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

Mountain Hydrangeas

Posted by Hugh on July 9th, 2023

Mountain hydrangeas (Hydrangea serrata) look very much like big leaf hydrangea (H. macrophylla) except shrubs are smaller, more compact in growth habit with smaller flowers and leaves. They are native to the cool moist woodland valleys in Japan and Korea mountains. (USDA hardiness zones 6-9). These unique hydrangeas fare better in cool climates in zones 5 (protected) and 6 than bigleaf hydrangeas (H. macrophylla).

Current cultivars are listed below. Currently, Tuff Stuff™ series from Proven Winners (PW) is available through local garden centers. Currently, five cultivars have been introduced and are ideal compact hydrangeas for a small garden. Plant breeders are also crossing Mountain hydrangeas with other species.

Mountain hydrangeas begin blooming in early summer on old wood and continue to produce lacecap flowers on new wood from late June into October for a long bloom display. Utilize them as foundation planting, low hedging, front bed edging, or as a single specimen.

Leaves are toothed, ovate, dull green, up to 6 inches long) and their summer lacecap flowers are long-blooming. Most of the florets are fertile and attract pollinators. Smaller numbers of showy sterile florets form along an outer marginal ring around the tiny fertile florets. Mountain hydrangeas bloom on both old and new wood.

In alkaline soils (above 6.5 pH) pink florets are likely and blue florets in acidic soils. To achieve bluer blooms, lower the soil pH for 5.5 or lower feeding an acidic type fertilizer like Miracid™ or Hollytone™ or one specifically labeled for hydrangeas, one containing aluminum sulfate. Mulch beds with pine needles.

Mountain hydrangeas should be grown in partial shade or in and out all day filtered sun. The soil should be humus-rich, moist and well-drained. Plants will handle more sun if soils are adequately irrigated. Little pruning is necessary if properly sited. Deadhead old spent flowers and prune out weak or winter-damaged stems in early spring.

Diseases are rare with some susceptibility to bud blight, bacterial wilt, leaf spot and mildew. Aphids are occasional visitors. Because of its compact mounding habit, annual pruning of Tuff Stuff™ hydrangeas is minimal other than to remove some broken branches.

Tuff Stuff® is a small reblooming hydrangea that bears pink lacecap flowers with creamy centers in alkaline soil; they are lavender-blue in acidic soil. Its serrated leaves turn burgundy in fall. At maturity Tuff Stuff often reaches 3×3 feet tall and wide.

Tuff Stuff Aha® grows 2-3 feet tall and wide. Tuff Stuff Ah-Ha^® hydrangea will bloom pink or blue, depending on soil chemistry. Flower buds are more cold-tolerant, which ensures good blooming even in USDA zones 5 and 6.

Tiny Tuff Stuff® bears similar flowers to ‘Tuff Stuff’ but grows more compact shrub @ 2 feet high and wide.

Tuff Stuff Red™ is the newest addition to the Tuff Stuff series. Large, lacecap flowers are a deep pink-red color which is set off by lustrous, deep green foliage.

Tuff Stuff^™ Red Mountain has improved bud hardiness and is a reliable rebloomer. This dwarf hydrangea grows 24 – 36 inches high and wide with blue or red lacecap flowers.

Other varieties with a H. serrata bloodline include: ’Blue Bird’, ‘Blue Billow’, ‘Pink Dynamo‘, ‘Diadem’, and ‘Preziosa’.

Colorful Bugleweed As A Groundcover

Posted by Hugh on June 29th, 2023

Bugleweed (Ajuga reptans), aka “carpetweed” and “carpet bugle”, is a fast-growing evergreen perennial ground cover in the Lamiaceae (mint) family. The species name “reptans” means creeping. It is native to Europe, northern Africa, and southwestern Asia. Cultivars are hardy in USDA hardiness zones 3-9 (unless otherwise noted).

Most bugleweed cultivars demonstrate aggressive plant vigor that helps to control erosion on a bank or hill or to simply add color to shady spots. It performs well planted underneath shrubs and trees. Their leaf color and stay attractive almost all year-round, and they flower from spring into early summer.

Depending on the cultivar, bugleweed produces glossy, dark green scalloped leaves and clusters of blue, purple, or white flowers that may reach 6-10 inches in height. Several cultivars strut variegated foliage colors and patterns. Floral spikes generally stand above the foliage although some cultivars are shorter.

Early spring flower spikes attract bumblebees, hummingbirds and songbirds. Generally, rabbits and deer do not trouble bugleweed.

Plants form dense mats of glossy foliage in sun to partially shady areas, although the foliage color of some cultivars is most vibrant in full sun. Bugleweed grows best in moist well-drained soils; it struggles in heavy clays and periods of drought exceeding two weeks, particularly in its establishment year.

Bugleweed spreads aggressively via stolons and often creeps into nearby lawn and garden areas. Plant bugleweed in mid-spring thru summer, spacing plants 8-15 inches apart. Every 3-5 years divide plants when they grow too crowded in the spring or fall to prevent overcrowding.

Crown rot can be a problem in very humid conditions and in heavy clay soils. Space plants for good air circulation and avoid overfertilizing. Ajuga is listed as invasive in some U.S. states because it may spread aggressively.

Bugleweed doesn’t require pruning but clip off spent flowers for a neat appearance; for rapid cleanup, raise the cutting height of your mower and make a quick pass.

Great Ajugas to Grow:

‘Catlin’s Giant’ – 8 to 10-inch spikes of deep blue flowers are held atop bronze-blue foliage. The plants grow 3 to 6 inches high and 12-24 inches spread.

‘Blueberry Muffin’ – vigorous, fast-spreading (6 inches tall/ 18 inches spread), deep blue flowers. (zones 5-9).

‘Black Scallop’ –blue flowers and purple-black leaves with scalloped edges.

‘Toffee Chip’ –spring leaves start out light brown, later turn grayish-green with creamy gold margins (zones 3-10).

‘Chocolate Chip’ – dwarf variety with chocolate-burgundy leaves and bluish-purple flowers.

‘Burgundy Glow’ – exceptionally hardy cultivar, 6 to 10 inches high, with blue flowers and tricolored foliage in shades of pink, cream and white.

‘Purple Brocade’ – hardy non-aggressive variety, 6-8 inches high, with bluish-violet 6-inch flowers and deep green leaves with purple markings

Goatsbeard

Posted by Hugh on June 19th, 2023

Goatsbeard (Aruncus dioicus) or “goat’s beard” is a North American perennial that produces feathery plumes of cream-colored flowers in late spring or summer. Goatsbeard is also indigenous to western Europe. This clump-forming woodland plant is hardy in zones 3-7a (?) and appears to flounder under the intense summer heat in Georgia and the Carolinas. The arching plumes are densely covered with small florets in 20-inch branched clusters.

Goatsbeard is often mistaken for Astilbe and both have dark green pinnately compound leaves. The perennial is dioecious (separate male and female plants); flowers on male plants are showier on female ones.

Flowers are at their peak for about 10 days and make good cut flowers. Female plants produce tiny brown seed capsules, which are poisonous. After flowering the plumes turn tan or light brown above the 3-4 feet mounds of finely dissected foliage. Each leaf has 20 or more toothed oval leaflets.

In the garden goatsbeard grows slowly the first few seasons. It grows best in moist, rich, well-drained soil in partial shade, although it will do fine in full sun if given consistent moisture. Set in multiples of 3-4 plants, spacing them 2-4 feet apart. Within 3 years, plants should fill-in and offer a spectacular floral show.

Goatsbeard is a relatively low maintenance plant. Keep the soil moist during dry spells. Cut back old stems in fall to just above ground-level and mulch with leaf compost.

Goatsbeard has no significant insect or disease problems and is reported to be deer resistant. Propagate by division or grow from seed.

Over 3-5 years goatsbeard looks shrub-like in a sunny perennial border or in a woodland landscape area. Over time plants will self-seed freely.

Addendum: “Dwarf Goat’s Beard” (Aruncus aethusifolius), native of Korea is a good choice in a smaller garden. It produces short spikes of cream-white flowers in June. Utilize as edging along a woodland path or grow in a front border; at its best in moist soil and in sun to partial shade. Deadhead faded flowers to encourage repeat blooming.

Bergenia Or Pigsqeak For Sun Or Shade

Posted by Hugh on June 9th, 2023

Bergenia (Bergenia spp), aka “pigsqeak”, is a herbaceous perennial with distinctive glossy, rounded leaves. Bergenias are native to the forest and alpine zones of China and Siberia. Eight species are available including heartleaf Bergenia (B. cordifolia), leather bergenia (B. crassifolia), and fringed bergenia (B. ciliata). Hybrid selections are also available. (USDA hardiness zones 4-8).

Bergenia’s colorful bloom spikes rise 12 – 16 inches tall in the early spring garden. Depending on the variety, the showy bell-shaped flower clusters come in white, pink shades, or purple colors.

‘Peppermint Patty’ bergenia — new from Walters Gardens (WG photo)

The key reason for growing Bergenia is for the huge, round, brassica-like leaves which are deciduous in the north and evergreen in the Southern areas of the U.S. In a shady garden, its bold textured almost leathery foliage standout among perennials with finely textured leaves, such as ferns, bleeding hearts, and astilbes or broad-leafed hostas and brunneras.

Bergenias are rated as good shade plants, although they also perform well in sun. Set plants in humus-rich soil and mulch annually in late spring with well-rotted compost. In northern areas they thrive in almost any amount of sunlight (zones 4-6) and preferably in afternoon shade in the Southern U.S. (zones 7-8).

Whenever you spot bergenias growing poorly, the soil probably drains poorly or holds to much water over the winter months. Plants spread slowly via rhizomes (underground stems). The best time to divide rhizomes is in spring (after flowering) or in the fall. Dig up the whole clump, discard the old woody center and cut the remaining rhizomes into several sections, making sure each one has at least one leaf attached.

Bergenia leaf spot and anthracnose are fungal diseases that trouble this perennial. Deer are not rarely troublesome. Clip off and discard diseased leaves promptly. Avoid overwatering and water mainly in the morning hours. Slugs and snails can lurk under the leaves and disfigure the foliage.

Native Catalpa Trees

Posted by Hugh on June 2nd, 2023

Catalpa Tree

Northern catalpa or cigartree (Catalpa speciosa) overpowers most private landscapes by their enormous presence (USDA hardiness zones 4-8). This 40-60 feet large native tree commonly grows along roadsides, particularly on bottomlands from Illinois and Missouri south thru Arkansas and Tennessee. Catalpa is not a tree seen planted in most residential neighborhoods because of its fast growth rate, messy behavior, and enormous size.

Without question catalpa is treasured for its showy fragrant white flowers in late May into June. The orchid-like blosoms are surely beautiful. Numerous two-inch long white flowers are borne on large terminal spikes, many unfortunately hidden beneath the enormous catalpa leaves. Each flower are marked with small gold spots within its frilly edged corolla. Narrow long cylindrical cigar fruits, 8 – 15 inches in length, are easily visible in the fall and winter months.

In summer catalpa’s huge heart –shaped pale green leaves measure 8 – 12 inches in length and width and provide excellent summer shade. Small birds often seek shelter within their dense tropical-like foliage cover.

The bad news is their spent blooms turn into a soggy, slippery, smelly mess when they drop onto a sidewalk, deck, patio, driveway, or pool side. In the autumn months add their trashy dried seed pods to your raking list; their sharp points may result in pin-point skin pricks incurred during fall cleanup.

Even mild winds can leave your yard covered with sticks and twigs that fall from this brittle-wooded tree. Wide-ranging, invasive roots can infiltrate foundations, sewer lines, collapse retaining walls, or penetrate underground swimming pools.

Catalpa trees are often visited by the catalpa sphinx moth whose larvae (caterpillars) are prized for bait by fishermen. Hummingbirds are a major pollinator that are attracted to its floral nectar. There are no listed cultivars of northern catalpa (C. speciosa).

Southern catalpa (C. bignonioides) is another native species native to the Gulf Coast region from northern Florida across the Mississippi. It grows smaller, averaging 35-50 feet in height (zones 5-9). Both species self-seed readily.

American Beautyberry

Posted by Hugh on May 28th, 2023

American beautyberry (Callicarpa americana) is a deciduous shrub native to open meadows, fence rows, or woodlands in the southeastern U.S. and northern Mexico (Zones 6-11). This vigorous shrub grows to 4-8 feet high and wide and belongs in the Lamiaceae (mint) family.

American beautyberry, also called French mulberry, has an open growth habit and arching branches. The ovate to elliptic, oppositely arranged leaves are coarsely toothed; they range from 3-8 inches in length and 1-3 inches in width. The small, light pink to purple or blue tinged flowers are arranged in dense, axillary clusters along main branches in early summer and develop bright, lavender to violet ¼ diameter fruits in September. White-berried varieties are available.

Beautyberry is widely adapted to moist, well-drained soils containing lots of organic matter. It is not finicky as to soil type as long as drainage is adequate. Mulch first year planted shrubs to conserve soil moisture. Irrigate during prolonged periods of hot, summer drought to prevent early fall defoliation.

Optimum fruiting occurs in full sun, although beautyberry does tolerate moderate shade and be less fruitful.

Prune in late winter to encourage more bushy, compact growth. Plants can be cut as far back as 1-2 foot from the base. Or shrub(s) can also be left to favor a more natural habit. Remove deadwood in spring. Propagate from cuttings or seed.

An unusually cold harsh winter may result in stem dieback, but pruning back shrubs will regenerate vigorous new shoots from the shrub base. Summer flowering and autumn fruiting will be unaffected.

Beautyberry is relatively disease and pest free. Leaf spots are possible but not usually a serious problem. Green leaves emerge in mid-spring on upright arching stems. Clusters of small lavender pink flowers bloom during the late spring and early summer. Clusters of purplish to bluish berries size and color-up in August through October. A pink-fruited and several white-fruited forms are available (see below). Fruits may persist into early winter and are a good food source for songbirds and small mammals.

Shrub size and its loose open form relegates American beautyberry to the back of a shrub border. In large landscapes mass several beautyberry shrubs together for a maximum fall berry show and winter wildlife habitat.

Cultivars

‘Welch’s Pink’ blooms in late spring into early summer and form beautiful pink berries in September that last into winter; grows 4-6 feet tall and wide, smaller than the species; initially found in east Texas and rated winter hardy in zones 7-11.

Var. lactae produces white berries in the fall.

Factoid: the sap from crushed leaves of American Beautyberry have proven to repel mosquitoes and biting bugs both on livestock and humans.

Watering Newly Planted Trees And Shrubs

Posted by Hugh on May 21st, 2023

Tree “gator bag” for irrigation

Tree watering

Proper watering of a newly planted tree or shrub starts the day it is planted. This is the final crucial step! Dig a wide shallow hole that will accommodate the roots of the new tree. Adding soil amendments is generally not necessary unless the shrubs are moisture-loving, acidic-loving types such as azaleas (Rhododendron spp.), blueberries (Vaccinium spp.) or mountain laurels (Kalmia spp.). Treat the original topsoil removed from the hole as “gold” as it contains some humus.

Water deeply after planting. For a 3-4 feet wide hole, add a minimum of 5 gallons of water. Add 2-3 inches of organic mulch such as shredded pine bark, pine straw (needles) or lawn grass clippings.

Under- or over-watering may kill the tree. Too much water drowns tree roots; it takes oxygen out of the soil around the roots. Yellowing or sudden leaf loss are common symptoms of overwatering, usually first noticed on the interior leaves.

Most tree roots grow in the top 6 to 12 inches below the soil surface. To water a newly transplanted tree, you might opt to using a soil needle, aka “root feeder” which is attached to a garden hose. Water goes deeply to the root zone. A root feeder is a valuable tool for watering older trees and shrubs as well.

Water newly transplanted trees thoroughly through September (in most states), then gradually cut back watering in autumn to allow plants to “harden off” as cold weather sets in. After the leaves drop, continue watering if natural moisture is significantly below average.

Newly planted trees and shrubs need adequate soil moisture to become established, especially through the first hot dry summer. Naturally shallow rooted trees such as Japanese maples (Acer palmatum), spruces (Picea spp.) and azaleas require more frequent watering than tap rooted species such as oaks, ashes and walnuts.

Drip irrigation system or soaker hose is common methods of timely supplying water. Treegator™ bags, available in 15 and 20 gallon sizes, slowly release water (and nutrients) to a newly planted tree. They’re available through garden centers, hardware and box stores across the U.S.

Additional facts:

Newly planted trees need more frequent watering than those established 3 years or more. Larger trees demand more soil moisture than smaller species.
Evergreens do require watering during the fall-winter period in areas with a rainfall deficit.
Clay and silt loams retain more soil moisture than porous sandy soils.
Weekly rainfall amounts of one inch per week during the growing season is rated satisfactory.

Western Sunflower

Posted by Hugh on May 16th, 2023

Western sunflower (Helianthus occidentalis) is actually native to eastern and central North America, not western North America (USDA hardiness zones 4-8). It is one of the shortest of the many sunflowers found in the U.S. You have seen this Midwest native growing in glades, prairies, dry meadows, fields and rocky open woodlands. It grows equally well in my east Tennessee garden.

Western sunflower is also sometimes commonly called naked stemmed sunflower because of the almost total absence of leaves from the flowering stems. Large, long-stalked, ovate to oblong-lanceolate, the basal leaves (some up to 8 inches long) form a 4-8 inches tall foliage clump. Its 2-inch-wide flowers with orange-yellow rays and yellow disks appear on stiff, almost naked (leafless), flower stems that typically rise to a height of 2-3 feet (less frequently to 4 feet) tall. It blooms from late summer into fall.

This ground cover sunflower is best grown in average, dry to medium, well-drained soils and in full sun. It is not fussy and tolerates a wide range of soils, including poor sandy soils. However, avoid planting in organic poor clay soils. It tolerates moderate drought. Over time it spreads aggressively by creeping rhizomes to form large colonies. Plants should be divided every 3-4 years to control spread and to maintain overall vigor.

No serious insect or disease problems trouble this sunflower and is tolerant of deer. You may need to stake taller plants, particularly plants not in full day sun.

Plant naturalizes readily in areas where it is planted. A good plant for holding dry soils and preventing erosion. Use flowers in fresh cut arrangements.

Uses: Sunny borders, wild or native plant gardens, cottage gardens.

Sweet Azalea

Posted by Hugh on May 15th, 2023

Sweet azalea (Rhododendron arborescens), aka smooth azalea, produces fragrant flowers in June. The native deciduous species grows along streams on woodland slopes and moist shrubby balds in the Appalachian Mountains from southern Pennsylvania and eastern Kentucky to North Georgia and Alabama. Here in Tennessee, you may spot this sweetly fragrant white blooms while hiking at the Gregory Bald near Cades Cove. (USDA hardiness zones 4-7)

Spring-summer dark green, 1-3 inches long leaves, are smooth, elliptic to obovate, and often blunt-tipped. Leaves turn red to purple in fall.
From late May to July, after leaves have emerged, the fuzzy-haired, funnel-shaped, white (occasionally pale pink) flowers open. Blooms average 2 inches across and are arranged in clusters of 3-6. Each white flower contains a red style and dark pink to red stamens which protrude beyond the mouth of the tubular corolla. Fruits are narrow, egg-shaped capsules (to 3/4” long).

Sweet azalea can reach 8 to 12 feet in height and width, occasionally to 20 feet. It requires full sun to partial shade in sandy soil with an acidic pH. Moist soil with good drainage is preferable. It spreads via underground runners and its shallow roots do not like cultivation around them. Deadhead an old sweet azalea in June, immediately after bloom to maintain its appearance.

Sweet azalea offers multiple seasons of interest. Pale pink or yellow fragrant flowers bloom from late spring to early summer and attract bees, butterflies, and hummingbirds. In the fall the foliage turns bright orange to crimson or purple color. The plant tolerates damage by rabbits but may be damaged by deer. Plant sweet azaleas in mixed planting borders, in open woods or shade gardens, in pollinator gardens, or rain gardens.

Sweet azalea grows 8-12 feet tall and wide

Selecting a proper planting site for sweet azaleas is of key importance. Full sun may scorch leaves and poorly drained soils may lead to Phytophthora root rot that causes reduced vigor, branch dieback, and wilting. Plant on a moist well-drained site in soil high in organic matter. Irrigate during prolonged dry weather.

A litany of disease and pest problems are possible if site conditions are poor Aphids, borers, lace bugs, leafhoppers, mealybugs, mites, nematodes, scale, thrips, and whitefly. Disease problems include but are not limited to canker, crown rot, root rot, leaf spot, rust, powdery mildew.

Six Mini-Shrubs For Small Gardens

Posted by Hugh on May 10th, 2023

Many green thumbers and veteran senior gardeners have opted to grow
in small garden beds. Here are six (6) small flowering shrubs that add lots of seasonal color from early spring to late summer. All six are easy to maintain; check the easy-care info at the end. Plants can also be grown in 12 inches or greater wide containers.

Sugar Baby Forsythia® (Forsythia x Nimbus) is a very compact, dwarf forsythia, 2.5 feet height and 3 feet wide that will delight in a small space. (Zones 5-8).

Forsythia ‘Sugar Baby’ (photo courtesy of PW)

Wabi Sabi® Viburnum (Viburnum plicatum tomentosum) bears pure white lacecap blooms in early spring on 2-3 feet tall x 3-4 feet wide compact shrub. Flowers lay flat on the horizontal branches. (Zones 5-8).

Baby Kim Lilac (Syringa x) is a delightfully fragrant lilac that is packed in a lot of flower power. Its dwarf habit takes up just a fraction of the space of other lilacs. Fragrant pale lavender flowers fade to white. Rarely pestered by deer or disease. (Zones 3-8).

Incredibelle Wee White® Smooth Hydrangea (Hydrangea arborescens) This compact floriferous hydrangea grows just 1-2.5 feet tall and is covered in pure white mophead flowers from late-spring to late summer. Stems are sturdy and never flop. (Zones 3-8).

Polypetite® Rose of Sharon (Hibiscus syriacus) is a brand-new space-saving althea that grows 3-4 feet tall and wide habit with a rounded shrub form. It rarely needs pruning. In summer, it’s loaded with large lavender-pink blooms contrast with its dark blue-green foliage. Polypetite® series are almost seedless, so no nuisance seedlings popping up everywhere in your garden.

Polypetite® Rose of Sharon (photo courtesy of PW)

Firelight Tidbit® (Hydrangea paniculata) is a compact panicle hydrangea grows 2-3 feet tall and wide. In mid-summer flowers start white and develop their pink coloration in late August. It has a long bloom period for 3+ months. The cultivar is an improved compact form of the taller 6-8 feet tall Firelight®. (Zones 3-8).

General Care: Grow shrubs in full sun (6+ hours), part sun (4-6 hours), or full shade (up to 4 hours) and well-drained soil. Feed all six shrubs with 10-5-10 granular fertilizer in spring or water-soluble Miracle-Gro® two times in spring and summer. Mulch around shrubs to conserve water and suppress weeds. When necessary, prune the first four (4) flowering shrubs in spring immediately after spring flowering; prune by 1/3 in spring. The two compact hydrangeas listed here are pruned on old wood in spring.