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

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.

How To Grow Milkweeds

Posted by Hugh on June 2nd, 2014

Common milkweed (Asclepias tuberosa)

Milkweeds, aka butterfly weed (Asclepias spp.), are the favorite food of the Monarch butterfly. Farmers and most gardeners rate them as a noxious weeds. They’re commonly spotted growing along roadsides or in unplowed ground (USDA hardiness zones 3-9). Milkweeds average 3 feet in height, but may vary from 2-6 feet depending on species. Most species are classified as herbaceous perennials.

As its common name suggests, milky sap pours out from the stems when cut. Leaves vary in shape with species (see below) and are either light to dark green in color. Flower color also varies by milkweed species, from pink, purple, or orange. They bloom from June to August and flowers of some species are fragrant. The cucumber-like seed pods set in autumn. Seed pods open and release hundreds of aerodynamic seeds carry over many miles by the wind.

Beginning in the southern U.S. and progressing northward U.S., milkweed blooming time coincides with the arrival of Monarch butterflies in your growing zone. Flowers are an important source of nectar for many insect pollinators, including butterflies and hummingbirds. Milkweeds are the primary host for monarch butterfly larvae (caterpillars). Female monarchs deposit their eggs on the milkweed plants and emerging caterpillars (larvae) emerge feast on the leaves. The resting pupa stage is on milkweeds.

Milkweeds are toxic to most predators of Monarchs, but are not harmful to feeding Monarch caterpillars. The caterpillars do not die, but the leaf toxins make the Monarchs poisonous to predators! There is tremendous variation in the poison levels of the foliage. A. tuberosa are rated low; A. verticillata and A. viridis are rated among the highest. Historically, milkweeds have been valued for their medicinal properties.

Milkweeds grow best in full sun and in a well-drained soil. Some are very drought tolerant and thrive in ordinary soils; they need little or no fertilizing. Some cope with wet soil conditions and others do not. Milkweeds blend well among other butterfly floral favorites in mixed borders, meadows and natural areas.

You may collect and save milkweed seeds in early fall. The seeds are best sown in the soil to overwinter there and germinate in the spring. You may also opt to sow vernalized (pre-chilled) seeds in a greenhouse or sun room in late winter or transplanted into outdoor beds after the danger of frost has passed in spring. Keep the soil moist but not soggy.

When plants have two sets of leaves, transplant them to their permanent, sunny location outside. Space plants about two feet apart, if planting in a row. A milkweed plant produces a long taproot which does not like to be disturbed after planting. Mulch can help conserve water.

The following seven (7) milkweed species are favorites of Monarch butterflies, bees, and other butterflies. Most are available from perennial and wildflower sources on-line.
Butterfly weed (A. tuberosa) – showy orange flowers; popular garden choice because of hardiness, long-life, and non-invasiveness; 1-2 feet height
Common milkweed (A. syriacus) – purple flowers blooms; aggressively spreads by rhizomes and self-seeds; 3 feet height.
Swamp milkweed (A. incarnata) – red flowers; 3-4 feet height
White milkweed (A. variegata) – striking clusters of snowy white flowers; 1-4 feet height
Whorled milkweed (A.verticillata) – small white flowers; bland narrow needle-like leaves; 1-3 feet height
Spider milkweed (A.viridis) – spring blooming green colored flowers; 1 foot height
Purple milkweed (A. purpurascens) – magenta colored flowers; 3 feet height
Scarlet milkweed (A. curassavica) – red and orange flowers; 2-3 feet height; annual (zone 9-11)

Doghobble for Shady Landscape Areas

Posted by Hugh on May 30th, 2014

cultivar -'Rainbow'

Mountain doghobble (Leucothoe fontanesiana) is native to woodland areas in the Southern Appalachian region (USDA zones 6 and 7). Florida coast leucothoe (L. axillaris) is another regional favorite, native from Virginia south to Florida. Over time it grow tall, usually 3-4 feet high as a rambling ground cover. Every 3 to 4 years hand pruning is needed to hold doghobbles to a desired location and height.

In nature doghobbles grow in acidic, well-drained, organically rich soil, often in close association with other U.S. native acid-loving shrubs such as rhododendrons, azaleas, and mountain laurels (Kalmia spp.) and selected ferns. Soil pHs in the range of 5.0 to 5.5 are preferred. Two-year established plants exhibit good drought tolerance; newly planted doghobbles require periodic watering when seasonal moisture is not plentiful from rain or snow. Mulching is often beneficial. Established plants rarely require fertilizing; use an acidifying fertilizer such as Miracle-Gro™ or Schultz™ as needed.

Doghobble is dominant under dappled or partial shade and grows less vigorously under deep shade. Florida coast will grow in full sun under good moisture. Both species are excellent choices as a shrubby ground cover planted under landscape shade trees, areas formerly occupied by ground hugging junipers. Often, new landscapes are bathe in full sun, but sun-loving ground covers like cotoneasters and junipers decline as the trees cast more shade.

Doghobbles produce creamy white fragrant flowers in May; their slight fragrance filters through their small space over the 2-3 week bloom time. Doghobbles are mostly insect and disease resistant, but leaf spot problems may occasionally ramp up in wet hot summers. Florida coast doghobble appears to be more leaf spot resistant than mountain doghobble.

Photo: ‘Rainbow’ is a popular cultivar with 3-color, variegated foliage.

Allium ‘Millennium’ Outstanding Summer Blooming Ground Cover

Posted by Hugh on May 26th, 2014

‘Millenium’ allium at Kingwood Center, Mansfield, Ohio

Allium ‘Millennium’ is a rhizomatous type allium (onion) introduced by plant breeder Mark McDonough over a decade ago (USDA hardiness zones 5-8). In nursery catalogs it is sometimes listed Allium nutans‘Millennium’. Fleshy strap-like 12-inch long glossy green foliage emits a slight oniony smell when crushed.

‘Millennium’ is a rhizomatous (clump growing) long-lived perennial. Individual plants grow vigorously, 15-20 inches high (in bloom), and spread 10-15 inches. Round-headed rosy purple flowers, 2 inches or more in diameter, appear in mid to late July. They stay in bloom well into August. Millennium tends to bloom 7 to 10 days later, compared to ‘Pink Feathers’, another clump forming cultivar.

Tight mounds of glossy foliage, beautiful flowers, and striking seed heads offer multi-season interest. Nectar-seeking honeybees and butterflies hone in on the flowers. Clumping alliums do not seed-in and become weedy like the bulbous onion types. The dry flower stalks stand upright thru the winter months.

Clumping alliums grow in average well-drained, slightly acidic soils (pH 5.5 to 7.0). They are frequently found in open moist sites such as in rain gardens. One-year established plants become exceptionally drought tolerant and thrive in xeric rock garden soils. Grow in either full to partial sunlight (minimum 4-5 hours) is preferred to maintain their tight clumping ground cover.

Plants may be dug up and divided either in mid-autumn or in early spring before new growth emerges. Alliums are also deer and rabbit proof and usually disease and pest free.