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

Prickly Pear Is Easy Care

Posted by Hugh on December 17th, 2011

Prickly pear cactus (Opuntia)

There are over 200 species of prickly pear cactus (Opuntia spp.) worldwide. Several make great container plants in the garden or inside the home. Prickly pear cacti may grow to heights of 10 feet or more in the arid regions of the Southwestern U.S.

Eastern prickly pear (Opuntia compressa var. ‘humifusa’) grows 12- 18 inches tall and 30-36 inches wide. It will grow a bit larger in a warm moist habitat. The reddish “pear” fruits ripen in the fall. They taste like kiwi fruits and can be made into jam and jelly. The 3-4 inch wide bright yellow cactus flowers bloom in early summer in the Southern Appalachian region (USDA zones 6 and 7).

Prickly pears need a well-drained soil, preferably sandy or gravely, and they’re planted in full sun. Irrigation and fertilizing are rarely needed. Overwatering causes pads to collapse and the root system to rot. Cacti plants may appear wilted after a cold winter, but perk up and become fully turgid by early spring.

They are easily propagated from pad sections directly into the garden or a container. Allow the cut end to air dry (heal over) for 5-7 days before setting, cut end down, to a 2-inch depth into garden or potting soil. Moisten the soil after planting and no further watering is needed. Pad(s) generally root in 4-6 weeks.

Prickly pear spines greet you with hostility. Wear thick heavy duty gloves to protect yourself from the large smooth spines and small, hair-like needle spines over the pads.

Trifoliate Orange –The Barbed Wire of the Plant World

Posted by Hugh on December 12th, 2011

Winter View of Trifoliate Orange

Trifoliate orange (Poncirus trifoliata) is a hardy citrus native to China. T-orange is hardy to -15° F. This strong growing large shrub or small tree can reach 15 to 20 feet in height. Its foliage is deciduous and compound, compared to citrus trees with single simple evergreen leaves.

T-orange prefers full day or partial (minimum of 6 hours) sunlight. After one year establishment, it can cope with moderate periods of drought. T-orange grows in a soil pH range between 6.2 to 7.5 in average well-drained soils. One 3-4 oz. annual application of 10-10-10 granular fertilizer per plant in late winter provides adequate nutrition.

Showy 1 ½ to 2 inch white, mildly fragrant flowers open from late April into early May in the Southern Appalachian region (USDA zones 6 and 7). Golf ball sized green fruits turn rusty yellow (not orange) in late summer and are quite aromatic. The bitter fruits are edible and loaded with seeds.

Numerous heavy- duty, 1-2 inch long spines (thorns) form along deep green stems. The dominant spines seem to attract plant buyers to this “Little Shop of Horrors”. Plant it as a hedge to deter trespassers, if that is something you need to do. Aggressive pruning or shearing shapes and limits its size, but be advised to wear thick protective gloves and pack some extra band-aids.

T-orange is used as a winter hardy rootstock in commercial citrus groves. Some concern has been raised of its potential invasiveness.

‘Flying Dragon’ is a dwarf form with stems and thorns contorted or twisted. It grows well in pot culture.

Dwarfing Rootstocks for Apple Trees

Posted by Hugh on December 3rd, 2011

Yummy Apples

No more climbing ladders to pick apples. Less waiting for first harvest for newly planted tree. These are some of the reasons for planting dwarf apple trees. Over the past 100 years numerous dwarf rootstocks have been introduced.

In addition to the degree of dwarfing, some rootstocks are more disease and insect resistant. The original East Malling Research Station in England (“EM rootstocks”) reduced tree size and led to earlier first harvests. However, EM rootstocks are not resistant to wooly apple aphid in the southeastern U.S.

A second series from England, designated Malling Merton (MM), are wooly aphid resistant. Recent rootstock introductions are the Geneva series (G), which are resistant to fire blight (Erwinia amylovora) and collar rot (Phytophthora spp.) diseases.

Popular Rootstocks Size control

EMIX*, Bud 9* 70% reduction in size

M26*, G16A, G11A* 60% reduction in size

EMVII*, G30A* 50% reduction in size

MM106 25% reduction in size

MM111 20% reduction in size

Disease and insect resistances of the various rootstocks vary. Check with your local Extension office to determine which pests are prevalent in your area. Apple trees on dwarf rootstocks should not be permitted to crop until the third year after planting. Those rootstocks indicated with * tend to be shallow rooted and require staking for tree support.

‘Nellie R. Stevens’ Holly Sets A High Standard

Posted by Hugh on November 20th, 2011

'Nellie R. Stevens' holly

‘Nellie R. Stevens’ (‘NRS’) is a tall growing red fruited female holly, a cross between the English (Ilex aquifolium) and Chinese (I. cornuta) hollies. ‘NRS’ comes highly recommended for Southern Appalachian landscapes (USDA zones 6 and 7).

Hollies are dioecious, requiring both male and female parents for fruit production. ‘NRS’ holly produces small numbers of seedless parthenocarpic fruits without a male pollinator being present. More fruits are produced naturally when ‘NRS’ is properly mated to the male cultivar such as ‘Edward J. Stevens’ and another I. cornuta holly. One male holly adequately pollinates 8-10 female plants located within several hundred feet. Red fruits are not as persistent as ‘Emily Bruner’, another holly favorite.

Hollies are spaced apart according to their intended use in a planting. ‘NRS’ is an outstanding “stand alone” specimen or you can hedge several together to form a tall privacy screen. Annual growth rate is moderate, about half that of Leyland cypress (x Cupressocyparis leylandii). ‘NRS’ holly is a lot more dependable and long-lived.

‘NRS’ is a strong grower at 25-30 feet tall and 15-18 feet width over 30 years. If planted as a privacy screen, plant on a minimum of 12 foot centers (between plants).

Hollies prefer an open sunny location and moderately acidic, well-drained soil. Established hollies are good foragers for nutrients and benefit from annual feeding with an acidic based fertilizer such as Hollytone®, Miracid® or Miracle Gro®.

European Beech Prefers Cool Climes

Posted by Hugh on November 18th, 2011

Fagus sylvatica 'Pendula' in a Boston, MA Park

European Beech (Fagus sylvatica) is native to the cool temperate regions of Europe. In the U.S. it is more at home in the Northeast, Upper Midwest, and Northwest regions (USDA Hardiness Zones 4 to 7) where summers are cool. European beech grows in full sun and moist, well-drained soils, ranging from mildly acidic to low basic. The tree suffers in the Southeastern U.S. heat and waterlogged clay soils.

Because of its large size and slow growth rate, European beech needs a few years to adapt to its planting site. Utilize this large specimen shade tree in public parks, golf courses, commercial properties and estates. European Beech grows 50 to 60 feet high and 40 feet wide with a dense, upright, oval form. It grows 10-20 % smaller than American beech (F. grandifolia) and its trunk bark is a darker gray.

European beech is a long lived. Trees planted by Thomas Jefferson at Monticello in 1807 survived almost 150 years. Very little vegetation grows under its dense tree canopy which carpets and shades the ground beneath with leaf mulch. Livestock, wildlife, and humans snack on beechnuts.

Leaves are dark green in summer and turn a stunning russet brown in the autumn. Two to three year old established trees can tolerate short 1-2 week long drought spells. Purple leaved cultivars tend to be less summer heat tolerant.

European beech responds well to heavy pruning and several together are grown as a tall hedge in Europe. Foliage and twigs are not tolerant of salt, including de-icing salts used on roadways.

European beech lists over 30 cultivars which includes these popular six:

‘Asplenifolia’- fern-like or cutleaf foliage.
‘Atropunicea’ (Copper beech) – spring/early summer purple leaves.
‘Dawyck’, aka ‘Fastigiata’ – narrow, upright branching habit.
‘Pendula’- weeping habit.
‘Riversii’- dark purple leaves.
‘Roseomarginata’ (Tricolor beech) – with green and white leaves with pink margins.

‘Morgan’ Oriental Arborvitae

Posted by Hugh on November 12th, 2011

'Morgan' oriental arborvitae in Knoxville, TN Garden

Among dwarf conifer collectors, ‘Morgan’ Oriental arborvitae (Platycladus orientalis) has become one of the most sought out evergreens over the past decade. Its oval form and seasonal coloration makes Morgan a standout. It performs well in part sun, but its chartreuse-yellow foliage appears more vibrant in direct sunlight. Its dense foliage grows in vertical layers.

Andy Pulte at the University of Tennessee, another conifer addict like myself, classifies Morgan arborvitae as a “chameleon”. By late fall a purplish tinge has bled into the foliage and has turned to coppery orange by late winter. Early spring warm temperatures will force new growth and a return to the chartreuse-yellow coloration.

Morgan has a long garden life and a slow 2-4 inch growth rate per annum. Plant in a well drained compost rich soil and space a minimum of 3-5 feet away from other shrubs and perennials.

Irrigate and fertilize Morgan during the first two years to insure its longevity. Acid-based water soluble fertilizers such as Miracle Gro™ or Miracid™, or slow- release Hollytone® are good products. Read and follow package directions.

Morgan arborvitae adds four-seasons interest and is a perfect fit into any small garden or container (zone 6 and further south). Once considered as a collectors’ only plant, Morgan is finding its way into mainstream nursery commerce. Morgan arborvitae adds four-season interest and is a perfect fit into any small garden.

Making A Case for Mugo Pine

Posted by Hugh on November 4th, 2011

'Mops' Mugo Pine at New Hope Garden Center, Blountville, TN

Mugo pine (Pinus mugo) is a slow growing needle evergreen shrub of variable heights ranging from 5 feet to 20 feet and more. Mature height depends on the cultivar planted and environmental conditions on site. Mugo pine is native over many hundreds of miles of alpine climes across Europe. It is winter hardy in USDA zones 3-7, but its heat tolerance in southern parts of zone7 is sub-par.

This shrub pine grows best in full sun, but can tolerate light shade. The key to successfully growing mugo is a moist well-drained loamy soil. Planting in wide shallow holes on raised bed(s) is highly recommended. Mugo has a disease prone shallow rootsystem. Add mulch to keep roots moist and cool. Two-year established mugo pines exhibit good summer drought tolerance.

The 1-2 inch long dark gray/blue stiff needles are borne in bundles of two. The densely packed needles exhibit a long 5-6 year retention life before succumbing to natural needle drop in early fall.

There is great variability among mugo pines in terms of growth rate, size and shape. The popular variety ‘pumilio’ often grows beyond its stated size and form. ‘Mops’ is the preferred dwarf cultivar, growing 3-5 feet tall and 5-6 feet wide. ‘Mops’ may be utilized as a groundcover, included in a low foundation planting, or set in a rock garden. Selected hand pruning of young developing shoots (“candles”) in late spring may dwarf ‘Mops’ or other cultivars even further.

Mugo pine is susceptible to root rot diseases in poorly drained soils. Pine sawflies and tip moths are key insect pests. Quick monitoring and spraying with acephate (Orthene®), cyfluthrin (Bayer Advanced Garden Multi-Insect Killer®), or carbaryl (Sevin®) insecticides will keep these serious pests in check.

Natural Evergreen Needle Drop in Autumn

Posted by Hugh on October 25th, 2011

Natural Needle Fall in Pine in October

Some needle loss on evergreens in the fall is natural. As night time temperatures cool, needles in the interior of many evergreen trees or shrubs regularly turn brown (or golden yellow) and drop off. Needle loss is most obvious on pines (Pinus spp.) and arborvitae (Thuja spp.) in the Southern Appalachian region (USDA zones 6 and 7).

The numbers of needles shed may vary from one year to the next. Unusually high needle losses may be a reaction to high summer heat and extended dry periods within the geographical area where you live.

Loss of two year and older needles is natural. Loss of current season and last year’s needles is painfully not a good thing and may be caused by a disease or insect pest. Roots of evergreens may contract a root disease such as pythium and phytophthora fungi. Often, a root disease may be fatal or the pesticide treatment(s) very costly.

Environmental and transplanting stresses may be the cause. Winter desiccation and de-icing salts can turn evergreens brown. Needle losses are usually higher on newly planted evergreens.

Weekly deep watering in the fall and late winter fertilizing of evergreens helps relieve transplant stress. Transplant shock (heavy needle loss) should not re-occur the following fall.

Note: More on fall-winter care of evergreens coming soon.

Winter Storage of Non-Hardy Tropicals*

Posted by Hugh on October 16th, 2011

Musa 'Siam Ruby' at Kingwood Center, Mansfield, Ohio

There is frost on your pumpkin. By late October, northern U.S. gardeners (USDA zones 3 thru 6) must protect non-hardy tropicals such as cannas (Canna spp.), bananas (Musa spp. and Ensete spp.), elephant ears (Colocasia spp. and Alocasia spp.) and angel trumpets (Brugmansia spp.). Most gardeners living in zone 7-b and further south have little difficulty overwintering most cold sensitive tropicals outdoors.

Cannas (rhizomes) and elephant ears (tuberous roots) should be lifted from garden beds and stored in dry peat moss above freezing over winter. Container plants require winter storage as well. Stems should be cut back to the soil line and soil is shaken away from the root mass. Rhizomes and tuberous roots are stored in dry soil or sphagnum peat moss between 35-45° F.

For angel trumpets and non-hardy bananas, gardeners have two options. Option one is to cutback and bareroot angel trumpets and Musa spp. bananas. Do not cutback single-trunk bananas (Ensete spp.) as you must leave the growing point intact. To induce dormancy, store them in a cool location such as in an unheated garage or cellar (35° F minimum for cannas and 45° F for bananas). Reduce watering to once monthly and stop fertilizing, causing leaves to drop.

Option two for angel trumpets and bananas is to grow them. Angel trumpets and Musa spp. bananas are cutback to 5-6 inch stubs (for space saving) and cared for in a sunroom or greenhouse. Feed them with half-strength house plant brand fertilizer (such as Schultz™, Miracle Gro™ or Hyponex™) at every third watering.

‘Diabolo’ Ninebark Has More Than 9 Lives

Posted by Hugh on October 7th, 2011

'Diabolo' ninebark tree form

The cultivar Diabolo ninebark (Physocarpus opulifolius ‘Diabolo’) is an aggressive grower. A knowledgeable gardener with a sharp pair of pruners may quickly and easily train Diabolo ninebark into a small tree. Plant a ninebark tree in a large container for multi-seasonal color around your deck or patio.

Its common plant name “ninebark” says a lot. The outer bark peels off, exposing a lovely dark cinnamon inner bark. Narrow gray-brown outer strips peel off as thin opaque tissue, many more than nine times.

In tree form, Diabolo grows more than 12 feet in height and 8-10 feet in width. When left unpruned, vigorous Diabolo can overwhelm its landscape space. Ninebark grows in any type of soil including marginal clay. To maintain a single or multi- stem tree shape demands bi-monthly pruning attention during the growing season to remove unwanted stem and root suckers. Tidy-up pruning takes less than 5 minutes.

Plant a ninebark tree in a large 25-30 gallon container or in the ground where you may enjoy its year-round beauty. Its root system is winter hardy in the Southern Appalachian region (USDA zones 6 and 7). Numerous ¼-inch wide white flowers appear in May which contrast beautifully against the reddish burgundy Diabolo foliage. By early August, the burgundy tinted leaves have faded to medium green. Autumn foliage finishes greenish yellow before dropping.

I recommend using the following hand pruners: Corona™ #3160 or Fiskars® Powergear Bypass Pruner.