Posted by Hugh on October 24th, 2016
Eastern White Pine (Pinus strobus)
Environmental and pathogenic problems continue to take their toll on Eastern White Pine (Pinus strobus). This valued landscape and lumber tree is native in the Eastern U.S. and Canada (USDA zones 3-8). Climate change is likely contributing to recent losses of white pines due a number of serious disease and pest problems that are reducing tree numbers.
A decade ago, pine beetles devastated large populations of white pines in the Southeastern U.S. Injury symptoms closely mimicked drought injury. Beetles lay their eggs and larvae tunnel into the branch wood. Needles turn straw brown, often showing up at tops of trees. Summer droughts have made infestations more severe.
White Pine weevil is another serious pest. Weevil larvae feed on the sapwood and kill the top growth (leaders). A common symptom is presence of pearl white resin leakage on limbs.
Pine Sawfly larvae (caterpillars) can cause rapid defoliation of branches if left unchecked; they feed in groups on the needles.
Pine needle miner larvae feed inside needles causing them to turn yellow and dry up.
Two kinds of scale insects feed on needles: pine needle scale (white, elongated scale) and pine tortoise scale (brown colored). Horticultural light oils are very effective applied in late winter.
White Pine Blister Rust. In some areas of the U.S., farmers and home gardeners are prohibited by law to grow black currants, which are alternate hosts for this disease. Red currants should not be grown within 300 feet of white pines. Infected branches may be pruned off. Some varieties of white pine are resistant to this disease.
White Pine Decline describes the slow decline of pine trees. Needles turn pale green, shrivel, and ooze sap. The entire tree is usually affected and mimics a root system. Causes seem to be a combination of environmental stresses, and shows up worse in dry clay soils. Tree usually does not recover and dies within 4-6 weeks.
Additionally, white pines are susceptible to urban air pollutants including ozone and road salt. Limbs are susceptible to ice breakage.
Posted by Hugh on October 21st, 2016
Cornus sanguinea ‘Midwinter Fire’ in November
Winter Scene at Biltmore Estates in Asheville, NC
Bloodtwig dogwood (Cornus sanguinea), indigenous to Europe and Asia, is an upright branched, round-topped, spreading deciduous shrub (USDA hardiness zones 5 to 7). In the wild the species matures to 8-15 feet in height and spread.
Its common name “bloodtwig” is misleading. Winter wood on 1-2 year old branches is not red. Instead, winter stems turn a striking orange-yellow at the base with reddish twigs on the tips. Fall leaf color is golden yellow some years and a blah red in others. The 3-inch long broad-elliptic to ovate leaves in spring and summer are dark green above and grayish, covered with tiny hairs underneath.
If your goal is to introduce more vibrant color into the winter landscape, select the cultivar ‘Midwinter Fire’. This compact form grows only 5 to 6 feet tall and wide after 3-4 years. It flourishes in any soil type that is well-drained and in full to partial sun. Brightest stem color occurs on young 1-2 year old wood. Annual pruning is an absolute! and take care of this chore in early spring. Every 3-4 years rein in the entire shrub by cutting back all stems to the ground in early spring (renewal pruning). Bloodtwig dogwood tends to ramble and you will want to remove root suckers to check spread of shrub.
Flat white 2-inch wide cyme flowers are not sensational but do attract numerous butterflies and other pollinators. Up close, flowers emit a stale fragrance in May to early June. In August-September blue-black fruits (1/4 inch wide drupes) form and later attract winter feeding birds. Fall color can be average yellow some years and bright orange-yellow in other years. Summer foliage is green and remains blemish-free.
Utilize as a specimen shrub or group 3-5 together for color impact in fall and winter as a hedge or short privacy barrier. Redtwig is a great choice for attracting wildlife, particularly to rain gardens. No disease or insect problems trouble bloodtwig dogwood and deer leave it alone.
Posted by Hugh on October 18th, 2016
‘Happidaze’ Sweetgum on Median Strip In Johnson City, TN
Sweet gum (Liquidambar styraciflua) is a low-maintenance deciduous shade tree. The species is native from Connecticut to Florida and west to Missouri and south to Texas and Mexico (USDA hardiness zones 5 – 9). A popular landscape shade tree, it typically grows to 60 to 80 feet tall with a straight central trunk. A young tree is pyramidal in outline, but an older tree gradually forms an oval to rounded canopy.
Most sweetgum cultivars is notorious for producing “gumball” fruits which are hard, spherical, bristly fruit clusters to 1 ½ inches in diameter. Happidaze® is a fruitless cultivar. The absence of messy fruits littering lawns and walkways all fall and winter long sets Happidaze apart from most sweetgum varieties.
Lustrous, long-petioled, deep green leaves (4-7 inches across) with toothed margins emit a sweet fragrance when bruised. Fall color is a rich red maroon. Yellow-green flowers appear in spherical clusters in April-May and offer no significant landscape value. Branchlets may have distinctive corky ridges.
Sweetgum is easily grown in moist, well-drained soils. The tree prospers in full sun and falters in shade. It prefers a slightly acidic soil pH between 5.8 – 6.5; leaves frequently turn chlorotic (yellow) in high alkaline pH soils. Feed in early spring with a slow-release fertilizer such as Osmocote® or Nutrikote®. Refresh the mulch cover around the tree every spring.
Sweetgum rarely succumbs to serious insect or disease problems. Leaf spot diseases, webworms, caterpillars, borers and scales may be occasional problems. Iron chlorosis, a lack of available nutrient iron, may occur in alkaline soils.
Sweetgum is excellent shade, lawn, park or street tree. Give this large tree room to grow and it will reward you with lots of cooling summer shade and glorious fall color for many decades.
Special note: Sweetgum cultivars ‘Rotundiloba’ (medium size tree) and tall narrow ‘Slender Silhouette’ are two other seedless (no gumballs) forms.
Posted by Hugh on October 12th, 2016
Flowering of popcorn plant
Big and bold is this tropical annual (USDA hardiness zones 9-11), known by several names including popcorn or peanut butter cassia (Senna didymotrya), formerly Cassia didymotrya. Popcorn plant is a legume family (Fabaceae), indigenous to tropical Africa. It is also been utilized as a cover crop or green manure crop in some areas of the world. It thrives where summers are long, hot and humid in the U.S.
Popcorn cassia grows 6-12 feet tall in temperate climates by the end of summer. In zone 6 (northeast Tennessee), expect 6 -7 feet. Direct seed into the garden in early May after danger of frost has passed. Growth rate ramps up as outdoor temps rise.
Popcorn cassia blooms from late spring into early fall and is often utilized as a garden accent plant for its tall flower spikes and lush tropical foliage. Bloom buds are jet black and pop open with showy yellow flowers. Each pinnately compound leaf may grow to 18 inches long, arranged in pairs of oval 8-18 leaflets that are up to 3 inches long. Plant(s) set in large containers grow a lot smaller and flower less.
Flower spikes may stand up to one foot tall. Each flower is ½ to 2 inches wide with showy prominent stamens. Opinions about floral fragrance can be quite subjective. Some say that the flowers smell like peanut butter. Flat 3-5 inch long brown pods form after flowering. Each may contain up to 16 shiny flat bean-like seeds.
Popcorn cassia grows best in full sun and in moist, well-drained soil. By mid-summer, plant is highly drought tolerant. Otherwise, irrigate and fertilize regularly to push growth and flowering. Use a liquid fertilizer such as Miracle-Gro™ or Daniels™.
Prune to keep plant more compact, but flower numbers will be less. Plant has no significant disease or pest problems and generally is not troubled by deer.
In late winter start new plants indoors from seed collected last fall. Pre-soak seed in water for 24 hours prior to sowing to improve germination.
Glenna Schaefer, garden expert at Kingwood Center in Mansfield, Ohio, tells me that two species, Senna hebecarpa and S. marilandica, are native to Eastern North America and are quite hardy there (zone 5).
Posted by Hugh on October 9th, 2016
“Tagged” Monarch Butterfly at NC Arboretum in Asheville, NC
*Blog is guest authored by Joy Stewart, University of Tennessee Master Gardener. She lives in Bristol, TN.
For such a small creature, weighing in at only half a gram, the Monarch butterfly has almost more remarkable facts and puzzling mysteries attached to it than one can count. No other butterfly in the world migrates like the Monarchs of North America.
Since they cannot survive cold weather, Monarchs must travel to warmer climates in winter. Monarchs west of the Rocky Mountains travel to the California coast. Monarchs east of the Rockies travel to the mountains in Mexico. They fly up to 3,000 miles, much farther than all other tropical butterflies. Since each individual butterfly only makes the trip once, butterflies heading south in the fall are the great great grandchildren of those that left their winter roosts the previous spring. Yet returning butterflies fly in masses to the same winter roosts, often to the exact same spot they left four generations ago.
Monarch Watch is a non-profit program dedicated to protection of Monarch butterflies through education, conservation and research. It is based at the University of Kansas, Lawrence, KS. Their activities include a Monarch tagging program whose purpose is to trace a butterfly from its point of capture to its point of recovery. Tagging data are used to determine pathways that butterflies take during migration, the influence of weather on migration, and Monarch survival rates.
Individuals can order tag kits from Monarch Watch, which include instructions on how to safely net Monarchs, how to apply the tags, and how to record and report your data. Tagging begins in late August in all regions of the US, and most data are collected in September and early October.
Even if you don’t tag a butterfly yourself, you can participate by reporting butterflies that you have spotted with a tag. Each tag contains an ID composed of letters and numbers plus a phone number and e-mail address for making your report.
Peak Monarch migration southward from the mid-Atlantic states occurs from September 18 through October 1. A simple accurate way to remember these dates is to watch for New England Aster and goldenrod to start blooming and you will know Monarch migration is underway.
Posted by Hugh on October 7th, 2016
Acer rufinerve late summer foliage
Snake bark trunk exhibited at Biltmore Estates, Asheville, NC
In the world of maples the snakebark trait is unique. Redvein maple (Acer rufinerve) from Japan belongs in this maple category (USDA hardiness zones 5-7). It is a small to medium deciduous tree or large shrub with an upright branching framework. A young tree starts off slowly and may grow only to 12-15 feet in 10 to 12 years. The species matures to 30 feet tall and 20 feet wide.
As spring season approaches, dormant buds turn red, swell, and 3- to 5-lobed green leaves emerge. Autumn foliage may turn yellow, burnt orange, or purple depending on the year and locality. Autumn leaf colors are best where soil moisture has been plentiful and the tree is grown under partial shade.
Raceme flowers run about 3 inches long bearing the winged samara seeds that ripen in fall. The species name rufinerve refers to the rusty red hairs along the leaf vein axils which slough off by mid-summer. The main trunk is green with gray-white striations
The cultivar ‘Winter Gold’ displays a bright yellow bark with tiny dark specks along the main trunk and main branches. Summer and fall bark is greenish yellow and is brightly yellow in winter. Like the species, Winter Gold prefers partial shade and moderate soil moisture. Enjoy as a specimen against an evergreen shrub background or plant nearby a patio for year-round viewing.
As previously stated, redvein maple grows best in a well-drained, moist, compost-rich, moderately acidic soil, and in partial sunlight. It struggles in full sun and in dry soils. Newly-planted and young trees should be kept mulched and adequately watered during extreme summer dry spells. Established trees are moderately drought tolerant and have few disease and pest issues. Pruning is rarely necessary except to develop a good central leader on a young tree.
Redvein maple and the Winter Gold cultivar are available from on-line mail order nurseries.
Posted by Hugh on October 4th, 2016
Leymus arenarus planted at Atlanta Botanical Gardens
Blue Lyme Grass (Leymus arenarus ‘Blue Dune’) is a vigorous spreading cool season grass (USDA Hardiness zones 3-9). It is native to the coasts of northern and western Europe. A closely related species, L. mollis, is native to the northern coasts of North America.
Blue lyme grass is a stand out because of its beautiful steel-blue foliage. Atlanta Botanical Gardens has sited it in woodland setting under filtered sunlight while the Dallas Arboretum grows it under full hot Texas sun. It will rapidly fill in hot arid places such as near hot concrete walkways and driveways.
‘Blue Dune’ is a standout selection with steel blue foliage. Clumps average 2 – 3 feet high and spread. In mid-summer arching powder blue flower spikes (inflorescences) emerge. Some gardeners may opt to remove the flowers to accent foliage only. It is also very tolerant of salt spray and drought.
Lyme grass is a spreading cool season perennial grass in full sun or partial shade. Foliage is evergreen into the lower 20s. Plants grow equally well either full all-day sun or under several hours of moderate shade. Practice low soil fertility as this grass can become too aggressive. It tolerates a wide range of soils from wet to dry. It tends to be less aggressive in dry, clay soils and foliage becomes more silvery blue in color.
Landscape Use: Lyme Grass can be used along woodland borders, in mass plantings, in containers or planters, as a border or edger, around decks, swimming pools, and other outdoor living areas, in landscape beds or islands, to stabilize steep slopes and sand dunes. It is resistant to deer, rabbits, drought, insects, diseases, mildew, heat and butterflies are attracted to its flowers.
Mow off old foliage in late fall or early spring to refresh the planting. Clumps are easily divided at this time.
Posted by Hugh on September 30th, 2016
Lawn moss (photo by Dr. Tom Samples, Extension Turf Specialist, Univ. of Tennessee, Knoxville
Lawn moss (Photo by Tom Samples)
Mosses, over 14,000 species of them worldwide, are major competitors with lawn grasses in certain landscape situations. They belong to their own plant family. They photosynthesize and draw moisture from tiny rhizoids (primitive root systems). They do not compete for soil nutrients with lawn grasses. Some can live in full sun, other kinds in shade areas. Mosses hug the ground, below the cutting height of lawnmowers.
Liming: Many mosses grow well in acidic soils (pH<7.0). Their presence in lawns does not mean that a lime application is necessary. A soil test can this determination. A broadcast application of granular or pelletized dolomitic or calcitic lime using a spreader is better method compared to a pulverized (powder) lime source.
Fertilization: Poor soil fertility favors the development of moss. Improve the competitive of lawn grasses by fertilizing at the proper time of year. For cool season grasses (Kentucky bluegrass, tall and fine fescues) species, spring and fall applications utilizing high nitrogen (N) fertilizer is a practical approach. For warm season (burmuda, zoysia), late spring and summer applications are best times.
Improving Soil Drainage and Aeration: Compacted soils favor growth of moss over grass, particularly in irrigated areas and excessive periods of rainfall. Core aerification of areas with wet clayey soils improves soil drainage to favor turf over moss.
Pruning: Trees compete with lawn grasses for light, water, and nutrients. Shade keeps soil moist which favors growth of moss. Selective removal of dense branching improves sunlight penetration and air circulation, which causes soil to dry out more rapidly favoring lawns over mosses.
Raking Up Fallen Tree Leaves: quick removal from the ground will dry out the soil surface quickly and improve light and air circulation.
Chemical Suppression of Mosses: the following products are sold at garden centers:
- Iron sulfate
- Ferrous ammonium sulfate
- Anti-moss products containing potassium salts
Alternative perennial ground covers including mosses instead of lawn grasses in heavily shaded areas.
Posted by Hugh on September 27th, 2016
U.S. Native Mapleleaf Viburnum (V. acerifolium)
Cyme flowers of Mapleleaf viburnum
The genus Viburnum is a rich source of over 150 species of great flowering shrubs worldwide. Many viburnums are native to North America including mapleleaf viburnum (Viburnum acerifolium). This totally underutilized deciduous viburnum is a great choice to plant in shrub borders, foundation, or hedging, as well as to naturalize in an open woodland area (zone 3-8).
Shrub grows 4 – 6 feet tall and 3 – 4 feet wide. In late winter before spring bud break, swelling flower buds turn distinctively pale purple. Creamy white 1 to 3 inch wide flowers (cymes) appear in early to mid-May. Flowers give way to pea-sized fruits that ripen to bluish-black in late summer, and persist through most of winter. Shrub may form basal suckers and form colonies over many years.
Mapleleaf viburnum is a relatively small, rounded, suckering, deciduous, woodland shrub. Leaves are generally 3-lobed, 2-5 inches long, and very maple-like; juvenile foliage on seedling plants may not always develop side lobes. Leaves are opposite, ovate to rounded, coarsely toothed. Fall color is variable from one year to the next. When best, it is hard to beat, leaves turning purple to magenta in the fall.
Mapleleaf viburnum is easy to grow in average, medium moist, well-drained soil and in full sun to part shade. This viburnum is an exceptional grower in dry, shady woodland locales. Prune as needed immediately after spring flowering. Lightly feed with a granular fertilizer such as 10-10-10 or equivalent. It appears to be pH insensitive. Mulch to maintain a weed-free planting. Mapleleaf viburnum has no serious insect or disease problems and damage from deer feeding is minimal.
Mapleleaf viburnum is sold primarily by nurseries that specialize in selling native plants on-line.