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

Arborvitae Fern

Posted by Hugh on June 1st, 2019

Selaginella braunii (winter bronzing)

Arborvitae fern (summer look)

Arborvitae fern (Selaginella braunii) is native to China (USDA hardiness zones 6-9). It is not a fern at all, but a Lycopod or “club moss”, a descendant of ancient spore-producing plants which date back to the Carboniferous and Permian Ages. Its small club shaped cones give it the plant moniker – ”club moss”.

Arborvitae fern is a slowly creeping rhizome with semi-evergreen leathery frond-like leaves. In early spring the tender light green emerges and stays brightly green if seasonal moisture is adequate. During cold winters the foliage is often bronze-tinted.

By the end of its 3 season, a small 3-inch wide plant may fill-in an 18-24 inch wide space. Arborvitae fern grows 6-12 inches (15-30 cm) high. Its textural and seasonal color make for a lovely landscape groundcover in partially to fully shaded areas. It also looks great in hanging baskets and large ground planters combined with other taller plants.

Arborvitae fern loves a moist well-drained, organically rich soil and in full to part shade. Amend a sandy or clay soil by generously incorporating a two- or three-inch layer of compost or humus. Plant quart or gallon-sized containers a foot or so apart. Water as needed to maintain moist soil. Once established, give it 1-2 years, it will tolerate moderately dry sites over short periods. Fertilize in early spring just as new growth begins with a slow-release fertilizer at low rates.

Arborvitae ferns are easy to grow, disease and insect resistant and deer proof. These and other club mosses can be easily divided at any time of year. They do not flower in the traditional sense, but you can nurture them from spores.

Best of The Oakleaf Hydrangeas (So Far)

Posted by Hugh on May 26th, 2019

‘Snowflafe’ oakleaf hydrangea

Fall leaf color of ‘Snow Queen’

More than 30 available oakleaf hydrangea (Hydrangea quercifolia) cultivars, you can select the perfect specimen to complement any size garden USDA hardiness zones 5 -9). Oakleaf hydrangea is a native plant that delights gardeners with four seasons of distinct features. In spring, oak-shaped leaves are followed by summer’s white-panicled flowers. When it sheds its colorful leaves in autumn, they reveal cinnamon-colored exfoliating bark that adds texture to the winter garden.

Oakleaf hydrangeas are native to the southeastern United States, and hardy in oakleaf hydrangea adapts better to different climates than the recognizable bigleaf hydrangea with mophead blooms.

Its superior disease resistance makes this shrub a low-maintenance choice for beginning gardeners. Oakleaf hydrangea are tolerant of moderate shade, an excellent choice as an understory shrub. Expect smaller numbers of flowers.

Large… For larger gardens pick your choice of either ‘Alice’ or ‘Allison’. Both grow 12-15 feet tall and wide with enormous 12 inch cone-shaped flower clusters may be longer than 12 inches. Additionally, Alison’s” handsome burgundy fall foliage. A third tall variety is ‘Harmony at 10 foot tall . Individual florets of panicles are densely packed,

Medium… One of the most popular oakleaf hydrangeas was introduced in 1971 when nurseryman Eddie Aldridge patented a cultivar that had double flowers. Snowflake grows 8 feet high and wide and the double florets bloom longer than other cultivars. Snow Queen is an equal beauty with single-flowered panicles and upright shrub form.

‘Little Honey’

Small… Two of the best dwarf oakleaf hydrangea cultivars are ‘Ruby Slippers and ‘Munchkin’ are plants that feature the desired qualities of their larger relatives, but in compact form. Munchkin’s blooms open white, as all oakleaf varieties do, and gradually turn pink with age. Ruby Slipper’s bears white flowers that fade to pale pink and finish rose color. Both shrubs grow to 5 to 5 ½ feet after 7-10 years. These dwarf forms are perfect for large containers on decks and patio.

And lastly… ‘Little Honey’, a branch sport of H. quercifolia ‘Pee Wee’, is a unique gold leaf oakleaf hydrangea. This compact spreading beauty grows 3-4 feet tall and 4-5 feet wide and is frequently utilized as an accent plant. Its flowers do not standout, but its gold colored foliage surely does.

Sacred Lily (Rohdea)

Posted by Hugh on May 21st, 2019

Sacred lily (Rohdea japonica), aka nippon lilies, are native to Japan and China. Rohdeas are truly collector’s plants (USDA hardiness zones 6-10). In the Orient these lovely shade perennials are highly revered. In traditional Japanese horticulture, sacred lilies (known as o moto) came to be associated with long life and good fortune. Containers are planted near the entry to courtyards and homes. Over the past two centuries colorful, contorted, ridged, dwarf, giant, or variegated leaf forms have been bred, almost all with Japanese names.

Rohdeas are members of the asparagus family (Asparagaceae). Plants are rhizomatous perennials that grow 8-18 inches high depending on cultivar.

Well-established clumps produce short-stemmed, creamy to greenish, white bell shaped flowers. The racemes appear in early spring. found at the base of the plant. Blooms are mostly hidden within the dense leathery foliage and therefore mostly inconspicuous. Red or orange ornamental berries follow in late fall and last through most of the winter.

Sacred lilies are simple to grow and live for many years. Plants prefer a moderately moist, humus-rich, well-drained garden soil. They’re especially adapted to deep shade. Several varieties appear to be reliably hardy to Zone 6. Rohdeas are not troubled by diseases, pests or deer.

Sacred lilies produce dark green, evergreen, strap-like (lanceolate) leaves. They look like a garden-hardy snake plants (Sanseviera). New plants start off slowly, but do multiply and form large colonies of ground covering. Numerous divisions over time can help you build a collection which you can trade back and forth with other collectors.

Where to shop for Rohdea japonica: www.plantdelightsnursery.com lists 7 varieties, the most that I’ve seen from a single nursery source. Plants are also traded on Ebay.

Try Maple-leaf Viburnum In Woodsy Areas

Posted by Hugh on May 16th, 2019

Maple-leaf Viburnum in bloom in late May In Tennessee Garden

Maple-leaf Viburnum (Viburnum acerifolium) is a small to medium deciduous shrub that is indigenous to many areas of the Eastern U.S. (USDA hardiness zones 3-8). This underutilized native viburnum is at its finest in a dappled shady woodland landscape. Slow-growing at first, a single plant may reach heights of 4-6 feet and 2-4 feet in spread. Maple-leaf viburnum displays multi-season interest for its spring bloom, late summer fruiting, and fall color.

Terminal clusters of white flowers (flattened cymes) form about a month emergence of the leaves in May to June. Oval green fruits soon follow that begin turning bluish-black in late summer. Flower clusters measure 2 – 3 inches across. Birds and other wildlife munch on the fruits during the winter.

Coarsely toothed, mostly three-lobed, medium green leaves turn reddish-purple to magenta color in fall. Leaves usually have small black spotting on the undersides.

Mapleleaf viburnum is more shade tolerant than most Viburnum species. It grows in average, medium moist, well-drained soil and in full sun to part shade; it tolerates a wide range of soils. Established 2 year old plants demonstrate good drought tolerance. Feed once in early spring with a granular fertilizer such as 10-10-10 or equivalent @ 1 -2 lbs. per 100 square feet. Keep shrub(s) mulched to retain soil moisture and reduce weed pressure. Irrigate during establishment and extended dry periods.

Within 4-5 weeks after flowering, prune to shape and maintain the shrub as desired. Plants will naturalize via root suckering to form colonies unless suckering is held in check. Suckering is a lot less in dry shade. In an open woodland area, it may take 5 or more years before it starts to naturalize.

No serious insect or disease problems trouble this woodsy viburnum. It may be utilized in shrub borders, foundations or hedges. Maple-leaf viburnum is primarily available from e-commerce native plant nurseries.

Black Mondo Grass

Posted by Hugh on May 11th, 2019

Ophiopogon planiscapus ‘Nigrescens’

Black mondo under shade tree

Black mondo grass or black lilyturf (Ophiopogon planiscapus) is sold as a number of cultivars – ‘Arabicus’, ‘Black Dragon’, ‘Nigrescens’, or ‘Ebony Knight’. This stoloniferous grass-like perennial belongs to the lily family (Liliaceae) (USDA hardiness zones 6-9). Its blackish-purple foliage (3/16 inch wide leaf blades) forms lush arching clumps. For the patient gardener, know that black mondo starts off slowly. Compared to other mondo grasses, this black form grows shorter @ 8 -12 inches in height.

Indigenous to Japan, black mondo typically grows in slow spreading clumps with arching, slowly-spreading clumps. The dark purple foliage appears almost black in most sites. In southern climates, black mondo is often planted under the shade of trees, because leaf blade color will fade under intense sunlight. White, bell-shaped flowers (up to 1/4 inch long), with pink to lilac tints, bloom in summer. Dark purple globular berries mature in fall.

Black mondo grows best in humus rich, slightly acidic, moist, well-drained, soils and in partial to full shade. Mondo prefers consistent, evenly moist soils. Although not reliably winter hardy in USDA Zone 5, many northern gardeners have been successful growing it in a protected area. Plant foliage is evergreen in Southern winter climates. Black foliage color is best in cool sunny locales of zones 6 and 7 and in light shady spots in zones 8-9.

In the landscape black mondo makes for a great edging plant or utilize it as a filler plant in containers. Its dark grassy foliage makes a great accent feature. As garden edging space plants 4-5 inches apart and they should fill within 3-4 years. Feed with a slow release fertilizer such as Osmocote™ or Nutricote™ in early spring. Rake away fallen leaves from nearby trees and shrubs in the fall so mondo grass can continue to grow through the winter months. Irrigate a new planting the first season and during prolong summer dry spell.

Annual Geraniums Make Garden Comeback

Posted by Hugh on May 6th, 2019

‘Calliope Dark Red’

Geranium basket

Once popular annual geraniums (Pelargonium x) are making a comeback with U.S. gardeners. Geraniums are also planted in window boxes or hanging baskets. Three types of geraniums are sold at garden centers: zonal or bedding geraniums (P. x hortorum), ivy-leaf geraniums (P. peltatum), and Martha Washington geraniums (P. x domesticum). Color choices include red, pink, rose, salmon, orange, lavender, violet, or white.

Of the 3 types, zonal geraniums are the most widely planted. Ivy-leafed geraniums (Pelargonium peltatum) have a trailing habit with ivy-shaped foliage. They are principally planted in hanging baskets and window boxes. Martha Washington geraniums (P. x domesticum) are primarily sold by florists as flowering pot plants and do not perform well outdoors.

High summer heat is challenging for all types of geraniums. Some types of geraniums stop blooming completely and perk up when cool temps return. Over the past quarter century plant breeders have given gardeners more heat-tolerant types, such as the Americana™, Eclipse™, Rocky Mountain™ cutting series; Maverick™, and Orbit™ seed series; and the interspecific hybrids trademarked as Caliente and Calliope.

Plant geraniums outdoors after all threat of frost has passed. Depending on the geranium type and variety, plants are spaced about 8 to 12 inches apart and around the same depth as their original planting pots. Mulch around plants to retain soil moisture and suppress weeds. Deadheading of spent blooms also encourages additional blooming. Avoid overhead irrigation, as this may bring on disease problems. Geranium cuttings root easily and held over as house plants.

Geraniums must have a moist well-drained soil and should be planted in a garden receiving at least 6 – 8 hours of sunlight. Let the soil go slightly dry between waterings. Do not overfertilize. Fertilize with a slow-release, granular product once in spring and/or with a water soluble fertilizer such as Miracle-Gro™ or Jacks™ 1-2 times over the summer. Remove old spent flowers to keep plants blooming. Ideal light exposure is in full morning sunlight and in light afternoon shade.

Russian Arborvitae For Cool Areas Of The U.S.

Posted by Hugh on May 1st, 2019

Russian arborvitae and Siberian cypress (Microbiota decussata) is an underutilize ground cover (USDA hardiness zones 3-7). This tough juniper-like evergreen hails from Siberia and demonstrates exceptional cold hardiness to -40 ° F. In extreme northerly sites, the lacy evergreen foliage may turn complete brown in the dead of winter and re-sprout in spring.

In the cool temps of zones 5 and 6 microbiota really prospers. It struggles (melts down) in zone 7 unless cozied up under afternoon shade. Its soft feathery green foliage develops a purple to russet cast where winters are abnormally harsh. An early spring warm-up quickly restores its cool medium green hue.

Growth rate is slow to medium. Feed, if needed, in early spring with a general purpose granular fertilizer such as 10-10-10 or equivalent. Pruning is rarely necessary except to check its spread or to remove any broken branches.

The flat sprays of low growing microbiota range between 8-15 inches in height and 6-8 feet in width over several years. Microbiota is a great alternative to some disease plagued ground cover junipers. It is tolerant of dry shade. Deer and most disease and insect pests don’t bother it. It wants good soil drainage and cool summer temperatures.

Adjacent to my driveway I use microbiota to cascade over a low retaining wall. Foliage tolerates windy exposed sites once it becomes fully established in 2 years.

I am seeing more independent garden centers selling this terrific ground cover. E-commerce specialty nurseries also sell it. Plant container grown nursery stock in late winter thru spring.

Varieties: Celtic Pride™ – an exceptional cold hardy form.

Enjoy Two Kinds Of Stachys In Your Summer Garden

Posted by Hugh on April 26th, 2019

S. monieri ‘Hummelo’ (photo provided by North Creek Nurseries, Landenberg, PA)

Stachys ‘Countess Helene Von Stein’

Many gardeners are acquainted with the wooly leaf perennial called lambs ears (Stachys byzantina). But the genus Stachys is also home to betony (S. officinalis) / (S. monieri). Alpine betony (Stachys monieri) is native to Europe and Asia (USDA hardiness zones 4-8).

‘Hummelo’ betony is very different in appearance from its gray velvety leaf relative called lamb’s ears (e.g., Stachys byzantina). Instead of silvery foliage, Hummelo betony’s foliage is dark green and glabrous (hairless). In Southern climes the foliage is evergreen. This colorful and compact growing plant makes an excellent addition to the full sun perennial border. Wiry stems make for a great cut flower as well.

Hummelo exhibits an upright plant form @ 18 to 20 inches tall and wide. Pollinators can’t resist the striking lavender-rose flower spikes in late June thru July, emerging above basal glossy green foliage mounds. The bright flowers can be easily mistaken for salvias.

In comparison, lamb’s ear (S. byzantina) forms a dense mat of woolly silver-gray leaves. Plants grow 12 -15 inches high and 18 – 20 inches wide. Spikes of purplish pink flowers appear on tall stems in early summer that detract from the foliage and, in my opinion, should be pruned off. Bloom stalks often re-develop and necessitate more pruning. Seedlings from this weedy species will spread to other parts of the garden.

The cultivar ‘Countess Helene von Stein’, aka ‘Big Ears’, is the preferred choice among landscapers. It exhibits showier velvet (hairy silver) foliage, better heat and humidity tolerances, and best of all, it rarely flowers and seeds-in. Over time Big Ears develops a wider vegetative mound than the species.

Both types of Stachys are easily grown in moist well-drained soils and full to part day sun (6 hours or more recommended). Soils should be kept evenly moist, but established plants have some drought tolerance. Plants spread by underground stolons. Set multiple plants 12-18 inches apart as a ground cover. Feed in early spring at planting time with granular 10-10-10 or equivalent fertilizer.

No serious disease or insect pests trouble either species. Pollinators can’t resist the striking midsummer colorful floral spikes. Deer and rabbits generally stay away. Snails and slugs may be troublesome in wet summers.

The Perennial Plant Association has selected Stachys monieri ‘Hummelo’ as 2019 Perennial Plant of the Year.

Planting Small Trees Under Power Lines

Posted by Hugh on April 20th, 2019

Three flower maple in mid-October at NYC Hi-Line

Look Up before you plant. From city streets to country roadside are a myriad of power (utility) lines, e.g. electric, telephone, and cable TV wires. Utility companies have a “right of away” clearance to operate their lines. In most municipalities, mature trees growing into their lines can be cut down or all offending branches removed. Large trees often end up massacred.

The mature heights of the following species rarely exceed 25 feet and eliminate tree/utility line issues. Most tolerant of a wide variety of soils, urban growing conditions and hardiness rating. Disease and pest resistant, drought tolerant, require minimal maintenance. This list includes a few large shrubs that can be trained into small trees such as smoketree, American witchhazel, and fringetree. All are hardy in USDA plant hardiness zones 5-9 except where noted.

Trident Maple (Acer buergerianum)

Hedge Maple (Acer campestre)

Flame Amur Maple (Acer ginnala ‘Flame’)

Japanese Maple (Acer palmatum) – lots of great choices; however many are not tree forms

Three Flowered Maple (Acer triflorum)

Shantung Maple (Acer truncatum)

Red buckeye (Aesculus pavia)

Autumn Brilliance® Serviceberry (Amelanchier × grandiflora ‘Autumn Brilliance’)

Princess Diana Serviceberry (Amelanchier grandiflora ‘Princess Diana’)

Snowcloud Serviceberry (Amelanchier laevis ‘Snowcloud’)

Pawpaw (Asimina triloba)

American Hornbeam (Carpinus caroliniana)

Redbud (Cercis canadensis)

American Fringetree (Chionanthus virginicus)

Smoketree (Cotinus coggygria)

Flowering dogwood (Cornus florida)

Chinese Dogwood (Cornus kousa)

Kousa dogwood in May

Cornelian Cherry (Cornus mas)

Winter King Hawthorn (Crataegus viridis ‘Winter King’)

Sweetheart Tree (Euscaphus japonicus)

Carolina Silverbell (Halesia tetraptera)

American witchhazel (Hamamelis virginiana)

Crape Myrtle (Lagerstroemia x) (zones 6-10)

Amur Maackia (Maackia amurensis)

Little Girl series of Magnolias (Magnolia x liliflora) – cvs. ‘Ann’, ‘Betty’, ‘Jane’, or ‘Susan’

Saucer Magnolia (M. soulangeana)

Star Magnolia (Magnolia stellata)

Select Crabapples (Malus ‘Adirondack’, ‘Prairifire’, ‘Sugartyme’, M. sargentii, M. floribunda)

Ruby Vase® Parrotia (Parrotia persica ‘Inge’s Ruby Vase’)

Crimson Pointe™ Plum (Prunus cerasifera ‘Cripoizam’)

Thundercloud Plum (Prunus cerasifera ‘Thundercloud’)

Newport Plum (Prunus ‘Newport’)

Okame Cherry (Prunus x ‘Okame’)

Japanese tree lilac (Syringa reticulata ‘Ivory Silk’)

Peve Minaret bald cypress (Taxodium distichum ‘Peve Minaret’)

City Sprite zelkova (Zelkova serrata City Sprite™)

Three New Summer Annuals You’ll Get Excited Over

Posted by Hugh on April 15th, 2019

Euphorbia ‘Diamond Mountain’

Senecio ‘Angel Wings’

Here are three new annuals which should delight:

Striking Senecio ‘Angel Wings’ has silky, silvery white foliage. Angel Wings senecio is beautiful to add to mixed containers or use it solitary on patio or deck planters. Warning: you can’t resist touching the long, broad velvety leaves.

Angel Wings grows 10-12 inches high and about as wide. Plant Angel Wings in full sun in an acidic, neutral or alkaline soil. This fast growing Senecio candicans is drought and salt tolerant.

Diamond Mountain® euphorbia explodes clouds of airy white flowers from spring to fall frost. Plants are low maintenance and demonstrate exceptional heat- and drought-tolerance. Diamond Mountain produces larger plants than Diamond Frost^® with a great garden presence; plant in large size containers. It grows 24 – 36 inches tall and wide. It performs at its best in part to full sun.

Diamond Mountain might look delicate and frilly but is much tough as nails. It needs little to no irrigation after initial 6 week establishment period and is extremely heat tolerant in the summer. No floral deadheading is necessary.

Angelface® Perfectly Pink

Angelface® Perfectly Pink is a new angelonia for your summer garden. Plants grow vigorously, 18-30 inches high and 12-18 inches wide. Plants sap up sun and humidity where they bloom at their best. Plant as soon as soil temperatures warm up. Angelonias are moderately drought tolerant within 6 weeks after planting. Plants ask for little additional care including no deadheading. Angelface series produce great long lasting cut flowers with a slight grape soda fragrance. Try some in a flower arrangements.

Feed all three annuals the same. At planting time apply granular fertilizer such as 10-10-10 (or equivalent) to nourish them up to mid-summer. At that time feed additionally with a water soluble fertilizer such as Miracle-Gro™ or Jacks™. Add compost on garden beds at planting time and regular fertilization of plants in containers will help ensure the best possible performance.