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

New Coreopsis Cultivars All The Rage

Posted by Hugh on April 12th, 2016

Coreopsis verticillata at Kingwood Center, Mansfield, Ohio

Coreopsis ‘Jethro Tull’ (photo from ItSaul Plants, Inc.)

Threadleaf coreopsis (Coreopsis verticillata), also called tickseed, is a popular summer flowering perennial. Coreopsis are native to the U.S. and produces hundreds of pale-yellow blooms. Depending on cultivar, plant grows 12 to 18 inches tall and 2 feet wide. Some gardeners even plant old-time favorites like ‘Zagreb’ and ‘Moonbeam’ as annuals (USDA hardiness zones 4 – 9).

Big flower tickseed (C. grandiflora) produces larger flowers on taller plants, up to 3 feet high. Flowers are bright yellow and daisy-like. Many cultivars re-bloom a second and even third time if mowed back after a bloom cycle has finished. They tolerate hot, humid summers, but garden soil should not be allowed to dry out. Height and spread vary by cultivar and level of care (irrigation + fertilizer).

Coreopsis are one of the easiest perennials to grow. For best show plant 3 or more of one cultivar for a sea of color in a sunny front garden border or in containers. Set out plants anytime from late April through September. Plant 12 to 18 inches apart in a sunny spot and in well-drained soil. Plant the crown just at or above the soil surface.

Removing spent flowers encourage re-blooming, prevents reseeding, and gives the flower bed a neater look. Yellow to gold flowers attract numerous nectar seeking bees and butterflies. Leaving the seedpods on plants will attract large numbers of goldfinches.

Divide clumps every 3 years for optimum plant performance. Aphids may be occasionally pests. Powdery and downy mildew on foliage in garden areas with poor air circulation; some cultivars are rated better for mildew resistance.

Recent Coreopsis Introductions:
‘Cosmic Eye’- daisy blooms with wine-red petals, tipped in soft yellow and surrounding an orangey yellow button eye; grows 18 inch high by 24 inch wide. Introduced by Darrell Probst and is reliably hardy in zones 4 – 9 with winter snow cover.

‘Jethro Tull’ – compact grower, 18 inches high by 24 inches wide with dark-green leaves and blanketed with single golden-yellow daisies with a ring of tubular petals; hybrid introduced by ItSaul Plants in Georgia.

‘Mercury Rising’ – another Darryl Probst introduction large velvety-wine daisy flowers with contrasting gold-orange button center, appearing in succession from mid summer to mid autumn. Some flowers may appear frosted in creamy-white. Cut plants by half in mid-July if plants begin to flop. (hardy in zones 4 – 9 with winter snow cover).

‘Route 66’ – threadleaf coreopsis discovered in 2005 in a Pennsylvania garden; plants grow 24-28 inches tall with bright yellow petals with large red eye; long blooming period from late June until mid October.

Summer Blooming ‘Little Lemon’ Goldenrod

Posted by Hugh on April 10th, 2016

Newly Set ‘Little Lemon’ Goldenrod in August

Goldenrods are members of the aster family (Asteraceae); approximately 100 species of goldenrods are native to North America. Across most of the Eastern and Midwestern U.S., goldenrods are frequently spotted growing in moist soils in open farm fields, in ditches, and along edges of streams. The golden yellow blooms attract countless bees, butterflies and other pollinators.

A new addition to my garden is ‘Little Lemon’ goldenrod (Solidago Little Lemon (‘Dansolitlem’ PP17297)]. Little Lemon is an exceptionally compact goldenrod with bright lemony yellow flowers that bloom from late July into August (USDA hardiness zones 5-8). Soft yellow is a sharp departure from the mustard yellow color of most goldenrods. Deadheading will induce secondary flowering into September.

Wild goldenrod species grow tall, much too big for most urban gardens. Compact growing Little Lemon should please city gardeners with limited growing space. Newly set plants should be mulched and watered regularly the first season until established. Established goldenrods are among the most drought tolerant perennials.

Fertilize at planting time and in late winter in successive years with 10-10-10 or equivalent. Few diseases and pests trouble goldenrods. Rust seems to be the biggest culprit, particularly if summer weather is unusually wet. Rust rarely kills goldenrod.

Little Lemon goldenrod combines well with other late summer blooming perennials and annuals such as Japanese asters (Kalimeris), ‘Short and Sassy’ heleniums, blanket flowers (Gaillardia), stone crop (Sedum), and stokes asters (Stokesia) in garden beds and mixed in containers. Their bright yellow flowers are great additions to fresh or dried flower arrangements.

Goldenrods hold their form through most of winter. On a brisk cold winter morning a hoarfrost over the skeletal remains of goldenrods is an inspiring view.

Utilize Sweet Flag For Garden Accent

Posted by Hugh on April 7th, 2016

Acorus gramineus ‘Ogon’

Sweet flag cultivar (Acorus gramineus) is an iris-like perennial usually planted for its wavy drifts of golden yellow foliage. This dwarf ground cover, indigenous to China, Korea and Japan, grows 6-12 inches tall. Sweet flag is a member of the acorus family (Acoraceae) (USDA hardiness zones 6-9 and should be winter protected in zone 5).

Green variegated leaf cultivars with striped yellow or green blades are also available. The narrow leaf blades barely measure ¼ inches across. A bright patch of sweet flag spread slowly by creeping roots (rhizomes). Foliage gives off a citrusy scent when pinched or stepped upon. Sweet flag copes with only light foot traffic. In June or July tiny greenish yellow sedge-like flowers appear followed by tiny fleshy berries; flowers and fruits offer little in ornamental value.

Growing requirements for sweet flag are similar to that of most sedges (Carex spp.). Sweet flag grows in average garden soil and in full sun to partial shade (depending on location). It can tolerate heavy shade but its rich golden hue is lost. To succeed, sweet flag wants above average soil moisture; it thrives in shallow boggy conditions such as around a water garden. Scorched leaf tips arise when the soil becomes parched. In southern climes, plant sweet flag in afternoon shade or full day filtered sunlight. Foliage stays evergreen in warmer zones.

Sweet flag has no serious disease or insect problems. In early spring a single application of slow-release organic base fertilizer is adequate.

Sweet flags are utilized as textural and color accent plants around water gardens, streams, ponds, or in moist open woodland gardens. It is also planted in rock gardens or border fronts. Sweet flag can be used to edge decorative containers.

Leading cultivars:

‘Ogon’ – the most popular form with golden-colored foliage.

‘Minimus Aureus’ – 3-4 inch tall miniature ground cover that forms a golden mat; plant some between stepping stones (emits light citrus fragrance).

‘Variegatus’ – grows 6-9 inches tall with white-and-green striped grassy foliage.

War On Aphids

Posted by Hugh on April 4th, 2016

Aphids on spiraea (picture by Dr. Frank Hale, University of Tennessee Entomologist)

Oleander aphid on Milk Weed (Asclepias)

Aphids are pests that feed on many kinds of garden plants. These tiny insects wreak massive destruction in multiple ways. There are many different kinds (and colors) of aphids. They’re small, 1/16 inch more or less, and feed on plant sap to obtain nutrients. In greenhouses they reproduce without mating; one aphid can start a new colony. Aphids can arrive with plant material, move from one crop to another, or from nearby garden weeds to favorite host plants.

Damage is caused in several ways. Large numbers can lead to reduced growth and vigor. As aphids develop, they deposit a sticky ‘honeydew’ substance on plants on which sooty molds grow – which can spoil the appearance and marketability. Feeding by some kinds causes severe plant distortion. Aphids can transmit disease viruses to healthy plants from sickly ones.

Aphids infest many greenhouse crops, garden vegetables and fruit plants, and landscape trees, shrubs and vines. Common favorites include roses, salvia, impatiens, pansy; vegetables such as pepper, cabbage and kale, tomato; tree fruits such as apple, peach and cherry; and cane fruits such as raspberries and blackberries. A complete list would run many pages long.

Their reproduction rates are incredibly fast and quickly get out of hand inside a home greenhouse where the environmental conditions are perfect. Numbers grow from a few to many thousands in a few weeks. Tiny aphids are often difficult to see and their body colors make them well-camouflaged. Numbers increase when environmental conditions are warm and moist, and plants are well-fertilized.

Don’t invite aphids into your greenhouse and garden. Inspect new plants before purchasing, particularly those bargain plants at flea markets or give-away by other gardeners. Aphid outbreaks can be managed with many effective biological agents and chemical pesticides.

What To Know About Flowering Vines

Posted by Hugh on April 1st, 2016

Hyacinth Bean Vine (Lablab purpureus)

Spanish Flag Vine (Mina lobata)

For some gardeners planting vines is not for the faint of heart. Vines need space, support, training, and for some – lots of pruning. Some vines don’t demand lots of room while others chew up lots of space. Small vines like clematis or annual morning glories (Ipomoea) may be grown in a large patio container for many years on heavy duty cord, wire or wood lattice trellis. Some woody vines become massive and need support on a solidly built pergola. To select the best vine for your space, consider the following tips.

Is the vine an annual or tender perennial or a long-lived woody vine like trumpet (Campsis), climbing hydrangeas (H. petiolaris anomalis), crossvine (Bignonia capreolata), and wisteria (Wisteria spp.)? Long–lived woody vines need to be cut back hard from time to time; the vine’s trunk and main branches may become enormous and need space to grow and a structure sturdy enough to support it.

Annual vines are great for tucking into small garden spaces, including on patios and decks. Instead of building a trellis, you might allow annual morning glories to weave through nearby shrubs and trees for support. Plant the annual vines in decorative containers and climb onto a nearby shrub or tree via tendrils.

Some examples of annual vines include hyacinth bean (Lablab purpureus), climbing black-eyed Susan (Thunbergia alata), Spanish flag (Ipomoea lobata), and morning glory vines. They usually do not hurt adjacent trees for support and die off in fall. Beware – some vines will disperse a large number of seeds.

Vine’s Level Of Annual Maintenance: Woody vines like trumpet vine and wisteria can become pruning nightmares and quickly become unmanageable. These vines grow tall, ramble, and often require working from ladders.

Growing Trilliums

Posted by Hugh on March 30th, 2016

Yellow Trillium at Duke Gardens, Durham, NC

Sweet Betsy Trillium (T. cuneatum)

Trilliums (Trillium spp.) are the beloved native wildflower around the world. Many species are native to the U.S. Five popular U.S. species are great white trillium (T. grandiflorum), yellow trillium (T. luteum), prairie trillium (T. recurvatum), drooping trillium (T. flexipes), and sweet Betsy trillium (T. cuneatum).

For 8 months and more, trilliums are ephermerals or “ghost plants”. Here in the mid-South (USDA hardiness zones 6 -7), they make their appearance in early April and stay around for 8-12 weeks. By the mid-July all evidence of trillium flowers and vegetation has disappeared. Some species may produce bigger and showier flowers, but all exhibit 3 leaves, 3 petals and 3 sepals.

They’re easy to grow and are a long-lived perennials when properly sited in the shady spot or woodland garden. Give them a place of their own where they will be left undisturbed for many years. Trilliums prefer a semi-shaded locale in organically rich, moist, well-drained soil. Prior to planting, amend the soil with loads of well-rotted compost, rotted leaf litter, etc. Keep the area moist in the spring and be patient because new trilliums from seeds may take 6-8 years to initiate flowers. Once the spring flowering cycle has begun, look for them to return and bloom annually.

Keep the bed weeded and add 1-2 inches of an organic mulch annually; feed the area every 1 to 2 years with small amounts of an organically based fertilizer or well-rotted (seed-free) manure. In late winter rake off most accumulated leaf and twig litter as it may prohibit trilliums from poking through. That’s it!

Trilliums may take 7-8 years when started from seed to flower. You do not find them for sale at local garden center,s and some gardeners believe that plants are expensive. This was true until 10 years ago. New methods in propagation have reduced the grower’s production time and plant costs. Often, plants will start blooming within 2-3 years.

Two native e-commerce plant nurseries that sell 2-year old trillium seedlings are Sunshine Farm in Renick, WV and Sunlight Gardens in Andersonville, TN.

Slender Deutzia Is Versatile Landscape Shrub

Posted by Hugh on March 28th, 2016

Deutzia gracilis foliage

‘Nikko’ slender deutzia

Most gardeners have never heard of deutzias (Deutzia spp.) which is very unfortunate. There are many species of deutzias. They bloom in spring and grow into many shapes and sizes.

Slender Deutzia (Deutzia gracilis) is a small densely branched deciduous shrub with upright to slightly arching branching (USDA zones 5-8). This diminutive mid-spring flowering shrub will brighten up any garden with its 2-4 feet high size. Small 1/4 inch wide white bell-shaped flowers cover the shrub for nearly two weeks. Elliptic to lanceolate leaves (to 2.5” long) are deep green with no fall color.

All are easily to grow in average, medium moisture, well-drained soil, and in full sun to partial shade. Best flowering occurs in full sun. Stems are wiry (“slender”) and are somewhat short-lived, requiring minor annual pruning immediately after flowering to remove dead twigs and tips of branches.

While disease and pest problems are rarely serious, keep an eye out for occasional aphids, leafminers, and leaf spots.

Exceptional cultivars:

‘Nikko’ is an outstanding low-growing selection that grows more compact form than the species. Well suited for small spaces or used as a groundcover, it forms a graceful, spreading mound 2 feet in high and spread to 5 feet in 10 years. Its gently arching branches are covered by white flowers. It makes a great container shrub or may cascade over a low wall. (National Arboretum introduction).

Chardonnay Pearls® is singled out for its attractive lemon-lime foliage and unique floral buds. This compact shrub grows to 3 feet tall and branches freely. Its unique pearl-white flower buds open to fragrant white flowers in May.

Angel Trumpet Blooms All Summer Long

Posted by Hugh on March 26th, 2016

Container grown plant

Brugmansia ‘Peaches and Cream’

Angel trumpet (Brugmansia) is tropical plant native from Venezuela to Peru (USDA hardiness zones 7-b to 10). Plants have shown to be surprising hardy outdoors in zone 6-b in a protected area. This beautiful shrub, sometimes grown in a tree form, reaches heights of 6-10 feet. It is a member of the Solanaceae family (tomato, potato, petunia, nicotiana and other great garden plants).

They are highly prized for its enormous fragrant trumpet-shaped flowers, some 10 inches or more in length. The exotic flowers emit a strong lemony scent over the evening hours; they’re pollinated by moths. Flower colors range from white, orange, yellow, and pink. Some varieties exhibit variegated foliage.

If you live in a northerly area, purchase angel trumpet in early spring and grow the plant indoors to get it well-established; move it outdoors after threat of frost has ended. Plant angel trumpet in a large 12-16 inch (or more) wide container in well-drained potting soil (media). If you live in a mild temperate climate such as in the southern U.S. or California, plant directly into a garden bed in a well-drained soil and keep well mulched. You may want to place the heavy container on a dolly and roll it around to different locations of the garden.

This fast growing plant demands lots of water, but it fails when over-watered. Keep soil moist and let soil dry out between waterings. Fertilize with a water-soluble fertilizer such as Miracle-Gro®, Peters®, and Schultz®. In the summer, when plant growth is more rapid and most blooms form, feed every two weeks according to package directions. Cut back on fertilizing in fall and do not feed over winter.

In northerly areas, bring angel trumpet(s) inside as outdoor temperatures begin to drop below 40°F. If you garden where winters are mild, protect by setting poles around it and wrap with milky white plastic. You may opt to cut back entire plant to the ground and mulch heavily to protect the crown during winter.

Occasionally snip off old spent flowers, and spur new growth. A container plant can be cut to the ground for winter.

For a large selection of angel trumpet hybrids, shop on-line at Plant Delights Nursery in Raleigh, NC.

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).