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

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

Check Out These Four Plant Select® Picks

Posted by Hugh on June 26th, 2017

Salvia ‘Furman’s Red’ in east Tennessee landscape in mid-August

If you’re search for top performing plants, especially very drought tolerant, take a look at the picks from Plant Select^®. This is a nonprofit collaboration of Colorado State University, Denver Botanic Gardens and professional horticulturists. Their mission is to seek out and distribute the very best plants for landscapes and gardens from the intermountain region to the high plains and beyond. Plants chosen for program exhibit these eight attributes:

Red Yucca (Hesperaloe) in Mount Carmel, TN

Flourish with less water
Thrive in a broad range of conditions
Habitat-friendly
Tough and resilient in challenging climates
One of a kind/unique
Resist disease & insects
Long-lasting beauty
Non-invasive

Here are four Plant Select® picks that prosper across most areas of Tennessee:

‘Furman’s Red’ Salvia (Salvia greggii ‘Furman’s Red’)

This hardy selection of a southwestern ever-blooming sage grows 18-24 inches high and wide (USDA hardiness zones 5b-10). Crimson to scarlet flowers form in repeated flushes from late spring, summer and autumn. It is deer resistant and drought tolerant; provide good soil drainage and does poorly in soggy winter soils. Wait to cut old plant back in spring.

Red Rocks® Penstemon (Penstemon x mexicali Red Rocks®)

This hybrid penstemon forms a bushy clump, 14-18 inches high and 12-14 inches wide of narrow green leaves (zones 4b-8). Short spikes of bright rose-pink trumpet flowers bloom, on and off, through most of the summer and attract butterflies and hummingbirds. Narrow, dark green leaves form an attractive mound. It sports a constant succession of bright rose flowers all summer. Red Rocks thrives in a wide range of sites and soils.

‘Standing Ovation’ Little Bluestem (Schizachyrium scoparium ‘Standing Ovation’)

This warm season ornamental grass grows 24-36 inches high and 15-18 inches wide (zones 3-8). It performs well in poor, dry soils. It holds its tight upright growing habit all 4-seasons. Spikey bluish-green leaves transition to a brilliant display of red shades, changing to deep purple from August into October. Seed heads stand upright through winter and provide winter interest and food for birds. It can be utilized in mass plantings or meadow designs.

Red yucca (Hesperaloe parviflora)

This shrub native to Mexico and Texas grows 3-4 feet tall and 1.5 to 2 feet wide (zones 5-10). Tall spikes of brilliant coral-pink, yellow-throated tubular blossoms curve skyward and attract hummingbirds from early summer to autumn. It prefers a porous loam soil and avoid frequent irrigation. Tidy up plant by pruning off brown foliage and seedheads in late winter. Deer resistant.

Ice Plants (Delosperma)

Posted by Hugh on June 23rd, 2017

Delosperma cooperi at Atlanta Botanical Garden

Delasperma

Ice plants (Delosperma spp.) are perennial evergreen succulents from South Africa. Two species are most popular in U.S. gardens starting with hardy ice plant (D. cooperi) (zones 6b – 9) and yellow ice plant (D. nubigenum) (zone 4 – 10). There are also many hybrid cultivars sold at garden centers and on-line.

North of zone 7, hardy ice plants (D. cooperi) are semi-evergreen and needs winter protection. This succulent mat-forming plant typically grows to 3 – 6 inches tall and spreads quickly to 24 or more inches in width. High gloss, bright red-purple, daisy-like flowers (up to 2 inches or 5 cm across) cover the plant from June to September. Bloom colors are iridescent. The succulent foliage is generally medium green.

Yellow ice plants (D. nubigenum) form a low mat of succulent, evergreen leaves, bearing loads of small starry yellow flowers starting in late spring. Plants grow 2 – 4 inches tall, and form a tight attractive mat. Foliage take on vibrant pinkish tint over winter.

Ice plants are best grown in dry, sharply-drained soils in full sun. Plants fail (die) in almost any kind of soil that is not adequately drained. Sandy and gravelly soils are the best. Ice plants are especially responsive in reduce reflected heat and glare when planted in areas covered with gravel mulch. Plants are exceptionally heat and drought tolerant. Feed only once annually with a very dilute fertilizer solution and water sparingly.

Ice plants are trouble free with regard to insect or disease problems. Aphids and mealybugs are occasional pests.

Garden uses: Ice plants grow well in containers or in the garden in a sunny area including rock gardens, rock walls, border fronts as edging or on slopes.

Depending on species and cultivars, plant and flower size varies; dwarf selections hug the ground. Here are four recommended selections from Plant Selects™:

Red Mountain® – large flowered blazing orange-red color and attractive growing habit (zones 4-9).

Starburst® – (D. floribundum) produces bright pink shimmering flowers with white centers (zone 5-9).

Mesa Verde® – (D. cooperi) short growing salmon-pink-flowers (zones 4-9).

Lavender Ice® – iridescent lavender blooms with dark eye; foliage turns purplish in winter (zones 4-9).

Less Invasive Butterfly Bush Identified

Posted by Hugh on June 20th, 2017

Buddleia ‘BlueChip’ at J C Raulston Arboretum, Raleigh, NC

Butterfly bush (Buddleia) is a popular garden shrub in many areas of the U.S. Buddleia invasiveness is a serious issue in the Pacific Northwest. The Oregon Dept of Agriculture, Plant Division, has approved for sale these buddleia cultivars in the state. The approved varieties produce 2% or less viable seed, meeting Oregon’s standards for sterility.

The approved list includes: ‘Blue Chip’, ‘Asian Moon’, ‘Purple Haze’, ‘Flutterby Grande Blueberry Cobbler’, ‘Flutterby Grande Peach Cobbler’, ‘Flutterby Pink’, ‘Flutterby Petite Snow White’, ”Flutterby Grande Sweet Marmalade’, ‘Flutterby Grande Tangerine Dream’, and ‘Flutterby Grande Vanilla’. Add to the list the cultivars ‘Miss Molly’ and ‘Miss Ruby’ as personal non-invasive favorites.

Butterfly bush should be planted in full sun for sturdy stems and high floral count. Cultivars vary in size, some tall ones are placed in the rear bed, and dwarf cultivars in the front of the planting border. Flowers are sweetly fragrant upclose. Shrubs are drought tolerant once established and are tolerant of urban pollution.

New sterile hybrids are hardy to zone 5-9. They grow in average well-drained garden soil with pH range between 5.5 to 7.5. Keep plants well mulched in summer and add additional amounts in late fall for winter protection in northern areas. Shrubs are light constant feeders; choices include slow release fertilizers like Osmocote® and Nutrikote®, or monthly liquid feeding of Miracle-Gro™, Daniels™ or Espoma®.

Butterfly bushs require little pruning, but large flowering types weigh down the branches. Cut back plants to the ground in early spring as flowers are borne on new growth (wood). Pests seem to be problematic when shrub(s) are stressed out because of a poor garden site. Spider mite feedings appear to be most severe during extremely hot dry summers.

Summer Lawn Care Tips

Posted by Hugh on June 17th, 2017

Properly mowed lawn

“Summertime and the living is easy”. That’s a good adage to follow for home lawn care as well. Most lawn care chores, such as fertilizing, seeding, thatch management, and weed cleanup, should be delayed until late August through early October in most locales (USDA zones 4-7). During the heat of summer, proper mowing and irrigation are the only work necessary. Key to success is to raise the mowing height over the summer months.

Follow the one third rule. Remove no more than one-third of the grass height when mowing. Wait a few days to mow the lawn again. Scalping (close cutting) often results in a weak and weed infested lawn. If you miss a few scheduled mowings, don’t try to do it all at one time. Gradually reduce height of cut over several mowings. Don’t pick up the clippings as they contain nutrients that can be recycled as they decompose. Raked up clippings may be added them to the compost pile.

During the summer, mow cool season lawn grasses, such as Kentucky bluegrass, perennial ryegrass, and fine fescue, at heights around three inches or slightly higher. When in doubt, set the mower as high as it will go. Lawns maintained at higher heights usually develop deeper roots and dry out slower than closely mowed turf. Mulching mowers are a good investment as they are engineered to lift clippings and strike them several times before they are returned to the turf.

Cool-season lawn grasses naturally slow down and go dormant in the heat of summer. If you must irrigate, water lawns deeply at one time @ 1 to 1 1/2 inches per week. Water early in the day if at all possible. During periods of high stress, dormant lawns need only 1/4 to 1/2 inch of water every 2 to 3 weeks to keep root and crown tissue alive. Keep foot and vehicle traffic to a minimum if visible signs of drought are obvious.