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

Bedding Geraniums Excel In Cool Weather

Posted by Hugh on March 24th, 2016

Bedding Geranium at Disney Epcot in mid-January

Bedding Geraniums in Containers at Disney Epcot in mid-January

Zonal Geraniums at Disney Epcot

Over the past decade, the zonal or bedding class of geraniums (Pelargonium x hortorum) have become summer favorites in northern gardens (USDA hardiness zones 3-7). Geraniums thrive in cool weather, but are also widely planted in zones 9-10 gardens where winter temperatures are moderate. Increasing numbers of colorful varieties beautify flower beds and container gardens.

Leaves are marked by distinctive bands or “zones” of dark markings. Single or double blossoms are clustered into ball-shaped heads. Most zonal geraniums are seed produced and color choices include red, pink, salmon and white. Plants are compact in habit.

Geraniums should be planted in a compost-rich, well-drained garden soil or peat-based media for containers. Plant in full day sunlight to attain maximum blooming potential. Space plants 8 – 12 inches apart. Mulch to moderate soil temps and reduce weed infestations. Feed a granular fertilizer such as 10-5-10 at planting time and supplement with any water soluble fertilizer such as Miracle-Gro®, Peters®, or Schultz® every 3-4 weeks up to the first days of autumn.

When purchasing plants at garden center, choose those that are compact in habit, with blemish-free foliage, and full with flower buds. Zonal geraniums do not require constant deadheading, but monthly removal of seed heads will increase bloom numbers.

Zonal geraniums are disease and pest resistant when properly sited in the landscape. Geraniums prosper with summer irrigation. Geraniums need good air circulation, but need protection from strong winds. Over dry summer intervals, geraniums require weekly watering. Do not over irrigate geraniums as it will increase fungal leaf spots and dreaded botrytis diseases.

Carolina Allspice Sweetshrub

Posted by Hugh on March 22nd, 2016

Carolina Allspice Sweetshrub

‘Hartledge Wine’ hybrid form

Carolina allspice sweetshrub (Calycanthus floridus), aka strawberry bush, bubby bush, sweet Betsy, et al., is a trouble-free medium size spring flowering shrub. This dense rounded deciduous shrub is native to Eastern North America (USDA hardiness zones 4-8). As its common name hints, flowers emit a sweet fruity fragrance. Intensity of floral fragrance is highly variable among seedling sweetshrubs.

Reddish brown flowers measure 2-3 inches across and bloom on short terminal twigs in May. Flowers give way to brownish, urn-shaped fruits (seed pods) may ripen in fall and persist through winter into spring. Glossy, 6-inch long, dark green leaves which, in some years, hang from twigs through winter. Fall leaf color is highly variable, turn a blah yellow to golden color. Some cultivars exhibit better autumn foliage color.

Sweetshrub requires little care in any well-drained soil in full sun to moderate shade. Adequately water the first year to get the shrub established. Species typically grows 8-10 feet tall and 6-12 feet wide, often taller in shade than in sun. It tolerates a wide range of soils as long they possess good drainage.

Sweetshrub has no serious insect or disease problems and deer seem to leave it alone. To maintain vigor, feed in early spring with a slow-release fertilizer such as Osmocote® or Nutrikote® according to package directions. Prune the shrub within 1-2 months after flowering in late spring, mostly to rein in size and shape. Warning: sweetshrubs tend to sucker, some varieties more than others.

Locate sweetshrub near a patio or deck where its sweet fragrance may be enjoyed. Plant several as a shrub border or deciduous screen.

Significant Cultivars:

‘Michael Lindsey’ was selected and introduced by plantsman Allen Bush. Its vibrant reddish brown flowers are highly fragrant; leaves turn golden yellow in fall.

‘Athens’ opens with soft buttery yellow flowers and delightful fragrance; grows 6 – 8 feet tall and wide.

‘Hartlage Wine’ is a hybrid between Chinese allspice (Sinocalycanthus chinensis) and C. floridus. Flowers are 3 inches wide, maroon to wine colored, with wide petals and very little fragrance; grows vigorously 8 – 12 feet tall by 10 – 15 feet wide; sporadic blooming through the summer.

‘Venus’ is a three-way hybrid cross with 3 – 4 ½ inch wide white fragrant flowers with yellow and purple centers; grows 6 – 8 feet tall and wide. (zone 5 hardy).

New Cannova® Cannas Worth A Try

Posted by Hugh on March 18th, 2016

Cannova ‘Scarlet with Bronze Foliage’

Canna ‘Cannova Lemon’

Cannova® Cannas (Canna x generalis) are one of a new series of seed produced hybrid cannas. In addition to profuse flowering, they’re highly rated for their compact bushy plant habit and ability to form multiple shoots. They bloom earlier and continue nonstop through summer up to first frost.

Their bold, banana-like foliage adds a tropical look to the summer garden. New shoots emerge from large pointed buds. Large elegant lily-like flowers come in various bright colors. Cannova Cannas come in 6 flower choices: red, rose, yellow, scarlet with bronze foliage, lemon, and mango.

Cannas are indigenous to the tropical and subtropical regions of the world, but thrive in cool temperate zones with warm summers. Cannas grow from rhizomatous root systems that are sensitive to sub-zero soil temperatures. In colder regions, cut off above ground shoots, dig up, and store them inside around 40 °F.

Cannova cannas are produced virus-free. In recent years many vegetative canna varieties have become infected with a virus disease which stunts growth, distorts and discolors foliage, and reduces flowering. Purchase only cannas that are guaranteed virus-free. Beware that the virus can be spread from already infected cannas via aphids to healthy ones.

Cannova Cannas usually arrive at garden centers already budded up or in bloom. Carryover plants re-bloom in late May to early June and thrive up to first frost. Deadheading spent flowers in summer will promote re-blooming.

For continuous flowering, cannas need at least 6 – 8 hours of direct sunlight during the growing season. Feed with 10-10-10 or equivalent fertilizer or water soluble fertilizers such as Miracle-Gro™, Nature Source™, or Schultz™. Plant in a compost-rich potting soil or garden bed and keep watered as needed. Optimum soil/media pH range is between 5.5- 6.2.

While disease and pest problems are few, keep an eye out for thrips, red spider mites, and pythium, rhizoctonia, and botrytis diseases.

Plant cannas in containers and grow on a deck or patio. Submerse container(s) in shallow ponds or water gardens. Site in a garden bed with other annuals and perennials.

Fothergillas Are Topnotch

Posted by Hugh on March 17th, 2016

Fothergilla x intermedia ‘Blue Shadow’ at Duke Gardens

Fall color of F. gardenia

In the Eastern U.S. two species, dwarf fothergilla (F. gardenii) and large fothergilla (Fothergilla major), are native. They are also labeled “witch alder”. Both species appear almost identical, except for flower and leaf size, and overall shrub size. Large fothergilla is indigenous to the mountain and Piedmont Regions of the Carolinas where soils are drier and slightly more acidic soil. It is also rated more winter hardy (zones 4-8) and prefers partial shade areas.

Fothergillas are four-season shrubs, members of the witchhazel family (Hamamelidaceae). Leaves are almost identical. Both species bloom abundantly with clean blemish-free summer foliage and superb fall color. Flower buds form atop terminal tips of branches.

Creamy white bottle-brush flowers, 1½ to 3-inch tall, appear in April to early May depending on the region of the country where you garden in. Flowers typically last 10 to 14 days and flowers emit a sweet honey scent. Summer foliage is usually blemish-free green to blue-green. Fall leaf color is variable from one year to the next from yellow, bright orange, or deep red. Weather and growing conditions play a role in fall colors each year.

Fothergillas prefer moist, humus-rich, well-drained, acidic soil; it lingers or dies in poorly drained soil. Shrubs tolerate partial shade, but flower numbers and shrub density are best in full sun. Root suckers form into a tight plant colony which widens over time.

Fothergillas are utilized as single specimen shrubs or plant several together as a shrub border, foundation planting or low hedge. Pruning is rarely needed for this slow growing compact shrub. They are not troubled by insect, disease, or deer browsing.

Leading Cultivars:

‘Mount Airy’ is a natural hybrid discovered at Mount Airy Arboretum in Cincinnati, Ohio by Dr. Michael Dirr of the University of Georgia; it grows 4 – 6 feet tall with good fall color and larger flowers (than dwarf fothergilla), and is more drought and winter cold tolerant (zone 4).

‘Blue Mist’ (F. gardenii) is a compact, 2-3 feet tall, slow-growing cultivar with a mounded habit; frosty blue-green summer foliage under moderate shade; subpar fall color in zone 7 and points south.

‘Blue Shadow’ (F. x intermedia) is a compact, 4-6 feet with striking powder blue (glaucous) foliage.

Three Easy Care Native Woody Plants

Posted by Hugh on March 15th, 2016

Red Buckeye in Flower in Early May

Plumleaf azalea in July

Red buckeye (Aesculus pavia) is a nearly perfect small native tree for either a full or part sun site. Decorative 5 to 9 inches long reddish flower candles form on tips of branches in late April and May (USDA hardiness zones 6 – 8). Hummingbirds will seek out the dark orange to scarlet tubular blooms.

Lustrous, dark green, palmately compound leaves cover branches from spring thru most of summer. Leaf diseases and summer drought may scorch or mar leaves in late summer. Most years, leaves drop prematurely by September ahead of other landscape trees.

Virginia sweetspire (Itea virginica) shrub flowers in late spring and has dark green, pest-free summer foliage that turns brilliant red in fall (USDA hardiness zones 5-9). It thrives in full sun to partial shade, and in moist, mildly acidic soils. Once established, it is also highly drought tolerant. Fertilize with a slow release fertilizer in early spring.

Virginia sweetspire grows 4 to 6 feet tall and wide, depending on cultivar. Pruning is rarely needed except to remove unwanted suckers after flowering is finished. Selected cultivars include: ‘Henry’s Garnet’ @ 5-6 feet; ‘Little Henry’ @ 4 – 5 feet; or ‘Merlot’ @ 3 – 3 ½ feet

Plumleaf azalea (Rhododendron prunifolium) is an Alabama/southwest Georgia native shrub that blooms in late July (USDA hardiness zones 6-9). Orange-red flowers brighten up its garden spot. A dark red flower selection is also available. Flowers are not fragrant, but do attract numerous butterflies and bees.

Plumleaf azalea grows in average well-drained soil and in part day sun or high shade. Irrigate weekly during summer dry spells. Shrub seems insensitive to soil pH; likely it prefers an acidic range between 5.5 to 6.5. No diseases, pests or deer trouble it. Pruning is rarely necessary. Plumleaf azalea grows 8-10 feet tall, but may be maintained to 5-6 feet in height and width.

Note: These wonderful natives are rarely sold at local garden centers. Find them at native plant or at e-commerce nurseries on-line.

Virginia sweetspire flowering in June

Patio Peach Blooms In Early Spring

Posted by Hugh on March 12th, 2016

Columnar Flowering Peach at Duke Gardens

Close-up of flowers

For small garden spaces patio peach (Prunus persica) is a gem. This miniature tree bears long narrow lush green (or reddish) foliage. Site selection is crucial to ward off potential disease and insect problems.

Patio peach is a genetic dwarf and may be grown in a large container on your deck or patio. Tree height averages 6-8 feet tall but many varieties may be shorter or taller. Most do not produce tasty edible fruits.

Grow in moist, well-drained, mildly acidic soil. The tree should receive full to partial sun (6 hours minimum) with good air movement to thwart major disease problems. Insect problems also abound with peaches.

Patio peach is glorious in bloom in early spring. Open blossoms are frequently injured by overnight frosts. Red, pink, or salmon flowers are mildly fragrant. Weather cooperating, bees and early arriving butterflies will pollinate the blossoms. The mostly inedible peach-like fruits mature in summer but are often hidden from view by the dense foliage.

Feed landscape-grown trees with granular 10-10-10 or equivalent in early spring. Container-grown trees are best fertilized bi-monthly (3 times a year) with water soluble fertilizers such as Miracle-Gro™, Daniels™, or Schultz™. Do not fertilize after August 15th. Irrigate tree(s) during summer dry spells. Prune patio peach immediately after spring flowering; remove dead, broken or diseased branches at anytime.

Check tree(s) spring into early summer (April thru early July) for wood borers and scale insects, particularly on the lower scaffold branches and main trunk. Treat with preventative insecticides every two weeks with Bayer Advanced Garden Insecticide™ to prevent peach twig borer, aphids, and spider mites. Also susceptible to numerous disease problems, including peach scab, peach leaf curl, leaf spots, bacterial canker, root rot, and mildew.

Colorful summer foliage on many varieties of patio peach

Popular Tomato Varieties In U.S.

Posted by Hugh on March 9th, 2016

Fun With Tomatoes

Many people who have “retire” from gardening still plant a patch of tomatoes every spring. Tomatoes don’t ask for a lot of care. There is nothing better than a thick slice of tomato with a burger or tuna salad sandwich.

Every region across the U.S. has their favorite varieties. The gardener’s favorite appears to be a meaty medium-sized (6 to 8 ounces) red globe type that oozes with flavor and is not tough skinned.

Determinate (D) varieties like Celebrity and Mountain Pride have a strong following because harvest time comes at one time and plants are highly disease resistant. Indeterminate (I) varieties, many called heirloom types, include Better Boy, Brandywine, Cherokee Purple, and Mortgage Lifter.

Leafing through spring seed catalogs, here are some popular varieties along with a brief description:

Better Boy—VFN hybrid; 8- to 12- ounce red fruit; 72 days; I.
Big Beef—large-fruited beefsteak with good disease resistance; I; AAS* 1994.
Brandywine - popular heirloom variety; great flavor red fruit; disease susceptible; I.
Celebrity—VFNT hybrid; 7- to 8-ounce red globe; firm, flavorful fruit; D; 72 days; AAS* 1984.
Cherokee Purple– popular heirloom variety; up to 1 lb. flavorful beefsteak with dark shoulders; I; 80 days
Cherry Grande—VF hybrid; large cluster of 1 1⁄2-inch firm, round, red fruit; D; 60 days.
Early Girl – VF hybrid; early ripening; 4 – 6 oz. round red fruit; I; 57 days
Floramerica – VF hybrid; 8 -12 oz. red fruit; 76 days; D; AAS* 1978.
Mortgage Lifter – old-fashioned huge variety, large fruits, few seeds & meaty.
Mountain Pride – VFFA hybrid; mid-season; 7 oz.; crack resistant; D.
Mountain Spring – VF hybrid; early; resistance to cracking; D.
Park’s Whopper – VFNT hybrid; 14 oz. fruit; 70 days; I.
Super San Marzano – small sweet paste & sauce type; highly disease resistant; D.
Super Fantastic – VF hybrid; 8-ounce red fruit; 70 days; I.
Sweet 100 – hybrid; large clusters of 1-inch, round, red fruit; I; 65 days.
Tommy Toe – heirloom cherry; ½ – 1 inch round red fruit; 70 days.

Growing Tomatoes 101

Posted by Hugh on March 6th, 2016

Small fruited indeterminate tomato

Tomato plants are at their best grown in full sun, adequately fertilized and spaced, and staked or caged for support. Have a backup disease control plan in case. Most tomato plants are set out as transplants, since it takes several weeks longer to harvest those direct seeded into garden soil. Transplanting means earlier harvests. Those gardeners with a longer growing season can staggered plantings to extend harvest into the fall season.

Northern U.S. gardeners with a short harvest season favor determinate varieties like Celebrity and Mountain Pride because the harvest interval is short and plants are highly disease resistant. Indeterminate “heirloom” varieties such as Better Boy, Brandywine and Mortgage Lifter are also widely planted but are disease prone.

Do not rush to set out transplants during cold spring air and soil temperatures as it may set plants back and result in later harvest. Set tomato transplants deeper than they were growing in the cold frame bed, peat pots, or plastic tray cells. At planting time remove all pre-formed fruits off transplants as they tend to retard plant growth.

Use a starter fertilizer after setting out transplants in the ground; do not mulch the ground immediately so the sun can continue to warm up the cold soil. Black plastic mulch laid before planting is beneficial to early plantings.

Generally garden centers have lots of leftover plants in June for a late summer – fall crop. Tomato plants, indeterminate (I) and determinate (D), can be supported off the ground by 2 methods to prevent fruit loss because of rots and sunburn. Wooden stakes are the most common type of support for indeterminate tomatoes. Wire cages, at least 18 inches in diameter, are made from concrete reinforcing wire and support either indeterminate or determinate varieties.

Tomato plants develop many branches (suckers) as they grow. Pinch the suckers out of the plants to encourage larger and earlier fruit and to make the plant easier to tie and spray. Determinate types are not pruned as heavily as indeterminate types.

Slow Release Fertilizers Save Money

Posted by Hugh on March 3rd, 2016

Organic Fertilizers On Shelf Of Garden Center

On garden center shelves in the spring are slow-release fertilizers. Trade names include Scotts®, Osmocote®, Fertilome®, Hi-Yield®, and Vigoro®. Many are formulated for lawn use. Cost for these products are more than traditional granular fertilizers but prices have dropped over the years and they are better to use environmentally.

How do you compare and choose slow-release fertilizers? First, find the product in the proper ratio based either on your soil test analysis or crop needs. A 1-1-1 ratio fertilizer (10-10-10 or 19-19-19) is standard for flower and vegetable gardens. If phosphorus levels are high or very high, look for a no- or low- phosphorus fertilizer such as a 20-1-20 or 4-1-4 ratio.

For landscape trees and shrubs, a ratio of 3-1-2 or 3-1-1 is more appropriate than a 1-1-1. Turf fertilizers such as 18-6-12 or 24-8-16 are examples of 3-1-2 ratios which can be used for trees and shrubs as well. Fertilizer for bulb crops (tulips, lilies, gladiolas, etc.) should be high in phosphorus.

The benefits of a slow-release fertilizer is they slowly supply a steady supply of nitrogen to plants all season long at a time when they can use the nutrients. Nitrogen is absorbed by the plant and not lost by leaching. Slow release fertilizer is rated more environmentally-friendly. They are heat sensitive. Less nitrogen is released when the soil is cold in early spring, and more goes to plants when they’re actively growing in summer.

Natural organic fertilizers are a separate class of slow release products. Milorganite™ (5-2-0) is a safe organic fertilizer manufactured from municipal waste. Blood meal (12-0-0), rock phosphate, muriate of potash, and cotton seed meal (6-2-1) are other examples.

Autumn Fern Changes With The Seasons

Posted by Hugh on March 1st, 2016

Autumn fern at Atlanta Botanical Garden

Autumn ferns in Container planting

Ferns are fine textured lacey-leaf groundcovers. Many kinds of ferns add a tropical accent to the shade garden. Autumn fern (Dryopteris erythrosora), aka Japanese wood fern, has evergreen or semi-evergreen arching foliage, depending how cold it gets in winter (USDA hardiness zones 5 to 8).

Its common name is misleading. Best frond colors are in spring; the fronds unfurl with a coppery-red or pink tint and gradually fade to bronze-green after 4-6 weeks. In late summer, bright-red spore clusters (sori) appear on the frond’s underside. In fall, fronds take on more of a russet tone.

Most winters autumn fern stays evergreen in zone 8. It grows happily beneath large shade trees or in dry soils. In the first year start off with plenty of water, compost, and mulch to get the root system established. It prefers an evenly moist soil, and mildly acidic soil pH between 5.5 and 7.0.

In early spring emerging fiddleheads (fronds) unfurl to form a vase-shaped clump, 18-30 inches tall and wide depending on age. At planting, space this fern 16-18 inches apart for dense coverage. Indifferent to heat, humidity, and cold, this moderate shade lover excels in full morning sun in zone 5 and 6, but wants more shade in southerly climes.

From then on, autumn fern performs season after season with little additional care. It has no serious pest or disease problems and soil nutritional needs are minimal. Applying 2-3 inches of leaf mold is almost equivalent to feeding with slow release fertilizer.

The cultivar ‘Brilliance’ grows 2 feet high and wide and offers long seasonal impact. Its frond’s color is exceptional, that is, the upper surface has a rich coppery tint and high gloss which holds through most of the summer and turns russet in autumn.