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

Promising Hemlock Adelgid Research

Posted by Hugh on July 2nd, 2012

Hemlock woolly adelgid

Proper care of hemlock trees is important for their survival. Hot dry summer weather appears to slow population growth. During periods of severe drought, shallow rooted hemlock trees should be irrigated. Prune dead and dying branches from trees to promote new growth. Also, limit the amount of nitrogen fertilizers to hemlock(s), as it promotes heavier woolly adelgid populations.

Cultural practices may reduce numbers of adelgids in hemlocks. Pets, as well as birds, squirrels and deer, may transport adelgids from infested to healthy hemlocks. Refrain from moving infested plants, logs, firewood or bark chips onto an uninfested property. Clean your auto and camping tents after returning from woodlands and recreational areas. Wash off pruning equipment after working in infested trees.

Two Japanese and two western North American hemlock species are much more resistant to hemlock woolly adelgid than are their eastern North American counterparts. Of these four resistant species, the western hemlock (T. heterophylla) is most similar to eastern hemlock in appearance, growth form, and utility. Although adelgids do infest these resistant species, they seldom reach densities high enough to cause injury.

Entomologists are also releasing predator insects which hopefully may add hemlock woolly adelgids to their diet.

Credit: Special thank you for information supplied by NC State University Extension.

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.

‘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.

‘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.

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.

Evaluating Weeping Bald Cypress Cultivars

Posted by Hugh on May 9th, 2012

‘Cascade Falls’ weeping baldcypress

Bald cypress (Taxodium distichum) is a large 75 -80 foot deciduous conifer tree. They are long-lived, often 100 years or more. Bald cypress is incredibly hardy from the warm humid Florida swamps to the cold winter temperatures and loamy soils of central Michigan. Bald cypress is tolerant of a wide range of soil and moisture conditions. It grows in full sun and in any average acidic (not alkaline) soil type.

‘Cascade Falls’ (CF) and ‘Falling Waters’ (FW) are two dwarf cultivars which are better fits in most gardens. Both exhibit a strong weeping habit. Their fern- like foliage is light green in spring and summer months, and finishes burnt orange to brown in the autumn. The small leaves fall and compose rapidly around the tree. Both are real standouts as small weeping trees. Their exfoliating bark is an added winter feature.

Cascade Falls grows to about 20 feet tall and 20 or more feet in width. FW has a graceful arching form which is 15-20 feet tall by 8-12 feet in width (after 20 years). FW grows taller with less staking and holds its narrow tree profile.

In the early years, staking is a must for both cultivars. CF grows as tall as you stake it. It arches down, eventually forming a mound. Bend up and stake the leader until the desired height is achieved. If not staked, CF tends to grow like a ground cover.

Bald cypress requires little other maintenance, possessing few disease and insect issues. It is deer resistant.

Sapsucker Feeding May Blacken Maple Trunks

Posted by Hugh on April 29th, 2012

Sapsucker Holes Create Sappy Trunk

You see or hear a sapsucker tapping in a yard tree and pay little attention to it. The bird perforates the tree or shrub trunk and main branches with numerous shallow holes, similar to a riveter working with sheet metal. A sapsucker feeds on the cambium sap and on insects under the bark.

The holes are deep enough to cause sap leakage, particularly in the winter months when sap pressure in maples (also dogwoods, elms, birches and yellowwoods) is the highest. The sugary sap coats the trunk, and sooty mold fungi grow over the sap secretions. The result is a yucky black stain similar to pitch!

What to do? Nothing!! The sapsucker is at work, doing his/her natural thing. Sapsuckers are members of the woodpecker family. They serve an important function: listening and removing damaging insect borers which may be feeding on the tree sapwood.

Unfortunately, sapsucker feeding does not always indicate that the bird has found insects inside the tree. Yes, the numerous holes are unsightly, but are not injurious to the life of the tree. The black sooty appearance on the trunk should wash off in the months ahead.

According to University of Arkansas Extension horticulturist Dr. James Robbins, favorite tree species for sapsuckers include maple (Acer spp.), pecan (Carya), birch (Betula spp.), pine (Pinus spp.), elm (Ulmus spp.) and some oaks (Quercus spp.). Sapsuckers are attracted to old holes and other bark injury and may return to the same tree(s) for several years.