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

Easy To Grow Dahlias

Posted by Hugh on June 16th, 2012

Fall Dahlia Show at NC Arboretum in Asheville

According to the American Dahlia Society there are 18 classes of dahlias, from the popular small flowered dahlietta types to the large flowered dinner plate type. Dahlias hail from South of the Border, down Mexico Way, and are not reliably winter hardy north of USDA zone 7-b.

Dahlias are easy to grow. They want a compost rich well-drained soil. Hot summers, lots of natural rainfall, and a constant nutrition yield strong tall plants full of bouquets of colorful flowers. Feed dahlias monthly from planting time through August with a water soluble fertilizer such as Miracle Gro®, Schultz®, or Hollytone®. Follow the package directions.

Dahlias are tubers and are planted them as you would seed potatoes. Tubers may be purchased at garden centers from early spring through mid-June here in the Southern Appalachian region (USDA hardiness zones 6 and 7). After the frost danger has passed in your area, plant dahlias in a sunny garden spot or in a large container filled with an organic soil-less potting media.

Dahlias require a minimum of half to full day sunlight. Give plants room to grow and add a 4-6 foot tall stake to support the large flowering types when blooming. Flowers tend to flop and the plant breaks apart over when soaked by heavy rain.

Tuber(s) are spaced 18-24 inches apart and set to a 4-6 inches depth in rich, well-prepared garden soil. Place the tuber on its side with the eyes (growth buds) facing up. As the dahlia shoot(s) grow taller, fill the hole with one inch of soil every 7-10 days until even with the ground surface. Summer heat and plentiful soil moisture promises great blooming dahlias. If needed, irrigate early in the day and keep water off the dahlia foliage.

Overwatering will cause root rots and a likely invasion of slugs on the foliage. Dahlias are also susceptible to Japanese beetles which shatter the flowers. Deer generally do not bother dahlias.

Dahlias bloom prolifically right up to frost. The plant will collapse (die above ground) and you will need to dig up the tender tubers and store them away through the winter months.

Torenia (Wishbone Flower) Blooms In Part Shade

Posted by Hugh on June 14th, 2012

Torenia in Hanging Basket

The list of summer flowering annuals for shady spots in the garden is not long. Garden impatiens (Impatiens x wallerana) is the first choice, seconded by begonias (Begonia x semperflorens-cultorum). Today, wishbone flower (T. fournieri) is now available.

Torenia blooms from spring to frost. It is best grown in a moist, organically rich, well-drained soil and in part sun to part shade. Growth and flowering are poor in deep shade. Torenia struggles in hot and humid weather and requires shade protection against the afternoon sun. Like impatiens, it is not drought tolerant. Mulch aids in soil moisture retention and keeps the soil cool.

The two-lipped bicolored flowers are trumpet shaped with broadly 5-winged calyxes. A pair of stamens connect the anthers forming a “wishbone” of a chicken (use a little imagination). Torenia species blooms are pale violet with dark bluish purple lower lips and a yellow throat. The 2-3 inch oval shaped leaves are light green and relatively disease and pest free if plants are set and cared for in the right garden location.

Two series of torenia are popular at garden centers in the springtime: Summer Wave® Torenia from Suntory Ltd. and the Moon® Torenia series from Danziger, available in cell packs up to 6 inch containers. Blue shades are most popular, but other color choices include: rose, purple, lavender, yellow and white. The throat inside each bloom may be yellow or white.

Torenias are excellent as edging plants in garden beds and planted in containers or window boxes. New cultivars are more compact, do not need pinching back, and bloom earlier. They grow 10-15 inches high and 20-25 inches wide.

Powdery Mildew: The Bane of Beebalm

Posted by Hugh on June 9th, 2012

Monarda didyma 'Jacob Cline'

Beebalm (Monarda spp.) is one of our great native perennials and herbs. Native Americans used beebalm as a tea, brewing it for colds, minor bronchial and digestive complaints, and also as a poultice to soothe insect stings. During the Boston Tea Party, rebellious colonists utilized beebalm as a tea substitute, calling it “Oswego tea”. To ward off mosquitoes and flies, people used beebalm leaves tucked under their hats.

Monarda is a member of the mint family, and edible leaves are aromatic and minty. Beebalm prefers a moist, richly organic, well-drained soil in full sun to light shade. Beebalm tolerates summer heat but not prolonged droughts. Fertilize plants in early spring and 6-8 weeks later with 10-10-10 or equivalent granular product or feed monthly through August with water-soluble fertilizers such as Miracle-Gro®, Daniels™ or Schultz™.

Beebalm grows from two to four feet tall depending on the cultivar, and will fit well into your herb or perennial garden. Bees, butterflies and hummingbirds are attracted to its colorful, nectar rich tubular flowers which open in early June in the Southern Appalachian region (USDA hardiness zones 6 and 7). Beebalm will re-bloom when the spent flowers are deadheaded.

Flower colors range from bright red, white, pink, lavender and purple. Beebalm seeds-in heavily over time, and a flower bed usually becomes overcrowded within two to three years, requiring clumps to be divided. Deadheading spent flowers stimulates re-blooming and reduces the re-seeding problem.

Beebalm has few pests – except powdery mildew, a serious foliage disease. Summer heat, high humidity, and overcrowded plants turns on powdery mildew to coat beebalm foliage white. Weekly spraying with garden fungicides from late June to frost is not a practical solution. Instead, select disease resistant varieties of beebalm.

A few of the better cultivars (M. didyma and hybrids) are:
‘Jacob Cline’ – large deep red flowers on 3-4 feet tall plants; superior mildew resistance.

‘Croftway Pink’– rose-pink flowers; not mildew resistant.
‘Marshall’s Delight’– deep pink flowers; good mildew resistance.
‘Snow Queen’– white flowers; not mildew resistant.

‘Claire Grace’ – good mildew resistance; lavender flowers on 3-4 feet tall plants (M. fistulosa).

‘Lady Francis’ Ivy Wakes Up A Shady Patch

Posted by Hugh on June 6th, 2012

'Lady Francis' Ivy in Columbus, Ohio

On a recently trip to the Ohio State University Horticultural Gardens in Columbus, I discovered ‘Lady Frances’, a relatively tame miniature ivy. The American Ivy Society classifies Hedera helix ‘Lady Frances’ as non-invasive, and it received the first “Ivy of the Year” award in 2001. It grows slowly and works as a ground cover or topiary in a garden bed or in a container as a “spiller”. Lady Frances also performs well indoors, growing near a well lighted window.

This ivy features small 1- inch long and wide green and white variegated leaves which should brighten up any garden spot. Lady Frances is winter hardy in central Ohio (USDA hardiness zone 5). Morning sunlight and afternoon shade are generally the rule in the Southern Appalachian region (USDA hardiness zones 6 and 7) and in all-day moderate shade further south. ‘Lady Frances’ possesses good heat and drought tolerances once established in the garden for one year. It exhibits good disease and insect resistances and deer generally leave ivy alone.

Never invite any ivy species (Hedera or Parthenocissus spp.) into your garden without a back-up plan for pruning it. Let it ramble as far as you want and clip it back. Keep most ivy cultivars from climbing into trees.

‘Lady Frances’ was discovered by Mo Halawi at Weidners’ Gardens in Encinitas, CA and was named to honor Frances Rynearson, American Ivy member from San Diego, CA.

Japanese Beetle Traps – Useful Monitoring Tool

Posted by Hugh on June 4th, 2012

Japanese Beetle Trap

A decade ago garden centers sold thousands of Japanese beetle traps until somebody questioned why anyone would want to lure this summer pest into their garden. Yes, the traps do work and may catch hundreds per week. You also attract hundreds more to feed on your plants’ flowers and leaves and, later in the year, the larvae will feed in the soil on lawn grass roots.

Most Japanese beetle traps contain two sex pheromones in a brightly colored container. Japanese beetles feed in groups and mate. Pheromone traps attract far more beetles than they actually capture. You’re inviting every Japanese beetle in the neighborhood into your yard, but only a small percentage end up in the traps. If you convince the entire neighborhood to hang up Japanese beetle traps, you may effectively stop their migration from yard to yard and effectively reduce their numbers.

Beetle adults feed on nearly 300 different host plants. Some of the more common targeted landscape plants include: roses (Rosa spp.), flowering cherry (Prunus spp.), flowering crabapple (Malus spp.), shrub althea (Hibiscus syriacus), hollyhock (Althaea rosea), linden (Tilia spp.), and grape vines (Vitis spp.). Adults feed all day on the flowers and/or leaves. Damaged leaf tissue takes on a lacey or skeletonized look as beetles feed between the leaf veins.

Japanese beetle traps are useful monitoring tools for determining whether the insect population numbers in your yard necessitates pesticide control. The following pesticides are used for reducing Japanese beetles:

Carbaryl (Sevin®)
Cyfluthrin (Bayer™ Advanced Pest Control)
Neem Oil (organic pesticide)
Acephate (Orthene®)
Triazicide® (for soil application against larvae)

Dwarf Southern Magnolia Cultivars

Posted by Hugh on June 1st, 2012

Small Tepal Flower of 'Little Gem' Magnolia

: Small 5-6 Year Old ‘Little Gem’ Magnolia

Southern magnolia (Magnolia grandiflora) is remarkably hardy in USDA zone 6. This evergreen magnolia prefers a moist well-drained, slightly acidic soil, and planted in a partial to full sun location. It is a long-lived large 70-80 feet tall tree, best suited to large commercial and residential properties, golf courses and public parks.

Four dwarf cultivars are available at garden centers:

‘Little Gem’ and ‘Hasse’ (35-40 feet in height)
Teddy Bear® and ‘Kay Parris’ (25-30 feet in height)

Little Gem is most popular and grows very shrub-like. Little Gem may encompass 20 or more feet of ground area. Hasse exhibits a tree-like habit and branching is primarily upright. Teddy Bear and Kay Parris grow slowly and are better selections for small landscapes.

Regarding the dwarf cultivars, the leaves and flowers are proportionally smaller that the species. The glossy foliage is thick and leathery, and dark green over both the upper and lower surfaces. Kay Parris foliage is reddish brown on the underside.

Goblet shaped flowers open intermittently from late spring through summer and are very fragrant. On trees ten years and older, one to several blooms open almost every day from May until late September. Ornate cone-like seed pods form after flower have shed their creamy white tepals (petals).

Pruning is rarely needed unless you desire to limb up the lower branches (for mowing under and such). Evergreen leaves drop through most of the year, most noticeable in late winter and early spring.

‘Helene Von Stein’ Lamb’s Ear Is More Behaved

Posted by Hugh on May 30th, 2012

Messy Floral Heads of Lamb's Ears

Stachys byzantina is a dense gray woolly perennial ground cover, which earns it the common name “lamb’s ear”. ‘Helene Von Stein’ is the single best cultivar, displaying larger leaves, and is more heat and humidity tolerant. Sometimes listed as ‘Big Ears’, it rarely produces flowers which may tarnish its lovely silvery gray foliage appearance.

Lamb’s ear grows approximately 12-18 inches tall and wide. High humidity, long exposure to moisture on the foliage, and poor soil drainage all lead to its decline and ultimate death. Do not irrigate lamb’s ear overhead.

Lamb’s ear grows in any average well-drained soil. After a short 6 month establishment period, it exhibits exceptional drought tolerance. It grows best in full sun in USDA zones 4-6 and under light afternoon shade further south. Leaves are evergreen in areas with mild winters, but will deteriorate under harsh winters. Excessive shade may invite foliar disease problems.

Common lamb’s ear spreads aggressively by runners. Erect, small-leaved spikelets of small purplish flowers appear from late spring thru the summer, rising several inches above the foliage. Gardeners may choose to remove the floral shoots to tidy up this ground cover or switch over to grow ‘Helene Von Stein’.

Lamb’s ears is a great choice in the front of a flower border or in a rock garden.

Stachys 'Helene Von Stein'

Add Hardy Begonia To Your Shade Garden

Posted by Hugh on May 28th, 2012

Hardy begonia

Hardy begonia (Begonia grandis) is the only species of begonia which is winter hardy in USDA zones 6-9 (zone 5 with protection). This shade-loving perennial grows 18 -24 inches high and wide, and displays a well-branched mounding habit. Foliage is medium to olive green above and reddish green with red veining beneath. Leaf shape is similar to angel wing begonia. Sprays of pink ¾ to 1 inch flowers rise above the foliage from early summer to fall.

Hardy begonia grows best in open shade. It thrives primarily in moist, humus-rich, well-drained soil where it mixes among other leafy shade garden favorites such as hostas (Hosta spp.), lungworts (Pulmonaria spp.), brunneras (Brunnera spp.), and ferns. A back-up irrigation plan in the hot summer weather is a must. Mulch generously around clumps in late fall for winter protection in zones 5 and 6. Hardy begonia dies back to the ground each winter, leaving little evidence that it was ever there.

Deadheading spent flowers will extend its blooming time and reduce the probability for self-seeding. Hardy begonia also spreads by tiny bulblets which can be dug up and transplanted in the late fall to increase the bed size. Hardy begonia has no serious insect or disease problems and is rated as rabbit proof. ‘Alba’ is a white flowering form.

Unfortunately, availability of plants through nursery and garden center sources is not plentiful, but can be purchased on-line.

Northern Maidenhair Fern Appear Delicate But Grow Tough

Posted by Hugh on May 23rd, 2012

Maidenhair fern (Adiantum pedatum)

Their leaves (called “fronds”) appear delicate, but maidenhair ferns (Adiantum spp.) are reliable long-lived perennials. Northern maidenhair (A. pedatum) thrives in most gardens within USDA zones 3-8, while the Southern counterpart, (A. capillus-veneris), predominates in warmer USDA 7-10. Unfortunately, planting of maidenhairs are not utilized in the Southern Appalachian gardens (USDA zones 6-8).

Fronds average 18-24 inches in length and form 12-15 inch wide colonies. Northern maidenhair flourishes in zones with a humid, warm summer its soil rhizome network as the only clue of its presence. Spritely green fronds emerge in the spring. Utilize them in partially- to fully- shaded landscape areas. In a container, permit the dainty fronds to spill over the edge of the planter.

Choose a dense moist woodland spot and generously amend the well drained soil with compost. Maidenhair prospers around ponds and other water features. A neutral to slightly alkaline soil is perfect. Gradually add limestone to adjust soil pH higher as needed and maintain good air circulation around plants.

When planting most ferns, set the roots in the hole so the crown is at or slightly shallow with the soil surface. Avoid planting deep! Lightly cover with 1-2 inches of an organic mulch such as bark chips, pine needles or leaf mold.

Most ferns are light but constant feeders. Feed bi-monthly from March thru August with a water-soluble fertilizer such as Miracle Gro®, Schultz™ or Hollytone® for optimum growth.

Protect Autos and Home Siding From Artillery Fungus

Posted by Hugh on May 20th, 2012

Mild Case of Artilery Spores on Home Siding

Artillery fungus (Sphaerobolus stellatus) deposits small tar-like specks on the siding of your house or on your car finish in early spring or fall. Artillery fungus is a wood-rotting organism living in the mulch around your home foundation. The fungus shoots its sticky, black spore masses as far as 20 feet out away. The tar spots adhere tightly to the paint or siding and are difficult to wash off.

No fungicides are labeled for control of the artillery fungus in mulch. Cellulose is the principal component of wood mulch and the primary food source for this wood-rotting fungus. Instead, select a bark mulch which contains lignin that decays more slowly.

Adding a fresh layer of a large nugget bark mulch over an existing mulch each year may reduce the sporulation of the artillery fungus. Do not apply more than 4 inches of mulch, as plant roots into the soil may become smothered. Covering existing mulch with a layer of pine needles may prevent sporulation of the artillery fungus. Mushroom compost, mixed with bark mulch, @ 40% by volume, will also suppress artillery fungus.

Another approach is to remove the contaminated mulch and replace it with a synthetic mulch, such as shredded rubber mulch and artificial pine needles. Synthetic mulches last much longer and not provide a growth medium for the artillery fungus. Planting groundcovers instead of mulching is another option.