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

Update On New Heuchera Hybrids

Posted by Hugh on March 31st, 2011

'Bronze Wave' heuchera

The best of the villosa cultivars are ‘Caramel’, ‘Citronella’, ‘Mocha’, and my newest favorite ‘Bronze Wave’. Blooms are tall and mostly insignificant. I often remove them to accent the foliage. All villosa cultivars are long lived and heat and humidity tolerant. Heucheras prefer a moist, well-drained, compost-rich soil. Plants are heat and humidity tolerant in the Southern Appalachian region (USDA zones 6 and 7). Grow the H. villosa hybrids either in direct morning sunlight in z-6 or in partial shade in z-7.

Space each plant 2-3 feet apart.

cultivars are not your grandmother’s puny heucheras. Plants are long-lived and vigorous. Cutback plant foliage and spent flowers to the crown either in late autumn or winter and feed with a handful of 10-10-10 granular fertilizer per plant. Water soluble fertilizers such as Miracle Gro™, Schultz®, and Espoma® are also good choices. Follow package directions. languishes in deep shade and dry soils and is best grown in a mulched bed.

When To Prune Spring Flowering Shrubs

Posted by Hugh on March 25th, 2011

Linden viburnum (V. dilatatum)

Seven reasons why you prune:

eliminate dead, diseased, insect riddled branches
control plant height and spread
shaping such as topiary, espaliered or pollardized trees
increase or decrease the numbers of flowers and fruits
rejuvenate an old shrub or tree
remove low branches over walkways
remove water sprouts and root suckers

Flowering shrubs bloom from late February thru May. Pruning them either before or while they are blooming makes little sense. Prune them within one month after each has finished flowering. Examples of spring flowering shrubs include: forsythias, spireas, viburnums, honeysuckles, mockoranges, deutzias, lilacs and most azaleas.

Shrub roses like the popular Knockout™ and Easy Eleagance™ series are cut back when forsythia is in full bloom. By this time, the harsh winter temps are over and rapid re-growth will follow after roses have been pruned.

Hydrangea shrubs are a mixed bag. Oakleaf hydrangeas are pruned immediately after flowering in late spring, while summer flowering PG and AG hydrangeas are pruned now in late winter and early spring.

Use only sharp pruning tools to make clean cuts. Cleaning, lubricating and sharpening saws, shears and loppers are a time-saving winter chore. Well cared for pruning tools provide years of dependable cuts.

‘Misty Blue’ Doll’s Eye Will Catch Your Eye

Posted by Hugh on March 22nd, 2011

White baneberry or doll’s eye (Actaea pachypoda) is a strikingly beautiful native perennial. The cultivar ‘Misty Blue’ was first discovered at Mt. Cuba Center in Greenville, Delaware. The bluish-green foliage is multi-stemmed and finely cut from mid-spring thru the summer months. Grow it in a moist shade garden environment.

Lovely fringed white flowers appear in April. In the fall clusters of white “doll’s eye” berry fruits sit atop brightly red pedicels. Each white berry is marked with a distinct black dot. Fruits persist over 4 – 6 weeks.

Baneberry is a long-lived perennial which thrives in a moist, well-drained, compost rich soil. White baneberry grows 2 – 4 feet tall and is best grouped en masse so that its lovely blue-green summer foliage receives the attention it deserves. Actaea is reliably hardy throughout USDA zones 3 – 8.

Because of its new status, availability of ‘Misty Blue’ baneberry is limited primarily from internet and mail order catalog selling native plants.

‘Jeana’ Phlox– no powdery mildew

Posted by Hugh on March 18th, 2011

Phlox paniculata 'Jeana'

Photo credit: North Creek Nurseries, Landenberg, PA, USA

Our native summer phlox (Phlox paniculata) continues to be challenged here in the Southern Appalachian region (USDA zones 6 and 7) by powdery mildew disease (p-m-d). Over the past decade gardeners have tried new, reportedly disease resistant cultivars.

Many have disappointed. To date, the cultivars ‘David’ (white, 3-4 ft.tall) and ‘Robert Poore’ (rose pink, 4-5 ft.) have been reliably p-m-d resistant standard bearers here.

Phlox paniculata ‘Jeana’ was found by Jeana Prewitt near her home in Nashville TN with one plant that she deemed to be radically different than all the rest. In over 10 years, through all kinds of wild weather phenomena, ‘Jeana’ has never been seriously injured by powdery mildew.

‘Jeana’ is a vigorous grower, and well branched to 48 inches in height. The sweetly scented florets open slowly and its lavender pink color remains vibrant over quite a long time from mid- summer through early autumn.

The short stems are strong sturdy, supporting a huge floral head. Instead of 15 – 25 flowers per panicle, bears 4-5 times as any other summer phlox. ‘Jeana’ attracts a large variety of insect pollinators, including numerous swallowtail butterflies.

Better Choices for Golden Moon Maple

Posted by Hugh on March 15th, 2011

Golden Fullmoon maple

Photo credit: Mr. Brian Upchurch, Highland Creek Nursery, Fletcher, NC

A few months back I asked Mr. Brian Upchurch, owner of Highland Creek Nursery*, his opinion of Golden Fullmoon Japanese maple (Acer shirasawanum ‘Aureum’) in our Southern Appalachian region (USDA zones 6 and 7). He responded: “I have grown it in the past and it doesn’t really thrive in the summer heat of the southeast. Many others have also tried”.

“Golden Fullmoon maple is absolutely gorgeous in Oregon and in parts of Europe. It is rarely seen in Japan, again due to the heat. If you do choose to get an ‘Aureum’, it looks great in the spring, and so-so for the remainder of the growing season.”

As better alternatives Brian suggests “Acer palmatum ‘Summer Gold’, Acer shirasawanum ‘Moonrise’ (PP 16,718), or perhaps even Acer palmatum ‘Orange Dream’ as similar (but not the same) plants. The color won’t be quite as good, but these hold up to the heat better than ‘Aureum’.”

“A new selection of A. shirasawanum called ‘Jordan’ looks promising, but there are no larger plants around. So it hasn’t stood the test of time.”

*Highland Creek is a wholesale only rare plant emporium in Fletcher, NC.

Blueberries

Posted by Hugh on March 12th, 2011

Blueberries (Vaccinium spp.) are healthy for you and exceptionally easy to grow organically (without pesticides). Why?- because blueberries are bothered by very few disease and insect problems. Success in growing blueberries depends upon pre-plant soil preparation. If you’re thinking about growing blueberrues for the first time, then allot this calendar year for soil preparation. Put off planting blueberries until the early fall or next spring. Good bed prep includes:

soil pH of 4.8-5.2 -achieved by an application of elemental sulfur plus acidic organic matter sources such as peat moss and old sawdust
raising and maintaining an organic level of 3% (and higher) incorporating composted leavs and yard clippings, old sawdust and peat moss

Good garden prep takes 12-18 months, so plan ahead. Add another two years for plants to become established and ready for picking. Spacings between plants are 5-6 feet apart for rabbiteye and 4-5 feet for highbush. For large plantings, allow 10-12 feet between rows for mowing, pruning, picking and other maintenance.

Recommended varieties for the Southern Appalachian region (USDA zones 6 and 7):

Highbush: ready for picking from mid-June for 4-6 weeks, cross-pollination not required but recommended. Duke is highly recommended, an early, big berry, excellent quality, and does not tend to overbear. Others are Bluecrop, Echota, Blue Ridge, Berkeley, Jersey.

Rabbiteye: ready in mid-July for 6-8 weeks, cross-pollination with 2-3 varieties is required. Plant Tifblue, Climax, Powder Blue, Centurion, among others.

Act Now for Crabgrass-free Lawn This Summer

Posted by Hugh on March 9th, 2011

What grows there? Hopefully, it’s not crabgrass this summer. Crabgrass (Digitaria spp.) is an annual weed grass that devour lawns, shrub beds and flower gardens. There are lots of effective crabgrass preventatives sold at garden shops, hardware stores, and farm supply centers.

There are numerous trademarked products. It is important to read and understand package instructions. The principal product tradenames (and active ingredients) are:

Barricade® (prodiamine)

Dimension® (dithiopyr)

Echelon® (prodiamine + sulfentrazone)

Pendulum® (pendimethalin)

Ronstar® (oxadiazon)

All products should not be used on newly seeded, sodded or sprigged lawns. In addition several store brands (not listed here) may contain the same or a different active ingredient.

Pre-emergent crabgrass control is your best option. Apply the herbicide in late winter to early spring before the crabgrass seed germinates.

Rather than choosing a calendar date as an application deadline, use forsythia, a common spring flowering shrub, for your timing guideline. If 80 % of forsythia flowers have dropped, expectations for good crabgrass control falls off if a pre-emergent preventative has not been applied.

These products provide 85% effective crabgrass control up to 100 days after application. A second application is required in late spring or early summer for a crabgrass free summer.

One additional tip is to irrigate after applying the herbicide, an equivalent of 1/2 inch of rainfall.

Pulmonarias: Wonderful In The Shade Garden

Posted by Hugh on March 6th, 2011

Although my multi-year addiction for hostas has never waned, I remain equally passionate about the lungworts (Pulmonaria spp.). Lungwort is also called Bethlehem sage and Jerusalem sage. Their uniquely splotched or variegated foliage wakes up a dark patch in any shade garden.

Lungworts are planted as ground covers and for color accents. In early spring (March), lungworts send up small lovely bouquets of small tubular flowers. Flower colors, depending on variety, range from white, lilac, pink and blue.

Lungworts are vigorous and long lived. Several are semi-evergreen in garden zone 6 and deciduous in zone 5. Their culture is almost identical to hosta. Grow them in compost-rich soil and keep plants mulched and moist in the summer months. Lungworts benefit from division every 4-5 years.

Pest problems are rare, although some cultivars may be susceptible to mildew. The species P. longifolia and hybrids thereof, with long narrow or lance-shaped leaves, are most adaptable to gardens in the Southern Appalachian region (USDA zones 6 and 7). They’re more resistant to mildew diseases and high temperature dieback. Occasionally, snails and slugs are problem pests.

Suggested companion plants include ferns, small leaved hostas, bluebells (Mertensia), coralbells (Heuchera spp.), foamflowers (Tiarella spp.), dwarf variegated Solomon seal (Polygonatum spp.), and lenten rose (Helleborus spp.).

Prune Some Hydrangeas Now

Posted by Hugh on March 3rd, 2011

Hydrangea paniculata 'Limelight' in July

PeeGee or panicled hydrangea (Hydrangea paniculata) and our native Smooth hydrangea (Hydrangea arborescens) are pruned now in late winter thru early spring. Why? – because these hydrangeas bloom on new or current season’s wood.

Over the years these two hydrangea species grow to enormous sizes. When they overwhelm their garden space, severely cut them back to within 6 -12 inches from the ground in late winter or early spring. Next, thin out the number of shoots (canes), leaving several of pencil size thickness. In the spring each cane will grow out new shoots which bloom this summer.

Severe cutting back is called renewal pruning. Timing will vary with the species of hydrangeas planted in your garden. After pruning apply a slow release fertilizer especially formulated for flowering shrubs. Follow the package directions. Apply a good organic mulch to a 2 – 3 inch depth around each hydrangea to conserve soil moisture this summer.

Oakleaf (H. quercifolia) and bigleaf (H. macrophylla) hydrangeas may also be pruned now, but flower numbers in spring and summer may be greatly reduced.

Winter Jasmine Rising

Posted by Hugh on March 1st, 2011

Retaining wall of winter jasmine

Is the worst of winter behind us? Winter jasmine (Jasminum nudiflorum) is often confused with forsythia shrubs which bloom 3-4 weeks later in the spring. This hardy winter blooming vine from China frequently blooms in late February and March when daytime temperatures climb into the mid-50s for a week or more. Evening chilling temps down into the low 20’s don’t seem to injure the flowers.

This vine thrives in many parts of the mid-Atlantic and southeastern U.S. (USDA hardiness zones 6 -8) in full sun to partial shade. Its dark green tri-foliate leaves are semi-evergreen in zone 6. New foliage emerges in April after flowering has ended.

Hundreds of bright yellow 1 ½ inch tubular flowers are lightly fragrant, originating along a thick network of green stems. Winter jasmine is a very aggressive grower and is often utilized for soil retention on steep banks or to cover over an unsightly retaining wall or fence. Some gardeners grow it as a low 3-4 foot tall shrubby mound, 4-5-6 feet wide.

Winter jasmine grows in almost any soil, and demonstrates good drought tolerance once established after two years. Every 3 or 4 years rejuvenate winter jasmine by cutting back vines severely immediately after flowering.

Prune as needed in early spring just after flowering has finished. If planting starts to look scraggly, cut back hard to 12-18 inches and feed generously with 10-10-10 or equivalent fertilizer.