer foliage is dark purple cast on its tips dark, black-purple foliage in fall. ‘Cheyenne Sky’ emerges with blue-green leaves in late spring, forming a tidy and well-behaved mound. In late summer deep wine-red leaf tips and airy sprays of dark-red flowers.

Feather Reed Grass (Calamagrostis x acutifora ‘Karl Foerster’ has a strong upright habit and blooms with showy flowers that ripen to tawny seed heads that decorate the plant through the fall and winter months. Other cultivars are: ‘Overdam’ and ‘Avalanche’.

Muhlygrass (Muhlenbergia capillaries) produce a loose, airy inflorescence that is nothing less than spectacular pink clouds in early fall. Muhlygrass typically grows to 3 ft. tall x 3 ft. wide when in flower (USDA hardiness zones 6-10). Pink Muhly is the most popular form; ‘White Cloud’ sports white flowers and grows more upright than pink form.

Little bluestem (Schizachyrium scoparium) are popular native warm season grasses. ‘Carousel’ (2.5 ft.) has green and cream stripes. ‘The Blues’ (3 ft.) has blue leaf blades with red stem accents. ‘Standing Ovation’ (4 ft.) has blues, greens, pinks, and purples. Sturdy spiky stems mature in the fall with a brilliant display of oranges, reds, yellows and purplish-browns.

Prairie dropseed (Sporobolus heterolepis) is a warm season, clump-forming grass. Fine-textured, hairy, long green leaves (to 20 inches long and 1/16 inches wide) typically form an arching foliage mound to 15 inches tall and 18 inches wide. Foliage takes on a golden with orange hues in fall, and light bronze in winter. Open, branching flower panicles appear on slender stems which rise well above the foliage clump in late summer to 30-36 inches tall. Flowers have pink and brown tints, and a coriander fragrance in fall.

*Sporobolus* *heterolepis* in late October

Fall Planting – Hyacinths

Posted by Hugh on September 11th, 2021

For over 400 years hyacinths have been popular spring-flowering bulbs, beloved for their colorful blooms and delightful floral fragrance. Modern day varieties are hybrids of a single species (Hyacinthus orientalis) that grows wild in Turkey, Syria, and other regions in the eastern Mediterranean. Over 50 cultivars are listed by Dutch growers.

Centuries of breeding have given gardeners taller and larger floral spikes, mostly double florets that are tightly packed along the stem. Each hyacinth bulb produces a single 8 -12 inch tall flower stalk. Flowers open in mid-spring around the same time as daffodils and early tulips.

Shades of purples and blues are very common, including Blue Jacket (royal blue), Delft Blue (soft lilac blue), and Miss Saigon (deep lavender blue) Aida (violet-blue). Other color choices include Woodstock (burgundy), Jan Bos (hot pink), Carnegie (white), Gipsy Queen (salmon), and City of Haarlem (pale yellow).

Hyacinth bulbs are planted in mid to late fall. Choose a planting area with well-drained soil. Full sun is best, particularly if you desire bulbs to re-bloom for several years. Hyacinths will grow in light shade, but multi-year planting numbers gradually decline. For visual impact, plant the bulbs in groups of 5 or more, spaced about 5 inches apart on center and 5 to 8 inches deep.

In the mid-Atlantic and mid-South states, (zones 5-7), hyacinths grow well in outdoor containers or mixed with other spring bulbs. You may also force hyacinth bulbs in pots that are chilled outdoors, or in unheated garages/sheds, or in refrigerators. Bring pre-chilled bulbs in your home for floral display winter into spring.

Like tulips, newly planted hyacinths perform at their best the first planting year. Some gardeners will grow bulbs for 2-3 years and redo the planting bed. Botanical gardens sow hyacinths and tulips as annuals. Hyacinth bulbs may re-bloom for several years, but lose their vigor and flower size. Soil-borne diseases will also reduce their numbers.

Once flowers have wilted and faded in spring, clip off the flower stalks to re-energize bulbs for next spring. Allow the green foliage to grow until it dies back in late May or early summer. Bulbs enjoy a dry summer dormancy in ground.

Favorite Bulb Emporium: Brent and Becky’s Bulbs in Gloucester, VA. Shop on-line or mail order.