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

Elephant Ears In The Garden

Posted by Hugh on May 11th, 2021

If gardeners want to add some tropical punch to the garden, elephant ears (Colocasia esculenta) and a close botanical cousin (Alocasia) are one of the first plants that I recommend (USDA hardiness zones 7b-10). Also called ornamental taro, plants take off and grow rapidly after spring planting (when all threats of freeze injury have waned). In the deep South, elephant ears are a garden fixture for 9-10 months before declining for a short winter dormancy nap.

Over the years I have grown the smaller (up to 6 feet tall) varieties in my small garden like ‘Black Magic (black matte finish), ‘Mojito’ (dark green /dark mottled patches), and ‘Tea Cups’ (cupped leaves that fill and spill water during rains).

For larger spaces Colocasia ‘Diamond Head’, ‘Black Coral’, and ‘Kona Coffee’ are striking for their dark leaf color and Colocasia ‘White Lava’ and ‘Maui Gold’ (chartreuse-gold blend) for their bright cheeriness. The largest Colocasia is C. gigantean ‘Thailand Giant’ that support leaves that grow 2-4 feet long.

Colocasia is a tender perennial that cannot survive winter months in many places. In USDA Zones outside of 7b-10, either use this tropical plant as an annual or dig up the tuber after the first frost and overwinter it in a cool dry area (possibly in dry wood shavings or peat) where the temperature does not fall below 45°F. The tuber should then be replanted again in late April. An easier method is to treat Colocasia as a container plant and move the container inside during the winter, given that you have space for such a large container.

Colocasia/Alocasia plants grow best in partial shade to partial sun. Full sun exposure, especially in warm areas, may damage these plants. They grow rapidly during the warmest days of summer. Feed plants with a slow-release fertilizer like Osmocote™ or Nutricote™ or a water soluble fertilizer like Miracle-Grow™ or Peters™. Don’t forget to irrigate –frequent watering, Plants prefer soils that drains well and does not stay soggy. In particular, Alocasia planted in very wet locations for extended periods is prone to root rot. Colocasia, on the other hand, grows best with full sun exposure and thrives in wet soil or in standing water.

Elephant ears can be grown in garden beds and in containers. Sources to buy include independent garden centers, mail order, and local nurseries.

Warning: Alocasia leaves are very poisonous plant. Keep the plant away from children and pets and call your doctor, or vet if someone or a pet ingests the plant leaves.

Mountain Laurels – A Native Shrub Many Gardeners Forget To Plant

Posted by Hugh on May 6th, 2021

Mountain laurel (Kalmia latifolia) is a U.S. native broadleaf evergreen shrub (USDA hardiness zone 5 – 7(8)). Whether you are hiking through area woodlands or driving through Biltmore Estates in Asheville, NC, flowering mountain laurels dominate the May-June landscape in Northeast Tennessee or Western North Carolina. Mature shrub sizes range from 5 feet (dwarf cultivars) to 12 feet in height and spread.

Over the past 30 years, mountain laurels have so improved, thanks to the breeding efforts of Dr. Richard Jaynes*. He has released several dozen cultivars, including dwarf forms and very colorful flowers. Some favorite varieties include ‘Carol’, ‘Sarah’, ‘Tinkerbelle’, ’Bullseye’, ‘Minuet’, and ‘Olympic Fire’.

Flowers open over a two week period beginning in mid-May here in the Southern Appalachian region (USDA hardiness zones 6 and 7). In the wild, mountain laurel tends to grow near a woodland clearing. In the garden, plant in a spot capturing partial day sunlight. Mountain laurel prospers a cool, moist, acidic (pH 6 or below preferred), compost-rich well drained soil. Established shrubs tolerate droughty soils after two years; otherwise, apply 2-3 inches of pine bark or pine needle mulch. Avoid exposure to high wintry winds.

Pruning is best performed within a few weeks after flowering is finished. Prune to shape, to limit shrub height and width, and to remove dead or diseased twigs and branches. Feeding shrubs with an acidic water soluble fertilizer such as Miracle-Gro®, Hollytone® or Schultz® spurs new growth and flowering for next spring.

Mountain laurels tend to perform more reliably than rhododendrons. They grow poorly in poorly drained soils and are susceptible to lace bug damage on the spring/summer foliage. Roots are susceptible to Phytophthora root rot. Worth repeating, mountain laurels grow best on compost–rich acidic soil

*Dr. Richard Jaynes’ book: “Kalmia: Mountain Laurel and Related Species”, 3rd ed. (Timber Press). Used copies available from Amazon Books online for under $20..

Mountain laurel (Kalmia latifolia) is a U.S. native evergreen broadleaf shrub (USDA hardiness zone 5-7 (8)). Whether you are hiking through area woodlands or driving through Biltmore Estates, flowering mountain laurels dominate the May-June natural landscape in Northeast Tennessee and Western North Carolina. Mature shrub sizes range from 5 feet (dwarf cultivars) to 12 feet in height and spread.

Over the past 30 years, mountain laurels have so improved, thanks to breeding efforts of Dr. Richard Jaynes*. He has released several dozen cultivars, including those with dwarf forms and with highly colorful flowers. Some favorite varieties include ‘Carol’, ‘Sarah’, ‘Tinkerbelle’, ’Bullseye’, ‘Minuet’, and ‘Olympic Fire’.

Flowers open over a two week period beginning in mid-May here in the Southern Appalachian region (USDA hardiness zones 6 and 7). In the wild, mountain laurel tends to grow near a woodland clearing. In the garden, plant in a spot receiving partial day sunlight. Mountain laurel prospers a cool, moist, acidic (pH 6 or below preferred), compost rich soil which is well drained. Mountain laurels tolerate droughty soils after two years in an pinebark or pine needle mulched site. Avoid exposure to high wintry winds.

Pruning is best performed within a few weeks after flowering is finished. Prune to shape, to limit shrub height and width, and to remove dead or diseased twigs and branches. Pruning and feeding with an acidic water soluble fertilizer such as Miracle-Gro®, Hollytone® or Schultz® invigorates new growth and flowering the next year.

Mountain laurels tend to perform more reliably than rhododendrons. While several plant maladies are possible, mountain laurels grow poorly in poorly drained soils and lace bug damage on the spring/summer foliage. Their roots are susceptible to Phytophthora root rot. Plants grow best on compost–rich soil

*Dr. Richard Jaynes’ book: “Kalmia: Mountain Laurel and Related Species”, 3rd ed. (Timber Press). Used copies available from Amazon Books online for under $20..

New Compact Anise Hybrid Shrubs

Posted by Hugh on May 1st, 2021

Scorpio Anise Shrub (Photo from Dr. Tom Ranney, NCSU Mountain Research Lab, Mills River, NC)

Two new hybrid anise (Illicium) shrubs have been released by the NCSU Mountain Crop Improvement Lab in Mills River, NC. These new star anise shrubs, bred by Dr. Tom Ranney, are hybrids between Illicium floridanum and I. mexicanum. These native evergreen shrubs are low-maintenance and adapt to a wide range of growing conditions (USDA hardiness zones 6b-9a – hardy in zone 6a in a protected landscape area).

These new anise hybrids grow 3 feet high x 5 feet wide in either full sun to part shade and moist, well-drained, moderately acidic @ pH 6.0 soil. Anise shrubs tolerate shady, damp, and wet sites as well.

Anise shrubs have two main bloom seasons, first in April-May and bloom sporadically in September -November. Flowers are solitary and mostly outward-facing to nodding. Individual blossoms last 5-10 days and emit a slight anise fragrance.

‘Orion’ (White) and ‘Scorpio’ (Red) Anise Shrub (photo from Dr. Tom Ranney)

The evergreen leaves are smooth (glabrous), moderately shade tolerant, and highly disease and deer resistant. These dense, well-branched shrubs exhibit lateral branches ranging between 7.5 and 18 inches in length. Green fruits, less than one inch wide, ripen greenish yellow late in the year.

‘Scorpio’ bears large 1-3 inch wide bright burgundy red flowers that bloom in spring with secondary flowering in early fall. This moderately growing shrub is compact, 3-5 feet tall and wide along with handsome evergreen foliage.

‘Orion’ bears large 1-3 inch wide yellowish-white flowers with numerous strap-shaped, radial petals, averaging 22 in number. Blooms heavily in spring and sparsely in early fall. This compact 3-5 feet tall and wide shrub has handsome evergreen foliage.

Planting A Tropical Look In Your Temperate Garden

Posted by Hugh on April 26th, 2021

This summer, whether you garden in Florida or Michigan, you can enjoy the tropical look in your garden with these 5 leafy plants, which are classified as “foliage annuals” because they are hardy in zones 10-12.

Caricature Plant (Graptophyllum pictum) in its natural tropical habitat grows 6-9 feet tall, typically 4-5 feet tall in zone 7. It is renowned for its colorful variegated foliage.

Elephant Ears (Alocasia/Colocasia), aka taro, are tropical perennial herbs with huge green or purple, heart-shaped, prominent veined leaves (zones 7b-9). Best sited in moist, organically-rich soil and adjacent to pools, ponds, and other water features. Mulch and irrigate during dry periods.

Hardy bananas (Musa basjoo) are rated hardy to northerly zone 6 and tropical Abysinian banana (Musa ensete) are winter hardy in USDA Zones 10-11. ‘Maurelii’ (red Abyssinian banana) is loved for its lush green foliage splashed with maroon-red tints and reddish leaf axils. Both grow 6-10 feet tall in temperate areas. Propagate by division.

Tapioca Plant (Manihot esculenta ‘Variegata’) is grown for its attractive palmately, 3-7 parted lobed, bright green foliage with variegated yellow midrib veins. Also called bitter cassava, this milky-sapped tropical shrub grows 6-10 feet high. Leaf lobes expand to 3-8 inches long. Small, apetalous, greenish-white flowers in short terminal panicles bloom through the summer season. (Zones 8-9). Propagate by stem cuttings.

Canna – many varieties including ‘Pretoria’ (aka ‘Bengal Tiger’) – 4-6 feet tall plant with bright orange flowers atop lush green / gold veined leaves; ‘Australia’ – huge deep red flowers atop long, burgundy-black stalks with lush chocolate brown/ silver banded foliage; ‘Tropicanna’ – tangerine flowers atop striped red, pink, yellow, gold, and green foliage. Shorter seed-produced canna varieties are also available. Deadhead old canna blooms to force reblooming.

General Care: Tropical plants are best grown in organic-rich, moist, well-drained soil in full to partial sun. Some plants tolerate part shade. Fertilize plants regularly during spring and summer. Canna bulbs are extremely heavy nutrient feeders. Site plants to protect from strong winds which can severely tatter the large leafy foliage. No serious insect or disease problems if sited and properly cared for.

Tropical plants can be grown in the ground or in containers. They are overwintered indoors for winter dormancy @cool 40°F or grown inside a heated greenhouse. Vegetative divisions or cuttings may be started in the fall.

Annuals To Plant In 2021

Posted by Hugh on April 21st, 2021

I spend spring, summer, and fall months visiting public gardens mostly in the eastern and southeast U.S. (Ohio/Pennsylvania south to Florida with camera in hand). I get ideas of new flowers to plant in my garden next year. Here are five flowering annuals that caught my attention.

Begonia ‘Canary Wing’ – this golden leaf plant along with bright red flowers lights up any shady patch in your garden. Canary Wing is a upright/mounded begonia with golden-to-chartreuse leaves and bright salmon red flowers. Leaf scorching, curling, and/or reddening of the foliage is a sign that ‘Canary Wing’ is receiving too much light.

Catharanthus (Vinca) ‘Kawaii Soiree’ bloom non-stop from spring planting to first frost in autumn. These compact growing annual vincas grow 6-10 inches tall and 12-18 inches wide and perform best in well-drained, humus-rich garden soils or in containers. Six colors in these compact growing vincas are available and more colors are coming: white, pink, coral, lavender, peppermint, red, and light purple. In general, vincas despise cool wet soils.

Gomphrena ‘Truffula™ Pink’ bloom nonstop from the first day after planting and fill their spot in the garden with a hot pink flowers until hard frost. Truffula^™ Pink performs best in hot, humid climates where it blooms all season long. Approximately 22-26 inches tall and wide, the blooms make ideal cut-flowers with a long vase life.

Henna Coleus (Plectranthus scutellarioides ‘Balcenna’) is noted for its serrated foliage. This tender perennial boasting chartreuse to copper-pink leaves complemented by dark burgundy undersides. attractively toothed, chartreuse to copper foliage. Grows 14-28 inches high.

Rockin’™ Golden Delicious (Salvia elegans) – grown for its great yellow-green (chartreuse) foliage. Grows 12-24 inches high and 15-30 inches wide. The more sun the foliage receives, the brighter the chartreuse color. Leaves may sunburn in very high light. In areas with strong sun this plant may benefit from afternoon shade. In northern areas it is valued as a foliage plant only. Red flowers arrive in late summer in zones 6 and points south. It is exceptionally heat and humidity tolerant and reliably hardy in the southeast U.S. (Zones 8-11). Golden Delicious is resistant to downy mildew resistant.

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’).