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

Seasonal Mowing Height Of Home Lawns

Posted by Hugh on June 22nd, 2016

Red fescue lawn properly mowed

Fescue Lawn mowed too closely

The arrival of summer’s heat and dry weather is a clear sign to raise the cutting (mowing) height of your lawn grass. Every grass species have a recommended height at which it should be mowed for best health. The cutting height will change with the season. Location in the yard is also important. Here on some basic tips.

Recommended Mowing Heights of Grass Species:

Burmuda grass* – ½ to 1 ½ inches

Zoysia grass* – ¾ to 1 ½ inches

Centipede grass – 1 ½ to 2 inches

St Augustine grass – 2 to 4 inches

Fescue – 3 to 4 inches

A general rule to follow is to remove only one-third of a grass plant at any one mowing. For example, if you regularly mow your fescue lawn at 3 inches, allow it to grow to 4.5 inches tall before mowing.

In temperate areas (zones 5 to 7), most lawns are composed of tall fescues and/or bluegrasses. These grasses are usually mowed at 2 1/2 to 3 inches high. In partial shade fescue may be cut slightly taller @ 3 1/2 inches. In summer, mowing height should be raised a minimum of ½ to 1 inch taller than spring. Raising the mowing height results in deeper rooting and better drought and heat tolerance.

In summer’s heat and drought, if your lawn does not need mowing, DON’T!! Reduce mowing frequency in summer unless your lawn is irrigated and fertilized. Cool season grasses such as fescues and bluegrasses naturally grow slower (“summer dormancy”).

Growth of warm season grasses (burmuda, zoysia, centipede, and St. Augustine) also slow down when soil moisture is low. Raise the mowing height of bermuda grass and zoysia grass lawns as autumn approaches to protect the turf from winter injury.

Scalping (too close cutting) favors growing of undesirable grass species and weeds. For example, low mowing in early spring leads to invasion of weedy annual bluegrass (Poa annua). Scalping fescue lawns results in seedling burmuda grass, crabgrass, goosegrass, and other weeds.

Butterfly Weed – Long-lived Flowering Perennial That Nourish Monarchs

Posted by Hugh on June 21st, 2016

Long-lived Butterfly Weed at Chanticleer Gardens in Wayne, PA

Milkweed (Asclepias tuberosa), aka butterfly weed, is a tuberous rooted perennial native in the Eastern and southern U.S. (USDA hardiness zones 3 to 9). It grows in dry/rocky open woodlands, prairies, farm fields, and along roadsides. Individual plants typically grow as a clump to 1- 3 feet high and 1 ½ feet wide. Unlike many of the other milkweeds (Asclepias spp.), the sap is not milky.

For almost six weeks, from late spring into summer, clusters of vibrant orange to yellow-orange flowers (umbels) cover the plant canopy. The narrow, lance-shaped leaves are attached to hairy stems. Flowers are an important nectar source for many butterfly species and leaves are a key food source for the caterpillars (larvae) of monarch butterflies.

Butterfly weed freely self-seeds in the landscape. Prominent 3 – 6 inch long spindle-shaped seed pods break open when ripe and release multitudes of silky-tailed seeds which may carry a long way by wind. Seed pods may be utilized in dried flower arrangements.

Butterfly weed is a prairie survivor. It grows in average, dry to medium, well-drained soils in full sun. It does well in poor, dry soils, and established plants are highly drought tolerant. Shoots emerge late in the spring and grow rapidly. It frequently included in butterfly gardens, meadows, prairies, or other plantings.

Plants are easily started from seed, but may take 2 – 3 years before flowering. Do not try to dig up plants in the wild as they rarely survive transplanting due to their deep taproot system. Seedlings are best left undisturbed once established, usually after two years.

Few disease and insect problems trouble butterfly weed if grown in the right location. Wet, poorly-drained soil leads to rot rots. Leaves are susceptible to rust and leaf spots, particularly if the ground is overplanted. Pesticide use is rarely warranted. In medical circles the plant is commonly called “pleurisy root”, once used to treat lung inflammations.

Their bright orange flower clusters are among our showiest native wildflowers and picked for floral arrangements.

Celebrate National Pollinator Week

Posted by Hugh on June 19th, 2016

Bee Activity in Baltimore, MD Garden

Butterfly Quilt Display at NC Arboretum in Asheville, NC

June 20 – 26 is National Pollinator Week. National Pollinator Week is a time to celebrate pollinators and spread the word about what you can do to protect them.

Nine years ago the U.S. Senate unanimous approved and designated a week in June as “National Pollinator Week”. National Pollinator Week is supported by the U.S. Department of Agriculture and the U.S. Department of the Interior. It marks a necessary step toward addressing the urgent issue of declining pollinator populations.

For science teachers, this is an excellent way to get children involved. Pollinator Week has now grown into an international celebration of the valuable ecosystem services provided by bees, birds, butterflies, bats and beetles. Pollinators provide many ecosystem services. Choose the plants that can improve the plight of pollinators. There are lists of favorite pollinator and butterfly larvae feeding plants on this website and others. I highly recommend information published by the Xerces Society.

It’s time to celebrate! Check out: Find Events – It’s never too early to start thinking about an event at your school, garden, church, store, etc. Pollinators positively affect all our lives, supporting wildlife, healthy watershed and more… let’s Conserve and Protect it! Have a positive influence on our environment! Become a smart gardener.

If you’re hosting an event for Pollinator Week, you might want to register it with the Pollinator Partnership, which has a map of local events. http://www.pollinator.org/pollinatorweek/

Medical Benefits Derived From Gardening

Posted by Hugh on June 16th, 2016

Raised bed Garden (photo by Susan Morgan)

Raised bed Gardening Workshop (photo by Susan Morgan)

Making Air Plant Ornaments (photo by Susan Morgan)

For hundreds of years, home gardeners have realized that growing plants is good for you both physically and mentally. A story recently published in British tabloid The Guardian reports that many patients suffering with cancer, dementia and mental health problems can benefit from gardening. Doctors are more and more prescribing gardening for patients with cancer, dementia and mental health problems.

Outdoor spaces including gardens can reduce social isolation among older people as well as help patients recover and manage conditions such as dementia. GPs are advising some of their patients to spend more time outdoors to heighten their sense of well-being. The additional physical activity brings immediate payback and even promotes better sleep habits. It reduces social isolation and strengthens community bonds.

At a London clinic, a group of patients, doctors, nurses and local residents have created a network of food-growing gardens where patients learn how to grow food, which is then sold to the hospital to feed patients. A hospital in Salisbury designed special gardens which helped rehabilitate spinal injury patients. Outside spaces and gardens can serve to be important elements in improving end-of-life care, half of whom die in the hospital.

Dementia patients can benefit from being near a garden. One study reported a 19% reduction in violence in patients staying in garden sites; there was a seven-fold rise in violence in the non-garden sites during a year.

The therapeutic benefits of gardening don’t require taking lots of pills. Gardens can reduce levels of depression, loneliness, anxiety and stress, help improve older people’s balance, and benefit for a wide range of diagnoses including heart disease and obesity.

Credit: Photos courtesy of Susan Morgan, The Horticultural Link | thehorticulturallink.com | eatbreathegarden.com

Buttonbush Offers Year-round Interest

Posted by Hugh on June 13th, 2016

Cephalanthus occidentalis at Chicago Botanical Garden

Buttonbush Is Large Shrub

Buttonbush (Cephalanthus occidentalis), aka Button-willow or Honey Bells, is a medium to large native shrub with many fine landscape attributes. This unique flowering shrub is a favorite in attracting beneficial wildlife. It populates bogs, swamps and pond areas, as well as dry limestone bluffs in the eastern U.S. and southeastern Canada (USDA hardiness zones 5–9).

White pompom flowers are the unique ornamental asset. Tiny fragrant flowers appear in creamy white balls that are 1 – 1 ¼ inches in diameter in late spring (in Philadelphia, PA) to early summer (northern New England). Long projecting styles from the flower heads gives it a distinctive pincushion appearance. Flower heads mature into hard spherical ball-like fruits containing tiny two-seeded nutlets. Dried seed balls persist all winter long.

Give the buttonbush room to grow. This multi-stemmed deciduous shrub grows 6-12 feet tall and 4-7 feet wide. On older shrubs stems and trunks appear twisted when twigs are bare of leaves in winter. Pruning is usually unnecessary and is done in early spring to shape or reduce plant dimensions. Old neglected plants may be revitalized by cutting them back near to the ground in late winter.

Buttonbush has year-round garden interest with late spring flowers, summer and fall foliage, and fall/winter fruits. Narrow oval green deciduous leaves emerge in spring and turn shades of red in fall. It has no serious disease or insect problems. Foliage is poisonous to humans and livestock; deer may snack on new spring growth.

Buttonbush is best planted in wet, humus-rich soils and in full sun to part shade. Favorite landscape sites include in rain gardens or the edge of ponds. Established plants after 1-2 years are moderately drought tolerant.

Fragrant flowers attract butterflies, bees, and hummingbirds for nectar. Leaves are the larval host for some butterfly species. Waterfowl, quail, and other birds feed on the nut-like seeds. Cut flowers look great in fresh summer bouquets or in dried arrangements.

Japanese Snowbells Worth A Try

Posted by Hugh on June 10th, 2016

Mid-spring flower

Styrax japonicus ‘Pendula’ at Atlanta Botanical Garden, Atlanta, GA

Japanese snowbells (Styrax japonicus) is a graceful, slow growing, low branched spring flowering tree. At present snowbells are not popular with U.S. gardeners , mostly because of unavailabliity (USDA hardiness zones 5-8). Snowbells are lovely understory trees, similar to our native dogwoods (Cornus florida). Small, pendulous, slightly fragrant, bell-shaped white flowers appear in May. Small white ½ inch oval-shaped drupe fruits are ornate by late summer.

Site selection is very important! At first spring warmup, snowbells often leaf out too early. They’re are best planted on the north side of a home or building to slowdown spring leaf emergence and possible frost injury to leaves and flower buds. Snowbells grow in full to partial sunlight and are suited to moist, mildly acidic, compost-rich, well-drained soil. Supplemental watering is advised the first two years for establishment. Fertilize in early spring with an organic or slow-release fertilizer designed for flowering shrubs.

Snowbells reach mature heights and widths of 18 to 30 feet, a perfect size for most urban gardens. Cracks or fissures over the gray bark of older branches reveal an orange inner bark, a unique feature on mature specimens during winter. Elliptic-ovate, glossy, 2 to 3 inch long, deep green summer leaves stay generally blemish-free. Most years, fall leaf color is of no consequence, sometimes turning clear yellow.

Snowbells have few disease or pest problems when properly sited and cared for. Fragrant flowers attract hundreds of bees and butterflies.

Notable cultivars:

‘Pink Chimes’ – pink, fragrant flowers on slightly weeping.

‘Emerald Pagoda’ – slightly larger star-like flowers, graceful weeping form.

‘Carillon’ (same as ‘Pendula’) – white with showy yellow stamens flowers and slightly weeping.

In most areas snowbells are still a collector’s plant, rarely sold at local garden centers. E-commerce nurseries are good sources.

Other Snowbell (Styrax) species:

American styrax (S. americanum) – cold-hardy and shrub-like.

Fragrant snowbell (S. obassia) – exfoliating (peeling) bark for winter interest.

Three Native Landscape Grasses To Try

Posted by Hugh on June 7th, 2016

Leymus grass at Atlantic Botanical Gardens

Blue Lyme Grass at the Atlanta Botanical Garden

Nassellia tenuissima in UT Gardens, Knoxville, Tennessee

Nassella tenuissima in UT Gardens, Knoxville, Tennessee

These three native grasses are easy to establish in average, dry to medium moist, well-drained soils and in full sun. They tolerate a wide range of soils including dry rocky sites, and are exceptionally drought tolerant. Figure on 1 to 2 years for each to become fully established.

Blue Lyme Grass (Leymus arenarus ‘Blue Dune’) is a vigorous spreading cool season grass, 24-30 inches tall, with steel blue foliage and arching growth habit. Blue Lyme is a vigorous grower in warm areas of the U.S. (USDA Hardiness zones 4-10).

Tall flower spikes appear in mid-summer. It grows in a wide range of soils, wet to dry, and in either full sun to partial shade. It grows less aggressive in dry, clay soils. Foliage remains evergreen in zone 8-10; otherwise, blades take on a beige tint in early fall.

Prairie dropseed (Sporobolus heterolepsis) is a clump-forming, warm season, perennial grass found in prairies, glades, and open land areas native to the Midwest U.S. (USDA hardiness zones 3-9). Light airy inflorescences (flower panicles) rise several inches above the fine textured, deep green foliage in September and October.

Prairie dropseed forms mounds of arching foliage, each 1 ½ feet tall and 3 feet wide. Leaf blades turn a golden fall color with orange hues and later to light bronze over winter. Flower panicles have pink and brown tints, and emits a hint of coriander or popcorn fragrance. Tiny rounded mature seeds drop to the ground from their hulls in autumn and serve up a morsel for seed feeding birds. It generally does not self-seed in the garden.

Mexican feather grass or silky thread grass (Naasella tenuissima) is a light airy ornamental grass that flutters in the slightest of breezes (USDA hardiness zones 5-10). Plant in groups of 5 or more to create waves of fine foliage. In the first year irrigate over the first 2-3 months until established and is highly drought tolerant from this point on.

Their green silky inflorescences will soften landscape areas from late spring into late summer, the plumes swaying in the slightest breeze. Plumes turn brown in late summer. Remove winter dead growth at the start of spring.

Prairie dropseed (Sporobolus heterolepsis)

Recommendations On Hardy Crape Myrtles

Posted by Hugh on June 4th, 2016

Lovely bark on ‘Tonto’ crape myrtle at Chanticleer

‘Acoma’ crape myrtle

Crape myrtles are dependable trees and shrubs in zones 7 – 10. In northern areas of USDA zone 6, a number of crape myrtle varieties (cultivars) are rated as winter hardy perennials but not develop into a full sized woody tree or shrub described on the plant tag. In northeastern U.S. cities such as Philadelphia, Wilmington or Baltimore, crape myrtles are rated as hardy perennials.

In record breaking cold winters main branches and trunks frequently dieback near the ground and need to be cut back near the ground. Dieback may occur 1-2 years every decade. By mid-spring new shoots should vigorously sucker back from the ground. From several new shoots, select 1, 3, or 5 strong shoots to develop a new single or multi-trunk tree or shrub. Fertilize when you see emerging shoots. It will likely bloom on the new shoots by late summer.

In the northeastern U.S. select varieties, some public gardens have found to be hardy. Andrew Bunting, plant curator at the Scott Arboretum (campus of Swarthmore College in Swarthmore, PA) reported the following cultivars survived the frigid winter 2013-4 with virtually no damage:

fauriei ‘Fantasy’ (35 ft. tree form, small white flowers)

fauriei ‘Townhouse’ (30 ft. tree, small white flowers)

indica ‘Carolina Beauty’ (tree form, small deep pink flowers)

indica ‘Pink Velour’ (10 12 ft. shrub, small bright pink)

x ‘Acoma’ (10-12 ft. shrub, large pure white)

x ‘Lipan’ (26-28 ft. tree, large lavender flowers)

x ‘Muskogee’ (26-28 ft. tree, large pink flowers)

x ‘Natchez’ (28-30 ft. tree, large white flowers)

x ‘Osage’ (15-18 ft. tree, large clear pink)

x Tuscarora’ (28-30 ft. tree, large dark pink)

x Tuskegee’ (28 ft. tree, large dark pink)

Many of the hardiest cultivars, now numbering 33 originated from the U.S. National Arboretum breeding program. If you wish to start out with just 3 or 4 varieties, select ‘Natchez’ and ‘Muskogee’ (tree forms) and ‘Acoma’ and ‘Osage’ (shrub forms).

Addendum: For many years Chanticleer Gardens in Wayne, PA has grown ‘Tonto’ in a partially protected area (see photo). 8-10 ft. shrub, red flowers, light tan bark

Three Native Flowering Shrubs For Your Summer Landscape

Posted by Hugh on June 1st, 2016

Itea virginica ‘Henry Garnet’

Plumleaf azalea bloom in July

Virginia sweetspire (Itea virginica) flowers in late spring with dark green, pest-free summer foliage that turns brilliant red in fall (USDA hardiness zones 5-9). It thrives in full sun to partial shade, and in moist mildly acidic soils. It is also highly drought tolerant once established. Fertilize with slow release fertilizer in early spring such as Osmocote or Nutrikote.

Virginia sweetspire grows 3 to 6 feet tall and wide, depending on the cultivar planted. Leaves turn ruby red in fall. Pruning is rarely needed except to remove unwanted suckers after flowering has finished. Recommended cultivars include: ‘Henry’s Garnet’ @ 5-6 feet, ‘Little Henry’ @ 4 – 5 feet; or ‘Merlot’ @ 3 – 3 ½ feet

Summersweet (Clethra alnifolia) is a deciduous shrub native to wet areas, such as low spots, stream banks, ponds, etc . (USDA hardiness zones 4-9). This densely-branched, round canopy deciduous shrub typically grows to 3-8 feet high (depending on cultivar) and bears highly fragrant white (or pink) flower panicles in mid to late summer. Flowers give way to dark brown seed capsules in autumn and persist through winter. Dark green, obovate, 3-4 inch long leaves develop fall in color shades ranging from yellow to golden brown; fall hues are highly variable from one year to the next. Flowers attract abundant butterflies and bees.

Fertilize with slow release fertilizer in early spring. Summersweet is trouble-free with little disease and pest problems. Roots tend to sucker and plants form small colonies. Leading cultivars are ‘Ruby Spice’@ rose-pink, 8 feet tall; ‘Hummingbird’ @ white, 3-4 feet tall; and ‘Sixteen Candles’ @ white, 4-5 feet tall.

Plumleaf azalea (Rhododendron prunifolium) is an Alabama/southwest Georgia native (USDA hardiness zones 5-9) that blooms in mid-late July. Bright orange-red flowers will light up any garden spot whether in full sun or partial shade. A dark red flower form is available. Flowers are not fragrant but still attract numerous butterflies and bees.

It grows in average well-drained soil and asks for little nutrition. Irrigate during summer dry spells. It appears to be soil pH insensitive, but likely prefers an acidic range between 5.5 to 6.5. Plumleaf azalea grows 8-10 feet tall, but may be maintained to a 5-6 feet height and width. No diseases and insects pests trouble it. Pruning is rarely needed except for shaping the shrub.

Note: Cultivars of Virginia sweetspire and summersweet shrubs are readily available for sale. Plumleaf azaleas are rarely sold at local garden centers but you can purchase them from e-commerce nurseries on-line.

Tips On Growing Delphiniums

Posted by Hugh on May 30th, 2016

Double-flowered delphinium

Modern day delphiniums (Delphinium spp.), also called larkspurs, are the result of 2 centuries of complex breeding efforts in Europe and U.S. Delphiniums are short-lived perennials, at their best for 2-3 years. They’re most attuned to the cool temperate climes of the northern U.S. Delphiniums belong in the Buttercup (Ranunculaceae) family (USDA hardiness zones 4–7).

Most tall flowering hybrids are derived from D. elatum. Pacific Giant hybrids typically grow 4-5 feet tall on long stems. New Millennium™ hybrids from New Zealand, reportedly are better performers in warm humid zones. Taller varieties are best staked or caged to support their weak hollow stems. Flower colors range from blue, pink, lilac, and white.

Plant delphinums in full sun and in mildly acidic, well-drained, compost-rich soil. Light midday shade is recommended in southerly zones. Soil pH between 6.0 and 7.0 is ideal. Soil drainage is key! Do not allow soil to become overly dry nor stay forever soggy. Delphiniums respond to a steady diet of fertilizer in spring and summer. Apply granular 10-10-10 fertilizer in early spring (or at planting), and follow up with a second and third monthly feeding starting in late June using water soluble products such as Miracle-Gro®, Daniels®, or Peter®.

After the spring flush of flowers is over, cut back plants by at least one-half to spur a brief secondary bloom cycle later in summer; flowers will form on shorter stems. In northerly areas, particularly those devoid of snow cover, protect plant crowns with loose straw or non-packing leaves; do not pile too much mulch as it might smother the crowns.

Delphiniums have few issues with disease and pest issues. High humidity and poor air circulation can cause powdery mildew. Do not irrigate delphiniums overhead or do so early in the day so foliage can dry off. Snails and slugs may be occasional pests.

Hybrids of D. elatum produce 5 to 6 feet tall floral spikes; site tall varieties in back of garden border. The Belladonna group (Zones 3–7), crosses between D. elatum and D. grandiflorum, produce loose, multi-branched spikes of white, blue, or lilac colored flowers. They grow 2 to 4 feet tall, easier to grow, and are longer lived.

Magic Fountain™ and Blue Fountains™ series are seed produced and grow 2-3 feet tall.