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

‘Tamukeyama’ Japanese Maple One Of The Best

Posted by Hugh on September 4th, 2014

Acer palmatum ‘Tamukeyama’ In Early Summer

Tamukeyama Japanese maple (Acer palmatum ‘Tamukeyama’) is a long-lived botanical treasure (USDA hardiness zones 5-8). Tamukeyama is a short 6-8 feet tall multi-stemmed deciduous tree. It grows slightly taller and its foliage tolerates hot summer sun better than ‘Crimson Queen’.

Tamukeyama grows best in full sun to partial shade. It prefers moist well-drained soil and shouldn’t be allowed to dry out. It is not particular as to soil pH, but performs best in compost-rich soil. Don’t plant on a hot dry site and protect from strong winds.

Its lovely cascading branches spread 12 or more feet wide. The finely dissected palmate leaves are 2-4 inches with 5 to 7, sometimes 9 lobes or points. Foliage color changes with the season and may scorch in southerly climes in full sun (zones 7b -8). In mid-spring small reddish-purple flowers open. Pairs of winged samaras ripen in September-October.

In the spring deeply-cut fine palmate leaves emerge crimson red, loses much of its deep burgundy color over the summer, and finishes bright red in mid-fall. Its gray (with reddish tints) bark and thin wiry cascading branches are impressive winter features.

When properly sited, Tamukeyama is rarely troubled by diseases or pests. Stem cankers and leaf spots are problems when soils are arid in a summer drought. Verticillium wilt may also occur on poor sites. In most springs Tamukeyama tends to avoid frost problems by leafing out 7-10 days later than many other cultivars.

If you worry about growing Japanese maples, Tamukeyama is a good reliable cultivar to select. It is very low maintenance. Summer is the best season to prune Japanese maples to prevent bleeding sap, a common malady observed in trees pruned in late winter or early spring.

Reawaken Your Garden This Fall

Posted by Hugh on August 21st, 2014

Fall flowering colchicum at Kingwood Center, Mansfield, Ohio

In many areas of the U.S., Labor Day traditionally signals return to school, the start of the football season, and an end to gardening for the year. Mother Nature surely did not schedule it this way.
Here are ten plants (plus an extra) that are blooming in late August thru the coming weeks:

Stonecrops or Sedums (Sedum x spectabile) – ‘Autumn Joy’, ‘Matrona’, ‘Autumn Fire’, ‘Brilliant’, many others.

Goldenrod (Solidago spp.) – S. rugosa ‘Fireworks’, S. sphacelata ‘Golden Fleece’, others.

Toadlilies (Tricyrtis spp.) – catching on with shade gardeners searching for fall bloom.

Fall anemones (Anemone x hybrida) – favorites include ‘Honorine Jolbert’, ‘Queen Charlotte’, ‘September Charm’.

Fall mums (Dendranthemum x grandiflorum) – select old-fashioned perennial types such as ‘Ryan Gainey’, ‘Clara Curtis’, ‘Sheffield Pink’.

Fall sunflowers (Helianthus spp.) – plants grow tall (4 to 7 feet) covered with showy yellow flowers.

Fall blooming asters (Symphyotrichum spp.)- ‘October Skies’, ‘Raydon’s Favorite’, ‘Purple Dome’ are three of the best to try.

Encore azaleas: ‘Autumn Ruby’, ‘Autumn Amethyst’, ‘Autumn Lilac’, and another 16 cultivars are hardy in zone 6. A number of the new Bloomathon™ azalea series are also zone 6 hardy.

Brassicas include the flowering cabbages and kales. For best results, plant mid-August and net plants to fend off cabbage butterflies. You may also spray weekly with Dipel® biological insecticide.

Collection of Flowering Kale at Dallas Arboretum in Winter 2013

Flowering Kale Collection at Dallas Arboretum in winter 2013

Pansies and violas– autumn is a revival for these cool-loving bedding plants. Change out those tired summer annuals with fresh pansies and violas. Pansies are actually violas. Viola blooms are petite and a rave with gardeners these days. Yes, you need to purchase more violas to fill the garden space. Violas bloom more in frigid January and February than pansies. Maximize winter bloom by completing planting before October 1 in zone 5 and before October 15 in zone 6.

Autumn crocus and colchicum are two bulbs that are planted in the cool fall (by late September in zone 5 and mid-October in zone 6). They will bloom next fall and many years thereafter.

Start A New Fescue Lawn In The Fall

Posted by Hugh on August 18th, 2014

Sodding Is An Option

Likely, summer heat and drought have taken their toll on your home lawn. Late summer and fall are opportune times to start a new home lawn. Rainfall is usually plentiful and cooler day-night temperatures should spur a rapid grass recovery.

If your home lawn is mostly weeds, including unwanted bermuda grass, think about starting over. First, you should kill off all existing vegetation without injuring nearby trees and shrubs. Herbicides containing glyphosate (Roundup™ is a popular brand) should be applied with a second follow-up application 2-3 weeks later.

You should test your soil at the local county Extension office to accurate amounts of lime and fertilizer to add. General recommendation: Apply granular fertilizer such as 10-10-10 or equivalent @ 20 -25 lbs per 1000 sq. ft. of ground. You can substitute 19-19-19 @ 10-12 lbs. per 1000 square ft. Rototill the fertilizer into the top 6 to 8 inches of soil and rake the ground smooth.

In USDA hardiness zones 4-7, cool season grasses such as tall fescue, ryegrass, and bluegrass are the preferred lawn grasses. Red or chewings fescue are best for cool shady areas. Bermuda, centipede, zoysia, or St. Augustine grasses are sprigged in late spring thru summer in warm climes (zones 7-10). See package directions for proper seeding rate in your area of the country.

Gently rake the seeds into the top quarter inch of soil and cover with 1-2 bales of straw (not hay). Keep the soil surface moist until seeds have germinated. If you have laid sod, spritz (lightly irrigate) daily until the sod has rooted into the soil, usually within 2-3 weeks.

Fertilize your lawn with a high nitrogen-based fertilizer that also contains lesser amounts of phosphorus (P) and potassium (K). The application rate is written on the bag directions. Fertilizing will not injure young seedlings or newly laid sod. Cool weather and adequate natural rainfall (or irrigation) adds to success.

Depending where you live, mid- to late- October is the deadline to seed a new lawn.

Avoiding Crape Myrtle Hardiness Problems

Posted by Hugh on August 15th, 2014

‘Acoma’ crapemyrtle on a street in Charlotte, NC

Late summer (September 1st) is your deadline to plant crape myrtles (Lagerstroemia spp.) in USDA hardiness zone 6. Your primary objective should be to grow deep plant roots. Crape myrtles are classified as perennials in northerly areas of zone 6. In many years their woody branches die back after a cruel cold winter. The hardy rootsystem recovers and the shrub will bloom later in thee summer.

Fall planting, particularly in northerly U.S. areas (zone 6 and cold zone 7), is often a mistake. Plant in full sun, in well-drained slightly acidic soil, and add 2-3 inches of an organic mulch. Crapemyrtles grow vigorously and flower best where summers are warm; they bloom poorly where summer temperatures are cool or where full day sunlight is lacking.

Purchase hybrid crape myrtles introduced by the U.S. National Arboretum (USNA). Most cultivars are hybrids of L. indica and L. fauriei . USNA cultivars are named after Indian tribes. Those with L. fauriei bloodline are hardier than L. indica alone.

In northerly areas avoid excessive watering, pruning, and fertilizing in the fall; these practices force new growth that does not adequately harden off and likely will be injured over winter. Two-year established crapemyrtles survive harsh winters better than first year plants because of their thicker trunk diameter and lesser tendency to grow luxuriantly in late summer.

Never fertilize newly planted crape myrtles in late summer or fall. In early spring apply a slow release fertilizer such as Osmocote™ or Nutricote™ to all crape myrtles, newly planted or not, according to recommended package directions.

In the fall garden centers sell crape myrtles at hugely discounted prices to reduce inventories. Consider Labor Day as the cutoff planting date for planting crapemyrtles.

The Giant Or Jumbo Class Of Hostas

Posted by Hugh on August 10th, 2014

Row of ‘Sum and Substance’ Hosta at Chicago Botanical Gardens

The “Giant” class of hostas is aptly named. Cultivars in this class are novelties. Their enormous leaves and plant sizes (height and spread) definitely will make a bold statement in any garden.

To attain their glorious best in plant majesty and leaf size, each cultivar must have a compost-rich, moist, well-drained soil with pH between 5.5 and 7.5. Moderate shade to dappled sunlight is the rule. Morning sun (where tolerable) may help to intensify the leaf color(s) of some. Intense afternoon sun is usually harmful, particularly on powdery blue leaf types. Clumps should be regularly fertilized and irrigated according to soil moisture needs. Five of the most popular cultivars are listed below:

Sum and Substance- 3 feet tall and 6 feet wide
Komodo Dragon- 2 1/2 feet tall and 7 feet wide
Empress Wu- 4 feet tall and 7 feet wide
Titanic- 2 1/2 feet tall and 6 feet wide
Blue Mammoth- 3 feet tall and 5 feet wide

‘Sum and Substance’… struts glossy heavily-textured green-gold leaves; near-white lilac flowers stand 6 or more inches above the foliage in late July. Foliage turns brighter gold in full morning sun in USDA hardiness zone 6. (2004 Hosta of the Year).

‘Komoda Dragon’…forms a mound of dark green, heavily rippled leaves. Four feet tall floral scapes of lavender arise in midsummer.

‘Empress Wu’…this hybrid of ‘Big John’ features heavy-textured, quilted, heart-shaped leaves that are topped by lavender flowers in mid-summer.

‘Titanic’…displays thick, glossy, prominently veined, green-centered leaves edged by a wide chartreuse margin. Lavender flowers appear from late July into early August. It is a sport of H. ‘Sum and Substance’.

‘Blue Mammoth’…features very large chalky-blue leaves that are heavily quilted and proven slug resistance. White flowers emerge in July.

These hosta giants standout as nice single specimen by themselves or plantd behind smaller growing shade-loving plants in your garden.

Four Old Fashioned Hostas Continue To Delight

Posted by Hugh on August 4th, 2014

‘Krossa regal’ (blue-green) & ‘Piedmont Gold’ hostas at Kingwood Center, Mansfield, Ohio

'Sieboldii Elegans' hosta at Indianapolis Museum of Art gardens in Indianapolis, IN

‘Sieboldii Elegans’ hosta at Fine Art Museum gardens in Indianapolis, IN

During my annual summer travel to public gardens around the U.S., several clumps of old-timey hostas that were popular in the 1960’s and ’70’s caught my eye. These hosta beauties still own their garden place. Here are listed only four, but there are so many more.

‘Gold Standard’is an old-time favorite. In August multiple pink-lavender floral scapes up to 30 inches tall rise above a 22 inch wide plant mound. Flower fragrance is faint, never overwhelming. Summer foliage has a high gloss; yellow-gold leaf centers darken to a deep avocado shade circumvented by a medium green margin. Leaves average 8 inches in length and 6-8 inches in width. Leaf venation is average, not prominently displayed as on some cultivars.

‘Elegans’, a variety of Hosta sieboldiana, is an extra large hosta with powdery blue heart-shaped leaves. Early spring foliage is deeply textured with powdery wax coating. The white flowers peak through the July-August foliage. This large hosta measures up to 30 inches high and 48-60 inches in spread depending on its age and care.

‘Piedmont Gold’ is another large selection (20-25 inches high and 50-55 inches spread). It stands out with bright golden-yellow foliage with a dusty or powdery finish. The near-white flowers open in July. exhibits good slug resistance.

‘June’ is an medium-size hosta that sports beautiful golden yellow centered leaves streaked with a wide blue-green leaf rim. Pale lilac flowers appear in July. June has moderate slug resistant and is the most sun tolerant of the four.

Plant these cultivars in a full to moderately shady site and in moist well-drained soil. Feed hostas in early spring with a slow release fertilizer such as Osmocote™ or Nutricote™. Hostas are low care perennials ideal in shady, woodland settings, tubs and patio pots, or as a single specimen or in multiples for edging beds.

Hostas are commonly divided in either spring or fall, but these four may be left alone for years.

‘Gold Standard’ hosta

Best Bluegrass Cultivars For Cool-Season Lawns

Posted by Hugh on August 1st, 2014

Lawn Are In Front Of Biltmore Estates, Asheville, NC

Across the northeastern U.S. and eastern Canada, cool season lawn grasses perform best. Bluegrass, often called “Kentucky bluegrass”, grows in zones with cool summer night temperatures and adequate annual rainfall. Bluegrass is not as heat and drought tolerant and a higher water use rate than tall fescue and warm-season grasses. Bluegrass performs best in moist sunny areas and red fescues and chewings fescues prosper in moist shady areas.

Because bluegrass seed is slow to germinate, it is best seeded from late August to mid-October and not in the cool spring. In mixed stands with tall fescue, bluegrass thrives in swales or sunken ground areas that tend to stay moist over extended time periods. Sod producers often mix a limited amount of bluegrass with seeds of the improved, turf-type tall fescues.

University and seed company trials of bluegrass continue to select better varieties for cool Northern regions. In the listing that follows, if a variety is not listed, it may have still performed well.

Recommended bluegrass cultivars for high-quality lawns, include Alexa II, Aura, Award, Bewitched, Barrister, Belissimo, Beyond, Diva, Everest, Everglade, Excursion, Ginney II, Granite, Impact, Midnight, NuChicago, NuGlade, NuDestiny, Rhapsody, Rhythm, Rugby, Skye, Solar Eclipse, STR 2485, Sudden Impact, Washington, and Zifandel.

Bluegrass is best fertilized in early spring and in late summer with 3-4 lbs. of nitrogen per 1,000 square feet annually and irrigated over long dry periods. Expect cool season grasses to look their best in the spring and fall, and brown off (go dormant) in the hot, dry summer.

In a transition zone tall fescues possess better heat and drought tolerances than either perennial ryegrass and bluegrass. Homeowners living here frequently mix bluegrasses with tall fescues and irrigate during hot dry summer periods.

Special thanks to Dr. Tom Samples for his assistance.

Crape Myrtle Diseases And Pests

Posted by Hugh on July 23rd, 2014

‘Hopi’ Crape myrtle

Not all crape myrtle cultivars are alike. Some are more susceptible to diseases and insect pests more than others. Overall, the U.S. National Arboretum (USNA) hybrid crapemyrtles are more disease and insect resistant, but not to all problems.

Some cultivars are susceptible to aphids, usually in the spring. Their sugary excretions over leaves and stems blacken them with a sooty mold. Eventually, leaves yellow and the shrub may bloom poorly. Spray leaves with malathion, diazinon, or an ultra-fine horticultural oil when you spot aphids or the sooty mold symptom.

In late spring and summer, metallic dark green flea beetles may chew the leaf margins in an irregular pattern. Damage is usually slight and does not warrant pesticide spraying.

In late July Japanese beetles chew on the flowers and skeletonize the leaves. Many pesticides are effective to reduce Japanese beetle numbers. Hand removal works but may becomes a daily chore. Pheromone traps are largely ineffective because they attract many more Japanese beetles than they trap.

A strong stream of water from your garden hose can blasted many injurious insects off the foliage. Insecticidal soap sprays are also effective.

Powdery mildew is a fungus disease that deposits a white powdery residue over the leaves and flower buds. Symptoms are worse in high humidity, during lack of rain, and in areas with poor air circulation. If left unchecked your crape myrtle can be weakened and eventually die. Most USNA crapemyrtles are resistant to powdery mildew. Spray susceptible cultivars at the first sign of disease with Funginex™ or Immunox™ and repeat sprays as necessary. Horticultural oil has been shown to be quite effective in controlling powdery mildew.

In the deep South crapemyrtles may shed some leaves with brown spots. This is symptom of Cercospora leaf spot fungus disease during periods of warm, wet weather. In severe cases, only the youngest leaves at the ends of branches remain. Repeated annual infections by cercospora may result in loss of plant vigor and reduced flowering.

These U.S. National Arboretum introductions have some resistance to Cercospora disease: Apalachee, Caddo, Catawba, Sioux, Tonto, Tuscarora, Tuskegee, and Yuma. You can prevent this disease on a susceptible cultivars by spray any fungicide products such as Bayer Advanced Rose and Shrub® or Thiram® when leaf spotting is observed; continue applying the fungicide at weekly intervals through mid-summer.

Gladiolas Are Wonderful Cutflowers

Posted by Hugh on June 21st, 2014

Glad in the summer garden

Across most regions of the U.S., planting gladiola corms (they’re not really “bulbs”) begins a week before the probable frost-free date has passed in the spring. Stagger individual plantings every 2-3 weeks through mid- July. Many people opt to grow them as cutflowers for their homes.

Purchase large or premium sized corms that measure 1 1/4 to 1 1/2 inches across; quality corms produce tall floral scapes in wide color array. Floral scapes range from 18 to 36 inches high depending on variety. Bargain bulbs produce smaller sized individual flowers and shorter scapes.

Glads grow in full sun and in average well-drained soil. Compost-rich, slightly acidic soil is best. Roto-till the ground to at least a 6-inch depth. Add a slow-release fertilizer designated for flowering bulbs according to package directions.

Sow bulbs 4-6 inches deep and 6 inches apart, pointy side up. If rainfall is lacking, glads should be irrigated weekly at least 1 inch of water. Add a 2-3 inch layer of organic mulch to conserve soil moisture. Staking each row of glads as plants often become top heavy when floral scapes are heavily budded up. Place a heavy duty post or stake at opposite ends of the row and weave two sturdy cords through the glads about 2-3 weeks prior to bloom when scapes are beginning to form.

Thrips are a serious pest of glads. Thrips are very tiny and tend to congregate inside the flowers, reducing floral life. Several insecticides, including soaps, are labeled for managing heavy thrip populations.

In most areas of the U.S. where winter temperature dip below 25º F, treat gladiolas as annuals (USDA hardiness zone 7 and northward). Some gardeners dig, clean off soil, and divide the corms in the fall. Grade by size and throw away all rotted or poorly formed corms. Undersized corms, called “cormels”, are usually discarded or planted in a nursery bed next spring to grow and size up. During winter glads are stored in mesh bags and stored in a cool area (36-41º F) that does not freeze.

How Hardy Is Chinese Fringe Flower (Loropetalum)

Posted by Hugh on May 24th, 2014

7-8 feet tall fringe flower at Atlanta Botanical Gardens (early April

late in flower cycle

Loropetalum or Chinese fringe flower (Loropetalum chinensis) has clearly caught on with professional landscapers and gardeners (USDA hardiness zones 7 thru 9). It is rated as marginally hardy in northerly zones 6-b, and has succeeded in consecutive mild winters in the past decade. The winter of 2014 had killed some established plants to the ground, but most had re-sprouted by late spring.

This early flowering fringe flowering shrub is a member of the witchhazel family (Hamamelidaceae). Fragrant creamy white flowers open from mid- April into May and in late March in Southern states. Fringe flower occasionally may re-bloom during the summer and fall. Reddish and purple foliage forms are now available in addition to dark green cultivars.

Depending on variety, shrubs grow from 6 feet to 15 feet and 4 to 5 feet wide. New compact cultivars may reach only 2 to 3 feet tall. Short compact cultivars are perfect as borders or as groundcovers in foundation plantings. Taller forms may be utilized as screens and some Southern gardeners train them into small trees.

Fringe flower excels in full day sunlight, but also grow well under light afternoon shade. Plant in moderately acidic (ph5.5-7.0), well- drained soil. Fertilize shrubs in spring and water regularly over summer dry periods.

The return of an old fashioned cold winter could alter your opinion of fringe flower. You might consider the following five cultivars as perhaps cold hardier: ‘Burgundy Blast’, ‘ZhuZhou’, ‘Cherry Blast’, ‘Garnet Fire’, and ‘Purple Diamond’. A new semi-dwarf cultivar named ‘Crimson Fire’ may also be slightly hardier.

At this writing gardeners should continue to rate fringe flower as not reliably hardy north of zone 7.