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

Try Popcorn Cassia For Its Lush Tropical Look

Posted by Hugh on October 12th, 2016

Senna (Cassia)

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).

Monarch Tagging Program*

Posted by Hugh on October 9th, 2016

"Tagged" Mnarch Butterfly at NC Arboretum in Asheville, NC

“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.

Grow Something Different With Redvein Maple

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.

Blue Lyme Grass Adapts To Almost Any Surroundings

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.

Seven Ideas for Managing Mosses in Lawn Areas

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.

Mapleleaf Viburnum For Woodland 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.

Five Landscape Plants On The Gardeners’ Taboo List

Posted by Hugh on September 24th, 2016

Lonicera nitida ‘Briloni’ is highly desirable

Avoid planting Red-tip photinia

To many people, maintaining a garden or landscape means a lot of hard work. Sometimes the weeds outgrow what you have planted. Some landscape plants promise a lot of beauty but deliver nothing but problems. Some trees are weak wooded, prone to pests or diseases, and outgrow their space. Some produce smelly odorous flowers. I urge you to avoid these five plants.

Callery Pears (Pyrus calleryana) grow 35 to 50 feet high. They’re labeled ‘Bradford’ or Cleveland Select’. Their weak branches make them highly prone to storm damage. The odor from spring flowers can be stifling. Older trees produce thousands of tiny pear fruit that give rise to multitudes of thorny seedlings that invade woodlands and vacant lots.

Red-tip Photinias (Photinia x fraseri) are beautiful shrubs. Their lustrous burgundy red leaves and snow white flowers will lure you into purchasing them. A small 3-4 foot plant in a #3 container may become 15 feet high and wide in less than 8 years. Bright red new leaves turn green in 4-6 weeks. By mid-summer leaves are attacked by a defacing fungus disease called Entomosporium leaf spot. Unless you spray often with a fungicide, the disease eventually kills the shrub.

Russian Olive (Eleaegnus angustifolius) is a large deciduous shrub or small tree, up to 25 feet tall. The tree forms a dense canopy with distinctive silver-gray, lance-shaped foliage. Yellow spicy odor flowers appear in late spring and hundreds of silver olive-like fruits laden down branches in late summer. A related species, autumn olive (E. umbellata) produces thousands of bright red fruits in the fall. Both species are rated as highly invasive. Sharp thorns form of twiggy branches and becomes a nightmare to prune.

Leyland Cypress (x Cupressus leylandii) gets more than 70 feet tall and up to 15 feet wide over 30 years. It is highly susceptible to Seridium canker and two other destructive pathogens. Fungicides are available to prevent or lessen disease severity, but this evergreen reaches monstrous sizes to treat all the problems. Drought stress also favors disease.

Honeysuckles (Lonicera spp.) originating from east Asia, many shrub and vine types, are invasive nuisances, particularly in the Eastern and Southern U.S. Their attractive trumpet-shaped, sweetly scented flowers make them attractive purchases. Three recommended exceptions: Winter Honeysuckle (L. fragrantissima), Boxleaf Honeysuckle (L. nitida), and native Coral Honeysuckle Vine (L. sempervirens) do not invade.

Starting Oak Trees From Acorns

Posted by Hugh on September 21st, 2016

Acorns Germinating Under Tree In February

Red oak acorns on tree

Acorns begin ripening and falling from oak trees (Quercus spp.) anytime from late August until mid-November. Ripening dates vary from one year to the next. Harvest the healthy plump acorns, either off the tree or from the ground. Remove and dispose of the cap. If you have collected several kinds, identify and label the oak species.

Plant all white oak species group, including white, bur, chestnut and swamp white oaks, immediately in the fall. Red oak species (pin, red, willow, shingle, sawtooth, et al) acorns may be planted in early spring or in late autumn.

White Vs Black Oaks: White oak acorns mature in one year and will often sprout on the ground outdoors in warm autumn weather. White oak acorns do not exhibit seed dormancy and will start germinating after falling to the ground. Red oak acorns mature in two years. Members of the red oak group possess seed dormancy and generally will not germinate until the following spring; they require a minimum chilling of 42 days chilling period. If stored properly and kept damp, red oak acorns can be held in cold storage for planting in late April through early summer.

If spring planting is desired, store acorns into a polyethylene plastic bag, designated “freezer bag”. Fill with lightly moistened peat mix or sawdust. Inspect acorns through the winter and keep mix slightly, but not sopping wet. Do not freeze acorns. Plant pre-chilled acorns of the red oak species group in early to late April in the ground or into containers.

Direct Sowing In Containers: Select the healthiest looking acorns (plump and healthy) and place 1-2 acorns to a 1 inch depth into loose potting soil in one-gallon pots (#1 size) with drainage holes on the bottom. The tap root will grow quickly to the bottom of containers. Keep the soil (media) moist.

Uniquely Different Chinese Flame Tree

Posted by Hugh on September 18th, 2016

Chinese Flame tree in Bristol, VA in early October

Pink lantern capsules

Chinese flame tree, aka bougainvillea goldenrain tree (K. bipinnata), is another tree option in U.S. southern landscapes (USDA hardiness zones 7-10). It is closely related to the more widely planted goldenrain tree (Koelruteria paniculata). This fast growing tree develops into a nice 20-40 feet tall medium-size tree with an irregular canopy.

Chinese flame tree is highly drought tolerant (after one year established). It grows in average soil, and leaves holds up in urban air pollution. No serious disease or pests trouble the tree and deer leave it alone. Showy long panicles of fragrant yellow flowers appear in summer, one of a very few trees that do so. By mid-September attractive rose-colored seed capsules, mimicking bougainvillea flowers, have matured. They’re often added in dry flower arrangements.

Flame tree is easily distinguished from more popular Golden raintree (K. paniculata) since the former is more upright branched and has 2x pinnately compound leaves, compared to the single pinnate compound leaves of goldenrain tree Leaves hold late into autumn and turn a blah golden color before abscising. The bark on Chinese Flame tree is smooth and light brown when young, and becomes ridged and furrowed as it ages.

In deep South landscapes, flame tree is more multi-stemmed and reaches a height of 40 feet and higher as a specimen lawn tree. It is frequently seen planted in parking lots and highway plantings because of its landscape versatility.

Beware that seedlings from both Koelreuteria spp. will appear anywhere and everywhere in your landscape and all your neighbors’ yards. Pods and stems will fall over the winter. Flametree are for sale at on-line specialty nurseries

Fritillarias – Very Different Spring Flowering Bulb

Posted by Hugh on September 15th, 2016

Red Fritillarias Interplanted with other bulbs

Yellow variety ‘Lutea’ at Keukenhof, Netherlands

Crown imperial (Fritillaria imperialis), aka fritillaria, is an impressive spring flowering bulb that is native of Southwestern Asia to the Himalayas (USDA hardiness zones 5-8). In late April to May, large drooping orange, red, or yellow bell-shaped flowers are topped by a small pineapple-like tufts of leaf-like bracts. The leafy fringe on top resembles a crown, hence the common name “Crown Imperial”. All parts of the plant emit a skunk-like odor.

Individual bulbs grow 3-5 feet tall and 1 to 1½ feet wide. Some gardeners will inter-plant multi-rows of mid- to late-season tulips, daffodils, et al. with the taller growing fritillarias. Each bulb produces flowers on top of a thick, stout, upright flowering stem. Lance-shaped green leaves (to 6 inches long) have wavy margins and appear in whorls around the lower one-half of stem.

Fritillarias are at their best in full sun. Plant bulbs 6-8 inches deep in compost-rich, moist, very well-drained, high pH soils. Space bulbs 12 or more inches apart in autumn for adequate winter chilling in the winter soil. Protect from high wind or be prepared to stake stems.

According to Brent Heath, from Brent and Becky’s Bulbs in Gloucester, VA, “if you garden in most areas of the Eastern or Midwestern U.S., fritillarias are very challenging to grow. Gardeners in the Southwestern U.S. have the best luck with growing fritillaries”. They suffer in heavy clay soils which tend to stay very wet during summer and winter months, resulting in bulbs to rot in the ground.

Foliage dies back by early summer as the bulbs go dormant. Bulbs are large but fragile and are best left undisturbed once planted. Bulbs are best mulched with medium to coarse bark mulch to provide winter protection. Fritillarias resent highly moist soils, particularly in the summer and winter months which leads to bulb rot. Plants are also susceptible to leaf spot, rust and mosaic virus. Most critters like voles, squirrels and deer leave fritillarias alone.

Tip: Excellent soil drainage is the key. Plant on a bed of gravel or coarse sand. Set each bulb on its side to keep water from collecting in the depression at the top of the bulb to prevent or reduce bulb rotting.

To create a spectacular display, plant 6-12 bulbs in the rear of a spring flower border where they can be clearly viewed but their unpleasant flower and foliage fragrance will not picked up.