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

Pest Update – More Pesticide Options Available Against Hemlock Adelgid

Posted by Hugh on June 29th, 2012

Cottony masses of hemlock adelgids (photo by Dr. Alan Windham, UT Extension)

You may be able to prevent or save tree and shrub hemlock(s) from woolly adelgid. This serious pest has two generations per year. The first generation hatches in March and April from overwintering adults (as many as 300 eggs per adult) in white cottony masses on the small twigs. The crawlers (nymphs) hatch and feed in April and May. The spring generation ends by mid- June. A second crawler generation emerges in July and feeds until mid- October.

Loss of a hemlock tree or shrub hedge does not over 1-2 years. It may take a buildup of 3-4 years before serious damage occurs. Inspect hemlock(s) several times of the year for white adelgid masses on the underside of twigs and needles.

Imidacloprid is the most popular insecticide of choice. It acts systemically. The pesticide must be watered into the soil within 24-36 hours, to carry it down the hemlock roots to be absorbed. Imidacloprid and other pesticides appear to be effective over two and more years.

Read and understand the pesticide label! Do not use around streams or ponds or in rocky soils. Pesticide rates will vary according to the size of the tree trunk or the height of the hedge. Most soil drenches contain imidacloprid, including Bayer Advance Garden Tree and Shrub Insect Control™, Merit 75 WP, Malice 75 WSP, Zenith 75 WSP. Safari 20 SG (dinotefuran) has slightly faster uptake by the tree. Safari may be used as soil drench or bark spray.

Most pesticides may be purchased from garden centers, home hardware, and farm supply stores.

Credit: Special thanks for information and photos supplied by NC State University and University of Tennessee Extension.

Vintage ‘Strawberry Candy’ A Sensational Daylily Performer

Posted by Hugh on June 26th, 2012

'Strawberry Candy' daylily

Some vintage daylily varieties are timeless performers. Strawberry Candy daylily (Hemerocallis x ‘Strawberry Candy’) is a daylily classic, one of the first to open in June in Southern Appalachian gardens (USDA hardiness zones 6 and 7). Its grass-like foliage is semi-evergreen here.

The 4- inch diameter flowers open strawberry pink with a prominent rose red eye and golden green throat. Its 24-26 inch height and spread make it a good fit in almost any landscape situation. Plant it in the front border of the flower bed, grow it in a container, or as a ground cover.

Flowers bloom almost all day long, from the early morning to late evening. It’s also a re-bloomer, returning in September – October for another brief bloom cycle. For Strawberry Candy to re-bloom, plant(s) must be fertilized and irrigated through summer’s heat and dry spells.

Daylilies thrive in full to partial sunlight (6- hours minimum sun). They grow in any well-drained garden ground, but thrive in moist compost-rich soil. One-year old established plants exhibit good drought and heat tolerance. Strawberry Candy clumps should be divided every 3-5 years in late winter or in early autumn.

Strawberry Candy is a strong grower and relatively disease and pest resistant. It was introduced in 1989, the creation of daylily breeders Pat and Grace Stamile. It was awarded the prestigious Stout Silver Medal in 1998.

‘Red Volunteer’ – Outstanding Veteran Red-flowering Daylily

Posted by Hugh on June 24th, 2012

'Red Volunteer' daylily

In the gardening world new does not always mean better. Red Volunteer daylily (Hemerocallis x ‘Red Volunteer’) is not new, introduced by Oakes Daylily Nursery, near Knoxville, TN in 1984. Daylily catalogs describe it as a “candle red self with a golden yellow throat”. It is a mid-season bloomer and the foliage is semi-evergreen.

The 7- inch diameter blooms stand 30 inches tall, not hidden inside the grass-like daylily foliage as some varieties do. Its vivid red flowers are real standouts. The red color does not fade in the summer sun, as red at 5 p.m. as it was at 8 a.m. in the morning. The color of many red daylily varieties is washed out by noon

Red Volunteer is a good multiplier, a rapid clump producer. A 2-3 year old well-grown plant may form 8 or more floral scapes, each with a dozen buds. Red Volunteer does not need to be divided every 5 years.

Red Volunteer blooms in mid- to late June in the Southern Appalachian region (USDA hardiness zones 6 and 7). While preferring a moist, compost rich, well drained soil, it grows well in a heavy clay soil. Once established in a garden for one year, Red Volunteer exhibits exceptional summer heat and drought tolerance. Its long grass-like foliage stays green and lush when adequately watered and fertilized.

Daylilies are mostly disease and insect resistant. Aphids and thrips, as well as slugs and snails, may cause minor damage to the foliage.

Red Volunteer was awarded the AHS Award of Merit in 1994.

No Scorch ‘Verdoni’ Dwarf Hinoki Cypress

Posted by Hugh on June 22nd, 2012

'Verdon' Hinoki Cypress

For a small urban garden many dwarf evergreen conifers are a good fit. There are so many to choose from and Verdon hinoki cypress (Chamaecyparis obtusa ‘Verdoni’) is one of the finest. Its fan shaped gold-edged green foliage will light up almost any garden locale. It makes a great garden companion with short growing perennials, summer flowering annuals, and other dwarf conifers.

Verdon’s scale-like leaves hold their golden hue through all four seasons, and do not scorch in the summer sun or the frigid cold of winter once established for two years.

Grow Verdon in a well-drained, compost rich garden soil and keep properly mulched for adequate soil moisture. Its growth rate is very slow, just 2-3 inches per year. In ten years it may grow to 3 feet in height x 2 feet in width. It is rated as hardy to -30°F (USDA hardiness zones 4-7).

Verdon may grow slightly asymmetric. Give it a permanent spot in the garden or grow in a container for several years. Lightly fertilize with 10-10-10 or equivalent granular fertilizer in early spring or feed a water soluble fertilizer such as Hollytone®, Miracle-Gro® or equivalent 2-3 times from March through August.

Dwarf conifers ask for very little extra care and prosper for many years in a sunny to partially shaded garden spot or in a container on a deck or patio. They are rarely troubled by disease or insect pests.

‘Color Guard’ Yucca Hold Gold Variegation

Posted by Hugh on June 19th, 2012

Unidentified Yucca Cultivar

Architecturally, yucca (Yucca filamentosa), aka Adam’s needle or Spanish bayonet, makes a strong landscape statement. Yucca is often difficult to fit with with other shrubs, except perhaps other xerophytic plants. Yucca is frequently used in an arid-looking or in a courtyard setting in gravel mulch.

Yucca prospers in full sun and a well-drained soil. This evergreen rosette (no stem) shrub is native from South Carolina south to Florida and Mississippi, but is surprisingly hardy as far north as USDA hardiness zones 5 (zone 4 with additional winter protection).

Yucca’s foliage stands upright and arching. ‘Color Guard’ is a gold-centered variegated form. The sword-like foliage reaches 3 to 4 feet tall and wide. The spine-tipped leaves are 1-2 ½ feet long and 3- 4 inches wide with green margins and striking creamy gold centers. Long curly white threads are found along the leaf margins. Variegation is steadfast and is not lost over the years as experienced with some other variegated cultivars.

In cool weather, the creamy-gold hue in the midsummer foliage takes on a pinkish tint in the autumn and rosey in the winter. Its deer-resistant foliage is covered in hundreds of curly white hairs. Branched clusters of 3-6 feet tall bouquets of fragrant creamy white bell-shaped flowers open from mid-spring into summer depending on where you garden. Flowers open from the bottom upward, keeping the plant in fresh blooms for 3 or more weeks!

Wet soil is yucca’s nemesis. Amend heavy clay soils with coarse sand or gravel for excellent drainage. It doesn’t mind very long dry spells (once it’s established in the garden for two years). Color Guard tolerates wind, heat, and humidity nicely and has few serious insect or disease problems.

Wear heavy gloves when pruning off dead flower stalks, decaying or dead foliage. Over the years plants tend to colonize or become stoloniferous. They may be cut from the mother plant and allowed to create small colonies.

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: