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

“Neo-Nicotinoid Free” — What Does This Means”

Posted by Hugh on May 27th, 2016

Pesticides on Store Shelf

Earlier this year several big box store and regional independent garden center chains announced that the plants they sell in 2016 will be “neonicotinoid-free”. Large regional nurseries and greenhouse operations are also jumping on-board the anti-neonic bandwagon. This means that pesticides containing the ingredient acetamiprid and imidacloprid are members of the neonicotinoid class, and are forbidden to be sprayed on plants sold at these stores.

Neonic insecticides are thought to be harmful to bees. Studies have shown that small amounts of neonics can harm bees feeding on the pollen and the nectar of treated plants and larger doses can kill. More and more gardeners are making it a point to stop using insecticides that contain neonics and to buy only plants not treated with these pesticides.

Terms like “bee-friendly” and “use of beneficial insects” carry greater value. Plant growers are learning that the term “bee-friendly” delivers a more positive message with buyers.

Neonic pesticides include: imidacloprid, acetamiprid, clothianidin, dinotefuran, nithiazine, thiacloprid and thiamethoxam. A short list of popular brand names pesticides that contain the ingredient Imidaclopyrid include: several Bayer Advanced™ Products, Ferti-lome 2-N-1 Systemic, Hi-Yield Systemic Insect Spray, Marathon, Merit, Ortho Bug B Gon® Year-Long Tree & Shrub Insect Control.

Neonics, imidacloprid in particular, are commonly applied to plants as foliar sprays and soil drenches. Because these pesticides are systemic, they’re taken up by the entire plant and can even spread into the surrounding soil. Depending on the type of neonic and amounts used, one application of a foliar spray can last up to 4 – 5 months in herbaceous plants and a year or more in woody plants. Soil drenches, which are commonly used on roses and trees, can last two or more years in the plant leaves (needles), twigs, and root system. Treated seeds will carry through the pesticide inside the developing plant.

Be aware: Imidaclopyrid is still sold by most of these garden centers.

Six Summer Annuals Your Grandma Did Not Know About

Posted by Hugh on May 24th, 2016

Pentas attract butterflies

‘Dragon Wave’ Begonias in Container

Angelonia (“summer snapdragon”)… are outstanding performers in the summer flower garden, yet so many gardeners have never heard of them. Angelonias demonstrate outstanding heat and humidity tolerances. Serenita™ (12-14 inches high), Serena™ (15-18 inches high), and Archangel™ (12-14 inches tall high) series, are available in purple, lavender, pink, and white colors.

Dragon wing® Begonias…Since their introduction in the late 80’s, these angel wing types of begonias have gained a following, particularly with landscapers and gardeners who need to plant large flower beds. Individual plants cover three times the space of a wax begonia (fewer plants means less cost). They are non-stop bloomers over 5-6 months. One caveat: plants usually grow quickly after planting, but are not floriferous their first month in the ground, but are the last to stop flowering in fall.

Euphorbia Frost® series… Mr. James Newburn, assistant director – curator at the University of Tennessee Gardens in Knoxville, calls euphorbias “the baby’s breath of the landscape world”. Euphorbias have dark green (bronze leaf also available) foliage and pure white flowers on delicate stems that create airy clouds. It is a heat tolerant, drought resistant plant, truly a “plant it and forget it” addition to containers, hanging baskets or landscape beds.

Egyptian Star Flower (Pentas)… large clusters of starry blooms that attract lots of butterflies and hummingbirds to the summer garden. Pentas grow well in containers and in garden beds in full sun and moist, well-drained soil. Kaleidoscope®, Butterfly®, and Graffiti® are rated the best series. Varieties grow 2 to 3 feet tall and 15 inches wide and flower colors from deep red, red, pink and white.

Scaevola (fanflower)… this Australian native thrives in hanging baskets, containers or as garden beds in full sun to part shade. It is easily to grow in average, medium, well-drained soils. Bombay® and Surdiva® series, in a choice of white, pink, or blue flower colors, are the leading ones to try.

Torenia (“wishbone flower”)… an alternative bedding plant instead of garden impatiens (Impatiens walleriana). Summer Wave® is a new trailing series that thrive in summer heat and humidity. Mounding series include Kauai® and Moon®. Torenias bloom all season in hanging baskets, containers, garden beds with a vigorous growth trailing habit. They also perform in partially shady beds and ask for very little maintenance. Plant them 10-12 inches apart in a well-drained soil.

Japanese Crape Myrtle Flaunts Stunning Bark

Posted by Hugh on May 21st, 2016

‘Fantasy’ crape myrtle at JC Raulston Arboretum in Raleigh

‘Townhouse’ crape myrtle

Most crape myrtle cultivars marketed through garden centers are hybrids that combine the large colorful flowers of Common Crape myrtle (Lagerstroemia indica) with the mildew-resistant foliage and cold hardiness of Japanese Crapemyrtle (L. faurei). Japanese Crape myrtle are cold hardy (USDA hardiness zones 6-b to 9) and are heat tolerant. They are rated hardy to winter minus 10 ºF.

Japanese Crape myrtle is a multi-stemmed, medium 40 foot tree deciduous tree. At the JC Raulston Arboretum (JCRA) in Raleigh, NC, the cultivar ‘Fantasy’ is 50 feet tall after 30+years. It flaunts a stunning flaking cinnamon brown bark. In my opinion, it’s the showiest of all crape myrtles. A close second is a 40 foot tall ‘Townhouse’ with a dark chocolate bark. Fantasy is rated less cold hardy than Townhouse.

Japanese Crape myrtle produces abundant pure white flower clusters averaging 4 inches in diameter. Compared to most other crape myrtles, flower clusters are looser than those of L. indica that do not droop as much following heavy rains. Tree blooms only once, usually in early summer in Tennessee, Virginia, and North Carolina.

Main multi-stemmed trunk grows upright with tips of branches slightly nodding, and rounded crown. It grows best in full sun and in moist fertile soil. It tolerates dry soils once established after 1 year. Do not plant on public lands, particularly non-irrigated sites such as highway medians, urban streets, and parking lots. Feed in early spring with a slow release fertilizer. Annual mulching around trees is highly recommended.

After flowering, Japanese crape myrtle grows through the summer and, in some years has trouble hardening off before winter. To prevent early frost injury, do not fertilize after mid-summer. Flowers are smaller compared to hybrid cultivars.

Compared with hybrid cultivars, Japanese crape myrtle is susceptible to aphids, scale, and powdery mildew. Its leaves are highly mildew resistant.

Hold In Confinement

Posted by Hugh on May 18th, 2016

Purple form of Ruellia at UT Gardens in Knoxville, TN

Purple flowering form of Ruellia at UT Gardens in Knoxville, TN

Oenothera speciosa held in check at gas station island

Some plants are incredibly aggressive. Herbicides like Roundup™ won’t phase them. They often escape and take over other areas of your garden or neighborhood.

Four notorious examples are ditch lilies (Hemerocallus fulva), swamp milkweed (Asclepias incarnata), Mexican petunia (Ruellia brittoniana), and pink evening primrose (Oenothera speciosa). You can grow these four weedy offenders in confinement. All will survive on totally inhospitable sites and their spectacular flower show lasts a month or more.

Ditch lilies grow in absolute worst conditions. They bloom for 2-3 weeks starting in late June (USDA zones 6 -8). Each bloom lasts one day, but the large floral scape holds many flowers. Orange is the common color, although other colors are found. Flowers are mostly sterile, but their rootsystems are aggressive.

Leaves of swamp milkweeds are favorite food source of monarch butterfly caterpillars (larvae). Their rootsystem spreads aggressively and they also seed in. Plants form clumps that survive over many years in wetland areas. Swamp milkweeds grow 3-5 feet tall on erect branched stems. Small, fragrant, pink to mauve flowers (1/4 inches wide) are common and a white flowering form is occasionally seen. Orange butterfly milkweed (A. tuberosa), also native, is far less aggressive.

Mexican petunia, aka Texas ruellia, is three-foot-tall evergreen shrub that bears many tubular, blue or purple, petunia-like flowers on dark stems through the summer. This fast grower may self-seed and roots are prolific. It is grown as an annual in cooler zones and will perennialize in zones 6-b where I live.

Pink evening primrose is another nightmarish perennial that blooms almost one month. It spreads aggressively by rhizomes. Plants die back after flowering in the summer heat.

All four are great choices for planting in confined spaces such as in parking lot islands or median strips along busy highways. Plant them in containers and keep blooms deadheaded to prevent seed formation.

Tulip Poplar And Cultivars

Posted by Hugh on May 15th, 2016

Most flowers are hidden among foliage

Mature Liriodendron tulipifera on East TN State University Campus in Johnson City.

Tulip poplar (Liriodendron tulipifera), aka yellow poplar and tulip tree, is a large stately deciduous tree of eastern North America (USDA hardiness zones 4-9). This fast growing native typically grows 60-90 feet tall. It is also an important timber tree.

A member of the magnolia family, flowers attract large numbers of bees. Ornate 2-inch-wide goblet-shaped flowers are yellow with an orange band at the base of each petal. Most flowers go unnoticed, hidden among the 8- inch-wide leaves that have emerged a week or two prior. Dry, scaly, cone-shaped brown fruits follow, each bearing numerous winged seeds. In some years (not all), bright green tulip shaped foliage turns golden yellow in fall.

The size of this native tree will become menacing to homeowners. Young tulip poplars grow with a pyramidal form and mature with a broad rounded canopy. Trunks of mature trees may reach 4-6 feet in diameter, usually rising column-like and devoid of lower branches. Tulip poplars grow rapidly and become too big for an average residential property. Branches are not weak wooded in the early years, but weighty branches on older trees tend to snap off branches in wind and ice storms. Shallow rootsystem grow in lawns and will likely uplift sidewalks in urban areas.

Although not prone to serious disease and insect problems, leaves may be plagued by sap feeding aphids which exude sticky sap over decks, patios and cars beneath. Over a dry summer tulip tree may shed up to one-third of their leaves, perhaps abit messy for some homeowners. Shallow root systems do limit the types of plants that may be grown within the drip line. During hot, dry weather the leaves tend to turn yellow and drop off.

Leading cultivars:

‘Arnold’ – columnar 50 feet tall and 20-25 feet wide

‘Aureomarginatum’ – green with gold leaf edge

‘Little Volunteer’ – compact 35-40 feet tall and 30-35 feet wide

‘Sun King’ Golden Aralia Glows In Summer Garden

Posted by Hugh on May 12th, 2016

‘Sun King’ Golden aralia

'Sun KIng' Aralia in Baltimore, MD Garden

‘Sun King’ Aralia in Baltimore, Maryland Garden

Plants with golden foliage brighten up a dark area in the garden. Sun King golden aralia (Aralia cordata ‘Sun King’) is no exception, hardy in USDA hardiness zones 3-9. Bright golden compound leaves emerge in mid-spring and Sun King aralia retains its bright color through the summer months.

This long-lived perennial grows 4 to 6 feet high and 3 to 4 feet wide. New growth emerges in mid-spring and growth rate is rapid; foliage dies back in late autumn. Many small clusters of tiny white flowers emerge, borne on 2 feet tall racemes in mid-summer. Lustrous purplish-black berries follow in early fall.

Sun King makes a bold almost tropical statement in a shade garden. Grow it in a compost-rich moist soil and in ½ day sunlight (morning sun preferred). It adapts to a wide soil pH range. The foliage will likely burn in full day sun. In zones 8 and 9, grow in dappled sunlight all day long to escape foliage burn. Aralia should be irrigated during long summer dry spells.

Sun King aralia mixes well in containers along with green and other brightly colored foliage plants. It combines with variegated Solomon seals, hostas, lungworts (Pulmonaria spp.), coral bells (Heuchera spp.), and astilbes. Golden aralia is deer resistant and its tiny white flowers in late summer attract numerous honeybees.

A native of Japan, Korea, and China, ‘Sun King’ aralia was introduced to the U.S. by Barry Yinger. Tony Avent at Plant Delights Nursery in Raleigh, NC says: “Aralia ‘Sun King’ is one of the most amazing new perennial introductions in the last decade”.

Deadheading Rhododendron Flowers

Posted by Hugh on May 9th, 2016

Rhododendron days after flowering

After deadheading

Large-flowered rhododendrons (Rhododendron catawbiense) benefit from “deadheading”, the practice of removing the old spent flower heads. Deadheading encourages increased branching, which frequently results in more blooms the following spring. It also cleans up their scruffy appearance. Small-flowered types (including ‘PJM’, lepidote rhododendrons, and azaleas) do not benefit from deadheading and are mostly self-cleaning.

Deadhead your rhododendrons within three weeks after flowering. Vegetative buds have yet to emerge. Later, when the new soft vegetative shoots are emerging, they’re easily damaged. Deadhead early in the day when plants are fully turgid and not wilted. Deadheaded rhododendrons look better and it directs the plant’s energy into growing rather than setting seeds.

Flower stems are very sticky, so wear protective hand gloves. Gloves in turn also become sticky and results in bud breakage. You can use a sharp scissors or needle-nosed pruners to make clean, more precise cuts. Periodically, dip the shears in rubbing alcohol (ethanol) to remove the sticky debris.

Deadheading is beneficial to rhododendrons, but is not a necessary practice. It can be very time consuming. Otherwise, rhododendrons require little annual pruning. They eventually outgrow their space and/or crowd out nearby plants.

Avoid Spotted Spurge in Lawn And Garden Beds

Posted by Hugh on May 4th, 2016

Spotted Spurge becoms weedy mess

Spotted spurge (Euphorbia maculata) is a dreadful perennial weed that can quickly take over a lawn or garden bed. It often grows in poor compacted soils or in-between cracks in pavement. Once established, it is difficult to eliminate it from your garden.

Ideal temperature range for seed germination is 75 to 85 °F, and spurge will germinate in soil temperatures between 60 and 100 °F. Spotted spurge is most active from February through September.

Spotted spurge grows low to the ground like a carpet. Tiny leaves are dark green with reddish stems. Oval-shaped leaves (1/8 – 1/2 inch long) have a dark spot in the center. Plant is covered with fine hairs and its small pink flowers often go unnoticed. Its tap root grows long and deep. Seeds are prolific and are very hardy. Spotted spurge can grow back from either root pieces or seeds. It is a prolific seeder or can spread rapidly.

Hand-pulling in flower beds and vegetable gardens is no easy chore, and you must stay on top of it. The plant fans out from a main root, so yanking it rarely gets all the deep roots. Wear gloves as the milky sap can irritate your skin. Repeatedly weeding a bed eventually weakens the plant and eliminates it.

Glyphosate (Round-up® and similar trade name products) are very effective against spotted spurge. These herbicides are translocated, and eradicate all vegetation after multiple applications. It may re-grow from its deep taproot or from seeds dispersed from a neighbor’s yard. Stay vigilant and re-apply as needed. Contact weed killers become less effective as the plant’s foliage matures later in the year.

Barricade® (prodiamine) is a pre-emergent herbicide that stops weed seeds from germinating in your garden. It will not kill weed seedlings that have already sprouted.

Heavy mulching with several layers of newspaper or wood mulch is also an effective method of controlling spotted spurge.

In areas where spotted spurge is rampant, solarization may be your last resort. Blanket the weedy patch with plastic to kill off all vegetation. Allow 6-8 weeks to kill this tough weedy pest. Remove the plastic and seed lawn grass or garden bed in late summer or next spring.

Reviving A Severely Damaged Crape Myrtle In The Spring

Posted by Hugh on May 1st, 2016

Winter-injured Crape Myrtle

New basal shoots on Winter-Injured Crape myrtle

Crape myrtles (Lagerstroemia indica and hybrid cultivars) are rated as hardy perennials and semi-hardy shrubs or trees in USDA zone 6 and parts of zone 7. Since the year 2000, an average of 1 out of 3 winters has killed some crape myrtles to the ground. By late May new shoots emerge from the very hardy rootsystem below ground or from lower areas on the shrub or tree that were not injured by winter cold.

In general, crape myrtles grow very rapidly, assisted by adequate soil moisture and spring fertilizing. New shoots may also push out in upper parts of the plant, but are removed. It is best to severely cutback the plant or multi-branches near the base to invigorate numerous new shoots to pop out in the coming weeks

Repaired crape myrtle(s) bloom on new summer wood, so flowering is not lost, just delayed a few weeks.

Additional cultural tips: feed your shrub or tree crape myrtle immediately after pruning, using 10-10-10 or equivalent fertilizer. Lightly mulch around the base of the plant for a neat weed-free look. Irrigate only during long summer dry spells. When large numbers of new shoots form, you may opt to re-prune and eliminate all but 1, 3, 0r 5 shoots. By reducing numbers, the remaining shoots grow taller and still bloom.

Never, never prune or fertilize crape myrtles in fall and through most of the winter season.

Chinese (Kousa) Dogwood

Posted by Hugh on April 27th, 2016

Mature Kousa dogwood at Longwood Gardens decorated with Christmas lights

Mid-May Blooming Kousa dogwood

Chinese dogwood, aka kousa dogwood, (Cornus kousa) is a small 25 to 35 foot flowering tree (USDA hardiness zones 5-9). It grows in either full or partial sunlight (4-hours sunlight minimum). Depending where you garden, kousa dogwood begins blooming from late April or in May, almost two weeks after our native flowering dogwood (C. florida) has finished flowering.

Kousa dogwood is a tree for all seasons. New leaves emerge shortly before the tree flowers. The creamy white, four-pointed bracted flowers expand to 4 to 5 inches across. Pink blooming cultivars are a rare find. Aggregate green fruits, similar in shape to oversized blackberries (size of a nickel or larger), ripen orangey-red in September. Most birds do not relish them, but I’m told that monkeys love them.

Seedling kousa dogwoods exhibit wide variability in form, height, flower traits, leaf markings, and autumn leaf coloring. The 2-4 inches long summer leaves are generally dark green and glossy; variegated leaf cultivars are available. Leaf margins may be wavy or ruffled. Fall leaf colors varies from dull purple to crimson red. Bark mottling begins after 5-7 years as thin chips begin to flake off the main trunk and main branches. Some mature 50 plus year old trees are stunningly beautiful in the winter.

Young Kousa dogwoods often grow shrub-like. You can easily develop a tree framework by pruning; eliminate all root suckers and thin out inner branches to stimulate flowering.

Plant in a well-drained, moist, slightly acidic soil. Fertilized and mulch in early spring and irrigated during prolonged drought spells as this dogwood is only moderately drought tolerant.

Kousa dogwood possesses above average disease and pest resistance. Several hybrid dogwood cultivars are marketed with kousa as one parent. One novelty hybrid cultivar (C. nutalli x kousa) is Venus® which struts 6-7 inch wide white bracts; flower numbers are fewer, but are enormous in size.