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

Stop Ignoring And Start Planting Hophornbeam

Posted by Hugh on June 28th, 2013

Hophornbeam (Ostrya virginiana) in Southeast Pennsylvania

Hophornbeam (Ostrya virginiana) is a medium sized tree native to the eastern half of North America (USDA hardiness zones 4-8). The tree is practically ignored by landscape designers and installers. Few nurserymen grow it.

Hophornbeam is often confused with the true hornbeams (Carpinus spp.). Both are called “ironwood”, referring to the hard muscular wood of both genera. Ostrya averages 35 to 40 feet in height and 20 to 30 feet in width in an open location. As the tree ages, its canopy becomes more rounded.

Year-round interest can be found in its flowers, fruit, foliage, tree form, and bark. The 3-5 inch long, doubly serrated foliage is medium to dark green in summer color, and finishes yellow-brown in the autumn before falling. Hophornbeam bears distinctive male and female flowers on the same tree. Small male catkin flowers, grouped in threes, are reddish to brown in color. Male flowers are visible on the tree in winter. The greenish female flowers give way to 2 ½ to 3 inches long, drooping hops-like seed pods. Tiny nutlets inside the seed pods persist most of the winter and are an important food source for birds.

Hophornbeam grows in either sun or shade, developing a full, dense canopy in full sun and in moist, well-drained, moderately acidic soils. It tends to be slow growing at first and becomes more moderate after 2 years when properly mulched and not environmentally stressed. It is remarkably shade tolerant and, in its natural woodland habitat, develops into a small 15-20 foot open-branched tree or large shrub.

A young tree exhibits smooth, muscular trunk with slender branches which grow in a zig-zag pattern. The bark gradually ages, shedding in small thin patchy pieces, valued by some for winter interest. The tree is rarely damaged by deer.

2013 Garden Participation Up, Total Spending Still Down

Posted by Hugh on June 24th, 2013

Garden Center Shopping Aisle

The National Gardening Association recently released their 2013 National Gardening Survey. Household participation in gardening rose 2% since 2011— now totaling approximately 85 million households.

Popularity in food/edible gardening continued to rise for the sixth straight year in a row, soaring past flower gardening in terms of dollars spent. The increase in male gardeners from the 18- to 34-year old accounted for the largest spending boost.

U.S. households continue to spend more at Home Improvement Centers (27% of the total gardening retail market) and at Mass Merchants (20%) than they do at local Garden Centers and Nurseries (17%) or local Hardware Stores (15%).

This is the second year in a row that lawn and garden sales rose, after being down the previous two years. The average annual spending per household was down $4 to $347. Time and lifestyle, not the weather, seem to be more important factors determining how people spend their dollars.

Total sales of green goods are still languishing. In the battle for consumer entertainment time and dollars, the lawn and garden industry is competing against movies-on-demand, video games, watching sports, and electronics.

Source: National Gardening Association

‘Tom Thumb’ Cotoneaster Perfect For Small Spaces

Posted by Hugh on June 22nd, 2013

New Spring Growth on 'Tom Thumb' Cotoneaster

The world of cotoneasters (Cotoneaster spp.) is primarily an assortment of medium to tall growing shrubs. Cotoneaster ‘Tom Thumb’ (syn. C. ‘Little Gem’) is very different. Its diminutive size fits into those small spots such as a rock garden or among dwarf conifers. Its dark green shiny foliage creates a textural contrast with many annuals or perennials.

Slow-growing ‘Tom Thumb’ may achieve 6 to 12 inches in height and 3 to 6 feet in width over 10-12 years. It hugs the ground, and often self-roots. It may be utilized as a deciduous ground cover, although this may be expensive option. Slightly taller bearberry (C. dammeri) or cranberry (C. apiculatus) cotoneasters are cheaper ground cover alternatives.

Its tiny spring flowers are mostly inconspicuous. Fruit numbers in the fall is never plentiful and have little ornamental value. In the autumn foliage turns bronzy red and is rarely an attention grabber. (USDA hardiness zones 5–7).

A native of western China, most nursery catalogs classify Tom Thumb as a variety of C. horizontalis, but others place it with C. adpressus or C. apiculatus. ‘Tom Thumb’ thrives in full sun or partial shade, and most pests don’t seem to bother it. Tom Thumb is not fussy about soil as long as it is well-drained. This slow growing plant requires little or no pruning.

Many cotoneasters are susceptible to fire blight, a bacterial disease.

Enjoy Night-blooming Evening Primrose By Flashlight and I-Phone

Posted by Hugh on June 21st, 2013

9:08 p.m. June 15 Newly Opened Night-blooming Evening Primrose

There are over 100 species of evening primroses (Oenothera spp.) worldwide, several native to the U.S. The night-blooming evening primrose (O. glazioviana) is a great reason to plan more parties. Invite friends and neighbors, including children of all ages, although you may keep them up past their normal bedtime hour. This night blooming hardy biennial or perennial (USDA hardiness zone 3 to 7) is native to Southern and central United States.

The cultivar ‘Tina James’, identified as “Lamarck evening primrose” is very popular and available from seed. It is named for Tina James, a Maryland garden writer, who hosts numerous primrose parties. The plant thrives in full sun and in a moist, compost-rich, well-drained soil. An established plant will tolerate poor and/or limey soils, drought, and light shade. A plant in too much shade tends to become leggy and require staking.

Each 3-inch wide four-petalled flower bursts open rapidly, usually in less than one minute. Time is slightly after dusk from mid-June to early July. The lightly fragrant yellow blooms are very showy until mid-morning. A 3-year established evening primrose grows into a bushy 3 to 5 feet tall herbaceous plant.

Evening primrose is a prolific seeder, likely around the mother plant. In the first year plant develops a flat rosette of leaves (similar to an African violet or strawberry plant). It initiates 3-5 feet tall yellow spires in its second year. Flowers are pollinated by night-flying moths and hummingbirds. Stage it growing in a container on your deck or patio and it will become a great conversation piece among your guests.

Night blooming evening primrose is reported to have medicinal properties that are not discussed here. It has no serious insect or disease problems.

Nocturnal Daylilies For Gardeners Who Work 9 To 5

Posted by Hugh on June 19th, 2013

Flowering at 9 a.m. the following morning

Around 10:00 p.m. the Evening Before

A typical daylily flower opens early in the morning and fades in late afternoon. There is a class of night-blooming (nocturnal) daylilies recognized by the American Hemerocallus Society (AHS). Flowers of nocturnal daylilies open anytime from late afternoon to dusk, bloom through the night, and close-up (wither) starting in mid-morning.

Introducing the true nocturnals…they open around dusk and remain in flower through the night. Probably, the best known of a nocturnal daylily is fragrant lemon-yellow ‘Citrina’, an introduction from China over a century ago. Recent additions to the nocturnal class include: ‘Alna Pride’ (7-inch peachy-yellow, red halo center), ‘Ethel Shepherd’ (6-inch gold peach, ruffled edge), ‘Lady Grosvenor’ (6-inch pale pink, yellow throat flower), ‘Quick Gold’ (6-inch butter gold), ‘Spread Gold’ (7-inch bright yellow, green-yellow center), and ‘Tall Angel’ (6-inch pink, green throat).

AHS also lists an “Extended Daylilies” grouping within the Nocturnal class. Extended Daylilies bear flowers which remain open for 16 or more hours a day. The flowers of many extended daylilies open in mid- to late morning and close in late evening, often after dark.

The popular golden yellow cultivar ‘Stella d’Oro’ belongs in the Extended Daylilies class. Blooms stay open 16 or more hours a day and hold up well into the evening hours. Others in the Extended Daylilies class include ‘Happy Returns’, ‘Pardon Me’, ‘Bitsy’, and ‘Buttered Popcorn’. They are short-growing (18 to 24 inch high) cultivars and re-bloom in late summer or early fall.

To get the most out of nocturnal daylilies, select for light and bright colors and high scent. Light yellow to orange colored blooms are more visible in the evening garden, particularly on moonlit nights. Adding landscape lighting also helps. Lastly, enjoy the delightful fragrance of some cultivars.

Nocturnal daylilies are rarely available at local garden centers. It is best to search e-commerce nursery sources over the internet. Tranquil Lake Nursery in Rehoboth, MA is a good shopping source. Many extended cultivars are easily found at local nurseries.

‘Silberlocke’ Korean fir Gets Lots of Favorable Comments

Posted by Hugh on June 16th, 2013

Abies koreana 'Silberlocke' in Oak Ridge, TN Garden

In any season visitors to your garden should immediately take notice of ‘Silberlocke’ korean fir. Korean fir (Abies koreana) is a densely branched pyramidal evergreen tree. Growth is slow in the beginning, eventually reaching 50 feet or more in mature height. The wide 3/4 inch long needles are dark green and glossy above and silvery on the underside. Upright purple 3-inch cones are a distinctive feature of this fir.

‘Silberlocke’, aka ‘Horstmann’s Silberlocke’, typically grows as a compact pyramidal shrub form, 8 to 10 feet tall in its first 10 years, eventually maturing to 18 to 20 feet tall and 12 to 18 feet wide. The needles are uniquely recurved and silvery-white beneath. Silberlocke was introduced in 1986 by German plantsman Gunter Horstmann.

When properly sited in full sun (minimum of 6 hours) and a compost-rich, well-drained soil. It prefers a cool well-drained site (USDA hardiness zones 5 to 7) and often fails in summer heat and humidity further south. If you garden in USDA zone 7 and/or the soil is a heavy clay loam, grow ‘Silberlocke’ korean fir grafted onto Japanese Momi fir Abies firma rootstock.

Silberlocke has few serious disease or pest problems. Stem cankers and Phytophthora root rot often kill most firs (Abies spp.). Generally, firs languish, if not die, in hot droughty soils and urban pollution. Maintain a 2-3 inch thick mulch layer around Silberlocke to conserve soil moisture and moderate root temperatures.

Feed once yearly with 10-10-10 granular fertilizer in late winter or apply an acidic water-soluble product such as Miracle Gro™, Jacks™, or Hollytone™ in spring and early summer.

Silberlocke’s silvery needle foliage and erect standing purple cones provide 4-seasons of interest. Plant availability is usually limited to specialty conifer nurseries from e-commerce. Again, specify grafted stock if you garden in zone 7.

Summer Chocolate™ Mimosa Tree Worth A Try

Posted by Hugh on June 12th, 2013

Summer Chocolate Mimosa at Dallas Arboretum

Mimosa tree (Albizia julibrissin) is treasured as a four month landscape tree for its tropical-like foliage and flowering. This small deciduous tree grows 20 to 25 feet tall and its horizontal branching reaches out widely.

Mimosa leafs out in late May with lush green, tropical-looking pinnately compound foliage and growth is very rapid. From mid-June thru early July, the fragrant lovely flowers appear above the foliage and attract numerous hummingbirds. Its autumnal leaf color is forgettable.

New mimosa cultivar Summer Chocolate™ makes a wonderful garden accent plant, prized for its dark purple foliage and pink feathery blooms. In late winter you may opt to cut back last year’s plant to the ground and re-grow it only for the colorful textural foliage, thereby eliminating flowers and seed pods.

Mimosa is not long-lived, perhaps surviving 15-20 years before a soil disease or other maladies destroy it. It is a pioneering species on abandoned sunny urban sites and poor highway soils. A 2-year old established tree is exceptionally drought tolerant; its roots improves soil tilth and nutrition. Mimosa fixes its own nitrogen.

Many gardeners in the Southern Appalachian region classify mimosa as an “exotic invasive” (USDA hardiness zones 6 and 7).

Give Lots of Space To Bottlebrush Buckeye

Posted by Hugh on June 4th, 2013

Aesculus parviflora in Louisville, KY

If you have lots of planting space, aggressive bottlebrush buckeye (Aesculus parvifolia) is what you want. This deciduous, multi-stemmed shrub grows 8 to 12 feet tall and 8 to 15 feet wide.A Southeastern U.S. native, bottlebrush buckeye is a late spring flowering shrub and requires little extra attention other than pruning. Plant in full sun in zones 5 and 6 and in partial shade in zones 7 and 8. It becomes very drought tolerant after two years establishment.

Older unkempt shrubs can become aggressive spreaders and grow taller and wider. Roots develop a strong suckering propensity. Suckers are easily checked by closely mowing around the shrub. Otherwise, a three gallon (#3 size container) shrub may eventually swallow up 300-400 square feet of ground in 20 years.

The white bottlebrush flowers in late spring-summer are spectacular. Reddish floral anthers add extra appeal. The white bottlebrush flower clusters are 12-18 inches long and stand tall above the foliage. Bottlebrush flowers for 2-3 weeks and attract numerous butterflies and other pollinators. A. parvifolia var serotina ‘Rogers’ blooms 3-4 weeks later than species.

Bottlebrush buckeye has bold dark green palmately compound (5-7 leaflets) foliage. This shrub belongs to nature’s “bold and beautiful” class. The compound foliage turns bright yellow for a short time in autumn before dropping.

Few diseases or insects mar the foliage compared to other buckeyes and horsechestnuts. Bottlebrush appears resistant to deer and rabbits, perhaps because of its aggressive growth habit.

The pear-shaped nuts (buckeyes), encased in husks, ripen in early fall. Collect early before critters swipe them. Fresh nuts should be planted immediately before they shrivel. Sow 2 inches deep in moist compost rich soil and several will germinate late next spring.

Bottlebrush buckeye is commonly available from e-commerce nursery sources on-line and from wholesale nurseries.

Why Some Vines Do Not Bloom

Posted by Hugh on June 1st, 2013

Closeup of Wisteria frutescens 'Amethyst Falls'

Why doesn’t my wisteria (Wisteria spp.) or climbing hydrangea (Hydrangea anomala subsp. petiolaris) vine bloom? There are primarily four (4) reasons why these vines have not flowered. In order of importance they include:

1. The flower buds, which usually formed on the previous summer’s wood, may have been pruned off. Do not prune vine after July 1st as it initiates next spring’s floral buds at this time.

2. Vine may have been over-fertilized, particularly too much nitrogen. Japanese (W. floribunda) and Chinese (W. sinensis) wisterias, as well as our less aggressive U.S. native species (W. frutescens), rarely require feeding. Wisterias gather all they need from any ordinary well-drained soil. Fertilized wisterias, particularly overfed vines, produce lush stems and foliage at the expense of flower production.

3. In some years flower buds are killed by low winter temperatures or late spring frosts.

4. Age matters. Your vine may not have reached “puberty”, is not mature enough to set flower buds. Hydrangea vines grown from cuttings often take 5 or more years to reach blooming age. Grafted vines bloom sooner.

To correct a long flowerless wisteria, vertically cut the surface roots within 12 inches of the vine with a sharp spade. Do this in May or June before flower bud initiation begins in July. This will unduly stress the vine by damaging the roots and likely cause the wisteria to induce flower buds for next spring.

Determinate Vs Indeterminate Tomato Varieties

Posted by Hugh on May 26th, 2013

Luscious Vine Ripen Tomatoes

There are many tomato varieties from which to select. You may find 100 or more varieties listed in garden catalogs. Depending on your garden space and needs, the two categories of tomato varieties to grow are determinate or indeterminate types.

Short bush type growers are called determinate tomatoes. They require no support and you can grow them on the ground or planted in wire cages. Determinate tomato plants grow well in containers. No pruning is required, as plants grow 3 to 4 feet tall. Determinates bear most of their fruit in a short time span, and most are harvested over a few weeks. Many have a short growing season and early harvest. You may plant the same variety weeks apart to stagger harvest dates through summer into fall. Most determinates are hybrid varieties, but a few are non-hybrid heirlooms.

Taller indeterminate tomatoes need to be supported on a trellis or a large tomato cage. They’re often pruned to keep the plant in bounds. Indeterminates easily grow 6 feet or more in height and take up lots of garden space. Flowers develop all summer into the autumn until frost kills plants. Indeterminates are better for those gardeners who just want a few fresh tomatoes every few days over 3-4 months. Indeterminates grow and yield poorly in a container.

Most heirloom tomatoes are indeterminate. Heirloom varieties have become very popular over the past decade. In the Southern Appalachian region (East Tennessee, Southwest Virginia, and Western North Carolina), varieties such as ‘Brandywine’, ‘Mortgage Lifter’, ‘German Johnson’, ‘Mr. Stripey’, and ‘Cherokee Purple’ show up at the annual Tomato Fest in Kingsport, Tennessee every year and win lots of blue ribbons.