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

Growing Nasturtiums

Posted by Hugh on March 1st, 2019

Nasturtium ‘Double Delight Cream’

Nasturtium mix

Old-fashioned nasturtiums never lose their appeal, whether in the garden or as a garnish on a salad, or added to stir-fries, or favorite pasta dishes. Depending on the variety, some may be grown as climbers on fences and trellises or as bushy plants in a window boxes and containers.

Around the world there are several species of nasturtiums, also called Indian cress. The two most common species grown in U.S. gardens are: Tropaeolum majus , a trailing (climbing) type, and T. minus, a bush (compact) type. Nasturtiums are considered annuals, although they can be herbaceous perennials in southerly climes (zones 8-11).

Nasturtiums flower best in full sun, but prosper in partly shaded locations, particularly where summers are torrid. They love cool, damp, well-drained soil. If plants begin to flag in the heat of summer, cut them back and they’ll regrow and flower again when cooler weather returns in fall.

Nasturtiums thrive on neglect and don’t require rich soil. In fact, if you amend soil with too much nitrogen-rich fertilizer or manure, lots of dark green foliage and few flowers will result. In plain soils, amend the site by mixing in a 1-inch layer of compost. Plants ordinarily don’t need fertilizing during the growing season. Mulching is an added plus.

Nasturtium flowers range from pastels, yellows, oranges, and red shades, in either single or double flowers. Colorful seed mixes are also available. Flowers of most modern day varieties stand above the foliage.

Some of the best selections include:

Apricot Twist’ (trailing variety) – 3 to 4 feet long and double apricot-orange splashed with raspberry red flowers.
‘Empress of India’ (semi-bush variety) – 1 – 2-foot vines and features large, bright scarlet flowers and blue-green foliage.
‘Jewel of Africa’ mix (trailing variety) – 4 – 6 foot long in yellow, red, cream, and pink flowers and unique variegated leaves.
‘Moonlight’ (trailing variety) – up to 7 feet long and produce unusual, pale yellow flowers.
‘Peach Melba’ (heirloom bush variety) – creamy yellow blooms with maroon markings near centers.
‘Tip Top’ series – compact ‘Alaska’ series with mottled leaves and bright flowers in yellow, red and orange.
‘Tom Thumb’ series – shorter (6-9”) type with large, vivid blooms in bright yellow, red and orange; excellent for small gardens.
‘Vesuvius’ – compact plant habit and brilliant deep salmon flowers and deep blue foliage.
‘Whirlybird’ series (bush type) – a mix of flower colors, or in separate colors, including cream, salmon, gold, and cherry rose. The flowers are semi-double.

After sowing, keep the bed well-watered and weed-free. Nasturtiums are relatively trouble-free. Aphids may feed on the new leaves and flowers; washed bugs off with frequent sprays of water or use insecticidal soap.

Nasturtiums are high in vitamins A, C (10 times as much as lettuce), and D. Harvest nasturtium young leaves, flower buds and open blooms in early morning; those collected later in the day are more pungent. Wash and dry the flowers and leaves and store in a plastic bag in the refrigerator. Unripe seed pods have a peppery flavor somewhat like watercress and may also be used in salads.

Saucer Magnolias

Posted by Hugh on February 25th, 2019

Saucer magnolia

Multi-trunked Saucer Magnolia

Saucer magnolias (M. x soulangeana) are deciduous hybrid magnolias (M. denudata x M. liliiflora) as broad shrubs or small trees. They typically grow 20-30 feet in height and width. Saucer magnolias are often called tulip magnolias because of the shape of the colorful blooms. Flower colors range from white, pink, rose, purple, magenta, and burgundy. Flowers are pink with white interiors.

There are hundreds of hybrid cultivars available in nursery commerce. Be aware that the early blooms are prone to spring frost injury. Saucer magnolias do not tolerate heavy wind or salt spray.

Large fragrant flowers (to 10 inches across) open before the leaves emerge. Sparse numbers of additional flowers may bloom sporadically later in spring on new growth, but the later flowers are usually less vigorous and less colorful than those of the primary bloom.

Saucer magnolias date back to the 1820’s and are widely planted across the U.S. and Europe. In the early spring garden, saucer magnolia is a landscape show-stopper. Lush summertime leaves are dark green and leathery—adding nice contrast to silvery-gray bark. The husky gray branches and big, fuzzy flower buds stand out in the winter landscape.

Saucer magnolias thrive in a moist, humus-rich, mildly acidic, well-drained soil and in full to partial sunlight. For optimum flowering, mature trees should have more sunlight. The tree’s shallow competitive roots are best maintained in a grass-free mulched area. Trees tolerate short periods in wet soggy soils without injury. Once established, generally after 1-2 year span, saucer magnolias are highly tolerant of summer dry spells. Summer leaves may turn yellow (chlorotic) in iron deficient alkaline soils. Disease and pest problems are rare.

Balled-and-burlapped (b&b) or container-grown plants are best planted from late winter up to the early days of autumn. Prevent soil compaction around root zone by limiting foot traffic over the root system. Magnolias seldom have serious pest or disease problems; inspect for magnolia scale. Deer generally stay away from magnolias.

Early Flowering Magnolias

Posted by Hugh on February 20th, 2019

‘Leonard Messel’ (Magnolia x loebneri)

Flower of Loebner Magnolia

If you live (and garden) in the northern climes of the U.S. and Canada, Magnolia ×loebneri Leonard Messel is an excellent choice of a flowering yard tree. It is a hybrid deciduous magnolia (M. kobus x M. stellata) (zones (4)5-9). Other similar crosses include ‘Ballerini’ and ‘Merrill’.

Leonard Messel magnolia grows to 20-30 feet tall with a rounded crown. It is more often grown in a multi-trunk form that as a single trunk tree. Flowers measure 4-6 inches across with 10-15 petals. Flowers give way to cone-like fruits that ripen in late summer with a reddish tinge; fruits split open to release individual red coated seeds suspended on slender threads. Fruits are sometimes absent on some hybrid magnolias if inadequately pollinated.

Flowering magnolias are best grown in moist, organically rich, well-drained soils and in full sun to part shade. Trees are generally intolerant of soil extremes (dry or wet) as well as to most urban pollutants. Young trees may take 3-4 years before first blooms appear. Magnolias are best sited in a site sheltered from high winds.

Leonard Messel magnolia has a multi-branched habit and start producing their lovely flowers at an early age. No serious disease or pest problems trouble this shrub when properly sited at planting. The 5-inch long, medium green obovate leaves remain blemish-free through the growing season. The gray bark of deciduous magnolias is an added plus, particularly over the winter months. Magnolias are care-free landscape trees.

New hybrid cultivars are now available in commerce featuring more compact habits and flowers that are white, blush-pink, lilac pink or pink. ‘Ballerini’ (Loebneri hybrid) produce flowers with 30 or more pure white tepals and are highly fragrant.

Monkey Puzzle Tree

Posted by Hugh on February 15th, 2019

Monkey Puzzle Tree in Vancouver, BC, Canada

Evergreen dark green leaves

Monkey puzzle tree or Chilian pine (Araucaria araucana) is an evergreen conifer that is indigenous to forested volcanic slopes in the Andes Mountains in Chile and Argentina (USDA Zone 7b-11). It is the national tree of Chile.

It typically grows 60-70 feet tall and 30-35 feet wide, but frequently reaches 100 feet or more in height in its native habitat. The tree exhibits a loose pyramidal form when young, but develops an umbrella-like crown with loss of its lower branches as it ages.

Dense, leathery, triangular, radially-arranged leaves are sharply pointed. The 2-inch long evergreen leaves are glossy, dark green, and closely overlapping each other. Leaves persist for 10 to 15 years. Branches develop along a straight trunk in tiers. Upward-arching branches are arranged in whorls around the trunk.. Monkey puzzle forms few side branches. The female cones are globular that are up to 8 inches in diameter; male cones are cylindrical and up to 5 inches long. Bark is gray-brown and ridged.

It is best grown in deep, moderately fertile, evenly moist, well-drained soils in full sun to part shade. Trees grow well in average soils provided they’re well-drained. Trees perform much better in mild summers than in hot tropical climates. In northerly areas, trees can be grown in containers and brought indoors in winter and kept in bright indirect sunlight.

Trees are dioecious (separate male and female trees). Seeds (pinones) are edible and reminiscent of pine nuts. They are rarely troubled by serious insect or disease problems. Needle necrosis and leaf spots are rare problems as are mealybugs, scale and thrips.

Monkey puzzle is related Norfolk Island pine (A. heterophylla), a popular house plant for sale at garden shops during the winter holiday season in the U’S. and Canada.

Know About Liriopes

Posted by Hugh on February 10th, 2019

Liriope ‘Pee Dee Ingot’

‘Big Blue’ Liriope

Monkeygrass (Liriope muscari) and creeping lilyturf (L. spicata) are native to Asia. They are known by several names including lilyturf, monkeygrass, spider grass and liriope (USDA hardiness zones 6-10). Some varieties are hardier than others.

In general, L. muscari have more narrow leaves. Depending on variety, spikes of lavender, purple, or white flowers arise in late summer followed by small black berries. Leaves are more flattened and shorter in length than those of L. muscari.

Monkeygrass (L. muscari) are taller growing clumps, 15 to 18 inches and 24 inches wide, and spread slowly by short stolons. Creeping lily-turf (L. spicata) spreads more aggressively and are listed as invasive plants in some Southeast U.S. states.

Liriopes are easy to grow in average well-drained soil and in either full sun or light shade. Space plants 15-18 inches apart. If necessary, amend the soil with compost, peat, or other organic materials. Irrigate liriopes well after planting and keep the soil moist their first growing season for proper establishment. Mulch around the plants to conserve soil moisture and reduce weed infestation.Feed in early spring with a granular fertilizer such as 10-10-10 or equivalent.

Divide wide clumps of older liriopes every 2-3 years in the late winter or early spring. Before new growth emerges in early spring, cutback old brown foliage with a mower; set mower height at 5 inches or higher. Liriopes have few disease or pest problems. The plants tolerate urban air pollutants and are deer resistant.

L. muscari makes an attractive edging along walkways, driveways and in woodland gardens. They make wonderful accents in plant combos in large containers. Deep rooting liriopes are often utilized for erosion prevention on banks and slopes. L. spicata spreads quickly by underground rhizomes and cover bare ground around trees or in problem areas.

There are too many varieties to list here. Here are a select few:

‘Big Blue’ – 15” x 24″ wide clump, arching, green ¼” wide leaf blades; lavender flower spikes in late summer.

‘PeeDee Ingot’ – 18″ x 30″ wide clump; gold foliage in full sun or chartreuse-green in partial shade.

‘Variegata’ – 12” x 18″ wide clump of medium green leaves and creamy yellow edges; lavender flower spikes mid-summer.

‘Monroe White’ – 12″ x 18″ wide clump; ½” wide, dark green leaves; full, white flower spikes in summer.

‘Silver Dragon’ (L. spicata) – 12” x 3 ft. wide; form slow growing colonies of narrow upright green white-striped foliage.

American Hornbeam – Versatile Small U.S. Native Tree

Posted by Hugh on February 5th, 2019

American hornbeam at NC Arboretum in Asheville

Multi-trunk form is common

American hornbeam (Carpinus caroliniana), aka ironwood or muscle wood, grows primarily in moist, slightly acidic soils along woodland rivers and streams (USDA hardiness zones 3-9). This native hornbeam adapts to either wet or dry ground as long as soil moisture drains off, and it does not flood over long periods. This durable small tree copes with tough urban sites, including non-irrigated parking lots and the outer edges of rain gardens. It grows equally well in full sun or partial shade.

Its autumn foliage turns intense shades of yellow, orange, and at rare times scarlet red, depending on soil pH and the seed provenance of the species. Over the past quarter century Johnson Nursery (wholesale nationwide and retail locally) in Menomonee Falls, Wisconsin has introduced several forms with good fall red foliage. Firespire™ is a grafted clone with semi-upright branching and vibrant red fall color. ‘J N Strain’ is from a known seed population which delivers above average red fall leaf color.

Ironwood blooms in spring as separate male and female catkins, none of ornamental significance. In autumn female catkins produce showy clusters of winged nutlets, that are an important food resource to numerous forest fauna. The main trunk and branches exhibits a muscular beech-like bark, a singular trait that earns it the common names of “musclewood” and “ironwood”. Either single- or multi-trunked, the trunk(s) and boughs are singular assets in the winter garden.

American hornbeam grows 25-40 feet tall and variable in width depending on cultivar. It is free of disease and pest problems when properly sited. Fertilize and mulch the tree in early spring. The rich green summer, colorful autumn foliage, along with its gray muscular winter bark identifies this as an excellent small shade tree. Group several seedling together to develop a deciduous privacy screen.

American hornbeam is more difficult to transplant than European hornbeam (C. betulus), its taller European counterpart.

Tips On Amending The Soil In The Planting Hole

Posted by Hugh on February 1st, 2019

Soil Amendments Ready For Mixing on Site

Adding large amounts of compost or organic matter to a planting hole greatly improve the soil’s water-holding capacity and aeration. Simply throwing piles of leaves into the bottom of the planting hole helps improve a soil. However, amending the planting hole is not recommended by most plant experts. Why? According to soil scientists, the plant roots stay locked within the rich planting media in planting hole, like a pot, and roots don’t grow out into the surrounding native soil. This is especially true in heavy clay soils.

Newly planted tree + mulch

Doing it right: A wide shallow hole is more correct and a lot easier that one that’s narrow and very deep. Thoroughly mix organic amendments with the surrounding soil into the planting hole. Use a rototiller or 4-tine fork to turn and thoroughly mix humus, leaf litter, or compost into the planting hole.

Adding organic matter has good properties to improve the soil’s water- and nutrient-holding capacity. Humus rich soils are more porous and alive with beneficial organisms such as earth worms and beneficial fungi. However, too much is no good either. The ingredients peat, bark, and coarse sand make the backfill.

Finally, get the tree depth in the hole correct. Placing a heavy tree or shrub in the planting hole will compress the loose fill, often resulting in a tree being planted too deep.

Extra facts: Acidic organic materials are valuable to acid-loving shrubs such as rhododendrons, azaleas, mountain laurels, blueberries. Acidifying fertilizers, such as ammonium nitrate, ammonium sulfate, and sulfur-coated urea can also raise soil acidity levels. Mulch acid-loving plants with acidic materials such as pine needles, bark, and nuggets, and oak leaves; all eventually decompose into humus.

Organic mulches also cool roots of tree and shrub species, particularly in warmer climes Native trees, such as Beech (Fagus grandifolia)), paper , gray, and river birches (Betula spp.), sourwood (Oxydendrum), black gum (Nyssa sylvatica), silverbell (Halesia) and dogwoods (Cornus spp.).

Re-blooming Poinsettia This Fall

Posted by Hugh on January 26th, 2019

Poinsettia display at Biltmore Estates

Assorted poinsettias

The winter holidays may be over, but your poinsettia plant is likely still looking pretty. If you opt to grow and re-bloom your plant next Christmas, follow this growing schedule.

Keep the soil evenly moist and set the plant in bright daylight. Feed bi-monthly with a house plant fertilizer. Inspect and rid your plants of all pests, particularly aphids, scale, or white flies by spraying from with insecticidal soap or Neem oil.

Spring –Summer Care:

Around mid-March prune the main stem and side branches back hard to 4 – 6 inches above the soil. On warm days, move the plant outdoors into bright light but not direct sunlight. Re-pot into a larger pot, one that is at least 2 inches wider, and contains good potting media (soil). Water thoroughly and set in a sunny window. On days with outdoor temps in mid-fifties or higher, move the plant outdoors and bring it back indoors if temps drop below 55°F. Once the danger of frost outdoors has passed, set the plant outdoors in a semi- shady to partial sunny site. Sink the potted plant in your flower bed over the summer. Periodically rotate the pot every 2-3 weeks to prevent roots from growing through the bottom hole into the garden soil. Prune to maintain a uniform plant shape by pinching out the growing tips every 2-3 weeks to encourage branching (until mid- August).

Fall Care:

At the start of the fall season, as night temperatures drop below 55-60°F, bring the poinsettia indoors to a sunny window or a greenhouse. Continue to water and feed.

Poinsettia, including Thanksgiving and Christmas cactus (Schlumbergera spp.) and kalanchoe, are short-day or long-night plants. Flowers are initiated when the night (dark) period is greater than 12 hours for 10-12 continuous weeks. If the dark period is interrupted or broken, the poinsettia will not flower and will produce leaves only.

Put your poinsettia on an exact photoperiod schedule, such as at dusk (5 p.m.) every day cover with a heavy paper bag, black cloth, or set in a dark closet. During the daytime hours, let the plant receive daylight in an east- or south-facing window. Any short light interruption at night, such as turning on the light in the closet, may break the flower cycle. A streetlight outside a window may prevent flower formation.

Begin scheduling the poinsettia in late September or early October. Remember– the dark period must be 12 or more uninterrupted hours to initiate flowers. A dark period from 5 p.m. to 8 a.m. over 10-12 weeks is ideal for many folks.

By early December your poinsettia should have colorful bracts and flowers for late December holiday season.

All About Soil Drainage

Posted by Hugh on January 20th, 2019

Flood barrier from walkway

Trunk filled with amended soil

Many landscape plants die because they were planted in soil that was too wet or soggy. Poorly drained soils are generally poorly aerated. A high water table in an area limits your choices of plants that you may grow. Plants that grow naturally along streams and ponds are good candidates for poorly drained sites.

During periods of heavy rainfall, water may stand on the ground surface. Consistently wet soils eventually becomes a breeding area for anaerobic soil bacteria; an odor may indicate their presence. Soils that are poorly drainage may have a dull or slate gray color.

During construction heavy equipment may compact the soil reducing air space or create a hard pan. Frequently, on construction sites, contractors may pile up topsoil and return it to plant grass seed or sod. Unfortunately, some topsoil may be remove and sold off leaving only subsoil for new homeowners.

Drainage issues may result from poor grading of land, permitting road, street, or sidewalk runoff to flow onto garden beds or lawn. Runoff water may also come from plugged eaves and downspouts.

Excellent soil drainage a must with Daphne shrub

Perform A Perk Test before planting a new garden or lawn. Dig a hole 12 inches deep and 2-3 feet wide. Fill the hole with water and time how quickly the water drains out the bottom. If water drains out slowly or stands for longer than 24 hours, your soil is poorly drained.

Alternative Perk Test… remove the top and bottom from a large 3 lb. coffee or tin can. Dig a 4-inch deep hole and as wide as the diameter of the can; insert the can into the hole and fill soil around the outside of can. Fill can with water and measure the water level after one hour. If the water level drops 2 – 5 inches, soil drainage is good. If the water level drops less than 2 inches, soil drainage is poor.

Soils with good porosity (drainage) in the top 12-18 inches are ideal for most plant species. Amend planting soil with perlite or coarse sand to improve soil drainage or opt to grow plants in containers or raised beds.

Selecting A Good Landscape Shade Tree

Posted by Hugh on January 15th, 2019

‘Duraheat’ river birch

Medium to large shade trees increase the value of your property. Their summer shade and wintry wind protection may also reduce utility bills by 20 to 25%. Trees attract wild birds for nesting, protection, and as a food source. Some deciduous species will brighten up the landscape with dazzling fall color. Choosing a fast growing tree, yet some may not be good option. Know the maintenance level of the tree(s) before purchasing. Is the tree susceptible to disease and/or insects? Are better resistant cultivars available? Fit the right tree to the right location.

Much of the information comes from the Morton Arboretum in Lisle IL (near Chicago) and is highly reliable. Trees are ranked by their actual growth rate the first 10 years after planting. I have added some outstanding cultivars that you should purchase.

Category 1. Fast-growing trees (at least 25 feet tall) after 10 years:

Acer rubrum ‘October Glory’

Silver Maple (Acer saccharinum)

London Planetree (Platanus x acerfolia) ‘Columbia’, ‘Yarwood’

Sycamore (Platanus occidentalis)

American Elm (Ulmus americana) ‘Washington’, ‘Princeton’, ‘Jefferson’

Category 2. Moderately fast growing trees (18 to 25 feet tall):

Hybrid Freeman Maples (Acer freemanii)

Red Maple (Acer rubrum) ‘October Glory’, ‘Red Sunset’

Sugar Maple (Acer saccharum) ‘Green Mountain’, ‘Legacy’, ‘Sweet Shadow’

River birch (Betula nigra) -‘Heritage’, ”Duraheat’

Thornless Honeylocust (Gleditsia triacanthos var. inermis)

Silver linden

Kentucky Coffeetree (Gymnocladus dioicus) ‘Espresso’

Sawtooth Oak (Quercus acutissima)

Shingle Oak (Quercus imbricaria)

English Oak (Quercus robur)

Pin Oak (Quercus palustris)

Little leaf Linden (Tilia cordata)

Redmond Linden (Tilia x euchlora ‘Redmond’)

Silver linden (Tilia tomentosa)

Tuliptree (Liriodendron tulipifera) ‘Little Volunteer’

Category 3. Slower growing trees (less than 18 feet tall after 10 years):

Young ‘Happidaze’ sweetgum

Ohio Buckeye (Aesculus glabra)

European Hornbeam (Carpinus betulus) ‘Fastigiata’, ‘Frans Fontaine’

Common Hackberry (Celtis occidentalis)

Yellowwood (Cladrastis kentukea)

Ginkgo (Ginkgo biloba) (male clones)

Ironwood (Ostrya virginiana)

Norway Maple (Acer platanoides)

Sweetgum (Liquidambar styraciflua) ‘Slender Silhouette’, ‘Happidaze’

Category 4. Medium sized landscape trees:

Trident maple (Acer buergerianum) Aeryn®

Golden raintree (Koelreuteria paniculata)

Crape myrtle (tree forms) (Lagerstroemia x) ‘Natchez’, ‘Muskogee’

Black gum, tupelo (Nyssa sylvatica) ‘Wildfire’, ‘Green Gable’, ‘Red Rage’

Japanese pagoda tree (Styphnolobium japonica) ‘Regent’

Willow oak (Quercus phellos)

Live oak (Quercus virginiana)

Bald cypress (Taxodium distichum) ‘Shawnee Brave’

Lacebark elm (Ulmus parvifolia) ‘Athena’, ‘Bosque’

Japanese zelkova (Zelkova serrata) ‘Green Vase’

Editor’s note: all ash species (Fraxinus spp.) have been delisted from the Morton Arboretum study because of their susceptibility to Emerald Ash Borer.