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

Vitex ‘Shoal Creek’

Posted by Hugh on June 9th, 2010

Chastetree (Vitex agnus-castus) is an 8-10 foot deciduous shrub or 12-15 foot tall small tree (hardiness zone 6-b thru 8). Branching habit is dense and vase-shaped (upright). It blooms over most of the summer, from June thru late August. Its 12-18 inch long blue-violet flower spikes exude a slight herbal fragrance.

‘Shoal Creek’ is a leading cultivar. Cold hardiness appears better than most, although this has yet to be proven. The finger-like compound leaves are covered with pubescent hairs. Summer foliage color is grey-green, with a faint bluish cast more visible in May and June. Its disease resistant foliage and butterfly magnetism rates this vitex in a class on its own. Foliage is highly deer resistant.

Stem die-back may occur in a cold winter, but this fast grower recovers rapidly. Since flowering occurs on new growth, prune off all dead, injured and crowded branches before the start of May. Vitex prefers full sun, but will tolerate part sun. Plant in a loose, well-drained soil and keep adequately watered during the first year. Afterwards, vitex possesses very good drought tolerance.

Catalpa Both Loved And Hated

Posted by Hugh on June 8th, 2010

Northern catalpa or Indian cigar tree (Catalpa speciosa) has enormous presence in any landscape setting (USDA hardiness zones 4-8). Finding a 70 – 80 foot tree with a massive trunk and thick sinuous limbs is not unusual from Ohio south thru Tennessee.

In summer its huge heart –shaped, pale green leaves may be easily reach 8 – 12 inches long and wide. Birds often seek shelter under its foliage cover. Catalpa offers a spectacular floral display lasting two weeks and more in May. The enormous coarse textured foliage offers some tropical appeal.

Numerous two- inch long white flowers are borne on large terminal spikes, many unfortunately hidden beneath the enormous catalpa leaves. Each flower has small gold spots within its frilly edged corolla. Narrow cylindrical cigar fruits, 8 – 15 inches in length are easily visible in the fall and winter months.

Catalpa trees are often visited by the catalpa sphinx moth whose larvae (caterpillars) are prized by fishermen for bait. Hummingbirds are a major pollinator, attracted to the floral nectar.

The tree is common along roadsides, particularly in bottomlands, often growing in poor soil. For most residential neighborhoods catalpa’s fast growth rate and enormous size make it of limited value. The brittleness of small limbs (twigs) requires almost constant clean-up around lawn areas.

Southern catalpa (C. bignonioides), another native form, grows smaller, averaging 35-50 feet in height (zones 5-9).

Indian Pink is a Summer Sizzler

Posted by Hugh on June 6th, 2010

Indian pink (Spigelia marilandica) is a strikingly beautiful native wildflower here in the southern Appalachian region (USDA zone 6 -7). Beginning in late May, bright red tubular flowers flare open, crowned by five sharply pointed pale yellow reflexed lobes (see photo).

Indian pink prospers around rich moist open woodland areas. The well-drained soil should have a pH range between 6.5 to 7.0. Generously amend a partially sunny site with compost or peat to stimulate plant vigor and repeat flowering. Healthy plants grow 12-18 inches tall. Spigelia leaves attach directly to the main stem without petioles.

Indian pink is slow growing at first, taking two to three years to reach maximum floral potential. Planting five or more in a clump creates a showier display. Eventually, a healthy grouping will colonize. Bloom time is lengthened by swift removal of the old spent flowers.

Indian pink often blooms for a brief second interval in late summer when soil moisture is plentiful. Plant debris mostly disappears before winter sets in. The brightly colored flowers attract numerous pollinating insects and hummingbirds. No disease and pest problems are observed.

Hardy Rosemary

Posted by Hugh on May 30th, 2010

Rosemary (Rosmarinus officinalis) ‘Arp’ is winter hardy in southern Appalachian (USDA hardiness zones 6-b and 7-a) gardens for two decades , including some very cold winters. Other rosemary cultivars which have succeeded include ‘Athens Blue Spires’, ‘Hardy Hill’, and ‘Salem’.

Locate a site with a “micro-climate” advantage such as next to a driveway or along the southside of a red brick home or a dark colored garage wall. Here winter temperatures vary by a few degrees warmer. Dark asphalt pavement absorbs and retains heat. Next to large bodies of water, such as a swimming pool and a water garden, may also be slightly warmer in the winter.

Plant rosemary in well-drained soil and in full direct sunlight. With rosemary and other semi-tender herbs, winter kill may also be caused by wet, soggy soil rather than cold.

‘Arp’ matures a handsome woody shrub with fine textured foliage. It grows 3-4 feet tall and wide, and blooms in early spring. The blue flowers are small and attract lots of insect activity.

Dreaded Rose Rosette Disease

Posted by Hugh on May 24th, 2010

No rose is resistant to this deadly virus disease. Symptoms of rose rosette disease (photo) vary greatly from the species or cultivar planted. Leaves may be small, distorted, and exhibit a conspicuous red pigmentation. Diseased canes may also be noticeably thicker than others around them, and/or may grow in a spiral pattern.

Multi-flora roses, a noxious shrubby weed, are most susceptible and often are first to contract the disease. Very small eriophyid mites transmit rose rosette disease by feeding off the plants which are already infected. Mites transmit the virus to healthy roses nearby. Control measures must be rapid and decisive.

Insect spraying will help. Spray roses with Sevin (carbaryl) insecticide for partial control of the eriophyid mite. Eliminate multi-floral roses within 300 feet from any rose plantings, preferably from all surrounding yards and gardens.

Prune out all diseased and suspected canes. Remove all prunings immediately from the property. If symptoms reappear on new re-growth canes, remove the bush from the property. When planting roses, space them far enough apart that foliage does not touch neighboring plants.

Lovely Lavender

Posted by Hugh on May 22nd, 2010

photo: ‘Munstead’ lavender

Lavender is a hardy shrub that thrives in dry alkaline soil. Lavender is commonly used as a food seasoning, a culinary substitute for rosemary. Dried flowers are crafted into table arrangements and lavender fragrance is captured in sachets and potpourris. Lavender is used to store clothes as a moth repellent. Some people store some under a pillow as a sleep aid, a form of “aromatherapy”. Bees produce a high-quality honey from the flower nectar.

There are two kinds of lavender. The shorter-growing cultivars of English lavender (Lavandula angustifolia) like ‘Munstead’, ‘Hidcote’, and ‘Lady Lavender’, flower in mid-May for one month. When cutback, English lavender blooms again in August. The taller more vigorous French lavender (recommend cultivars ‘Provenance’, ‘Grosso’ and ‘Super’) flowers only once in late June. For lavender oil production, I recommend ‘Super’.

Lavender is only successful planted in soil that is exceptionally well drained. An ideal soil pH range is 6.5 – 7.2. Grow on raised mounds and space plants 3 feet apart in the row and 6-8 feet in the row, if grown commercially. Other than for harvesting, prune plants back one-third in a ball shape in September. Lavender has very few disease and pests problems and possesses high drought tolerance.

FireBlight on Apples and Pears

Posted by Hugh on May 20th, 2010

Fireblight is a serious bacterial disease that afflicts apple and pear trees. Fireblight may appear in two distinct forms. From April to early May flowers and fruit clusters may blacken (die). From May to mid-June a more serious symptom (photo) is sudden dieback, almost overnight, of branch tips . Leaves appear as if someone had poured gasoline over the tree and torched it. Infected branch tips may also look curled, as a so-called “shepherd’s crook”.

To prevent the spread of fireblight, prune off all diseased wood, cutting back 6 – 8 inches into adjacent healthy shoots. Pruning is done either when first seen or when the tree is dormant. Disinfect the pruning shears after each cut, dipping the blades into either rubbing alcohol or 20% bleach to water solution. Remove all diseased prunings from the property. Do not compost.

When planning an apple or pear home orchard, avoid planting very susceptible varieties such as ‘Lodi’, ‘Gala’, ‘Jonathan’, ‘Rome’, and ‘ Yellow Transparent’. Among pear varieties, ‘Bartlett’, D’Anjou’, ‘Bosc’ and ‘Clapps Favorite’ are most susceptible, and ‘Moonglow’, ‘Maxine’, ‘Magness’, and ‘Seckel’ are moderately resistant to fireblight. Most Asian pear varieties are very susceptible.

No-Spray Shrub Roses

Posted by Hugh on May 17th, 2010

Photo: Carefree Sunshine Rose at UT Gardens in Knoxville, TN
Over the past decade the Knockout®, Carefree® and Home Run® series of shrub roses have altered the appearance of residential and commercial properties. From 2006 -08, no-spray rose trial was conducted at two University of Tennessee Research and Education Centers in Jackson and Crossville, TN and the USDA Horticultural Research Lab in Poplar, MS.
Over 135 cultivars were evaluated. “The ultimate disease test for roses is to test them south of the Mason-Dixon line where disease pressure is highest”, according to Dr. Mark Windham, UT Research Pathologist.

Shrub Roses Resistant (R) or Moderately Resistant (MR) to Black Spot and Cercospora Leaf Spot:
Carefree Sunshine (MR) – F
‘Fiesta’ (MR)
‘Golden Eye’ (R]
‘Hansa’ (R) – F
‘Homerun’ (MR)
Knockout Rose (R)
‘My Girl’ (R) – F
‘My Hero’ (MR)
‘Palmengarten Frankfurt’ (MR) – F
Pink Knockout (R)
‘Super Hero’ (MR)
’Wild Spice’ (MR) – F
‘Wild Thing’ (MR)
‘Wildberry Breeze’ (R) – F
F indicates rose is fragrant

Best of the Climbing Roses So Far– ‘White Dawn’

Posted by Hugh on May 15th, 2010

Since its introduction in the rose world over 60 years ago, ‘White Dawn’ has proven to be a top garden performer among climbing roses. The dark green, glossy foliage is very blackspot disease resistant. This very vigorous climber (hardiness zone 5 – 9) grows to 12 to 20 feet. Pure white double flowers are medium-sized (2-1/2″ to 3″). ‘White Dawn’ tolerates poor soils if drainage is good. It blooms best in a bright sunny spot.

‘White Dawn begins blooming in mid-May in the southern Appalachian region (Zone 6-b to 7-a) and repeats, off and on, through the rest of the growing year. Feed roses starting in early April and monthly to early September with Miracle-Gro®, Schultz®, or equivalent water soluble rose food @ 1 tablespoon per gallon.

Prune climbing roses in late winter (March) when new growth begins. On young climbers, simply remove all diseased, dead and tall nuisance canes. On older climbers, cutback the oldest rambling canes, favoring strong healthy one-year shoots which produce most of the rose blooms in May.

‘White Dawn’ is the first climbing rose to earn the University of Tennessee “No Spray” designation.

Growing Tomatoes in Containers

Posted by Hugh on May 10th, 2010

Apartment renters and townhouse and condominium owners till the soil in containers on their patio and deck. For containers the shorter growing determinate type tomatoes are a better choice. Spread out the harvest interval, by not planting all your tomatoes at one time. Start your last tomatoes from seed for June planting and harvest beginning in late September and October.

Container grown tomatoes need a deep container- at least 16 to 18 inches tall. A 5- gallon (or larger) pail or pot works well. Drill out several 1- inch wide drainage holes and add a few rocks in the bottom for ballast. Plant in a good growing media and add some inorganic fertilizer or organic bone and blood meal to increase fertility. Container-grown plants require more frequent fertilization than field-grown, as there’s less soil from which to obtain nutrients. For water soluble fertilizers, apply every two weeks.Here are some good varieties to try. The yield will vary with the variety:
• Slicers
– Bush Early Girl
– Bushsteak Hybrid
– Spring Giant
– Better Boy
– Jetstar
– Bush Celebrity
– Mountain Fresh Plus VFFN
– Super Bush
– Saladette (Roma type)• Cherry
– Golden Nugget
– Sweet 100 Patio
– Tiny Tim
– Patio
– Supersweet 100
– Sun Gold