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

Goldenrods

Posted by Hugh on September 6th, 2021

Goldenrods (Solidago spp.) represent about 100 species of perennials that grow ubiquitously alongside U.S. roadsides, prairies, open woods, and riverbanks. (USDA hardiness zones 4-9). A few species are also native in South America and Eurasia. Goldenrods are grown for their bright yellow or golden flowers that form late in the summer. They are easy to grow, and the tiny yellow flowers are a bountiful source of nectar for bees and butterflies, including Monarchs; seeds are eaten by songbirds fall and winter.

Goldenrods, Asters and Ironweeds at Dawes Arboretum In Ohio

Goldenrods grow in almost any soil that is well-drained and in full sun. Removing spent flower clusters will encourage more blooms. Deadhead the old spent flowers to avoid prolific self-seeding. Every 3-4 years, divide plants in spring or fall.

Showy goldenrod (Solidago speciosa) is an eye-catching selection with abundant tiny, bright yellow terminal flower clusters atop stiff, narrow-leaved, reddish stems; 2 – 3 feet tall starting in mid- to late-summer.

Wreath goldenrod (Solidago caesia), aka blue stem goldenrod grows 1.5 – 3 feet tall on wiry, arching, glabrous, greenish-purple stems which are covered with a silver-white waxy coating (zones 4-8). Yellow clusters of tiny flowers bloom along the purplish stem in early autumn. Lance-shaped, medium green leaves (2 – 5 inches long) are toothed with sharply pointed tips.

‘Fireworks’ rough-stemmed goldenrod (Solidago rugosa) is probably the most popular variety, this 3 – 4 feet tall clump-forming plant is covered with stiff bright yellow inflorescences in early autumn, reminiscent of exploding fireworks.

‘Golden Fleece’ goldenrod (S. sphacelata ‘Golden Fleece’) grows 18 – 24 inches tall and 24 – 36 inches wide; forms showy sprays of golden yellow flowers from mid-September into October. Its heart-shaped leaves are semi-evergreen.

Ultra-dwarf varieties:

Little Lemon® (‘Dansolitlem’) – light yellow flowers on ultra-compact plants – 14 inches tall and 18 inches wide.
‘Cloth of Gold’ – deep yellow flowers on 18-24 inch tall stems.
‘Crown of Rays’ – bright yellow flowers on 2-3 feet tall stems.

‘Little Lemon’ Solidago (Photo courtesy of North Creek Nurseries)

No serious insect or disease problems trouble goldenrods and plants are moderately deer tolerant. Spot anthracnose, powdery mildew, rust, fungal spots are occasional problems if summer weather is unusually wet or the planting becomes too crowded.

Goldenrods make colorful companions with excellent additions to a perennial border or meadow favorites such as little bluestems (Schizachyrium scoparium), assorted fall asters (Symphyotrichum), beebalms (Monarda spp.), coneflowers (Echinacea), big bluestems (Andropogon gerardii), Joe Pye (Eupatorium), and Arkansas bluestar (Amsonia hubrichtii).

Fall Anemones

Posted by Hugh on September 1st, 2021

Japanese anemones (Anemone x hybrida) are popularly called “fall anemones”. These late summer-fall blooming perennials are long-lived and make fine additions to flower borders and open woodland areas (USDA hardiness zones 4 to 7). Many colorful varieties are available and their flowers are great additions to cut floral arrangements.

Showy 2-4 inch wide flowers stand 2-4 feet tall (depending on variety) for 4 to 5 weeks in autumn. Starting in late August flowers rise up atop long wiry stems from dark-green basal mounds. Each flower is composed of 6-9 overlapping white/pink petals with numerous yellow stamens in center. The dark green leaves are 3-lobed.

Fall anemones thrive in garden spaces with full or partial day sunlight and in moist, well-drained ground. At planting time, add lots of compost to a mildly acidic garden soil (pH 5.5 to 7.0 preferred). Fall anemones do poorly on dry sites and in heavy clay soil. Plants also fail in soggy clay soil over winter. Leaves tend to burn in hot, dry, sunny conditions. In warmer climes of zone 7, set fall anemones in morning sun and partial afternoon shade. When planted in too much shade, plants tend to be floppy and require staking.

Plants are mostly deer tolerant and have few disease and insect problems. Flowers attract numerous late season pollinators. From the Greek, the word anemone means “windflower”. Observe the flowers swaying in the gentle autumnal breezes, and do shelter plants on extremely windy sites.

Over time fall anemones tend to naturalize via creeping rhizomes and seed in freely. In the spring dig up extras to share with gardening friends.

5 Cultivars to plant:

‘Honorine Jobert’ (2-3 inch wide single pure white flowers on 3-4 feet tall stems) –heirloom plant introduced in the mid-19^th century and awarded the Perennial Plant of The Year in 2016

‘Queen Charlotte’ (3-inch semi-double rosy pink flower on 2-3 feet tall stems)

‘September Charm’ (3-inch single rose-pink flower on 3-4 feet tall stems)

‘Whirlwind’ (4-inch semi-double white flowers on 3-4 feet tall stems)

‘Serenade’ (3-inch double deep-pink blooms on 3-3.5 feet tall stems)

Lots of Choice With European Hornbeams

Posted by Hugh on August 26th, 2021

Seasonal foliage and nutlet capsule

European hornbeam (Carpinus betulus), aka ironwood and musclewood, is an underused tree that is an excellent urban street and park tree. (USDA hardiness zones 4-7). The tree develops a full, dense canopy and little maintenance requirements. The species typically grows 40-60 feet (less frequently to 80 feet) tall with a pyramidal to oval-rounded crown.

Its dense summer foliage is medium green, to 4 inches in length with little susceptibility to foliar diseases and insects. In the fall foliage turns yellow-orange. Some leaf retention over winter months is likely. Trunks have smooth gray bark and distinctive muscle-like fluting. Flowering catkins are visible in early spring before the foliage emerges. Male catkins are yellowish and female catkins are greenish. Fruits are small nutlets in 3-lobed bracts that appear in late summer.

The tree is commonplace in landscapes across Europe as a street tree, privacy screens and windbreaks, and in topiary forms. Hornbeam adapts to a wide variety of soils as is tolerates hot and dry conditions once established after 2 years. Full to partial sun is ideal, although tree will tolerate partial shade. The species tolerates drought and short term flooding. It prefers well-drained/loamy, sandy or clay soils with an acidic pH. Plant where the soil stays cool. Annual mulching is an added plus.

Dense, compact and narrow when young, developing an upright oval crown with maturity. Long, thick, corrugated dark green foliage is resistant to insects and diseases and turns a pleasing yellow in fall. Handsome gray fluted bark. An excellent choice for hedging and windbreaks.

Annual fertilization of young trees is recommended, not so much for older trees. Disease and pest free although powdery mildew. Japanese Beetles may slightly damage the foliage, but rarely needs pest control. Little or no pruning is generally required.

‘Fastigiata’ displays a narrow, columnar form to 35 – 40 feet tall and 25 – 30 feet wide. This cultivar is more available in U.S. nurseries than the species.

‘Columnaris’ is stately and extremely formal-looking, with a limbed-up trunk, strong central leader, and branches arranged tightly near the trunk.

‘Frans Fontaine’ is a narrowly columnar form that grows 35 feet high and 20 feet wide.

Columnar forms display strong upright architecture in winter

Kalimeris – Late Summer Flowering Perennial

Posted by Hugh on August 21st, 2021

Japanese asters (Kalimeris spp.) are synonymous with boltonias (Boltonia). It is native of China, Japan and Siberia. It superficially resembles Boltonia, but differs enough to be assigned to the genus Kalimeris in the 1990s.

Kalimeris incisa ‘Blue Star’ is a superior form. This clump-forming species is noted for its long summer bloom period featuring 1 ½ inch wide, daisy-like flowers of pale lavender rays and yellow centers. The flowers are very aster-like. (USDA hardiness zones 4-8). Plants typically grow 12-18 inches tall and wide. Oblong-lanceolate green leaves are 3-4 inches long.

Kalimeris is easily grown in average, medium moist, well-drained soils in full sun to part shade. Established plants tolerate droughty clay, provided the ground is not poorly drained. It stands up well to hot and humid summers. Foliage may be pinched back in early summer to stimulate more branching and increased bloom count. Shear stems after flowering to encourage re-bloom in early fall. Plants may self-seed in optimum growing conditions.

Japanese asters perform equally well in large containers. Plants require very little maintenance. It may be propagate by seed or cuttings. Space individual plants in a flower garden or group several together for mass plantings.

Another Japanese aster cousin, K. pinnatifida, is also popular. Semi-double daisy-like flowers are composed of 1-inch wide white ray petals and a pale yellow center disk. They bloom continuously from early summer to fall. The cultivar ‘Hortensis’ produces white double flowers.

Over the years plants tend to sucker and colonize among themselves and do not spread to other places in the garden. Divide older 3 to 4 year clumps in spring to maintain their overall vigor. Fertilize in early spring with a slow release fertilizer like Osmocote™ or Nutrikote™. Disease or pest problems are rare.

Smart Water Use In The Summer Garden

Posted by Hugh on August 17th, 2021

When the heat of the summer settles in, water is in high demand. Here is some practices to implement when planting a water-wise garden,
irrigating lawngrass, and better mulching practices to improve soil moisture levels:

Lawn grass species vary in their water needs. Cool season grasses like fescues and bluegrasses are moderately drought tolerant, turn off-color during dry periods (“their summer dormancy”), and recover when adequate rainfall returns. Warm season grasses like bermuda and zoysia grasses are more drought tolerant than fescues and bluegrasses.
Irrigate in the morning to reduce water loss to evaporation and minimize disease risks.
Plant more drought tolerant plants. For examples, cacti , euphorbias, and succulents are low water users. Many prairie flowers such purple coneflowers (Echinacea), black-eyed Susans (Rudbeckia), blanket flower (Gaillardia), yarrows (Achillea), hyssop (Agastache), Russian sages (Perovskia), lavenders (Lavandula), and sedums are some favorites.
Repair leaks in hoses and faucets.
Don’t use fine mist sprinklers and avoid watering on a windy day.
Drip or trickle irrigation systems are better water users than overhead sprinklers
Target sprinklers to irrigate plants and not driveways and walkways.
Collect rainwater in rain barrels or rain gardens.
Mulch using organic amendments such as pine bark, pine needles, and wood mulches will reduce surface evaporation. Newspapers, cardboard, and grass clippings serve as good mulches.
Summer pruning to reduce vegetative competition.

Deer Resistant Perennials

Posted by Hugh on August 11th, 2021

Most deer-resistant plants share several traits or characteristics: 1. Aromatic flowers / foliage; 2. thorny, bristly, or hairy (pubescent) leaves or stems; 3. toxic plants. If “deer pressure” (population) is exceptionally high, deer don’t heed plant lists like this one.

Available food resources, species of deer, seasonal weather are all factors. Flowers, foliage, fruits, and seeds of plants are not off-limits to other critters. Expect damage from native butterflies, moths, and beneficial insects. Design your garden to include plants that are not munched on. Otherwise, construct a tall fence to keep deer away.

Yarrow (Achillea)

Black cohosh (Actaea racemosa)

Anise Hyssop (Agastache foeniculum)

Bugleweed (Ajuga reptans)

Bluestar (Amsonia spp.)

Artemisia

Goatsbeard (Aruncus dioicus)

Butterfly weed (Asclepias tuberosa)

Baptisia (Baptisia australis)

Siberian bugloss (Brunnera macrophylla)

Karl Forester reed grass (Calamagrostis)

Calamintha nepeta subsp. nepeta

Coreopsis

Montbretia (Crocosmia)

Delphinium

Hayscented fern (Dennstaedtia punctilobula)

Foxglove (Digitalis)

Male fern (Dryopteris filix-mas)

Bleeding heart (Dicentra spectabilis)

Foxglove (Digitalis purpurea)

Coneflower (Echinacea)

Globe thistle (Echinops)

Barrenwort, fairy wings (Epimedium)

Cushion spurge (Euphorbia polychroma)

Joe Pye (Eutrochium)

Bigroot geranium (Geranium macrorrhizum)

Geum

Lenten rose (Helleborus x orientalis)

Candituft (Iberis sempervirens)

Bearded iris (Iris germanica)

Dead nettle (Lamium)

Lavender (Lavandula spp.)

Shasta daisy (Leucanthemum)

Blazing star (Liatris spicata)

Cardinal flower (Lobelia cardinalis)

Rose campion (Lychnis coronaria)

Ostrich fern (Matteuccia struthiopteris)

Beebalm (Monarda spp.)

Daffodil (Narcissus)

Catmint (Nepeta)

Evening primrose (Oenothera)

Oregano (Origanum)

Herbaceous Peony (Paeonia x lactiflora)

Oriental poppy (Papaver orientale)

Beardstongue (Penstemon digitalis)

Russian sage (Perovskia atriplicifolia)

Balloon flower (Platycodon)

Jacob’s ladder (Polemonium caeruleum)

Lungwort (Pulmonaria)

Rodgers Flower (Rodgersia pinnata)

Rosemary (Rosmarinus officinalis)

Black-eyed Susan (Rudbeckia spp.)

White Wood’s aster (Eurybia divaricata)

Assorted salvias (Salvia spp.)

Compass/ Cup Plant (Silphium spp.)

New England aster (S. novae-angliae)

Goldenrod (Solidago)

Lamb’s Ears (Stachys byzantina)

Germander (Teucrium)

Meadow rue (Thalictrum)

Mullein (Verbascum)

Mexican Bush Sage

Posted by Hugh on August 6th, 2021

Mexican bush sage (Salvia leucantha), aka velvet sage, is a perennial that lights up the late summer / fall garden (USDA hardiness zone 7b-10). Indigenous to Central America and Mexico, it can be grown as an annual that grows to about 3-4 feet tall. In the U.S., bush sage is only hardy from the lower Piedmont to the coastal plain, and extreme winters may kill it.

Bush sage is prized for its dense, arching spikes of showy flowers. Choice of flower colors include purple, blue, and white. Bloom stalks bear persistent flower bases which are velvety and purplish. Bicolor flowers (white corollas and purple calyces) are stunningly spectacular. The individual flowers maybe short-lived and very abundant.

Bicolor flowers — white corollas and purple calyces

Plants prefer full sun (6 or more hours of direct sunlight daily) and humus-rich well-drained soil. Plants are moderately drought tolerant. Bush sage should be kept adequately water during hot dry intervals of summer; irrigate weekly the first growing season if rainfall is less than 1 inch.

Bush sage may freeze and experience crown death in wet soggy winter soils. Wait to cut back dead stems from late February thru early April as new growth emerges. Plants may be trimmed back 2 or 3 times during the spring and summer months to promote dense, more compact plant with heavier late seasonal bloom.

Bush sage may be propagated by seed or overwintering cuttings collected in late summer. Purchase potted plants at garden centers in spring or start seedings indoors 6-8 weeks prior to the last spring frost date in your area.

In Tennessee, North Carolina, and Virginia when winters are exceptionally mild, plants may survive in protected locations covered with leaf mulch. When winter temps are severe, expect plants to die.

Flowers are attractive to hummingbirds and butterflies and ignored by deer and rabbits.

Mexican Bush Sage

12 Plants With Silver Foliage

Posted by Hugh on August 1st, 2021

Silver King Artemisia (Artemisia ludoviciana ‘Silver King’) is an aggressive form with bushy, upright patch of fragrant silvery foliage and loose sprays of grey flowers in midsummer. Prune back hard after flowering to rejuvenate foliage. Deer and drought resistant. (z 3-7).

Silver Mound Artemisia (Artemisia schmidtiana ‘Silver Mound’) – soft feathery leaves grow into compact, cushion-like mounds. It has multiple
landscape applications including edging, rock gardens or containers. Deer and rabbit resistant. (z 3-7)

Heuchera ‘Dolce Silver Gumdrop’ –a compact, tidy mound of silver metallic foliage brightens up any shade garden along with multiple stems of tiny pink flowers. This H. villosa hybrid develops a rosy blush as the season progresses. (z 3-8).

Brunnera macrophylla ‘Jack of Diamonds’ – giant version of the classic ‘Jack Frost’ – with a twist. Huge 9-10 inch, dark green veined leaves, have a heavy silver overlay and overlap at base. Clusters of baby blue, forget-me-not type blossoms rise above the spring foliage. (z 3-8).

Cheddar pinks (Dianthus gratianopolitanus ‘Firewitch’ (Fuerxe’) – ground hugging low mats of silvery blue evergreen foliage grows about 4-6 inches tall (flowers top out at 7-8 inches tall), and 18-24 inches in diameter. (z 3-8).

Licorice Plant (Helichrysum petiolare) is grown for its silvery, densely-felted foliage and trailing habit. It is a shrubby, woody-based tender perennial grows 1-2 feet high (3-4 feet wide) on upright to trailing stems densely clad with soft, woolly, oval-rounded, gray-green leaves (1.5” long). Tiny white flowers are insignificant and often removed by gardeners as they appear. Plant foliage has a slight licorice aroma in the heat of the summer. (z 9-11).

Lavender (Lavandula angustifolia) is an evergreen 3 feet tall perennial
is a dwarf shrub that blooms in the summer and has aromatic leaves, flowers, and dry seed heads. Utilized as a border, a low hedge, in massing, in containers, and in herb gardens. (z 5-9).

Spotted deadnettle (Lamium maculatum ‘White Nancy’) – a silvery leaf groundcover that grows 6-8 inches high and spreads 2-3 feet wide. If foliage declines in mid-summer, mow back or shear plants to stimulate fresh new growth. White flowers in late spring is an additional asset. (z 3-8).

Japanese Painted fern (Athyrium niponicum var pictum) is a lovely deciduous fern with soft blue-green fronds with a silvery overlay accented by contrasting dark burgundy midribs. (z 3-8)

Dusty Miller (Senecio cineraria), also called Silver Ragwort, is a hardy herbaceous perennial typically grown for its grayish ornamental foliage. Leaves are covered with fine matted hairs, giving them a felted or woolly, silver or white. (z 7-10)

Dichondra ‘Silver Falls’ – is a vigorous annual vine with round silver foliage on silver stems. It is very heat and drought tolerant often used as a trailing plant in baskets, window boxes and other planter containers. (z 9-11).

Lamb’s Ears (Stachys byzantina ‘Helene von Stein’) is an improved non-blooming form that results in larger fuzzy, silver foliage (8 inches tall x 15-18 inches wide). Helen von Stein, aka “Big Ears” makes a great edging plant with mounding habit. Neat, non-blooming plant that does not reseed. (z 4-9).

Plants With Silver Foliage

Elephant Ears In Motion

Posted by Hugh on July 21st, 2021

Elephant ears (Colocasia esculenta) and their aroid cousins have become commonplace in not only hot, humid southern gardens, as well in temperate landscapes. Gardeners grow them in large containers and overwinter them indoors in a non-freezing environ. Also, my neighbors in zone 6 blanket in-ground plantings with several inches of loosely packed leaves overwinter.

Colocasia ‘Coffee Cups’ develops into a stunning 3 to 6 foot tall clump glossy olive green foliage with jet black stems. Leaves fold and form into a cup-shape. As the leaf fills with water, the stem gives enough for the leaf to dump out its catch before refilling… totally fascinating. Elephant ears thrive in an organically-rich garden soil or in large containers or urns.

A similar variety, Colocasia ‘Teacups’ struts prominent purple veined underside. Leaves are especially colorful in sun. Stems are strong and leaves are cupped to allow rainwater to collect in the cup! When it fills full, the stems bend just enough to pour out the water. This action is repeated — the leaf refills. Leaves are purple veined on their underside, especially colorful in the sun.

Both “action” varieties grow vigorously over the season, 3 to 6 feet high, growth rate depending on quality of the soil, irrigation frequency, and feeding rate. It grows best in full to partial sunlight (6 hours minimum) and thrive in moist soils.

In northern areas clumps are dug up and stored in a home garage with 40°F minimum temperature. In late winter or early spring clumps may be divided and repotted for the move outdoors once all danger of frost has passed.

Generally, elephant ears are free of disease and pest problems; occasionally aphids, whiteflies, spider mites, stem and root rots require attention.

Generally, elephant ears require low maintenance other than frequent irrigation during dry weather periods. Feed with a water soluble fertilizer such as Miracle-Gro™ and Jack’s™ and organic Espoma™ Plant Food. Halt feeding plants in late August.

Mallow Plant Breeders Developing Resistance To Hibiscus Sawfly

Posted by Hugh on July 16th, 2021

Mallows, hardy hibiscus, and perennial hibiscus (Hibiscus moscheutos) are vigorous shrub-like growers on sturdy 4-5 feet tall (and 2-4 feet wide) stems. The species is native to wetland areas from Ontario and Massachusetts south to Ohio, Indiana, Alabama and Florida.

Huge colorful 4-6(9) inch wide flowers have five overlapping petals with reddish-purple to dark crimson bases which form a sharply contrasting central eye. Flowers, your choice of white, creamy white, pink, and red, have a prominent and showy central staminal column of bright pale yellow anthers.

If site conditions are ideal, expect a long succession of large numbers of flowers, each bloom lasting only 1-2 days from July to September. New flowers open each day. Alternate, broad-ovate to lanceolate leaves (3-8 inches long) with toothed green margins above and white-hairy beneath. Most leaves exhibit 3-5 shallow lobes.

Hibiscus sawfly larvae (Photo by Dr. Alan Windham, Univ. of Tennessee, Nashville

Hibiscus sawflies can cause a lot of foliage damage in a short time. On a warm humid morning you will find the greenish larvae on the backside of leaves, chewing between veins. A sawfly adult is a primitive wasp-like insect. Adult females have a saw-like blade at the tip of the abdomen that is utilized to cut slits into plant tissue into which they deposit eggs.

Insecticides like permethrin, cararyl (Sevin®), Conserve®, and insecticidal soap provide good control if sprayed on the entire plant. Imidacloprid, a systemic insecticide, can be applied to the soil around the plant before feeding activity is noticed. Sawflies are relatively easy to control with foliar sprays, but because hibiscus sawflies produce up to six generations in one season, susceptible plants need to be sprayed on numerous occasions.

Hibiscus sawfly also attacks other ornamentals hollyhock (Alcea rosea), and other hibiscus species. The insect shows little or no interest in other economically important hibiscus relatives, including cotton, okra and rose of Sharon.

Plant breeders are developing resistant plants that are less susceptible to the ravenous appetites of the sawfly. Three genotypes show promise in breeding for hibiscus with resistance to the hibiscus sawfly: H. acetosella, H. aculeateus, and H. grandiflora. New resistant varieties are now arriving at garden centers now with lots more coming in the near future.