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

ALL ABOUT ASTILBES

Posted by Hugh on April 16th, 2021

Astilbes, aka false spireas or false goat’s beard, brighten shady gardens with their colorful blooms in early summer. Their plume-like flowers stand tall above astilbe’s deep green lacy foliage. Flower colors vary from white, pinks, and reds, including lavender and violet. Flowers attract butterflies and other pollinators.

Astilbes are generally planted in spring when the soil is cool and moist. They can prosper in a garden over many years if you purchase healthy plants and plant them on the proper site offering adequate light. Plants excel on partially shaded sites, particularly those exposed to 2-3 hours of morning sunlight. In cool northern climes, most astilbe varieties grow under full day sun. Under full shade plants grow, but bear smaller and fewer flowers. (USDA hardiness zones 3-8).

Plant astilbes in a well-drained soil that has been generously amended with compost or humus. Mulch the bed with compost, shredded bark or pine needles to add nutrients, retain soil moisture, keep roots cool, and suppress weeds. Irrigate astilbes over dry periods lasting two weeks and more. Feed plants with a water soluble fertilizer such as Miracle-Gro™ or Peters™ products every 3-4 weeks through mid-summer.

Compact astilbe varieties grow very well in containers. They may be mixed with shade tolerant annuals and other perennials. Locate the container in a shady spot and water regularly to ensure the soil never completely dries out. Astilbes may be planted under deciduous shade trees or along a shady woodland path or pond.

Many cultivars of astilbes are available. Some compact varieties grow only 10-12 inches tall, while others may produce 4-foot flower spikes. Smaller astilbes are ideal for tight spaces, the front of flower borders and in mixed containers.

Astilbes bloom for many years before plants need to be divided. Plants are best divided in early spring or in the fall, using a sharp spade or knife to divide the root crown into sections.

Two species of astilbes are common in U.S gardens: mostly tall growing Arendsii varieties (A. x arendsii) hybridized in Germany and compact growing Chinese hydrids (A. chinensis).

Five Hardy Evergreen Ferns

Posted by Hugh on April 11th, 2021

Autumn fern (*Dryopteris erythrosora*) in early summer

In the southeastern U.S., ferns are important additions to shady perennial and woodland gardens. Ferns can be used as a ground cover to soften the hard edges of water features, rocks and paths, and make wonderful filler for mixed container plantings. Ferns do not flower or seed, but instead, reproduce by spores that usually form on the underside of leaves (fronds). Ferns, whether deciduous or evergreen forms, are mostly clump forming or spread by rhizomes. Divide clumps every 3-5 years in spring or fall.

The five evergreen species featured here grow in partial shade, but are also tolerant of deep shade. Most ferns prefer humus-rich, moist, acidic, well-drained soil. Ferns can be planted in spring or fall when rain is plentiful. Trim off worn and torn fronds in late winter, and new spring growth will freshen up open plant places. Established ferns tolerate summer heat and humidity and are moderately drought tolerant.

When planted on the proper site, ferns are generally free of pests and diseases. Slugs and snails tend to be the most common problems and crown rot can develop if soil drainage is poor. Most (not all) ferns tend to be deer resistant.

Here in the mid-South region, these five evergreen ferns – Christmas fern, Autumn fern, Tassel fern, Korean Rock fern, and Holly ferns are garden favorites. Look for them at garden centers plant nurseries, and specialty retail shops.

• Autumn fern (Dryopteris erythrosora) – native to woodland hillsides and mountain slopes in Japan, China and Taiwan, grows 1-2 feet high by 2-3 feet wide new. New fronds emerge with a coppery-pink tint in spring and gradually transition to glossy deep green by mid-summer. (z 5-8)

• Christmas fern (Polystichum acrostichoides) – this native fern grows in a fountain-like clump to 2 feet high with dark green, leathery, lance-shaped, evergreen fronds at Christmas; also tolerate dry and slightly alkaline soil. z 3-9

• Japanese Tassel fern (Polystichum polyblepharum) – grows 1-2 feet high by 1-2 feet wide with lustrous, dark-green fronds from central crown. Outward spreading, vase shaped clump; an elegant evergreen fern with overlapping pinnae. z 5-8

• Korean Rock fern (Polystichum tsus-simensis) – grows 12-15 inches high with round shiny dark green fronds with black stems and delicate dark veining through the pinnae (leaflets). New spring leaves start out with a purplish cast. z 6-9

• Japanese Holly fern (Cyrtomium falcatum) grows 1-2 feet high by 2-3 feet wide with arching, glossy, dark-green fronds with thick, leathery pinnae. Spores spread by wind and naturalize freely into other parts of the garden, (z 6-10).

New Soiree Kawaii® Vincas

Posted by Hugh on April 6th, 2021

Vinca (Catharanthus), also called Madagasar periwinkle, is a popular summer flowering bedding plant. Soiree Kawaii® series of catharanthus hybrids from Suntory (C. roseus) continue among the favorites at California Spring Trials since their introduction three years ago. Vincas start blooming, and continuously thereafter, from spring planting to the first frost in autumn.

Soiree Kawaii vincas perform best in well-drained, humus-rich garden soils, and work equally well in containers. One caveat is that vincas despise cool wet soils. Fertilize plantings every 4-6 weeks with a water soluble product like Miracle Gro® or Peters®. Mulch beds and irrigate over extended dry spells. Plants don’t let up with colorful flowers through the hot humid days of summer.

The name Soiree Ka·wa·i·i means “cute” in Japanese to describe the adorable flower size and shape. Compared to most vincas, petals are dissected and offer a finer floral texture in garden beds and containers. Their bright, attractive flower petals are irresistible to pollinators, especially hummingbirds and butterflies. These micro-blooming vincas grow compact and spreading, and are exceptionally floriferous.

Vincas are valued for their neat mound-like growth habit. The dark foliage makes flowers pop in any setting. But what’s even more impressive is how nicely these plants fill out beds and containers. They do well in the landscape as a border, filler or in mass plantings.

Currently, six colors in these compact growing vincas are available. Soiree Kawaii Flower colors include: white, pink, coral, lavender, peppermint, red, and light purple. New! in 2021 is Blueberry Kiss®. Plants grow 6-10 inches high and 12-18 inches wide.

Soiree Kawaii vincas are perfect for all kinds of containers, including window boxes and hanging baskets, and they mix well edging wide planters. No pinching is needed. The attractive dark glossy green foliage compliments the profusion of blooms, creating tidy mounds of floral color.

Modern day vincas exhibit improved disease resistance compared to olden varieties that your mother once grew. Among diseases, be aware of Phytophthora aerial blight and Alternaria leaf spot. Potential insect pests include mites, whiteflies, aphids and thrips.

Fragrant Snowbell

Posted by Hugh on April 1st, 2021

Fragrant snowbell (Styrax obassia) is a small deciduous tree or large shrub that grows 20 to 30 feet tall (15-25 feet wide). It is indigenous to Japan, Korea, and Manchuria (USDA hardiness zones 5-8). Fragrant snowbell exhibits multi-season interest: spring flowering, showy fall leaf color, and an attractive bark.

Fragrant, bell-shaped, white flowers (racemes) are borne on 4 to 8 inch long chains in mid-May. Each raceme is composed of several dozen single pendulous white flower that fall and carpet the ground. The
fragrant blooms dangle from rounded dark green foliage in late spring. Small light green ¾ inch drupe fruits ripen to dark brown and disperse the seeds in fall.

Large coarse textured ovate leaves are fully emerged and cover many of pendant flowers. Foliage is dark green with a dense pubescence (tiny hairs) on the leaf underside. Fortunately, fragrant snowbell produces loads of flowers to still offer a stunning bloom show. Leaves transition to golden yellow in autumn. Bark is smooth and the trunk becomes slightly furrowed with age.

Fragrant snowbell is best planted in full sun to partial shade and in medium moisture, acidic, compost-rich, well-drained soil. Prune in late winter to control tree shape. Old spent floral racemes and seed capsules may linger into the following spring. Styrax species are best planted in late winter into spring. No serious insect or disease problems trouble this underplanted landscape tree.

The Scott Arboretum, located on the campus of Swarthmore University, has selected fragrant snowbell as an ideal candidate for a small urban street tree. This low branched tree is also suitable for growing under utility lines and their roots will not upheave walkways and paving.

Getting Rid Of Difficult Weeds

Posted by Hugh on March 26th, 2021

Chameleon plant (Houttuynia)

Some aggressive perennials like Chameleon plant (Houttuynia cordata), variegated Bishop’s weed (Aegopodium podagraria), along with many woody briars can be extremely difficult to eliminate from a landscape area or garden bed.

Variegated Bishop’s weed (Aegopodium podagraria)

If a weedy garden bed contains no desirable plants, you can over spray weeds with glyphosate, a nonselective herbicide.(Roundup™ is common trade name). This chemical does not kill all weed species and repeated applications may be needed on difficult weeds. Hand digging is a more laborious option.

Broadleaf herbicides (weedkillers) include products labelled 2.4-D, Triclopyr® and Trimec™. The latter herbicides manage many kinds of plants, including broad-leaved weeds in the lawn. Grasses are not injured. Be careful! Winds may allow herbicide to drift onto trees, shrubs, and perennials resulting in plant damage.

Depending on the weed species, it may require repeated applications over a year for the targeted area to become weed-free. Some weeds may be leafless (defoliated), yet their thick roots and stems may still be living. In small weedy patches, try painting the herbicide solution on the targeted weed with a small paint brush.

Mechanical barriers such as spun-bond weed fabric, and multi-sheets of newspaper or cardboard also choke out tough perennial and woody weeds such as English ivy (Hedera helix), crown vetch (Coronilla varia), wild brambles (Rosa spp.+ Rubus spp.), Japanese honeysuckle (Lonicera japonica), and purple wintercreeper (Euonymus japonicum ‘Coloratus’).

Cardboard mulch (partially rotted) + leaf litter gets rid of unwanted English ivy

Steps In Planting A Hedge

Posted by Hugh on March 21st, 2021

Ilex x ‘Oakland’ at NC Arboretum, Asheville, NC

Why Plant A Hedge:

Living privacy fence offers privacy from street traffic and neighbors
Serves as a sound barrier to reduce noise
A windbreak to reduce harsh winds
Snow fence to reduce snow accumulation
Wildlife protection and food for birds from berries and seed.

Planning: Select vigorous disease and pest free trees and shrubs that suit your region. Wise plant choices create a healthy hedge that’s easy to maintain. Select slow to moderate growing shrubs and trees as fast growing plants require more pruning (hedging).

Your choice of shrubs or seedling trees also should be guided by the style of hedge you want. Formal hedges with solid architectural form will neatly frame landscapes spaces – creating rooms. Deciduous flowering shrubs, such as lilac, spiraea, forsythia, and evergreens, such as boxwood, arborvitae, holly, are effective hedges although much of their flower power is lost. The height and depth of the hedge is determined by the vigor of the varieties of shrubs chosen.

Planting a Hedge

1. Stake and mark the planting area, whether in a straight or a curved one. Use a measuring tape as a guide. Be aware of the location of underground utilities.

2. Space plants apart, permitting the plants to reach their mature heights. avoid overcrowding or developing an “instant hedge”. Stagger plants in two rows for a thicker hedge that will fill in more quickly serve as a sound barrier.

3. Dig the planting holes and remove the shrubs from pots and set them at the same dept. Space according to what shrubs you are setting and refill in the planting holes.

4. Water shrubs as needed during the first growing season.

5. Mulch – Spread a 2 to 3 inch layer of shredded bark mulch around plants to conserve water. Do not pile up mulch around the plan stems (trunks).

Deciduous: European beech (Fagus sylvatica), Linden (Tilia spp.), European hornbeam (Carpinus betulus), Hedge Maple (Acer campestre), Arrowwood viburnum (Viburnum dentatum), Rose of Sharon (Hibiscus syriacus), Firethorn (Pyracantha coccinea), Forsythia (Forsythia spp.), Various spireas (Spiraea spp.), Flowering quince (Chaenomeles x), red chokeberry (Aronia arbutifolia ‘Brilliantissima’), Japanese barberry (Berberis thunbergii).

Evergreens: Emerald arborvitae (Thuja occidentalis ‘Smaragd’), Western arborvitae (Thuja plicata), Green Giant arborvitae (Thuja standishi x plicata), Canadian hemlock (Tsuga canadensis), Schip or Cherry Laurel (Prunus laurocerasus ‘Schipkaensis’), Glossy abelia (Abelia × grandiflora), Japanese holly (Ilex crenata), Inkberry holly (Ilex glabra), Boxwood (Buxus spp.), Hicks yew (Taxus x media), Junipers (Juniperus chinensis), Native Cedars (Juniperus virginiana), Japanese Euonymus (Euonymus japonicus).

Three Really Cool Shade Plants

Posted by Hugh on March 16th, 2021

What three wildflowers can handle intense woodland shade. To most gardeners, hostas, Solomon seal, coral bells (Heuchera spp.), brunneras, and ferns are popular favorites. Expand your plant choices with these three shady favorites which are long-lived, low-care gems – Fairy wings (Epimedium spp), bellworts (Uvularia spp.), and shredded umbrella plant (Syneilesis).

Fairy wings (Epimedium spp.), aka barrenworts, thrive in shady spots. They’re a plant collector’s dream. Over 70 species, hybrids, and cultivars can be found in the garden marketplace. No two cultivars are alike in flowering, foliage size and color. The species alone may vary from 6 to 20 inches in height, 10 to 24 inches in spread, and flower power.

Fairy wings are a plant collector’s dream. Some species are evergreen and most are deciduous. Foliage colors may also vary seasonally. Some start out chartreuse, turn dark green in summer, and finish in autumn shades of red. Others may develop a red or silvery tint in the summer.

Their dainty flowers appear in early spring, but are rarely hurt by cold morning temps. Flowering intervals last 3, sometimes 4, weeks and attract early arriving pollinators. Deer rarely bother fairy wings.

Bellworts (Uvularia spp.), aka merrybells, contribute to spring’s awakening in U.S. woodlands and shade gardens. On two species, U. grandiflora and U. perfoliata, the flower stems poke through (perforate) the center of the leaves. Medium green leaves turn clear yellow in early fall. A third species called “wild oats” (U. sessilifolia) is native to Canada and eastern and central U.S. woodlands.

Bellworts bloom in April and May here in eastern Tennessee. They’re among the easiest of wildflowers to grow. Their nodding bell-shaped flowers appear delicate looking, but are hardy and enduring. Over the years individual clumps colonize among themselves from thick fleshy underground stolons.

Shredded umbrella plant (Syneilesis aconitifolia), native to eastern Asia, are abit more finicky to grow. In early spring exquisite dissected umbrella-like leaves emerge covered with hairy silver hairs. Plants stand 18 -24 inches tall atop sturdy stems. As the plant ages, pubescent hairs disappear and leaves turn deep forest green. Over the years, small plant colonies arise from underground rhizomes (2 feet wide in 5-7 years). Flowers are mostly inconspicuous.

All three plants prefer partial to full shade in humus-rich, moist, well-drained woodsy soil. They perform best in dappled morning sunlight. Fairy wings and bellworts tolerate dry calcareous (limestone) soils. Plants tolerate short dry spells lasting 2-3 weeks once they have established after the first year. Humus will supply much of the needed nutrients. Young emerging shoots may be damaged by slugs.

All three plants are rarely found at local garden centers. Shop at on-line nurseries which specialize in shade or woodland plants. Plant Delights Nursery in Raleigh, NC sells the newest cultivars of epimediums.

Love in A Mist (Nigella)

Posted by Hugh on March 11th, 2021

Nigella in the May Garden at Biltmore Estates, Asheville, NC

Love-in-a-mist (Nigella damascena) is a popular cool weather annual. It is also known by several other names including “ragged lady” or “devil in the bush”. Nigella belongs to the buttercup family (Ranunculaceae) and is native to southern Europe, North Africa and southwest Asia. In its natural habitat, nigella is found on neglected, damp patches of land.

Nigella is grown for its very different 1.5 inch wide blue flowers that sit atop stems lushly covered with fine lacy (“misty”) foliage. Plants typically grow to 1.5 to 2 feet tall (1.0 to 1.5 feet wide). In hot humid areas, plants bloom in late spring, but flower numbers significantly decline by midsummer as high temperatures become the norm. Flowers give way to unusual, egg-shaped, horned seed capsules (up to 1 inch diameter) that appear covered with bristles.

Nigella is easily grown in average, medium moisture, well-drained soils and in full sun. Sow seed in the garden as soon as the ground can be worked. In cool summer climates, additional sowings can be done every 3-4 weeks until mid-summer. Seeds are sown indoors about 6-8 weeks prior to last spring frost date, but plants dislike transplanting and results can be disappointing. Plants like consistent moisture and feed with 10-10-10 or equivalent fertilizer at a low to moderate rate .

To extend nigella’s blooming period, gardeners may reseed 2-3 times during the growing season. Deadheading spent flowers often extends the bloom period, but reduce development of the unique seed pods. The black seeds will self-seed freely in the garden.

I first saw nigella as part of a dried winter floral arrangement. Using their dried flower stems and seed capsules are popular among flower arrangers. Cultivars (some with double flowers) are available in white, pink, rose, violet and purple. Semi-double flowers come in shades ranging from pale sky blue to denim. ‘Miss Jekyll’ series include blue, ‘Alba’ (white), and ‘Dark Blue’. ‘Oxford Blues’ and ‘Moody Blues’ are two others.

No serious disease and pest problems trouble nigella.a

Six Early Spring Wildflowers To Grow In Your Woodland Garden

Posted by Hugh on March 6th, 2021

Celandine poppy (Stylophorum diphyllum) is a popular Eastern U.S. native loved for its 12-18 inch tall 4-petaled, yellow flowers. Its blue-green, pinnately lobed leaves are silvery on the underside. It seeds-in readily, which is a good thing, as plants disappear by late May and comeback early next spring in abundance (USDA hardiness zones 4-9).

Virginia bluebells (Mertensia virginica) is a native clump-forming perennial wildflower that grows 1-2 feet tall and produces lovely terminal clusters of 1 inch long, trumpet-shaped, sky blue flowers. The oval bluish green leaves foliage is also attractive (zones 3-8).

Trout lily (Erythronium americanum) is recognized for its thick, fleshy, mottled, brown and purple basal leaves that mimic brook trout. Solitary, bell- or lily-shaped yellow nodding flowers are perched above the foliage. Plants typically grow 4-6 inches high (zones 3-8).

Bloodroot (Sanguinea canadensis) produces showy 1.5 to 2 inch wide, 8-10 petaled white flowers that arises through palmate, deeply-scalloped, grayish-green, basal leaves. Each flower lasts only 1–2 days with lots more of new ones coming on. Flowers open up in mid-morning sun and close at night. Following spring flowering, leaves remain and widen to 9 inches across until mid to late summer when they go dormant. (zones 3-8)

Twinleaf (Jeffersonia diphylla) is a clump-forming plant that typically blooms on 8 inches high leafless (naked) stalks. The stalks develop leaves and grow to 18 inches in height by the time the fruit ripens. The long-stemmed, blue-green basal leaves (to 6 inches long) are divided into two lobes, mimicking two separate leaves, hence the common name. White cup-shaped flowers (1 inch diameter) bloom singly atop rigid leafless 8 inch tall stalks. Each flower contains eight petals (USDA hardiness zones 5-7).

The last of the six spring wildflowers to bloom is Shooting star (Dodecatheon meadia). From each basal rosette of lance-shaped leaves emerge 1-4 sturdy, leafless, center flower scapes, rising to 20 inches height. Atop each scape is a flower (umbel) containing 8-20, nodding, 1 inch long flowers. Each flower has five petals that are swept-back (reflexed) with a cluster of yellow stamens, giving the flower the appearance of a shooting star plummeting to earth. Flower colors range from white to pink to light purple (zones 4-8).

These spring wildflowers inhabit rich moist woodlands soils in partial to full shade. All are associated with limestone soils. Under ideal site conditions, they often colonize or naturalize by self-seeding. Bumble bees are often seen pollinating these spring ephemerals. Bees gather the nectar and pollen produced by these and other wildflowers when early-spring food sources are scarce.

Growing Crinum Lilies

Posted by Hugh on March 1st, 2021

Crinum Lilies, aka “River lilies”, “Cape Coast lilies”, and “Creole lilies”, are native to Southeast Asia. Crinum lilies are more akin to Amaryllis (Hippeastrum) than true lilies (Lilium). Considered to be an old staple in Southern gardens, crinum lilies are seen growing around old cemeteries, old farmsteads, and in ditches (zones 7-10).

Over time long-lasting crinum may bloom and rebloom all summer long. They grow tall (40-50 inches high) and the foliage makes bold statement in many residential gardens. Crinum Lilies prefer lots of sun and soil moisture during its period of active growth. Plant in humus-rich soil that has excellent drainage. Crinum bulbs resent constantly wet ground, particularly during the winter months.

Exhibiting moderate drought tolerance, keep them adequately watered during prolonged dry spells. When starting out, make sure to plant receives plenty of water along with good soil drainage. Once flowers have bloomed, reduce the frequency of watering.

Crinum Lilies excel in the summer garden. Good light and direct sunlight are crucial for this fragrant plant. Crinum Lily should receive at least 2-4 hours of direct sunlight. Some hybrids fare well in partial shade.

If planting in pots or tubs, lift them to protect over the winter months and return outdoors when safe. Store them dormant @ 35-40 °F. When planting them in large pots and tubs, add some coarse gritty sand for drainage. Mulch heavily to blanket the ground to protect bulb(s) from cold or harsh weather.

Feed crinum lily with plant fertilizer monthly when they are blooming using a high phosphorus fertilizer like 10-10-10 or equivalent. Do not feed the plant in the fall and winter months.

Crinum Lily forms a lovely cut flower. When a flower begins to fade, prune or snap it off, and a new bud nearby will open a few days later. Remove (prune off) dying bottom leaves and excess leaves to maintain a neat plant.

Enjoy crinum lilies for decades. Bulbs are best divided over the fall and winter months. Newly divided small-sized bulbs may require 1-2 years to reach flower size. During the summer, you’ll find that it’s more difficult with the foliage present.

Shopping for crinum lilies? Visit or mail order: Plant Delights Nursery in Raleigh, NC, Jenks Farmer in Columbia SC, and Brent and Becky’s Bulbs in Gloucester, VA for a good selection of crinum lily bulbs.