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

Evergreens For Wet Soggy Soils

Posted by Hugh on October 19th, 2014

Emerald™ arborvitae at Daniel Stowe Botanical Garden, Gastonia, NC

Most needle evergreens falter in moist soggy soils. These sites usually have a heavy clay or fine particle sand content. Some arborvitaes (Thuja spp.) and Atlantic white cedar (Chamaecyparis thyoides) tolerate temporary wet soggy conditions better than most evergreens (USDA hardiness zones 3-8). An assortment of shapes, sizes and colors are available. All are U.S. natives.

Eastern arborvitae (T. occidentalis) tolerates dry to boggy wet sites. Emerald™ and ‘DeGroot Spire’ is two popular favorites, growing 12-15 feet or 8 feet tall respectively over 15-20 years. The scale- like foliage is uniquely twisted and spiraled. ‘Hetz Midget’ or ‘Tiny Tim’ are dwarf globe or ball forms that grow 12 inches tall and 16 inches wide. The light green scaly foliage turns bronze over winter.

Western arborvitae (T. plicata)) also tolerates tight wet soils. It grows tall and is fast-growing with a tightly pyramidal growth habit. Most popular is the hybrid ‘Green Giant’ (T. plicata x T. standishii) cultivar. Summer foliage is dark glossy green and bronzes over winter. Green Giant grows to a mature height of 50-60 feet tall and 8-10 feet wide. For something very different, ‘Whipcord’ is a dwarf cultivar with unusual thread-like branches and an arching plant habit. It grows to only 2 feet tall by 3 feet wide in 10 years.

Atlantic white cedar (C. thyoides) (zones 5-9) is often observed growing on soggy sandy sites, but dislike clay soils. Winter foliage turns a deep plum color and back to green by the start of spring.

Three popular selections of C. thyoides include:

‘Rubicon’, aka ‘Red Star’ – upright dense form with star-like foliage (6 feet tall by 2 feet wide).

‘Heatherbun’ – compact, globe-shaped form (6 to 8 feet tall by 4-5 feet wide).

‘Shiva’ – dwarf multi-stemmed form with upright spreading branches and silvery lacy foliage (5 feet tall by 4 feet wide) .

Bird’s Nest Spruce

Posted by Hugh on October 16th, 2014

Picea abies ‘Nidiformis’ at Boone County Arboretum in Kentucky

Bird’s nest spruce (Picea abies ‘Nidiformis’) is a dwarf cultivar of Norway spruce and is native to northern Europe (USDA hardiness zones 3-7). This slow growing compact shrub will attain 4 feet in height and 5 to 6 feet spread over 15 – 20 years.

The shrub grows in a round form with a distinctive flat depression or “bird’s nest” cavity on top. Lush, dark green needle foliage has a medium to fine texture and deer stay away from this sharp needle conifer. Short ½ inch long needles radiate along the slightly uplifted branches.

Bird’s nest spruce grows in average acidic, well-drained soil; it is best planted in full sun to partial shade with good air circulation. In the mid-south, this shrub conifer tends to struggle during periods of extreme heat and drought. Best specimens are seen in gardens from northern Virginia and northward and through the Midwest U.S. where summers tend to be less humid and a bit cooler.

When needles appear pale or off color, feeding spruce and eriophyid mites may be the problems. Pesticide controls are very effective; also hosing down the shrub with a coarse spray of water will wash away most mites. This naturally dwarf plant rarely requires pruning, other than to remove any damaged, discolored and/or diseased twigs.

Bird’s nest spruce has year-round appeal. It is frequently included in foundation or low border plantings. It is exceptionally winter hardy and may be planted in a large container.

Extra: Picea abies ‘Maxwell’ exhibits a similar form except its top is flat but not depressed.

Growth Rates Of Four Privacy Screen Evergreens

Posted by Hugh on October 13th, 2014

Leyland Cypress Privacy Screen

In a hurry to create a little privacy from neighbors, then add a tall evergreen privacy screen to your planting chores. Four most popular conifers are rated by annual growth rate. If you recall the children tale of “The Tortoise And The Hare”, fast does not mean best.

Leyland cypress (x Cupressocyparis leylandii) (zones 6-9) has the fastest growth rate at 40-50 feet tall and 20-25 feet wide in less than 25 years. Growth rate averages 3 – 4 feet annually. Leylands are very care-free the first 10 years, except they’re suffer during long summer dry spells. Plant them 12-15 feet apart with frequent irrigation the first 2-3 years. They become too tall for their space. As shrubs age, their susceptibility to fungal diseases also increases. Pruning off dead or diseased wood is the only remedy, usually requiring working on a tall ladder. Plant spacing is 12 -16 feet apart.

Japanese Cedar (Cryptomeria japonica) (zones 5-8) is another fast grower at 30-40 feet tall and 20-25 feet wide in 30 years. Winter foliage tends to turn bronze colored, but green needle color returns in early spring. Cryptomerias may become susceptible to Cercospora leaf spot disease if shrubs are crowded too close together. Three-year and older established shrubs are very drought tolerant. Plant spacing is 12-14 feet apart.

‘Green Giant’ arborvitae (zones 5-7) is a hybrid between west coast native arborvitae (T. plicata) and Japanese arborvitae (T. standishi). Growth rate starts slow, but Green Giant gets 25-35 feet tall and 15-18 feet wide in 30 years. They are moderately drought tolerant and mostly disease and pest resistant. Plant spacing is 10-12 feet apart

Emerald® Eastern arborvitae (Thuja occidentalis ‘Smaragd’) (zones 3 -7) is slowest grower of the four, a semi-dwarf shrub with a compact, narrow pyramidal habit. Also called “Emerald Green” arborvitae, it has glossy, dark green, flat sprays of scale-like foliage. Grows 20 to 30 feet tall and 10 to 15 feet wide at maturity. Disease and insect problems are few. Plant spacing is 8-10 feet apart.

Shrubs You Should Not Prune In Fall Season

Posted by Hugh on October 10th, 2014

Flowering quince (left) and Forsythia (right)

Why would anyone prune spring flowering shrubs in the autumn season? After a long cold winter, why miss out on the delightful fragrance of lilac and viburnum flowers the following spring?

Predicting how cold, warm, or dry the coming winter season is rarely possible. Pruning cuts are wounds and weather extremes may cause injury to the previously-cut branches.

Partial list of spring flowering shrubs:
Azaleas (Rhododendron)
Beautybush (Kolkwitzia)
Deutzias
Fothergilla
Forsythias
Honeysuckles (Lonicera)
Magnolias (most deciduous types)
Mahonias
Mockorange
Flowering quince (Chaenomeles)
Spireas (Spiraea)
Lilacs (Syringa)
Viburnums
Weigela

These shrubs form their flower buds in the summer. Pruning them in the fall removes some, if not, all flower buds. Tall unruly shrubs can be partially pruned back if they spoil the appearance of your home and grounds. Expect some loss of spring blooms. You can complete the task in late spring.

Remove dead and dying branches at any time. Channel all the plant’s energy to the strongest buds and prune out weak wood. Thin out crowded and crossing branches to open up the interior of the shrub to better sunlight penetration and air circulation. This also reduces fungal diseases such as powdery mildew common to lilacs and other shrubs. Some heavy scale and adelgid infestations can be pruned off.

If a shrub is in poor health, you may want to attempt “renewal pruning”. You may opt to cut back most of shrub, leaving a few strong water sprouts around the old shrub base. Root suckers below ground can also rejuvenate an old shrub.

Storing Vegetables Outdoors Over The Winter

Posted by Hugh on October 7th, 2014

Use covered cold frame for vegetable storage in winter

In early fall before killing frost arrives, harvest of fresh vegetables is central on gardeners’ minds. You might consider storing some (not all) vegetables outdoors to take advantage of frigid winter temperatures ahead. Limited refrigerator space in your kitchen is not taken up.

Some root vegetables- namely beets, carrots, rutabagas and parsnips- are long keepers. These vegetables store best when harvested near, but not past, their maturity. To maintain safe eating quality, veggies need to be stored within a narrow temperature range between 33 and 40° F.

Carefully gather root crops without bruising or cutting the edible portions. Use a sharp knife to pare away stems and leaves. Gently wash away most of the soil from roots. Cover in damp sand or blanket with a 6 inch layer of loose (not packing) tree leaves or organic mulch.

A second option is to build your own root storage bin in a shady area near the home. Pack the vegetables into a tub, wooden box, 5-gallon bucket, or a plastic storage box (punctured with drainage holes). Start by placing several inches of moist sand on the bottom of the container. Lay a single layer of root vegetables that are not touching one another on the sand. Cover them completely with sand.

If the box is deep enough, add another layer of veggies and sand layer until box or bin is nearly full. Finish covering with a layer of moist sand. Plan accordingly as a full container may likely be too heavy to lift. When you are preparing a meal, remove stored vegetables as needed over the fall and winter months.

If you live in a cool (not frigid) winter climate, overwinter cool crops (broccoli, cauliflower, kale, cabbages, head lettuce) in a cold frame. Cover the harvested crops with a 6-12 inch layer of loose straw or leaves. No part of the green vegetable tissue should be left exposed. If covered with the glass slash, place a cloth blanket over so the sun does not heat up the cold frame. Plan to consume all veggies before the cold frame is needed to start new vegetable and flower plants in late winter.

Planting Of Norway Maple Declining In U.S.

Posted by Hugh on October 4th, 2014

Dark green foliage of Norway maple

Fine grain bark of Norway maple

Norway maple (Acer platanoides) is a hardwood tree native throughout the of Europe and widely planted in the U.S. (USDA hardiness zones 4-7a). At maturity a tree reaches 40 to 50 feet in height (to 75 to 80 feet is not unusual) and 35 to 50 feet in width. Its dense leafy canopy values it a shade tree for planting along streets, large residential properties, golf courses, and in parks.

Norway maple prefers full to partial sun and grows best in moist, well-drained soils. Established trees tolerate hot dry conditions. It transplants reliably and tolerates urban air pollution and moderately compacted soils.

Leaves are 3-5 inches long and 4-7 inches wide. The 5 palmate-lobed leaves are sharply pointed. Yellow fall leaf color is rarely stunning except in specific cultivars. Upper leaf surface is medium to dark green, and dull green, shiny, and hairless underneath.

Small yellowish green flowers appear from early to mid-spring (depending on location) and give way to 2-winged 1 ½ inch wide samaras fruits that whirligig to the ground in fall and winter.

Many cultivars are available at nurseries and garden centers. Norway maple has declined in popularity because seedlings germinate freely along roadsides and woodland areas, competing with native vegetation in the Northeast U.S.

Norway maple has few serious disease or pest problems. Tree is susceptible to verticillium wilt on dry clay soil sites. Its shallow root system frequently cracks or lifts driveways and sidewalks and competes with lawns. In northern areas, bark of young trees may be susceptible to sunscald and frost cracking over the winter months.

Cultivars:

‘Cleveland’ grows 40 to 50 feet high and a narrow 30 to 40 feet wide. Upright branching of young and middle-aged trees is ideal form for urban street planting.

‘Crimson King’ is a popular selection that grows 40 to 50 feet tall and wide; its purple-green spring/summer foliage darkens to maroon or bronze color in autumn. Cultivar tends to grow slower.

‘Emerald Queen’ is a fast-growing selection with an oval-rounded habit (50 feet high and 40 feet wide) and dark glossy green summer foliage. Bright yellow fall color is better than most.

‘Schwedleri’ grows 40-60 feet high and wide; this popular old selection renown for reddish bronze spring foliage which fades to greenish-bronze by early summer.

Tropical Looking Big Leaf Magnolia

Posted by Hugh on October 2nd, 2014

Bigleaf magnolia at Daniel Stowe Botanical Garden, Gastonia, NC

Bigleaf magnolia (Magnolia macrophylla) is native to the southeastern United States as far north to Ohio (USDA hardiness zones 5-8). A mature tree attains heights of 30 to 40 feet and develops an irregular pyramidal form. In the northern areas the tree is deciduous and semi-evergreen in the southeastern U.S.

Its enormous size foliage makes it a true horticultural oddity, something different for a residential site. Its unusual leaf size relegates planting on woodland sites where weak branches and extra large leaves are protected from ice and wind storms.

It grows in full sun or part shade and prefers a well-drained, acidic sandy loam. An established tree is moderately drought tolerant. Its large leaves decompose slowly and create a litter problem. No serious insect or disease problems bother this magnolia if properly sited.

A tree may take 10 or more years before first blooms form. Goblet-shaped flowers are creamy white, rose-purple at the petal base, and up to a foot across. They open in early summer, mostly high in the tree and mostly hidden within the dense foliage. Up close, flowers are pleasantly fragrant. Fruit is round to cone-shaped, rose-colored, and nearly 3 inches long; they’re unique, persistent, and attract numerous bird species. When cones open, each red coated seed is held by a thin silk-like thread.

Leaves are alternate, simple, 12 to 36 inches long and 7 to 12 inches wide. They’re bright green above and silvery gray below. Petioles are 2 to 4 inches long. Its yellow fall color rarely stands out. Leaves are intolerant of most urban pollutants.

It is sometimes called large-leaved cucumber tree — a reference to cucumber magnolia (M. acuminata), a deciduous magnolia from the eastern US which has cucumber-shaped fruit. Bigleaf magnolia has round or egg-shaped fruits that bear little resemblance to cucumbers.

Bigleaf magnolia may be purchased from on-line tree nurseries.

Black Gum Should Be Planted More

Posted by Hugh on September 30th, 2014

New Red Leaf on ‘Wildfire’ black gum

Zigzag Growth of ‘Zydeco Twist’ black gum

U.S. native black gum (Nyssa sylvatica), aka sour gum or black tupelo, is a medium to large shade tree. A young tree has an attractive pyramidal habit and dependable fall color. In the past transplanting black gum has been an issue, but modern advances in growing and planting practices have been solved. New cultivars have favorably changed how we rate black gum as a landscape tree.

Black gum is found throughout most of eastern North America, from Ontario south to Florida, and west to Texas (USDA hardiness zones 4-9). It is widely adapted to dry upland sites, but does tolerate periodic flooding. Black gum handles either partial to full sun. It is best planted in moist, well-drained, acidic soil.

Black gum grows 30 to 50 feet tall with a spread of 20 to 30 feet. In the winter its pyramidal silhouette reminds one of pin oak (Quercus palustris). A tree tends to modify its growth leader to a rounded canopy as it ages. Summer foliage is dark green, and in the fall color blends varying from bright yellow, orange, crimson, and purple. A well-established black gum exhibits good drought tolerant and rarely requires supplemental irrigation. Dormant twigs and buds resist deicing salts.

The tree is primarily dioecious, although you may find some bisexual flowers and fruits scattered through a male tree. Ornamentally, flowers are insignificant. Small blue-black drupe fruits are consumed by a variety of birds and mammals in the fall.

Seedling and some cultivar forms are susceptible to leaf spot diseases in wet summers. Take a peak at these five superior blackgum cultivars:
• Red Rage® (‘Hayman Red’) – reportedly leaf spot resistant and outstanding fall color.
• ‘Autumn Cascades’- a weeping form with irregular form and outstanding fall color.
• ‘Wildfire’- new leaves emerge with reddish tint; glossy green summer foliage and red fall color.
• Green Gable™ – strong pyramidal form (50 feet tall and 25 feet wide), glossy green foliage and outstanding fall color
• ‘Zydeco Twist’- slightly contorted, zigzag branches adds to its many ornamental attributes.

The Mighty Bur Oak

Posted by Hugh on September 25th, 2014

Bur oak in early fall in East Tennessee

Bur oak or mossycup oak (Quercus macrocarpa), aka blue oak and mossy overcup oak, is a majestic native oak native to the midwest and eastern U.S. (USDA hardiness zones 3-8). It a member of the white oak group (rounded leaf lobes, no bristly tips). This large sized deciduous oak grows 60-80 feet tall with a broad-spreading, rounded crown at maturity. Specimens over 90 feet tall are not hard to find. This large shade tree is most suited to large residential and commercial properties, golf courses, or parks.

The tree tends to be slow-growing, particularly when first planted. It naturally grows in deep prairie well-drained soils and in full sun. It adapts to a wide range of soil conditions, including bottomlands. Bur oak is often seen growing in calcareous (limestone) upland soils and is remarkably drought resistant. It is relatively intolerant of flooding.

Strings of yellowish-green separate male and female catkin flowers appear in spring as the leaves are emerging. Leaves are dark green and leathery, 6-12 inches long, and 5-9 rounded lobed. In fall leaf color turns a blah yellow-brown. By late September most leaves have often dropped due to secondary disease and past problems. Twigs and the main branches are often ridged with corky wings.

It may take 35 or more years to produce its first acorn crop. Large sized mossy cup acorns, almost 2 inches long, are oval shaped, and fringed by a burry cup that covers 1/2 to 3/4 of the acorn length. Acorns are an important fall-winter food source for wildlife. Acorns (nuts) have low tannin toxicity; it is best to leached or boiled out the tannins prior to consuming lots of them. Its wood is highly valued like white oak (Q. alba).

Bur oak is a long-lived low-maintenance tree. It is susceptible to numerous secondary diseases, none of which seriously injure the tree. It is resistant to dreaded oak wilt (Ceratocystis fagacearum) disease. Troublesome insect pests include scale, oak skeletonizer, leaf miner, galls, oak lace bugs, borers, caterpillars and nut weevils. Bur oak tolerates urban pollution better than most oaks.

My New Favorite Pruning Shears

Posted by Hugh on September 22nd, 2014

Dramm Model #18012 Hand Pruners

When stepping out to work in the garden, a pair of hand pruners (shears) is the first tool in my pocket or belt pouch. A good pair of pruning shears is indispensable to snip off old spent flowers and stems from perennials such as hostas, daylilies, peonies, etal; shrubs like rhododendrons, lilacs, hydrangeas; to clear away encroaching vegetation from a path; remove dead, pest ridden, and diseased twigs or small (1/2 inch diameter) branches.

Over the years I’ve owned a number of pruning shears from top manufacturers. My requirements for a good pruning shears are as follows:

Blades forged from high grade stainless steel, less likely to rust and stay sharp longer
Comfortable hand grips, less prone to cause calluses after heavy use
Colorful hand grips so pruners are not easily lost in the garden
Trustworthy locking mechanism that, when engaged, the blades close and don’t reopen in a pocket or belt pouch. Cutting action does not lock up by a faulty locking clip
Sharp, stay sharp longer, and cut almost effortlessly
Scissor cut and not anvil type

The Dramm model #18012 is the newest hand pruners in my garden tool shed. Dramm, Inc. is a 75 year old company from Manitowoc, WI, best known for their line of premium watering products for the garden. The model #18012 is a lightweight pruning shears that fits comfortably in a small hand. It is designed for cutting small ¼ inch diameter wood and soft green stems. It is not designed for cutting through thick woody branches, but is fabulous for everyday small tasks.