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

Pineapple Lilies For Summer Garden

Posted by Hugh on July 25th, 2017

Eucomis comosa ‘Oakhurst’

E. comosa ‘Sparkling Burgundy’

Pineapple lilies (Eucomis spp.) are native of South Africa and are easy to grow (USDA hardiness zones 7-10). Several hybrid cultivars are winter hardy in zone 6 if provide a protective layer of mulch or loose leafy compost.

Plants have basal rosette of strap-like, wavy-edged, purple-spotted, dark green leaves which spread upward and outward to 24 inches. Leaf color varies with the cultivar. Emerging from each rosette is a thick purple-spotted flower stalk to 36 inches in height in mid to late summer bearing masses of tiny, starry, greenish-white flowers, also cultivars with dusky purple shades. Their unique flowers are crowned by a tuft of greenish leaf-like bracts.

Grow pineapple lilies in containers or in a garden bed with flowering perennials and annuals. Plant bulbs 6 inches deep in fertile, well-drained garden soil and in full sun. Shade will reduce flowering and bloom stalks are weak and require staking. Space plants 18-36 inches apart depending on the vigor and size of the cultivar. Pineapple lilies perform best if dry during winter dormancy.

In spring or at planting, apply a granular 10-10-10 or equivalent fertilizer or a slow release product such as Osmocote® or Nutrikote®. Keep plants well-watered during their first growing season for optimum flowering.

Plant in a wide container in loose porous soil-less media. Space bulbs 5-6 inches apart for a striking display. Place the top of the bulb is just below soil surface. Keep well-watered during the growing season (April to early October) and feed with a water soluble fertilizer such as Miracle-Gro®, Peters®, or Schultz®.

In colder regions pineapple lilies are ideally grown in containers and over-wintered indoors. Set in a freeze-free place and allow soil to dry out and bulbs to go dormant. Remove withered dead foliage. Begin watering again in late March or April.

Leading Cultivars:

‘Sparkling Burgundy’ – dark burgundy spring foliage that gradually turns olive green, and its burgundy color returns in early fall; smoky pink florets stand on 20- to 30-inch floral stalks crowned by tufts of purple bracts (zone 6b – 10).

‘Oakhurst’ – narrow leaves start off green and gradually develop an intense burgundy-red color; 18- inch tall smoky red floral stalks open pink with tufted top (zone 7 – 11).

Distyliums Substitute For Cherry Laurels and Hollies

Posted by Hugh on July 22nd, 2017

Distylium ‘Cinnamon Girl’

‘Emerald Cascade’ distylium

Distyliums (Distylium x), aka Isu tree, are being billed as “the best new plants you’ve never heard of”. Get accustomed to seeing these boxwood-like shrubs in local garden centers, e.g., if you live within USDA hardiness zones 6b-9. Distyliums are the result of selective breeding efforts to improve an evergreen shrub native to China at elevations above 3000 feet.

Hybrid distyliums are heat and drought tolerant and cope with wet soils. Their foliage is highly disease and insect resistant. They are an excellent replacements for those evergreen shrubs susceptible to one or more disease and pest problems. Examples include euonymus (Euonymus fortunei), cherry laurels (Prunus laurocerasus), junipers (Juniperus spp.), hollies (Ilex spp.), and Indian hawthorn (Rhaphiolepis spp.).

Distyliums perform best in full to partial sunlight and in moist well-drained soil. Shrubs thrives in moist, well-drained, slightly acidic soil; do not plant on poorly drained site. Keep plants mulched for a mostly weed-free planting and to conserve soil moisture. Feed with a slow release fertilizer such as Osmocote® or Nutrikote® at the start of spring. Prune after flowering to size and shape shrub.

These five cultivars are all hybrids (D. myricoides × D. racemosum):

Vintage Jade® grows in an arching mounding form low and spreading at 2-3 feet high and 5 feet wide, ideal low hedges and borders along walkways or paths.

Cinnamon Girl® has bronze foliage at 3 feet tall and 5 feet width. plum-purple new growth which turns blue-green as the leaves and mature to blue green.

Blue Cascade® grows slightly upright at 3 feet high and 4 feet wide with dusty bluish cast to the foliage.

Emerald Heights® has dark green glossy foliage and slightly upright form at 5 feet high and wide.

Coppertone® 3-4 feet evergreen shrub with a rounded to spreading habit. New leaves are coppery red mature to blue green.

Distyliums belong to the witchhazel family (Hamamelidaceae). Small, reddish maroon flowers bloom in March and go pretty much without notice. They make wonderful foundation, screening and hedging shrubs in almost any landscape. Add them to mixed plantings in large containers.

Four Top Rated Coreopsis You Should Know About

Posted by Hugh on July 19th, 2017

Coreopsis ‘Gold Standard’ (photo by MT Cuba Center)

Coreopsis ‘Last Dance’ (Photo by MT Cuba Center)

Coreopsis (Coreopsis spp.) are flowering perennials (and annuals) native to the eastern U.S. In 2016, MT Cuba Center* in Greenville, Delaware reported on the overall garden performance of 13 species and related cultivars and hybrids in the Mid-Atlantic region. Over a period of 3 years, the MT Cuba staff evaluated habit, floral display, disease resistance, and longevity. Several popular cultivars performed poorly because of disease susceptibility and winter survivability.

Four underutilized native species and cultivars earned outstanding performance ratings. All four also displayed excellent resistance to powdery mildew, downy mildew, and leaf spot diseases.

‘Summer Sunshine’ coreopsis (C. palustris ‘Summer Sunshine’) is the highest-rated coreopsis in the 3-year trial. Vigorous mounds of foliage grow to 30 inches tall and remain lush, sturdy, and dense all season long. In late September plants are covered with golden yellow flowers with dark central cones. The amazing display lasts for six weeks, and provided an important late-season food source for pollinators. ‘Summer Sunshine’ is a rhizomatous selection that slowly increases in size by 2.5 feet over three years.

Coreopsis ‘Flower Tower’ (photo by Mt Cuba Center

‘Flower Tower’ coreopsis (C. tripteris ‘Flower Tower’) appropriately named, towers over the competition at an astonishing 8 feet tall. Stems are thick and sturdy and capable of staying vertical in even the strongest winds. It is the tallest coreopsis in the trial, and also has the largest flowers, measuring 2½ inches across. ‘Flower Tower’ is perfect for large-scale landscapes, perhaps not in average sized gardens. This rhizomatous selection spreads very slowly, about 2 feet over three years.

‘Gold Standard’ coreopsis (C. tripteris ‘Gold Standard’) is another superior selection that typically grow to 7 feet tall, with a floppy habit and uninspiring floral display. ‘Gold Standard’ is a slightly shorter (5½ feet tall) and has incredibly sturdy stems. By late July, a multitude of sunshine yellow flowers appear above the robust foliage in mid-August and the floral display lasts over two months. ‘Gold Standard’ has a rhizomatous habit and spreads slowly (about 2 feet over 3 years).

‘Last Dance’ coreopsis (C. integrifolia ‘Last Dance’) is a fall-blooming tickseed whose uniformly compact habit is a vast improvement over other versions of C. integrifolia. ‘Last Dance’ is slow to emerge in the spring. It often does not reach 1 feet tall until June, and eventually tops out at only 2 feet tall. The 2 inch, extra-large, golden flowers have strongly pleated petals which make them look thick and substantial. ‘Last Dance’ is the last tickseed to flower, blooming throughout October. ‘Last Dance’ spreads via rhizomes at a rate of about 12 inches per year.

*Blog readers are encouraged to read the entire Coreopsis Report on the Mt Cuba website.

Don’t Totally Dislike All Box Elder Trees

Posted by Hugh on July 16th, 2017

Foliage of ‘Kelly’s Gold’

A. negundo ‘Falmingo’

Box elder (Acer negundo) is a native fast-growing and suckering medium-sized tree (USDA hardiness zones 4b-8). Branches are weak wooded and easily damaged in wind and ice storms. Box elder grows almost anywhere in any average soil, medium to wet, and in full sun. The species fails on a shady site. This weedy maple is tolerant of drought and flooding, perfect choice in fence rows, abandoned fields, and in vacant urban lots.

A mature tree typically grows 30-50 feet tall with an irregular rounded crown. Flowers and leaves emerge from mid-April to late May, depending on region of the country. Dioecious trees, either male or female, bear yellow-green wind-pollinated flowers in mid-spring. Compound foliage comprised of 3-5 leaflets. Non-showy flowers appear in pendant clusters in spring on separate male and female trees. In late summer winged nutlets (samaras) ripen on female trees and often hang on well into winter. Seedlings will likely become a nuisance weed in gardens. Fall color is often a blah yellow but in some years may surprise.

Box elder is a high maintenance tree. The tree is plagued by boxelder bugs, which do not harm the tree but can be a serious nuisance pest to homeowners as bugs invade houses in fall and winter months. Tree is also susceptible to aphids and borers. Anthracnose, powdery mildew and canker are occasional disease problems. Planting it in some cities is illegal. There are lots of better trees to choose from.

Cultivars have been developed with variegated or colorful foliage, improved plant habit, and better fall color. These 5 cultivars are mostly available from on-line nurseries:

‘Flamingo’ – 30-35 feet tall, variegated leaves (light green, with white and pink), a male clone (seedless).

‘Kelly’s Gold’ – 15-20 feet tall, bright yellow new growth, a male clone (seedless).

‘Sensation’ – 30 feet by 25 feet tree, reddish foliage in fall, a male clone (seedless).

‘Variegatum’ – 40 by 25 feet tree, variegated leaves (white margins), a female clone.

‘Aureomarginatum’-small 30 foot tree with dark green/white variegated foliage, female clone.

Thistle-like Bear’s Breeches

Posted by Hugh on July 13th, 2017

Acanthis spinosa at Kingwood Center, Mansfield, Ohio

Archiecturally beautiful flowers

Spiny bear’s breeches (Acanthus spinosa) is a clump-forming perennial treasured for its attractive thistle-like foliage and architecturally bold flower spikes (USDA hardiness zones 5b-9). Plant requires little maintenance and is long-lived. Deeply-cut, arching, glossy green, spiny, thistle-like leaves attain 2-3 feet in length on older plants and remain attractive through the growing season. Leaves bear mostly hidden spines on the tip of leaf lobes.

In late June through July (in zone 7), wands of hood-bracted flowers stand upwards of 2 feet above the dark green foliage mound. White-lipped blossoms expose purple (mauve) calyces. Foxglove–like flowers vary from white, pink or purple and attract lots of bees.

Good soil drainage is absolutely essential. Bear’s breeches is easily grown in average medium soil in full sun to part shade. The plant lingers or fails on poorly drained sites. In richly organic soil, plant mounds may reach 3-4 feet tall and wide. Plants tolerate considerable shade, but at the expense of flower numbers.

Foliage needs some afternoon shade in southern U.S. hot summers (zone 7-9). Over the years bear’s breeches will aggressively spread by underground rhizomes. Additional seedlings may pop up from the mother plant. In the early years it establishes slowly in the garden. Older clumps may be difficult to eradicate; new shoots can sprout if a small section of root is left behind.

Bear’s breeches has no serious insect or disease problems. In wet summers snails and slugs cause considerable damage to the foliage if left unchecked. The showy flowers are long lasting in cut floral arrangements. Be wary that each flower harbors a tiny sharp spine. Deer and rabbits generally stay away from this spiny plant.

Bear’s breeches (A. mollis), also indigenous to Southern Europe, bears softer spines, and is not as cold hardy as its spinier cousin (A. spinosus). Protect A. mollis from afternoon sun.

Best of MT Cuba Center 2017 Monarda Study*

Posted by Hugh on July 10th, 2017

Monarda ‘Jacob Cline’

M. didyma ‘Violet Queen’

Monarda, commonly known as bee balm or wild bergamot, is a popular summer flowering perennial. Their large, brightly colored flower clusters brighten the season. Flowers attract many types of wildlife, including hummingbirds, bees, butterflies, moths, and seed-eating birds. Unfortunately, many cultivars are susceptible to powdery mildew disease which causes defoliation and plant loss.

Over the past three years, MT Cuba Center in Greenville, DE evaluated the performance of 40 selections of bee balm. Staff assessed their overall garden performance in the mid-Atlantic region. Particular attention was given to plant habit, powdery mildew resistance, leaf retention, and flower coverage. There found no perfect bee balms. However, several cultivars are worth mentioning.

Monarda fistulosa ‘Claire Grace’ ranked high in the trial due to its sturdy, upright habit and prolific floral display. Compared to species, ‘Claire Grace’ has a sturdier habit, darker purple flowers, better resistance to powdery mildew, and more attractive, glossy green foliage.

Monarda ‘Dark Ponticum’ stood out in the trial for its incredibly healthy-looking foliage. The dark, bluish green leaves give the plant a very lush and attractive appearance throughout the entire season. Powdery mildew can occur but does not affect foliage health of the foliage. Violet-purple flowers attract lots of bees.

Monarda ‘Violet Queen’ is a prolific bloomer and a bee favorite. Flower color is similar, though slightly lighter than ‘Dark Ponticum’. ‘Violet Queen’ has short, silvery leaf hairs which give the leaves a dull green appearance comparable to M. fistulosa.

Monarda ‘AChall’ (Grand Marshall™) has gorgeous, deep red-purple flowers, a compact habit (28 inches tall), and excellent powdery mildew resistance. Growth habit is very uniform and plant spreads slowly.

Monarda ‘Judith’s Fancy Fuchsia’, ‘Colrain Red’, and ‘Raspberry Wine’ are all very similar in habit, flower color, and performance. Of the three, ‘Judith’s Fancy Fuchsia’ displays better disease resistance. Plants bloom 44 – 48 inch tall with abundant large, purplish red flowers in early July. Floral production is identical among all 3 cultivars, each producing 80% flower coverage at peak bloom.

Monarda ‘Purple Rooster’ has the darkest, truest purple flowers of any cultivar in the trial. Its upright, rigid stems create a strongly vertical aesthetic while the dull green leaves are highly mildew resistant and have a rough, sand-papery texture, not glossy as other beebalms.

Monarda ‘On Parade’ performs similar to the trio of purplish-red cultivars, ‘Judith’s Fancy Fuchsia’, ‘Colrain Red’, and ‘Rapsberry Wine’. All grow to about 4 feet tall with fair mildew resistance. ‘On Parade’ stands out for its brilliant, orchid purple flowers.

Monarda ‘Gardenview Scarlet’ (didyma type) is the only true red-flowering cultivar with consistent powdery mildew resistance. It has large, 4 inch wide flowers that attract lots of hummingbirds. Cultivar is similar to ‘Jacob Cline’, except it grows only 36 inches tall, almost 1 foot shorter.

Runner-up popular favorites:

‘Prairie Gypsy’

‘Jacob Cline’

‘Purple Mildew Resistant’

‘Cambridge Purple’

‘Peter’s Purple’

‘Pink Surprise’

*I encourage blog readers to read the entire Monarda Trial Report on the MT. Cuba Gardens website.

Causes of Sudden Leaf Scorch

Posted by Hugh on July 7th, 2017

Leaf scorch on full moon maple

Scorched sugar maple leaves

Leaf scorch or foliage burn is caused primarily by environmental stress factors such as drying winds, drought, mechanical root injury, and winter injury . Natural pathogens, such as viruses, fungi, or bacteria, can be secondary causes. Spraying the wrong pesticide or accidentally allowing spray to drift onto a nearby susceptible landscape plant can result in chemical foliar burn. Applying too much fertilizer may also injure roots and mimic drought- like symptoms.

If sun intensity gets too strong, leaves may turn brown, typically along the edges, or take on a bleached out appearance. Shallow-rooted trees like Japanese maples (Acer palmatum) are often troubled by leaf scorch. Drying winter winds may cause leaf burn on conifers if soils are frozen. Too much sunlight and lack of adequate soil moisture will result in brown-edged leaves or leaf tips.

Leaf scorch symptoms commonly show up on edges of leaf, leaf tips and/or between the veins. Yellowing becomes increasingly severe and tissue dies at leaf margins and between veins. Sudden changes in summer light intensity, such as from a loss of an adjacent large branch or an entire shade tree, may scorch the foliage of low-growing (understory) shrubs and small tree in spring and summer.

Deep watering of soil will enhance moisture uptake. Too much water, such as periodic flooding, can also be injurious. Do not fertilize most trees, shrubs and perennials after September 1^st. It stimulates shoot growth.at a time that plants should be going dormant. Leaf scorch symptoms may result.

If tree roots have been injured, prune off top growth to compensate for loss of roots. Stressed trees and shrubs should be mulched with an organic-based mulch to help conserve soil moisture.

Ground Cover Types Of Flowering Abelias

Posted by Hugh on July 4th, 2017

Abelia grandiflora ‘Confetti’ at UT Gardens, Knoxville, TN

Abelia Kaleidoscope’ (note aberrant shoots)

Flowering abelias (Abelia x grandiflora) come in all shapes and sizes (USDA hardiness zones 6-9). Over the past decade the ground cover types have become very popular. They’re also utilized as accent plants in large containers. In zones 7 -8, they are evergreen.

The term “ground cover” is used here to emphasize cultivars that grow low, mostly wider spreading than tall. From late spring to early fall, almost four months, white tubular flowers (pink in bud) are in bloom. Flowers attract a wonderful assortment of bees and butterflies to any landscape.

Abelias grow in average, well drained soil and in full to partial sunlight (6-hours minimum) for best flower numbers and leaf color expression. Plants are exceptionally heat and drought tolerant after 1st year. Feed 1-2 handfuls of 10-10-10 or equivalent granular fertilizer per plant in late winter or in spring. Mulching plants is recommended. Pruning is not a big chore. Remove unwanted and dead branches at any time and cut back aberrant leaders (suckers) to maintain uniform plant height.

Flower abelias have demonstrated very good resistance to drought, diseases and insects. Deer generally don’t bother them, but will eat them in a pinch.

Leading Variegated Leaf Forms:

‘Kaleidoscope’ is currently the most popular in the ground cover category. It grows 2 to 3 feet tall and 3 to 4 feet spreading. In the spring its new variegated foliage is vibrant green in the center and creamy yellow along the edges. Summer foliage is very golden-yellow and does not burn in the summer heat. In the fall foliage becomes a colorful blend of red, orange, green, and yellow.

‘Confetti’– offers finely textured medium green, variegated creamy white and pink foliage. Pale pink tubular flowers appear in summer into fall. This rounded, semi-evergreen shrub grows about 3 feet tall and 4 feet wide.

‘Mardi Gras’ – white to pale lavender flowers with pink tinge; dark green with creamy white edge that turns dark pink to red in fall; Leaves are mostly white, green centers, and edged in salmon-pink. Foliage takes on a golden tint in winter. Shrub grows to only 2.5 to 3 feet tall and 3-4 feet in spread.

‘Silver Anniversary’ – grows 3 feet tall and 3-4 feet in spread. It has highly glossy, creamy white-variegated grayish green leaves which develops an outstanding burgundy color in fall.

Agaves Like It Hot, Dry and Sunny

Posted by Hugh on July 1st, 2017

Agaves in Burbank, CA

Variegated agave in sidewalk planting in Burbank, CA

Agaves (Agave spp.) are long-leaved succulent landscape plants. These native perennial succulents grow in desert-like environments (USDA hardiness zones 8 and warmer). Plants grow in a rosette form with long their fleshy leaves frequently tipped with one or more sharp spines and a prominent bloom spike with cup shaped flowers. Most are native to the Southwest U.S. and Mexico.

Agaves are exceptionally drought tolerant and ideal for xeric gardens. Temperature hardiness, sunlight, and soil drainage are the three key components to successfully growing agaves. Agave have a large tap root and do not transplant well, so carefully select an appropriate site where to plant. The majority of the roots are surface roots and do not require a deep hole if planted when young.

Porous, well-drained soil is an absolute must! When planting in clay soils, deeply amend bed or container soil with coarse sand or pea gravel in a 50:50 ratio. Water the plant diligently the first week after planting and gradually wean it back to 2-3 times monthly in containers, all depending on season of the year and outdoor air temps.

Never overwater agaves! They are famous for their low water use. In early spring apply a slow release fertilizer such as Osmocote™ or Nutrikote™. This should supply nutrient needs for the entire year.

Most agaves naturally dieback after blooming. They form new plants (“pups” or offshoots) at the base of the “mother” plant. Many gardeners opt to remove the spent floral spike with long handle lopper pruners to avoid their sharp spines. Agaves should be re-potted every year, usually in the spring in new media. Prune off old lower leaves if they detract from the plant’s beauty.

Non-hardy types are moved indoors or in an unheated garage where temps drop below 37°F and grown in an east facing window. Over the winter months reduce frequency of watering intervals and do not fertilize.

Agaves are deer-resistant. The tall bloom stalks attract hummingbirds.

Agave parryi var.

Four popular agaves:

Century plant (Agave americana) – a lovely flower (inflorescence) and leaves have a white stripe running along the center.

Parry’s or Mescal agave (Agave parryi) – an attractive slow growing compact form that measures 2-3 feet across. Leaves are grey green tipped with a spine (zone 7 hardy).

Ocahui Century Plant (Agave ocahui ) (zone 7b -10) – this 2-3 feet wide ball-shaped agave has attractive rigid dark green leaf blades with attractive red margins and sharp flexible spines. Bloom spike will eventually reach nearly 15 feet tall with yellow-green flowers.

Black spine agave (Agave macroacantha) – a medium sized rosette form and 1 ½ feet long thick grey green leaves, each tipped with a 1-inch long sharp black spine. Small grey and red flowers form on sturdy 7-10 feet high stems.

Firebush Is One Tough Texas Flowering Plant

Posted by Hugh on June 28th, 2017

‘Lime Sizzler’ firebush

Hamelia patens (photo from Texas Ag Extension website)

Firebush. aka scarlet bush (Hamelia patens), is indigenous from Mexico to Central America (USDA hardiness 10-11). Treat it as a tempermental perennial in zone 9, and an annual everywhere else it is not hardy. This fast growing plant blooms through most of summer into fall with showy clusters of tubular red buds and flowers. Firebush thrives in Texas heat from July to September where it finishes as a 4- to 5-foot mound. In the Tropical South, established plants may grow 10 to 12 feet high.

Once established, Firebush is highly drought tolerant and thrives in any average soil that is drains well. Full sunlight is preferable; shoots grow off weak and spindly in 1/2 day shade with reduced flowering. Leaves appear in whorls of between 3 and 7 at the nodes of the stems, and are about 6 inches long and lightly haired. Firebush leaves vary by species, individual plants, and seasonal growing conditions locally. Most often leaves are light to dark green but sometimes purplish or red depending on cultivar. In fall foliage often turns bright red.

Firebush is also called “hummingbird bush” because hummingbirds are attracted to its tubular red flowers. Flowers are in cymes; the terminal and axillary inflorescences are widely forked and showy. Flower buds last longer than the actual flowers themselves. These inflorescences are 2 to 4 inches long and almost as wide. Flower buds emerge yellow, becoming orange. Occasional shearing keeps plants in a nearly perpetual state of bloom.

New in the Southern Living Plant Collection in 2017 is Lime Sizzler™ Firebush which features green and yellow variegated foliage with sizzling red-orange flowers from late spring through fall. Performs well in the landscape or in a container. The cultivar ‘Firefly’ has leaves and flowers about half normal size.

Aphids can be a nuisance on new spring leaves. Caterpillars, lubber grasshoppers, scales, mealybugs and mites may cause damage. Firebush demands little special care after its first year in the garden Irrigate periodically during first year. Lightly shear the plant a couple of times during the growing season to promote the heaviest flowering