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

Transform These Three Shrubs Into Trees

Posted by Hugh on February 9th, 2017

‘Diabolo’ Ninebark as young tree

Foliage of Viburnum sieboldii

Some large shrubs can be trained into lovely small flowering trees. These three flowering shrubs may be trained into small 15-25 feet tall, single or multi- trunk trees:

Siebold viburnum (Viburnum sieboldii) is a tall upright branched deciduous shrub (USDA hardiness zones 4-7). This native from Japan grows to 15-20 feet tall and 10-15 feet wide within 10-12 years.

In mid to late May, showy white flat-topped flowers appear in abundance, measuring 3-4 inches across. Flower heads are composed of small sterile center flowers surrounded by larger white fertile flowers. Flowers give way to ½ inch wide red berry-like fruits (drupes) on showy red fruiting stems in late summer; they ripen to black in fall and attract winter feeding birds. The 3-inch long, medium to dark green leaves has no memorable fall color.

Panicle hydrangea (Hydrangea paniculata) also originates from Japan and China and is exceptionally cold hardy (USDA hardiness zones 3-8). Depending on cultivar, this vigorous grower reaches 8-15 feet tall as a shrub and to 25 feet tall as a lovely patio tree. From mid-summer into fall, huge 6-8 inch long, creamy white terminal flower panicles contain both fertile and sterile flowers. Its dark green, blemish-free ovate foliage is coarse textured. Select tall growing cultivars like ‘Limelight’ or ‘Grandiflora’ to transform into trees.

Diabolo ninebark (Physocarpus opulifolius var. Diabolo) is an upright, spreading, deciduous, shrub (Zone: 3 to 7). ‘Diabolo’ is a purple-leaved cultivar that grows 6-8 feet as a shrub and 12-15 feet tall in tree form. It is easily identified for its exfoliating bark on older branch and trunk wood which peels off in thin strips to reveal the reddish to light brown inner bark. This heightens its winter interest. Small pink or white flower heads, resembling flowering spireas (they’re related), appear in late spring. Flowers give way to drooping clusters of reddish seed capsules. The 3-5 lobed, 4-inch long ovate leaves start out dark purple and bleach out to dark green in the heat of summer, and turn a blah yellow in fall.

All three landscape shrubs grow well in average, mildly acidic (pH 5.5 to 7.0), moderately moist, well-drained soils and in full to partial sun. All three are relatively drought tolerant after their first year. Prune siebold viburnum and ninebark immediately after spring flowering. Wait until late winter to prune panicle hydrangea. No serious insect or disease problems are attributed to these shrubs when they are properly sited in the landscape.

Butterfly Weed Named 2017 Perennial Plant Of The Year

Posted by Hugh on February 4th, 2017

Fall seed pods of Asclepias tuberosa

Milkweed (Asclepias tuberosa), aka butterfly weed, is a long-lived tuberous rooted perennial indigenous to the southeastern U.S and mid-western U.S. and Canada (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 2- 3 feet high and 1 -2 feet wide. Unlike many of the other milkweeds 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 an important larvae food for 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 perfect choice meadow or prairie garden for full sun. 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 wild plants as they rarely survive transplanting because of their deep taproot system. Young seedlings are best left undisturbed for two years to become established.

Few disease and insect problems trouble butterfly weed if grown in the proper site. Wet poorly-drained soil usually results in rot rot diseases. Leaves are susceptible to rust and leaf spots, often in overcrowded plantings. In medical circles the plant is commonly called “pleurisy root”, and once used to treat wheezing and coughing.

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

‘Hello Yellow’ is a yellow flowering cultivar.

Pest Alert: Update On Emerald Ash Borer

Posted by Hugh on January 31st, 2017

Green ash tree (F. pennsylvanica)

EAB exit holes (photo by Dr. Frank Hale, Univ of Tenn Extension Entomologist)

Across the U.S. and Canada, ash trees are dying from infestations of Emerald Ash Borer (EAB), an Asian insect pest. In many U.S. cities, ash (Fraxinus) is a major urban tree genus. Since 2002 EAB has become a serious pest that has killed more than 40 million ash trees in 18 states.

This hardwood tree is important to the timber industry. The wood is used in the manufacture of furniture, flooring, ship building, etal. All native species of ash are susceptible, including American ash (F. americana) and green ash (F. pennsylvanica).

Early detection of the pest in special traps can slow its spread and minimize the impact. Some tree and landscape companies can perform trunk injections and soil treatments. In many states tree injections are done by ISA Certified professionals. In many cities property owners must decide to treat, remove or retain infested trees.

This invasive beetle lays eggs on the tree bark. The hatched larvae tunnel underneath the bark and will kill the tree within three years or less. Here are some guidelines to slow the rate of EAB infestation:

Don’t transport firewood from place to place, even within the state where you live. Don’t bring firewood along for camping. Instead, buy the wood from a local source.
Don’t buy or move firewood from outside the state. If someone comes to your door selling firewood, inquire about the source.
Watch for signs of infestation. If you suspect that your ash tree may be infested, visit your state website online or call a certified arborist, one certified by the International Society of Arboriculture (ISA).

Stop The “Crape Murder”

Posted by Hugh on January 28th, 2017

Beautiful structure of multi-year old crape myrtle

Remove old seed heads in March (this photo taken 5 months later in August)

In Tennessee (where I live) and in the Southeastern U.S., bad crape myrtle (Lagerstroemia x) pruning continues to be done by professional landscapers and homeowners (USDA hardiness zones 6-9). This practice, also called “topping”, reduces tree (or shrub) height. Over 25 years, Southern Living magazine called this “crape murder”.

Crape murder is not going away. More crape myrtles are improperly pruned than correctly pruned. Usually, the practice will not kill the tree, but it can result in less flowering and shorter tree life. Wood decays frequently occur.

If a crape myrtle becomes too large for a certain location, either it was planted in the wrong spot to begin with or the wrong variety was purchased. Before you plant, select crape myrtle varieties that will fit their location at maturity. That information is printed on the plant tag.

Never top crape myrtles! Generally, crape myrtles require very little annual pruning and are best pruned in late winter once the worse of the winter weather is over. Most branches only need thinning, e.g., removal of last summer’s spent flowers and seed heads. Remove any branches that cross or rub against one another. Eliminate suckers around the base of the tree and water sprouts (vigorous upright growth) inside the tree canopy.

According to Dr. Allen Owings at the LSU AgCenter, Hammond Research Station, Hammond LA, properly pruned crape myrtles exhibit:

Stronger Branch Wood
More Flowers
Larger Flowers
More Pollinating Insects
Better Bark Features
Fewer Water Sprouts
Fewer Suckers
More Birds Nesting
Less Fungal Decay in Wood
Fewer Insects and Sooty Mold
Less Leaf Spot
Better Air Circulation

Encourage friends and neighbors to prune crape myrtles properly. When allowed to grow and mature, they become beautiful majestic trees. If you do not know how to prune crape myrtles, hire a certified tree arborist where you live. Consult the International Society of Arboriculture (ISA) website for a list of certified arborists in your area.

50+ Flowering Pollen/Nectar Plants For Bumblebees

Posted by Hugh on January 24th, 2017

Russian sage is a bumblebee favorite

Lots of insect activity on Buddleia

Here are three key points in planning your pollination garden. To attract U.S. native bumblebees:

First, add both early(*), mid-summer, and late(**) flowers in the mix for a three seasons long garden.

Second, mass together many of the same kinds of flowers, not just one or two plants, so that bees will spot them easier and to visit the planting frequently.

Lastly, keep pesticide applications away from areas where trees, shrubs, perennials, biennials, and annuals are blooming. In particular, do not use systemic pesticides containing Neonicotinoids which are reportedly toxic to bees.

Agastache (Agastache spp.)
Ageratum (Ageratum houstonianum)
Bachelor buttons (Centaurea)
Beebalm (Monarda spp.)
Betony (Stachys officinalis)
Black-eyed Susan (Rudbeckia spp.) **
Borage (Borago officinalis)
Buddleia (Buddleia spp.) **
Bugleweed (Ajuga reptans)
Calendulas (Calendula) *
Catmint (Nepeta x faassenii)
Clovers (Trifolium spp.)
Comfrey (Symphytum officinale)
Coneflowers (Echinacea spp.) **
Cosmos (Cosmos spp.) **
Crocus (Crocus spp.) *
Cranesbill (Geranium spp.)
Culvers root (Veronicastrum virginicum)
Curry plant (Helichrysum)
Forget-me-not (Myosotis) *
Foxglove (Digitalis purpurea)
Goldenrods (Solidago spp.) **
Giant thistle (Cirsium rivulare)
Hollyhock (Alcea)
Honeysuckle (Lonicera spp.)
Heath (Erica carnea) *
Heather (Calluna vulgarus) *
Lavender Lavandula angustifolia
Lenten roses (Helleborus spp.) *
Liatris (Liatris spicata)
Marigolds (Tagetes spp.)
Marjoram (Origanum vulgare)
Mints (Mentha spp.)
Mountain mint (Pycnanthemum virginianum)
Mullein (Verbascum)
Nasturium (Tropaeolum majus)
Ornamental onions and chives (Allium spp.)
Peruvian verbena (Verbena bonariensis)
Pincushion flower (Scabiosa)
Poppies (Papaver)
Primroses and cowslips (Primula spp.) *
Pussy willow (Salix)
Red Valerian (Centranthus rubra)
Rosemary (Rosmarinus officinalis)
Russian sage (Perovskia atriplicifolia)
Sage (Salvia officinalis)
Sea thrift (Armeria) *
Sedum (Sedum spectabile) **
Snapdragon (Antirrhinum) *
Sweet alyssum (Lobularia maritima)
Sweet William (Dianthus barbatus) *
Sunflowers (Helianthus spp.) **
Thistles (Echinops)
Thyme (Thymus spp.)
Toadflax (Linaria vulgaris)
Wallflower (Erysimum cheiri) *

Our Native Bumblebees In Trouble

Posted by Hugh on January 22nd, 2017

Bumblebee pollinating

Recently, the U.S. Fish and Wildlife Service recognized ten more animal species as Endangered Species, providing them protections under the Endangered Species Act of 1973. These 10 species include 7 species of bees. Endangered status will afford the rusty-patched bumblebee protection under federal law.

Bumblebees build their nests in the ground (and other places). Honeybees, however, who are not native to the U.S., build and live in their mostly above ground hive (nest) for many years. Populations of rusty-patched bumblebee were once widespread across the U.S. and Canada. Today, their greatest populations are found in the northeastern U.S. and Canada, and their numbers are spotty in several locales.

Bumble bees face many threats including loss of habitat, diseases, pesticide usage, and climate change. Unlike honeybees, which co-habitate in large colonies (>10,000 individuals) in perennial hives, bumble bees produce smaller annual populations (50-1,500 individuals). Due to their smaller annual population sizes, life cycle, and genetic makeup, they are a lot more susceptible to extinction.

Bumblebees typically nest underground, and overwinter in undisturbed ground – one that is not planted or mowed. Bumblebees frequently nest in compost piles, woodpiles, stone walls, or empty bird houses.

According to the Xerces Society, here are some things that gardeners can do to help bumblebees:

Plant long flowering plants that start blooming early and finish late. Provide bumblebees with pollen and nectar from late winter through early autumn.
Choose flowers of plant species native to your region that the bumblebees evolved alongside with. Plant species from around the world may be beneficial as well. Flowers should closely look like open pollinating species. Don’t plant varieties with double petals that make it hard for the bumblebee to access the pollen.
Purple, blue and yellow flowers attract bumblebees. Bees cannot see the color red.
Avoid using pesticides in your flower garden.
Learn and understand the natural habitat of bumblebees
Involve gardening friends and neighbors providing and conserving bee habitats.

For additional tips on conserving bumblebees, visit the Xerces Society website: http://www.xerces.org/bumblebees/

Comparing Western Red Cedar And ‘Green Giant’ Arborvitaes

Posted by Hugh on January 21st, 2017

20 year old Thuja plicata in east TN

Needle foliage of Western Arborvitae

Western red cedar or giant red cedar (Thuja plicata) is native to the Pacific Northwest. In the eastern U.S. it is called western arborvitae and landscapers typically do not plant it. Instead, they plant the hybrid cultivar ‘Green Giant’ arborvitae, a cross between western red cedar (T. plicata and Japanese arborvitae (T. standishii).

Western arborvitae is typically found in cool moist forest areas and bottomlands from southern Alaska along the Pacific coastline to northern California and from British Columbia to western Montana (USDA hardiness zones 5-7).

Western arborvitae is the largest tree in the cypress family, averaging 100 feet and more in height and long-lived from 400 to 1000 years in the Pacific Northwest. However, east of the Mississippi River, expect dimensions 50-60 feet high and 15-25 feet wide at its base. It features horizontal branching with sprays of scale-like dark green foliage which is aromatic when crushed. Flowers are inconspicuous and small, half-inch long light brown cones follow and mature in fall.

Cultivar ‘Green Giant’ grows even faster into a large 50 – 60 feet vertical specimen tree. It is widely planted as a tall privacy hedge or screen. Screen grows to 50-feet in height and spread of 15 to 20 feet at its base. Young ‘Green Giant’ transplants grow 2- 3 feet annually if planting is adequately fertilized and irrigated. Summer needles are bright green and retain its green color through the winter, far better than Japanese cedar (Cryptomeria japonica) and Leyland cypress (x Cupressocyparis leylandii).

Western arborvitae grows best in moist, humus-rich, well-drained soils in full sun to partial shade. It thrives where summers are moist and cool. One year old established plants exhibit good drought tolerance, more so with age.

Western arborvitae exhibits no serious disease or insect problems. Bagworms may become serious pests. Root rots may occur if soil drainage is poor.

Currently, Green Giant arborvitae is replacing Leyland cypress as landscape privacy screening. Leyland cypress has proven susceptible to 3 serious disease problems in the southeastern U.S. Low growing shrub forms of western arborvitae are also available.

Landscaping Plantings Around A Garden Railroad

Posted by Hugh on January 18th, 2017

Tiny 'Curly Top' False Cypress Trained As Small Evergreen Tree

Tiny ‘Curly Tops’ Sawara False Cypress Trained As Small Evergreen Tree

Mix of Dwarf Conifers and Japanese Maples

Garden railroad layouts are becoming more popular. A number of dwarf and compact growing plants play a major role in landscaping around the layout. Many miniature forms of taller varieties are available. Here are several great plant choices to add the your garden railroad:

Trees and Shrubs – offer scale or tall canopy to the landscape:

Dwarf Japanese maples (Acer palmatum) choose from tree and shrub forms

Dwarf Korean boxwoods (Buxus microphylla)

Dwarf hornbeams (Carpinus spp.)

Drawf hinoki cypresses (Chamaecyparis obtusa)

Sawara False cypresses (Chamaecyparis pisifera)

Dwarf or compact growing cotoneasters (Cotoneaster spp.)

Dwarf hollies (Ilex spp.)

Miniature forms of Alberta spruce (Picea glauca ‘Conica’)

Dwarf (Lepidote) rhododendrons (Rhododendron spp.)

Dwarf sweetbox (Sarcococca spp.)

Dwarf hemlocks (Tsuga spp.)

Dwarf little leaf elms (Ulmus parvifolia) such as cvs. ‘Jacqueline Hillier’ and ‘Lois Hole’

Ground covers (serve to prevent erosion and added greenery in lieu of lawn grasses):

Maidenhair fern (Adiantum spp.)

Bugleweed (Ajuga reptans)

Low growing sedges (Carex spp.)

Ivies (Hedera spp.)

Dwarf hostas (Hosta spp.)

Certain euphorbia shrubs and ground covers (Euphorbia spp.)

Selaginellas (related to ferns)

Irish moss (Sagina)

Sedums (Sedum spp.)

Maintenance to your garden railroad landscape: timely pruning is an important chore. Bi-annual pruning in summer and winter is essential, particularly after the bed has been established. Plants that make good bonsai candidates may be added to a garden railroad landscape. Examples include ginkgo, junipers, plum yews (Cephalotaxus) and yews (Taxus).

Also, you may select several colorful annuals to the planting mix. Choose low growing forms such as such as petunias, snapdragons, star zinnias, French type marigolds, dwarf dahlia varieties, impatiens, moss rose (Portulaca), and annual spiderworts (Tradescantia). Taller flowering types such as select salvia species, angelonias, cupheas, lantanas, and gomphrenas may require pruning back every 3-4 weeks to maintain landscape scale and to keep plants flowering.

Feed plants with weak solutions of water soluble fertilizers such as Miracle-Gro™, Jacks™, or Schultz™ Plant Food. Regulate frequency of watering as not to flood plants or overstimulate them.

Powdery Mildew Disease Resistant Cultivars

Posted by Hugh on January 15th, 2017

Powdery mildew on herbaceous peony

Powdery mildew on Garden Phlox

Gardeners have learned to associate certain plants with a troublesome disease(s). Powdery and downy mildews have become epidemic in many regions of the U.S. Best ways for managing mildew diseases are prevention, good cultural practices, and spraying.. First, avoid planting susceptible cultivars. Plant in the proper location and space plants far enough apart so they’re not touching. Surrounding vegetation should not block air movement through the garden.

Follow good cultural practices such as reducing or eliminating overhead irrigation practices. Fertilize to optimize plant health, but avoid over-fertilization with nitrogen as it stimulates young, succulent growth which can be more susceptible to infection.

Some moderately susceptible cultivars may require protection with fungicide sprays, particularly if environmental conditions are highly favorable for onset of mildew diseases. Dig up and eliminate susceptible cultivars of lilac, roses, crape myrtle, impatiens, zinnias or summer phloxes. Plant breeders continue to provide gardeners with better disease resistant cultivars. In recent years, notable examples of resistant plants include:

Crape myrtles – ‘Catawba’, ‘Hopi’, ‘Cherokee’
Crabapples – ‘Prairifire’, ‘Sugar Tyme’, lots others
Dogwood (Cornus florida)– ‘Cherokee Brave’, ‘Appalachian Joy’, ‘Appalachian Snow’, ‘Appalachian Mist’

Dogwood hybrids (C. florida x C. kousa) – ‘Stellar Pink’, ‘Stardust’, ‘Galaxy’, ‘Constellation’ , ‘Aurora’
Sycamore – ‘Columbia’, ‘Liberty’, Yarwood, Exclamation™
Summer phlox – ‘David’, ‘Robert Poore’, ‘Delta Snow’, ‘Speed Limit 45’
Lilac – ‘Bloomerang’, ‘Betsy Ross’, S. meyeri ‘Miss Kim’, S. pekinensis

Monardas (beebalm) – ‘Marshall’s Delight’, ‘Blaustrumph’, ‘Colrain Red’.

Rhododendrons – R. yakushimanum, R. macrophyllum, R. ‘Nova Zembla,’ R. ‘Palestrina’
Roses – Simplicity™ and Meidiland™ roses, Rosa rugosa varieties
Zinnias – Z. angustifolius ‘Profusion or Zahara series; Pulcino and African varieties

One final thought: if foliage infections break out on garden plants in very late summer or fall, spraying a preventative fungicide is generally not necessary or impractical. Instead, practice good garden sanitation, a thorough clean-up of infected leaves and stems. For infected annuals and perennials, gather up infected debris and discard. Do not add it to a compost pile, but throw it curbside for pickup or add to a burn pile, obtaining the proper burn permits.

Five Simple Pruning Tips For DIYers

Posted by Hugh on January 11th, 2017

March Rejuvenated viburnum 3 months after cutback

Small Dramm pruner perfect for small 1/4 inch pruning cuts

Gardeners are frequently scared about making pruning mistakes. There are lots of gardening books filled with lots of before and after photos. Let’s face facts…your yard tree or shrub does look like the ones pictured in the pruning book.

Here are my simple 5 steps for pruning:

Why and When to prune: You can prune a tree or shrub any day of the year. The best time is generally in late winter. Choose a comfortable weather day to work outdoors so you’re not in a hurry. Remove low growing branches in any month. Branches that are dead, broken, infested with scale insects, or diseased can also be sawed or lopped off anytime. If the job involves major pruning, e.g. 30% of branches removed, spring or summer pruning is best time.
Flowering shrubs or trees — when do they bloom? Spring flowering shrubs and trees are best pruned immediately after or within one month after flowering. Can’t wait?…then prune when you’re ready. Crabapples, ornamental cherries, redbuds, dogwoods, azaleas, lilacs, forsythias, and spireas bloom on old wood in spring. Summer flowering woody plants bloom on new wood. Examples include most (not all) hydrangeas, chaste trees (Vitex), crape myrtles, althea (Hibiscus), butterfly bush (Buddleia), and roses.
Make the big cuts first. Take your time! Observe the tree from several points to determine the best cuts. Making many small cuts is okay, but they’re a lot more time consuming. Small pruning cuts heal faster than bigger ones. Completely rejuvenated shrubs are cut back 6 – 12 inches above the ground. Applying pruning wound paint is not necessary.
Use sharp pruning tools — Don’t plan to do all work in 1 year. If the tree has been neglected for several years, it may take 3-4 years to bring back desired shape and health. To repeat, don’t remove more 30% of branches in any one year.
Large shade trees — hire a certified arborist who should be properly insured and licensed. Maples, oaks, lindens, elms, birches, and others should be pruned every 5 years. Tree topping should be avoided as this practice results in a tree potentially more hazardous.