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

Burls on Tree Trunks

Posted by Hugh on October 12th, 2023

An unusual swelling on trunks of trees and occasionally on large branches are “burls”. They’re round, swollen-looking growths on tree trunks and large scaffold branches. Should or shouldn’t you be concerned? Burls are not uncommon and can be found on cherry, maple, oak, buckeye, ash, willow, locust and walnut in Eastern forests. Root burls may also be found on rhododendron and laurel.

The cause of tree burls is a bit of a mystery. Plant scientists don’t know why they occur. In general, burls develop because of invasions (bacteria, fungi, and insects) or stressors (freeze damage, mechanical, and environmental injury). Certain tree species are genetically predisposed to develop one or more burls while other nearby trees may not likely form any.

Are burls bad for trees?… Usually not. Burls typically don’t do any harm to trees. On rare occasions, a burl may disrupt the tree’s vascular (circulatory) system. As it turns out, though, getting rid of them may pose the significant risk. Cutting burls would leave large wounds on the tree’s trunk and branches, which could lead to an infection or weaken the tree’s structural stability.

Burls may occur on tree roots and go largely undetected. Also, it is best not to remove the bumps on tree branches or tree trunks. However, you may clip away sprouts that emerge out of the burls.

Burls themselves generally don’t cause problems for your tree, but you should try to determine the root of the growth and address it. Consult a certified tree arborist to determine the cause and solution.

Since burls can be a result of insect or fungi damage, inspect for signs that point to an insect or disease infestation. Look for small holes in the trunk and branches, sawdust, or insects crawling around. Also, inspect the trunk or branch wood for evidence of decay including cavities, missing bark, root damage or wounds.

Conifer species in Alaska (Photo courtesy of Mary C. Rice)

Finally, burl wood is expensive and treasured by woodworkers and carpenters alike. Consult a Certified Tree Arborist in your state or city by searching the International Society (ISA) directory.

Uniquely Different Weeping Mulberry

Posted by Hugh on October 3rd, 2023

Common (White) mulberry (Morus alba) is a fast-growing, medium sized, deciduous tree that typically grows to 30-50 feet tall and wide. It usually develops a wide-spreading rounded crown with age. This native to China is utilized either as a landscape shade and/or a fruit tree. (USDA hardiness zones 5-9).

White Mulberry prefers a rich, moist, well-drained soil and full sun. The tree tolerates a wide range of environmental conditions including moderate shade, pollution, salt spray, extreme heat, infertile soils, a wide range of soil pH, and moderate drought. It is notoriously shallow rooted.

Mulberries are easy to identify by their large lobed leaves and their edible fruits – a delicious treat as well as a weedy seed problem. Individual leaves may be unlobed, mitten-shaped, or 3-lobed. Mulberry trees are polygamo-dioecious; they produce only male or female flowers on one plant or both flower types are present on the same tree. In June and July, female trees produce an annual crop of white, red, purple or black fruits that resemble long, thin blackberries. Prune mulberry in late fall or winter to avoid sap bleeding in spring.

Mulberries are a popular food source for many species of birds. Unfortunately, the fruit and resulting bird droppings are messy and will stain pavements, automobiles and areas around the home. Weeping cultivars are mostly fruitless which limits its threat as an invasive species.

No serious insect or disease problems trouble mulberries. The tree is not deer resistant. Borers are troublesome in some years in the South. Whiteflies, scale, mites and mealybugs are occasional pests. Bacterial blights and leaf scorch, powdery mildew, and root rot are usually indicators of poor site selection.

Weeping mulberry trees are exceptional unique, trouble-free, and should be planted more. Three major weeping forms are available.

M. alba ‘Pendula’ has a dwarf weeping form that matures to 8-15 feet, sometimes to 20 feet height. It creates a unique and beautiful presence in any garden! Its matchless contorted trunk and branches are revealed from late autumn thru winter.

M. alba ‘Chaparral’ is a superior weeping, male seedless form that grows 8-12 feet tall and is equal width. This male fruitless selection produces yellowish-green catkins in spring.

M. alba ‘Nuclear Blast’ (‘Itoguwa’) is a 3-4 feet tall and wide shrub oddity! Thread-like foliage appears shredded or deformed.

Gooseneck Loosestrife

Posted by Hugh on September 22nd, 2023

Gooseneck loosestrife (Lysimachia clethroides) can be both a delight and a weedy nuisance – depending on where you garden. (USDA hardiness zones 3 – 8). This native of southeast Asia grows aggressively in some locations in the U.S. where it has escaped into woodlands, wet areas, and on sunny, sheltered mountainous slopes. The perennial has upright rigid branching which bear unique white flowers (racemes) that bloom from June through August.

Gooseneck loosestrife is a fast-spreading plant that prefers partial sun and moist well-drained soil. Keep this aggressive perennial in check as it spreads aggressively via rhizomes and may become weedy from seed dispersal. It grows less aggressive in shady, dry soils although flower numbers are fewer and growth may be leggy.

Gooseneck loosestrife grows 2 -3 feet height and 3 feet spread. It can also be utilized as a groundcover. Leaves are slender with a tapered point. Raceme flowers average 12-18 inches in length and pure white. The fall foliage takes on gold to yellow tints. In northerly latitudes, gooseneck survives frigid winters by blanketing a 2–3-inch layer of mulch around the plant base.

In early spring, cut back all the stems to within 2 inches of the ground. Spring growth emerges from the crown and flowers appear in June until October. Keep it cornered in planting areas bounded by hardscaping. Every 3-4 years divide rhizomes in the spring to both limit its spread yet invigorate this rhizomatous plant. Judicious deadheading of spent flowers triggers reblooming and reduces seed formation. Flowers are particularly attractive to butterflies. It is relatively deer resistant.

Commercially, gooseneck loosestrife is produced by the cutflower florist industry. Floral stems may last over a week. Gooseneck earns its name for its flower spikes that mimic the curve of a goose’s neck.

Varieties:

‘Lady Jane’ (seed and vegetative produced) produces pure white blooms in late summer.

‘Geisha’ grows 2 feet tall with creamy yellow margin foliage; less aggressive (tamer) than species; 1-foot-long nodding white flower racemes in late summer.

Three Salvias To Try

Posted by Hugh on September 16th, 2023

Back in early spring you may have planted several kinds of salvias (sages). The arrival of the cool autumn weather turns up the flower power of sages. They’re members of the mint family and the leaves emit a mild anise scent when crushed.

Looking ahead to summer of 2024, here are three salvias that you might try in your garden. All are native to central South America (zones 8-10). There are no guarantees that plants will survive TN, VA or NC winters as they’re rated as tender perennials there.

Blue anise sage (Salvia guaranitica) is primarily grown as a garden annual in TN. Through most of summer into fall, its electric blue, two-lipped, tubular, 2 inches long flowers contrast strikingly with the blackish stems. ‘Black and Blue’ is hardier than other cultivars and often survives milder winters if well-mulched. Plants develop a shrubby, somewhat open habit with upright branching, to 3-5 feet tall as a perennial and 2 ½ to 3 feet tall as an annual in garden beds and in large containers. ‘Black and Bloom’ is a newer variety rated more heat, humidity, and drought tolerant. It will survive milder winters. Dark green roundish leaves measure 2-5 inches in length.

Friendship Sage (Salvia x) is a showy violet-purple blooming sage. The variety ‘Armsted’ will perennialize in zone 7b and further south. It has a very long bloom season and flowers are pollinator favorites. Armsted is grow vigorously, forming a bushy 4–5-foot plant covered with spikes of purple flowers which stand above the foliage.

Fuzzy Bolivian Sage (Salvia oxyphora), aka Bolivian Spearhead Sage, is fairly new in the local garden trade, but their bright, hot pink, fuzzy blossoms will surely make them a favorite. (Zones 8-10). Fuzzy Bolivian Sage grows vigorously and can reach 4 feet high by the end of summer. The plant’s deep green tropical-like foliage is glossy green with clear, almost invisible hairs. The fuzzy hot pink spikes of flowers appear in late June and plants continue blooming through the October frost, with terminal clusters of hairy rosy-pink tubes.

General Care: Plant any of these salvias in humus-rich, medium moisture, well-drained soil in full sun to partial shade. Salvias become moderately drought tolerant 6-8 weeks after spring planting. Use in the middle of the flower gardens or in containers. This is a reliable nectar source for butterflies and hummingbirds and is seldom damaged by deer.

Perennials With Great Fall Color

Posted by Hugh on September 10th, 2023

*Geranium sanguineum i*n December landscape

In general, perennials are not rated very high for their fall leaf color. This is very wrong as some produce stunning autumnal foliage colors. In addition, some ornamental grasses produce colorful floral heads (inflorescences).The first six are perennial dicots and the next six are grasses with awesome inflorescenses.

Bloody cranesbill (Geranium sanguineum) – short 9-12 inches high clump forming groundcover that bears purple flowers in May-June. Its deeply cut foliage green leaves turn shades of red after first frost. (Zones 3-8).

Red leaf mukdenia (Mukdenia rossii) – fanned, maple-like leaves emerge bright green in spring, age to bronze-green in summer, and finish green with bright red streaks in Fall. White bell-shaped flowers stand above the foliage in early spring. Use as a groundcover for woodland gardens, border edging, or add to mixed containers. (Zones 4-8)

Arkansas bluestar (Amsonia hubrichtii) – an erect, clump-forming perennial with clusters of 1/2 inch wide, 5-petal, powder blue flowers in late spring, feathery green summer leaves, and gradually turns golden yellow starting in late summer. Stems rise to 3 feet tall. Similar in appearance is Amsonia ciliata, minus conspicuous hairiness over the new leaves. (Zones 5-8).

Leadwort (Ceratostigma plumbaginoides) – 6-10 inch tall rhizomatous groundcover with blue flowers from late summer into Fall; clean medium green summer foliage turns bronze or red in fall. (Zones 5-9).

Autumn Fern (Dryopteris erythrosora) – glossy, copper-tinted new fronds emerge through the growing season into Fall; its frond color is perfect color for the Fall garden. (Zones 5-8).

Dwarf Variegated Solomon Seal (Polygonatum odoratum ‘Variegatum’) – 2-3 feet bright green elegant foliage that is splashed or streaked with white. Sweetly scented creamy white flowers form along its arching stems. Leaves turn an attractive gold color in Fall. (zones 3-8)

Muhlygrass (Muhlenbergia capillaries) produce loose, billowy inflorescences best described as pink clouds in early Fall. Pink muhly grows to 2.5 – 3 feet tall and 3 feet wide in flower. ‘White Cloud’ sports white flowers and grows more upright than pink muhly. New in 2022 was M. reverchanii Undaunted® that produces rosy pink floral sprays in early fall (USDA hardiness zones 6-10).

‘Black Mountain’ bluestem (Andropogon ternarius) varies across its natural range, growing up to 5 feet tall in some areas. ‘Black Mountain’ stays at 3 feet and under and grows more compact and refined than species. Flowering stems emerge bluish-green and develop reddish hues later in summer. Inflorescences (flower heads) have spikelets covered in silvery, white hairs. (Zones 6-9).

Several Varieties of Switch Grasses (Panicum virgatum) develop a great fall color. ‘Shenandoah’ – leaves develop rich black-burgundy tips in late summer; ‘Northwind’ – bright gold-streaked fall foliage; ‘Cheyenne Sky’ – dense, upright clump of blue-green blades turn wine red in early summer along with purple inflorescence in late summer. Leave switch grasses for winter interest. (Zones 5-9).

Feather Reed Grass (Calamagrostis x acutiflora) is a cool season plant and is one of the first ornamental grasses to emerge in spring and produces flowers and seeds early. Cultivars ‘Stricta’ and ‘Karl Foerster’ seed heads turn golden and shorter cultivar ‘Overdam’ turn tan in autumn. (Zones 4 – 9).

Swamp Hibiscus

Posted by Hugh on September 5th, 2023

Swamp hibiscus (Hibiscus coccineus), aka scarlet rose mallow, is a hardy perennial plant that grows in swamps, marches and roadside ditches in the Southeastern U.S. (USDA hardiness zones 5-9). It can grow 6 to 8 feet tall and 2 to 3 feet wide. Its 5- to 6-inch-long leaves are palmately lobed into 3, 5, or 7 parts. These finger-like lobes are slender and have jagged teeth along their margins. Deep red flowers are 5 to 6 inches wide appear in mid to late summer.; a white bloom form ‘White Texas Star’ is also available.

Plants are late starters calendar-wise. This herbaceous to semi-woody perennial dies back in the winter and returns in late May, generally following the emergence of (H. moscheutos).They’re fast growers and will reach 5-6 feet the first season. They can grow to be over 6 feet tall and may need staking, depending on their height and position. Swamp hibiscus bloom continuously, although blooms may last only 1-2 days. The plant also attracts butterflies, hummingbirds, and bees.

Swamp hibiscus is easily grown in the Mid-South (TN, NC, VA, KY, WV). Plant in locations with full sun to partial shade and with moist, occasionally wet soils. Propagation is through seed or stem cutting. This plant is slightly salt tolerant.

Flowers of swamp hibiscus appear in late summer to early fall and are large (up to 6 inches wide) and vibrant in color. Swamp hibiscus thrives in sunny, humid, and moist conditions. It grows well in loamy well-drained soils, but is equally at home in wet boggy sites, such as around a pond or edge of a stream. Set them at the back of a perennial border, against a courtyard wall, or in rain and pollinator gardens. The plant attracts butterflies, hummingbirds, and bees. Flowers are a wildlife food source. Deer may damage the brightly colored flowers.

Swamp hibiscus prefers hot and humid summers. If you garden in a northerly area, protect plant roots and crown with a 3-4 inch layer of organic mulch (grass clippings, fallen leaves, or yard waste) in late autumn. Swamp hibiscus can easily susceptible to leaf burn if seasonal rainfall is low. Avoid planting in a windy site.

In early spring fertilize with a 6-month slow-release formula like Osmocote or Nutricote. One pruning option to limit plant height is cut the previous year’s shoots down in late winter. Additionally, cut new spring growth back in early June (4-5 weeks after growth emergence) to encourage branching and lower overall shoots to 3-4 feet by summer’s end.

Plants may be damaged by stem canker, rust, leaf spots, aphids, and Japanese beetles. Swamp hibiscus will usually outgrow most injury by outgrowing these pests and present an attractive floral show. If grown partially shaded, tall plants may need staking.

About Penstemons

Posted by Hugh on August 30th, 2023

Some 40 years ago, Dr. Dale Lindgren, plant breeder at the University of Nebraska released ‘Husker Red’ penstemon (Penstemon digitalis). This pioneering variety has purple-green foliage and white flowers. New penstemon varieties continue through the breeding pipeline with larger and colorful blooms, more compact habit, or dark foliage. (Z 3-8).

Penstemons (Beardstongue) belong to the Plantain family (Plantaginaceae) and are native to North America; it also includes other flowering gems like snapdragons and foxglove plus 250+ beardtongue species. Many penstemon species include tiny alpine varieties and those that inhabit prairie soils. Most species and varieties grow 1 to 3 feet tall, but there are numerous exceptions size-wise.

Many species have lance-shaped foliage of varying widths and spikes of tubular flowers. Flower colors include pink, red, white, purple, and (rarely) yellow. Some species are short-lived perennials. Beardstongues need full sunlight to perform their best. Most tolerate summer temperatures into the 90s and moderate humidity levels. In general, they do not tolerate wet soil, especially over the winter months. They tolerate drought, but 1-inch of water weekly in the summer will keep plants vigorous and promote better blooming. (USDA 3-9).

Most perform well in fairly nutrient-poor soils and tend to put out too much tender growth in rich soil. Apply an organic fertilizer only once a year. Do not feed with manure.

Beardstongues attract spider mites which can be flitted away with a strong spray of water, insecticidal soap or neem oil. Botrytis leaf mold or powdery mildew are diseases. Good air circulation around plants is a plus and avoid watering plants overhead. Plants don’t need pruning. In late fall cut foliage back to 2-3 inches. They can be propagated by division, stem cuttings, and seed. Plants may self-seed freely.

P. digitalis ‘Husker Red’ grows about 2-1/2 feet tall, blooms in early to mid-summer with 1-inch tubular, pink-flushed white flowers; 4-5 inches long deep maroon leaves arranged in a basal rosette.

P. digitalis ‘Dark Towers’ has burgundy foliage throughout the summer, and deep-pink bell-shaped flowers.

P. digitalis ‘Midnight Masquerade’, a Dale Lindgren introduction, produces a sturdy clump of dark burgundy purple foliage and tubular purple-pink flowers.

P. digitalis ‘Blackbeard’ – lilac purple flowers with their white flaring tubes high above the low mound of deep eggplant purple leaves; 28-34 inches height; Walters Gardens introduction.

P. ‘Dakota Burgundy’ – shorter and more compact than ‘Dark Towers’ with glossy, purple-black foliage that plays off masses of tubular, lavender-violet flowers.

P. barbatus ‘Piña Colada’ – a series of 6 cultivars, with blue, rose, or white flowers on compact plants.

P. ‘Red Riding Hood’ – upright tubular red flowers on a low, bushy mound; strap-like green leaves that resemble pine needles; not recommended for humid Southern gardens.

P. hirsutus ‘Pygmaeus’ – lavender blooms with white lips above dense green leaves on this dwarf plant that reaches up to 6 inches tall. (Z 3-9).

P. heterophyllus ‘Electric Blue’ – vivid blue flowers and compact form to 18 inches tall. (Z 6-9).

Pine-Leaf Penstemon (P. pinifolius) – summer blooming with loose spires of 1-inch narrow scarlet tubular flowers; needlelike foliage; 8-10 inch tall, perfect for dry rock gardens. (Z 4-10).

For additional information, check out The American Penstemon Society website.

Why Crape Myrtles Is Not Blooming

Posted by Hugh on August 23rd, 2023

No flowers On Your Crape Myrtles? Look at these five common problems:

1. Not Adequate Sunlight

Crape myrtles need 6-8 hours of full sun a day. Too much dry heat will cause poor flowering as well as leaf scorch.

2. Too much /Too Little Soil Moisture

Crape myrtles are tolerant of moderate drought, dry weather spells lasting 2-3 weeks. They bloom poorly if planted in wet soggy soils. but coping with prolonged drought can be at the expense of flowering ability. Mulching with composted bark or wood chips aids to conserve soil moisture.

Water crape myrtles deeply and at 7–10 day intervals until rains return. Irrigate the tree root zone and not overhead to avoid fungal leaf diseases.

3. Fertilize Crape Myrtle

If crape myrtles are not blooming or producing only a few flower clusters, they may be nutritionally hungry. Similarly, excessive fertilizing can actually delay blooming or cause fewer blooms than normal. The culprit here is usually too much nitrogen in the soil. This will cause your Crape Myrtle to grow lots of shoots and leaves, often at the expense of blooms.

Feed your crape myrtles, but don’t overfeed. Spread 2-3 handful of an all-purpose fertilizer like a 5-10-5 that is low in nitrogen. A crape myrtle planted on your lawn may be receiving too much high nitrogen. Or the lawn grass may be absorbing the fertilizer and the crape myrtle may be starved of nutrients.

4. Poor Pruning Of Crape Myrtles is a key reason why the crape myrtle is not blooming. Has a landscape company or you have committed “Crape Murder” by severely cutting them back to 5-8 feet? This is butchering your tree or shrub. Crape myrtles need very little annual pruning other than clipping off the old flowers and seedheads.

“Crape Murder” – don’t let this happen to you!

Severe cutting back crape myrtles destroys their natural look. New willowy shoots sprout from the stumps in spring; sprouts are generally too weak to hold new flowers. Also, bloom numbers are fewer. Crape myrtles need very little pruning. In late winter you may choose to prune away dead, diseased, weak or crossing branches.

5. Select The Right Variety For Your Landscape

Measure the planting site (height and width) before purchasing a crape myrtle. Select the correct variety that will best grow into the space. This will reduce also annual maintenance, particularly the need to prune.

Some of the best crape myrtle cultivars are ‘Natchez’ (white blooms), ‘Acoma’ (white), ‘Muskogee’ (light lavender), ‘Dynamite’ (red), ‘Zuni’ (medium lavender), ‘Hopi’ (pink), and ‘Sioux’ (clear pink). All seven cultivars display high mildew-resistant varieties. Finally, choose a variety that is hardy, disease-resistant, and matches your desired height and color.

Several of these factors may be inter-related — 1. soil moisture and fertility and 2. sun/shade and pruning. Crape myrtles are best grown in USDA hardiness zones 6b to 9.

Summerific Hibiscus Are Awesome

Posted by Hugh on August 16th, 2023

Among my favorite summer flowering perennials are the hardy herbaceous hibiscus (Hibiscus moscheutos). During the early days of August, Walters Gardens, a premier perennial plant breeder, requests garden writers to celebrate and promote their awesome product line of Summerific hardy hibiscus. Last week, the first week of August, was dubbed Summerific Week. It’s never too late to promote a great plant.

Summerific® Hibiscus, aka rose mallow, get noticed for their flower power. Plants are indeterminate, e.g., they produce flower buds at the internodes along the length of the stem, not just near the top of the plant. The individual blooms are 5- 8 inches wide and available in many colors.

Summerific Week is a promotion that these hibiscus are fabulous summer flowering perennials. These herbaceous hibiscus grow fast but are long-lived garden plants. They have various leaf shapes and colors and are cold hardy to Zone 4.

Rose mallow boasts huge, vibrantly colored flowers. Give them lots of water and full sun (6+ hours). Full sun means more flowers. Grow rose mallows in a good garden loam and do not allow plants to wilt severely. Give them lots of space as plants are robust growers. Most Summerific® varieties grow at least 4-5 feet tall and wide.

Creeping Jenny – Accent /Weed

Posted by Hugh on August 13th, 2023

Topiary at Columbus Ohio Conservatory – Creeping jenny (top) & *Ficus pumila* (sides)

Creeping Jenny (Lysimachia nummularia ‘Aurea’, aka creeping yellow loosestrife, golden moneywort, and several more colloquial names). It is an herbaceous, semi-evergreen perennial in the primrose (Primulaceae) family native to Europe (USDA hardiness zones 3-8). Introduced in North America this ornamental ground cover grows aggressively. Be careful what you invite into your garden as this fast-growing plant can quickly take over a large part of your garden.

Creeping Jenny prefers moist partly shaded areas, but it grows almost as well in the sun, spreading quickly into lawns and planting beds. Also called ground ivy, this low-growing “creeper” is valued for its foliage, which makes colorful ground cover.

Kidney-shaped or rounded leaves lay low to the ground along vining stems or runners. Growing only a few inches in height, stems branch out. Leaves root readily when nodes contact soil and develop into a broad carpet. Aggressive creeping jenny also spreads via a slender rhizome.

It prefers moist areas such as wet meadows, swamps, banks of streams and ponds, along edges of roads and ditches. Among gardeners creeping jenny is becoming an invasive weed and ecological threat because of its competitive nature. It spreads both vegetatively and by seed dispersal. The tiny yellow cup-shaped flowers form at the leaf axils and are rarely noticed.

For its ornamental value, Golden Creeping Jenny can be used in containers, hanging baskets, and rock walls or as a ground cover. It will likely spread aggressively into borders or nearby lawns; creeping Jenny is difficult to control. After a harsh winter the plant’s recuperate potential is incredible.

Control of Weedy Creeping Charlie: Hand pulling or hoeing is difficult. Most effective control is any broadleaf herbicide that contains triclopyr, generally in combination with 2, 4-D, and Dicamba.