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

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.

Exclamation™ London Plane Tree Is A Game-Changer

Posted by Hugh on August 13th, 2014

Exclamation! Planetree (photo by Dr. Jim Ault, Chicago Botanical Gardens)

Exclamation! London Plane Tree (Platanus x acerifolia Exclamation!™) is probably one the most improved cultivars to date (USDA hardiness zones 4-8). Exclamation! was introduced by Dr. George Ware at the Morton Arboretum and released through the Chicagoland Grows® program.

Exclamation! develops a strong central leader, a uniform upright pyramidal shape (when young), a vigorous growth rate, and is highly resistant to both anthracnose and powdery mildew diseases. Mature height is thought to be approximately 60 feet tall and 45 feet broad. Under optimum conditions young trees may grow 3 feet annually and 1 1/2 feet after 8-10 years. The tree seems to take on a stovepipe form around its base as reaches maturity.

London planetrees resist the harsh environs associated with parking lot islands, median traffic strips, and urban street plantings. They stand up to urban air pollution, poor drainage, compacted soil, wet or droughty soils. Its medium green foliage color holds all summer long, turns yellow for a short interval in autumn before abscising. Numbers of gumball fruits are reportedly less than on other planetrees. Its exfoliating patchwork bark of white, tan, brown and green is absolutely exquisite and develops very early in the tree’s life.

In urban areas plant London Plane 35-40 feet apart. They become a massively large tree in a short time. Include a root barrier along the edge of the sidewalk and curb. Roots grow aggressively and can lift sidewalks and curbs, invade sewer pipes, and crack building foundations. London planetree may be pruned into hedges, screens, and arbors. Mature trees do holdup to extensive root pruning.

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.

Tall Sedum – The New Mailbox Plant

Posted by Hugh on August 7th, 2014

Planting Of Tall Sedums Around Mailbox

Tall sedums (Sedum x spectabile) are a popular late summer blooming perennial often nicknamed “showy stonecrops” (USDA hardiness zones 3-9). Members of the succulent plant family, tall sedums have thick round leaves and are recognized for their drought resistance. Star shaped flowers are clustered in colors ranging from whites, pinks, and reds, depending on the cultivar. Bloom clusters attract bees and butterflies.

Sedums are best grown in full sun but can cope with half day or less of sun. Numbers of flower buds in clusters are less and stems tend to be floppy when planted in shady garden areas. They thrive in average well-drained soil with neutral to slightly alkaline pH. Old-timey cultivars tend to flop late in the summer and need staking. Avoid this problem by cutting plant(s) back by half in early June.

Sedums are best divided every 3 or 4 years. They are also easy to propagate from stem or leaf cuttings. Cuttings set in the summer root quickly in sand or perlite. Disease problems are rare and mealybugs, scales, slugs, and snails are occasional pests.

For decades ‘Autumn Joy’ (‘Herbstfreude’) has been the popular favorite. Here are six other tall sedums (hybrids of S. spectabile and S. telephium) to try:

‘Autumn Fire’- dusty-rose (August) to red (October) flowers on 18-24 inches tall on sturdy stems.
‘Brilliant’- compact 16-18 inch high plant and hot pink flowers.
‘Matrona’- bright pink flowers, purple stems on 24 inch high plant.
‘Neon’- dense flower clusters with deep rose color compared to ‘Brilliant’, a sister sibling.
‘Stardust’- plants 18 inches high, open to large silvery white flowers, aging to pinkish tinge.
‘T-Rex’- light rose pink aging to dark pink flowers atop 26-28 inches tall and 18 inches wide. Very upright branching and leaf edges sharply toothed.

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.

Plumleaf Azalea – Late July Flowering Shrub

Posted by Hugh on July 30th, 2014

Plumleaf azalea in bloom at Biltmore Estate, Asheville, NC

Plumleaf azalea (photo by Jay Jackson, Appalachian Native Plants, Inc. in Tennessee)

Plumleaf azalea (Rhododendron prunifolium) is a native deciduous azaleas that indigenous to the Chattahoochee River Valley on the Georgia-Alabama line (USDA hardiness zones 6-9). The bright orange-red blooms surprise in late July to early August. Compared to many of the spring blooming species, flowers are not fragrant. Fall leaf color is uneventful.

This 5-8 feet tall and wide shrub is best protected from the harsh afternoon summer sun. It grows in well-drained, compost amended soil. Plumleaf azalea prospers in the East Tennessee and Western NC calcareous clay soils without pH correction. Irrigate plants their first two years of establishment and they will reward you over many summers. Set the shrub into a wide, shallowly dug hole which has been generously amended with compost and/or peat; maintain 2-3 inches of an organically-based mulch around the shrub base.

Plumleaf azaleas are usually available from mail order companies on-line. It is best to purchase and plant them by late spring so that their fine shallow rootsystem becomes deeply knitted into the soil before winter arrives.

Plumleaf azalea is the signature plant of Callaway Gardens in Pine Mountain, Georgia where I purchased the first of three in my Tennessee garden. It is a frequent parent cross with other azalea species.

Prune shrubs anytime after blooming to maintain desired height and spread. Plumleaf azaleas bloom on new current season’s wood.

Hosta Award Winners

Posted by Hugh on July 26th, 2014

'Niagara Falls' Hosta with dark green, well-defined leaf veining

‘Niagara Falls’ Hosta with dark green Foliage with well-defined veining

Without question, hostas are the most popular perennial for the shade garden. Their lovely foliage provides color, texture and architecture in their garden space from April to a hard autumn frost. They are hardy, long-lived, and relatively maintenance-free.

Hostas range in size from miniature 2 to 3 inches tall types to enormous large leafy clumps 36 or more inches high and broad. Most cultivars grow in shady and semi-shady areas, but a few are sun-tolerant under frequent irrigation. Hostas are also called “plantain lilies” and “funkia”. Their white, lavender, or purple flowers are fragrant. Blooms attract passerby hummingbirds.

The American Hosta Society (AHS) keeps registration records on named cultivars, now numbering over 36,000. AHS members and commercial growers have a voice in selecting the most beautiful and best performing cultivars by region across the U.S. Each year AHS judges award one cultivar their prestigious Benedict Medal.
Benedict Medal winners:
2014 to be announced
2013 First Frost
2012 Niagara Falls
2011 Blue Mouse Ears
2010 Sagae
2009 June
2008 One Man’s Treasure
2007 Whirlwind
2006 Gold Standard

American Hosta Growers choose the Hosta of the Year Award. This outstanding cultivar performs well in most areas of the U.S. and is easy to reproduce. The Hosta of the Year Award is announced two years in advance so that garden centers and nurseries will have plants available for sale.
Hosta of the Year Award winners:
2016 Curly Fries
2015 Victory
2014 Abiqua Drinking Gourd
2013 Rainforest Sunrise
2012 Liberty
2011 Praying Hands
2010 First Frost
2009 Earth Angel
2008 Blue Mouse Ears
2007 Paradigm
2006 Stained Glass
2005 Striptease
2004 Sum and Substance