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

Japanese Pagoda Tree Becoming Popular In U.S. Cities

Posted by Hugh on July 1st, 2014

Japanese Pagoda Tree in Raleigh, NC

"String of Pearls" Fruits

U.S. east coast cities are finally planting Japanese Pagodatree (Styphnolobium japonicum). This medium-sized tree grows to 50 feet high, but 75 feet is not uncommon in the southeastern U.S. Pagodatree is native to eastern Asia (USDA hardiness zones 4 –8) where it is more known as Scholar tree. In the early 20th century it was frequently seen planted around schools and Buddhist temples in Japan.

Pagodatree grows in full to partial sun (6-hours minimum) and in a moist well-drained, slightly acidic soil. Pagodatree tolerates urban drought, air pollution, and moderate salinity around coastal areas. The tree has no serious disease or insect problems. A small number of cultivars, including weeping and upright (columnar) forms, are listed.

‘Regent’ is the most popular cultivar, high valued as a vigorous grower and lustrous green foliage. A newly planted tree blooms earlier and exhibits superior disease resistance than the species. Annual growth rate ranges from 18 to 24 inches. Summer foliage is comprised of 8-10 inch long, pinnately compound leaflets numbering 7 to 17. In some years its golden fall color can be spectacular.

What really makes pagodatree special is its July-August flowering time, when few landscape trees are blooming. Its pea-like, creamy-white flowers are showy and fragrant. Flower clusters, 12 inches long and wide, drape from branch tips. Another unique feature is the 3 to 8 inches long green “string of pearls” fruits which form in late summer and persist way into fall. Birds don’t appear drawn to the berries which shrivel to black and linger through the winter. By spring the tree has self-pruned many of the twiggy fruit rachises.

A young pagoda tree exhibits a semi-upright, vase shape habit and develops a full rounded canopy as the tree ages. A mature tree exhibits a lovely grayish-brown furrowed bark. Pagodatree is related to Mescal Bean tree (Calia secundiflora), native to Southern Texas into Mexico (Zones 8-10).

Blazing Star– Electric Summer Flowering Perennial

Posted by Hugh on June 27th, 2014

Blazing star (liatris)

Blazing star (Liatris spp.) is a popular summer flowering perennial. Also called gayfeather, it belongs in the aster family. This tall, upright, clump-forming perennial is found in moist meadows and at the edge of a marsh. (USDA hardiness zones 3-9). Liatris makes an excellent addition to a rain garden.

Its distinctively reddish-purple flower spikes win over a lot of gardeners. Individual flowers, each only ¾ inches across, comprise the floral head which open from the top down to the base. White blooming forms are also available. Multiple stalks rise from the crown, cloth in narrow, grass-like, medium-green leaves. Stem leaves are long and gradually decrease in size near the top. L. spicata ‘Kobold’ is an outstanding compact cultivar that has become the standard bearer in most gardens.

Blazing star grows 2 to 5 feet tall, depending on the fertility of the garden soil. Space plants 12 to 18 inches apart. Once established, plants require very little care. They thrive in their garden space upwards of 3 years, then should be divided, or replaced with new plants.

Blazing star grows in average well-drained soils in full sun. This prairie species is not tolerant of poor drained soils, particularly soggy soils in winter. It excels in moist, fertile soils. Other Liatris species demonstrate better drought tolerance. It’s tolerant of summer heat and humidity. They can be grown from seed, but some are slow to establish. Kobold may spread from seed in its garden spot.

The brightly colored blooms attract numerous birds, butterflies, and unfortunately rabbits. Deadheading will spur re-bloom within 4-5 weeks. A mid-summer fertilizer is advised. Blazing star suffers from no serious insect or disease problems. Taller plants may require staking or other support; ‘Kobold’ rarely requires staking. Flowers make excellent fresh and dried cutflowers.

Lovely Tall Stewartia Deserves Your Attention

Posted by Hugh on June 24th, 2014

June-flowering Tall Stewartia at Biltmore Estates, Asheville, NC

Not enough gardeners know about stewartias (Stewartia spp.). Six species are found under cultivation, 2 native to the U.S. and 4 of Asian origin. One of the rarest seen in U.S. gardens is tall stewartia (S. monadelpha) (USDA hardiness zones 5-8). Tall stewartia is a more site forgiving than Japanese stewartia (S. pseudocamellia), the most popular planted in U. S. gardens.

Tall stewartia develops into a 25 to 30 feet high shrub or small tree. The bark on the trunk and adjacent branches gradually ages to a lovely cinnamon tint. Spring/summer foliage is medium green, 3-inches long, and slightly glossy on the surface. Leaves turn red to burgundy red before abcising in late autumn. Numerous small white frilly petalled flowers with gold stamens appear in June. By early fall reddish brown fruits have fully developed and are of little ornamental value.

All stewartias are fussy in one respect. Their roots should be planted in a moderately acidic (pH 5.8 to 6.8), organically rich, and most important, in a well-drained soil. Just a hint of soggy ground might be enough to trigger an outbreak of root rot disease and their demise. Extreme summer drought is also punishing to stewartias. Planting on a slope is often a wise practice.

Tall stewartia exhibits better heat tolerance than other species. It is best protected from direct mid-day sun in zone 7 and further south. Most stewartias are meant to be viewed 12 months a year. Plant them in full morning sunlight nearby a patio or deck, or near a window where it may be viewed from inside your home. Install up-lighting to capture branching silhouette and lovely flaky cinnamon colored bark in the evening hours. Cinnamon bark coloration gets better as the tree ages.

Pests and other diseases are rarely problems except for Japanese beetles, which can skeltonize leaves over 3 to 4 week time span. Numerous pesticides, including short-lived pyrethrins or insecticidal soaps, are effective, but must be reapplied every 3-4 days until the bug onslaught has subsided.

Gladiolas Are Wonderful Cutflowers

Posted by Hugh on June 21st, 2014

Glad in the summer garden

Across most regions of the U.S., planting gladiola corms (they’re not really “bulbs”) begins a week before the probable frost-free date has passed in the spring. Stagger individual plantings every 2-3 weeks through mid- July. Many people opt to grow them as cutflowers for their homes.

Purchase large or premium sized corms that measure 1 1/4 to 1 1/2 inches across; quality corms produce tall floral scapes in wide color array. Floral scapes range from 18 to 36 inches high depending on variety. Bargain bulbs produce smaller sized individual flowers and shorter scapes.

Glads grow in full sun and in average well-drained soil. Compost-rich, slightly acidic soil is best. Roto-till the ground to at least a 6-inch depth. Add a slow-release fertilizer designated for flowering bulbs according to package directions.

Sow bulbs 4-6 inches deep and 6 inches apart, pointy side up. If rainfall is lacking, glads should be irrigated weekly at least 1 inch of water. Add a 2-3 inch layer of organic mulch to conserve soil moisture. Staking each row of glads as plants often become top heavy when floral scapes are heavily budded up. Place a heavy duty post or stake at opposite ends of the row and weave two sturdy cords through the glads about 2-3 weeks prior to bloom when scapes are beginning to form.

Thrips are a serious pest of glads. Thrips are very tiny and tend to congregate inside the flowers, reducing floral life. Several insecticides, including soaps, are labeled for managing heavy thrip populations.

In most areas of the U.S. where winter temperature dip below 25º F, treat gladiolas as annuals (USDA hardiness zone 7 and northward). Some gardeners dig, clean off soil, and divide the corms in the fall. Grade by size and throw away all rotted or poorly formed corms. Undersized corms, called “cormels”, are usually discarded or planted in a nursery bed next spring to grow and size up. During winter glads are stored in mesh bags and stored in a cool area (36-41º F) that does not freeze.

Expect Garden Visits From Pipevine Swallowtail

Posted by Hugh on June 18th, 2014

Pipevine swallowtail on thistle

Pipevine Swallowtail (Battus philenor) is a beautiful butterfly common over a large geographic area of North and Central America. Pipevine swallowtail can be sighted in open meadows, parks, along streams, and hopefully in your garden.

The butterfly larvae (caterpillars) feed on plant members of the pipevine family (Aristolochiaceae), particularly Dutchman’s pipevine (Aristolochia spp.), including Virginia snakeroot. This native vine, found in the Eastern United States, is a fast-growing perennial that can be easily trained to a fence or trellis. It may take 1-2 years for a pipevine to mature into a sizeable vine to become noticed.

Initially, young black or red caterpillars are not poisonous. They feed the poisonous leaves of pipevine and become toxic to predators, particularly birds; but the swallowtails are not harmed. The caterpillars generally eat for 10-15 days, grow, and mature. Full grown caterpillars are mostly black and covered with red spines. Other similarly colored swallowtail species try to mimic the pipevine swallowtail.

An adult butterfly develops quickly inside the green and brown chrysalis and emerges to fly, mate, and lay eggs over 7-10 days. Swallowtail wing span averages 3 to 3 ½ inches across. As autumn nears, pipevine swallowtail may remain in the chrysalis stage through the winter and emerge next spring. In areas with a long growing season, it may reproduce twice, but often the second generation overwinters in the chrysalis.

Pipevine swallowtail butterflies drink nectar from a large selection of flowers. Favorite nectar plants include milkweeds (Asclepias spp.), thistles, honeysuckles (Lonicera spp.), joe pye (Eupatorium spp.), lilac, anise hyssop (Agastache), phlox, purple coneflower, clover, beebalm (Monarda spp.), teasel, garden sage (Salvia), buttonbush, butterfly bush (Buddleia), azaleas, summersweet shrub (Clethra), and many others.

‘Going Bananas’ Daylily Blooms Continuously

Posted by Hugh on June 15th, 2014

Hemerocallis 'Going Bananas' Flowers Wide Open

‘Going Bananas’ is an extended-blooming daylily. This diploid cultivar flowers a three month long continuous blooming cycle (rather than stopping and starting again) from early summer into fall. Each bloom stays open longer, at least 16 hours per day. Each trumpet-shaped flower opens wider, a new genetic trait in daylilies.

Going Bananas features slightly fragrant, 4-inch wide clear lemon yellow blooms with ruffled edge. It is a hybrid between Hemerocallis ‘Happy Returns’ and H. ‘Brocaded Gown’. Flowers are lighter yellow and wider opened than its parents. It form a large number of scapes, each bearing 10-15 buds. Going Bananas is extremely vigorous and clumps should be divided every 4-5 years in the fall to maintain vigor.

Daylilies grow in average, medium moist, well-drained soil in full sun to part shade. Deadhead spent flowers daily for neatness and remove the woody scapes when completely bloomed out. Plants are tolerant of summer heat and humidity, but relish deep watering over dry spells to maintain foliage attractiveness.

Daylilies are popular sun perennials planted singly with other flowers in a garden or a container. Several can be massed together as a ground cover on steep slopes to retard soil erosion. When not in flower, the grass-like foliage is valued for color and texture. Daylilies are extremely adaptable perennials with no serious insect or disease problems.

‘Stella D’Oro’- First And Last Daylily To Bloom

Posted by Hugh on June 13th, 2014

‘Stella d’Oro’ daylily

For over a quarter of a century, wherever daylilies (Hemerocallus spp.) grow, you will find the very popular gold-flowered ‘Stella d’Oro’ daylily (USDA hardiness zones 2-9). It’s one of a few daylilies that blooms 3 out of 4 seasons. Its small size makes it an ideal choice as a ground cover.

This short clump growing daylily grows 10 to 15 inches tall and 15 to 18 inches spread with grass-like foliage. Blooms measure 3-inches across. Multiple uses include in rock gardens, front of beds or as edging, or planted in a container. Several plants grouped together make them stand out.

Stella d’Oro grows in an average soil that is adequately drained. Good loamy soil is preferred. Full to partial sun (6 hours minimum) is ideal for maximum flowering. Purchase daylily divisions that have 2 to 3 fans and spaced them 18 inches apart. Cut foliage back to 6 to 8 inches.

Every 5-6 years daylily clumps should be dug up and divided. Early fall is the best time to divide daylilies. Late winter is also a good replanting time. Mulching fall planted beds reduces problems with frost heaving and offers some winter protection.

Don’t allow daylilies to become overcrowded by surrounding shrubs, perennials, and weeds. Plants are highly disease and pest resistant. Stella d’Oro is moderately susceptible to daylily rust, a more serious problem in the southern U.S. Rabbits don’t bother daylilies.

Feed all daylilies in early spring with a slow release fertilizer such as Osmocote 14-14-14, Nutricote 13-13-13, or equivalent products. For reblooming varieties like Stella d’Oro, should be fed a second time in early July with a water soluble fertilizer such as MiracleGro™, Schultz™, Nature’s Source™, or Daniels™. Do not allow them to suffer through a summer drought.

Stella d’Oro has earned the Stout Medal, the American Hemerocallus Society’s highest award.

‘Hyperion’ Daylily Still Popular 90 Years Later

Posted by Hugh on June 11th, 2014

'Hyperion' Daylily at a Columbus, Ohio Mall

‘Hyperion’, a mid-season June-July bloomer, was designated the 2011 Award of Merit winner by the British Horticultural Society. That’s not bad for a daylily (Hemerocallus spp.) variety that was introduced in 1924. It’s still very popular among gardeners and garden designers. You see it everywhere, planted in shopping mall parking lots or along NC highways.

‘Hyperion’ is a deciduous diploid cultivar (USDA hardiness zones 3-8). It adds an old-fashioned elegance to any sunny garden spot as well a sweet lemony fragrance. For almost a month long, its striking 5-inch clear yellow blooms stand 30-36 inches tall. The 24-inch mounds of medium green, strap-like foliage stay mostly blemish-free throughout the summer.

Daylilies thrive in full sunlight (6-hours minimum) and in average moist well-drained soils. They do prefer a deep, fertile loam. Established plants are drought tolerant, but do need minimal watering their first summer during dry spells. It is not unusual, particularly during a wet summer, to develop a brief second cycle of flowering. You may want to deadhead spent floral scapes for neatness.

Hyperion is excellent for naturalizing and a good choice for erosion control on steep embankments. Clumps grow rapidly should be divided every 5 years to maintain vigor and prevent overcrowding. Late summer or late winter (before the spring growth surge) is a good time to divide daylilies. Feed plants in early spring with a slow release fertilizer such as Nutricote™ or Osmocote™. Spring mulching aids in weed suppression and less watering.

Daylilies attract numerous butterflies, and rabbits don’t appear to favor them. Deer, however, are a different creature!

Smoketree – Reliable Urban Tree Or Shrub

Posted by Hugh on June 8th, 2014

Billowy Fowers of Common Smoketree

“Smokin” may be a corny way to describe the billowy inflorescence (floral head) of common smoketree (Cotinus coggygria). It is native from eastern European to central China. U.S. native, American smoketree (Cotinus obovatus), is far less popular as its inflorescence is much smaller and less showy.

Dusky 6-8 inch diameter ball-shaped inflorescences appear in late May and remain a stunning sight through the month of June in the Southern Appalachian region (USDA hardiness zones 6 and 7).

Common smoketree is grown as a shrub or “smokebush”, but many gardeners eventually wind up shaping it into a multi-trunk small tree. As a small tree it may reach a mature height of 15-20 feet high and 12-15 feet wide, a good fit for most small urban gardens. A young trees or shrubs may start out growing asymmetrical, branched heavily on one side; within a few years the plant grows more symmetrical.

Smoketree grows best out in the open under full sun and in well-drained soils. A young tree establishes quickly, if kept adequately watered during its first two summers. Established trees demonstrate above-average drought tolerance. There are very few serious insect and disease problems that bother smoketree.

Circular spring leaves emerge a rich green, red, or purple color and expand to 1 ½ to 3 inches wide. Foliage of modern cultivars are colorfast and do not fade over the summer. Occasionally, autumn foliage colors are blends of red, orange, yellow, and/ or purple.

Cultivars with purple or burgundy foliage and larger billowy (smoky) inflorescences are in current vogue. Verify the hardiness of your favorite cultivar before planting as some purple-leaved cultivars are questionable.

‘Grace’, a hybrid cross of European and American smoketree is very popular and winter hardy. ‘Nordine’, ‘Royal Purple’ and ‘Velvet Cloak’ are popular purple leaved selections. ‘Golden Ghost’ is a beautiful gold leaf form.

Burgundy and gold leaf cultivars are also grown as foliage perennials. The previous year’s stems are cutback near the ground in late winter to show-off the colorful foliage and are devoid of flowers.

Mexican Sycamore Thrives In Warm Wet Locales

Posted by Hugh on June 5th, 2014

Mexican Sycamore at Dallas Arboretum (late December)

Mexican Sycamore (Platanus mexicana) is a fast growing deciduous tree hardy in Northeast Mexico (USDA hardiness zones 7 -10) where it inhabits soils that are semi-arid and subject to periodic flooding. Summer leaves are medium-sized, only 8-inches wide. When leaves fall away in autumn its beautiful chalky white bark is a winter asset. The bark peels off in thin strips and eventually becomes a maintenance chore as the tree develops in size.

This large tree grows at a torrid pace, 50-80 feet tall and 30-40 feet wide, with a very aggressive root system. A 10- year old specimen at the Dallas Arboretum was already 25 feet high and 15 feet wide under regular irrigation. Susan Morgan, Dallas, TX horticulturist, reports that Mexican sycamore has become a favorite with arboretum staff. Roots tolerate periodic flooding. It is highly resistant to leaf scorch compared to American sycamore (P. occidentalis).

Large palmate leaves are silvery above and silvery and fuzzy underneath. Tree is monecious, with male and female flowers separated on the same tree. Sycamores are often pollinated by wind. Female flowers will develop round bristly balls which many people call “gumballs”. An established tree exhibits exceptional drought tolerance. The arboretum trees were grown from seed.

Fall leaf color is quite variable from one location to the next as well as environmental conditions during the growing year. Under ideal rainfall and soil moisture leaves take on a rich golden color. This south of the border species adapts to alkaline soils, an unusual trait for sycamore.