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

The Mountain Mints – The Pollinators’ Favorite

Posted by Hugh on May 11th, 2020

Mountain mints (Pycnanthemum spp.) are clump-forming native perennials. They typically grow 1-3 feet tall depending on species (USDA hardiness zones 4 – 8). About 20 species of mountain mints are found in the southeastern U.S. As their name suggests, they belong to the mint family, very evident by their square stems and aromatic leaves when crushed. Botanically, they’re also closely related to beebalms (Monarda). Mountain mints grow in open woodlands, dry prairies, and grassy meadows.

Mountain mints are rhizomatous perennials that grow 2 to 3 feet tall and spread as wide as site conditions allow. Their slender upright stems have oppositely arranged leaves that are either broadly lanceolate in form or narrow and willow-like in appearance.

Only two mountain mint species will be highlighted here. Slender mountain mint (P. tenuifolium), also called common horsemint or Virginia thyme, is easily identified by its narrow, almost needle-like foliage and are covered with small ¼ inch white tubular flowers with purple anthers in mid-summer (in Tennessee).

Number two is short-tooth mountain mint (P. muticum) which grows slightly more compact and its growth rate is more aggressive. Its foliage is very different and more lustrous, 1-3 inch long, broader (½ -1 inch across) and pointed leaf tips. Clusters of tiny tubular white to pinkish flowers appear in mid-summer. Flowers are accompanied with showy frosted (silvery) bracts.

Blooming period lasts 4-6 weeks, from early to mid-summer. Leaves emit a mild mint fragrance and flowers are not fragrant. Slender mountain mint is highly rated by the Xerces Society, with designated “Special Value” to Native Bees, Bumblebees, and Honey Bees. Flowers of mountain mints attract a wide range of insects including many kinds of bees and butterflies.

For best flowering, mountain mints should be grown in full sun, but do tolerate light shade. Slender mountain mint is rated as more drought tolerant. No serious insect or disease problems trouble the mountain mints. Foliar rust disease may occur in wet summers.

Easily grown from seed, these two species can be started indoors in late winter. OR, sow seeds outdoors after the threat of frost has past in your area; plants should be well established by the end of their first growing season. Established plants have a taproot and spread via rhizomes. Control their spread by mowing or trimming. Mountain mints are easily propagated by cuttings and clump division.

Mountain mints naturalize freely in native plant gardens, butterfly gardens or meadows, garden borders. The foliage is a natural mosquito repellent; the minty leaves can be added to teas.

Growing Coneflowers

Posted by Hugh on May 6th, 2020

*Echinacea purpurea* ‘Pow Wow White’ – highly dependable variety

No question, coneflowers have changed greatly over the past quarter century. Varieties are now available in many color shades and plants demonstrate improved longevity. Current cultivars grow alot shorter. However, some hybrid forms have been disappointing, barely surviving 1-2 years.

When choosing coneflowers, Purple Coneflower (Echinacea purpurea) is my #1 favorite for dependability (USDA hardiness zones 3-8). The species is native to most of the Eastern and Midwestern U.S. They bloom in July, August, and into September, their nectar-filled flowers attract butterflies and bees, and their winter seed heads provide food for birds and other critters.

Yellow Coneflower (Echinacea paradoxa) is native to the Ozark region in Missouri and Arkansas. The yellow blooming E. paradoxa have been bred with E. purpurea. Flowering starts in June, and puts on a long show even as the petals fade. This species has a small geographic range due to habitat loss.

Pale Purple Coneflower (Echinacea pallida) are native from the central U.S. Petals tend to be long, narrow, and droopy along with washed out lavender color. Leaves and stems are particularly fuzzy. They bloom from June to July and grow in most U.S. gardens under proper care.

Tennessee Coneflower (Echinacea tennesseensis) are native the state, but their habitat has been in decline over the past half century. Only recently has it been removed from the endangered species list. It is a mid-summer bloomer and grows 2 to 2 ½ feet tall.

Coneflowers perform best in full sun and within a low to moderate range of soil fertility. While good soil drainage and watering during prolonged dry spells are good practice. Keep in mind that most coneflowers establish deep taproots and resent constant irrigation and over-feeding. To insure their winter survival, coneflowers are best planted before July 1st.

*E. tennesseensis –* important in breeding new hybrid coneflowers

Golden Chain Tree

Posted by Hugh on May 1st, 2020

Golden Chain Tree (Laburnum anagyroides) is a small deciduous tree or large shrub. This small landscape tree is a member of the Bean Family (Fabaceae) and is native to central Europe (USDA hardiness zones 5 to 7).
It is rated as a short-lived tree that grows to 25 or 30 feet in height as a tree and 15-20 feet tall as a multi-stemmed shrub.

Each leaf is composed of three leaflets, long-stalked (petioled), and arranged alternately on the stem. Foliage appears first before flowers. The pea-like golden flowers form in long drooping clusters. Long, dangling, multi-clusters of bright yellow, wisteria-like flowers are a spectacular sight in late spring. Long flattened bean-like pods soon develop and ripen in early fall. The popular hybrid form ‘Voss’ tends to produce fewer pods than either of its parents.

Golden Chain Tree grows in full to part sun, but prefers light shade in mid-afternoon (Zones 6-8). It is a fairly easy grower in any well drained soil. The tree often fails when planted on water logged ground. Regarding soil pH, it grows well in slightly acidic, neutral, or slightly alkaline soils.

Young trees should be staked for support and trained to develop a strong central leader. Prune out weak secondary leaders and promote strong lateral branches. This weak wooded tree may be broken by winter ice storms. Annual spring pruning help to rejuvenate the tree’s framework.

Cultivar: ‘Voss’ Golden Chain Tree (Laburnum x watereri ‘Vossii’) is cultivated hybrid cross between two species – L. alpinum and L. anagyroides. The cultivar, introduced in Holland in the late 19th century, is rated as slightly more heat tolerant. Voss was selected for its more dense growth habit and long flowering racemes of up to two feet.

All parts of this plant are HIGHLY TOXIC (poisonous). Keep pets and children away from the tree. Stem cankering (pitting), leaf spot diseases and aphids may be occasional problems.

Golden Chain Tree is primarily available from on-line specialty nurseries.

Golden Chain Tree

Growing Angel Trumpet (Brugmansia)

Posted by Hugh on April 26th, 2020

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

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

If you live in a northerly area, purchase angel trumpet in very early spring and grow it indoors to get it better established. Move the plant outdoors after threat of frost has passed. Plant angel trumpet in a large 16 inch wide (or bigger) container in well-drained potting soil (media). If you live in a mild temperate climate (zone 7 or higher), plant directly into a garden bed in a well-drained soil and keep well mulched. You may desire to relocate the weighty container atop a dolly around to various locations of the garden.

This fast growing plant demands lots of water, but will fail if constantly over-watered. Keep soil moist but allow soil dry slightly 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 2-3 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 to spur new growth. A container plant should be cutback to the ground for winter. Beware: sap from this plant is highly poisonous when ingested by humans, pets, or livestock.

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

Wet And Wonderful

Posted by Hugh on April 21st, 2020

Rodgersia pinnata ‘Superba’

Ligularia dentata

Two outstanding summer flowering perennials are Rodgersia (two forms) and Ligularia. Both are grown for their broad foliage and showy flowers. They share one special need: consistent soil moisture through the spring and summer months. Don’t attempt to grow either one of these awesome plants unless their water needs will be satisfied. These plants prefer wet, boggy feet (roots).

Rodgersias (Rodgersia pinnata) sport bold pinnately compound leaves that emerge with a dark bronze tint. Leaves measure more than a foot wide and 3-4 foot high perennial. In early summer, white bloom panicles rise 2 to 3 feet above the foliage and bloom over 3 to 4 weeks. A secondary species, Chestnut-leaved Rodgersia (R. aesculifolia), is another clump form with bold green foliage and bears creamy-white flowers in mid-summer (USDA hardiness zones 5 to 8).

Varieties of rodgersia: ‘Chocolate Wing’ — cherry blossom pink and cream blooms); ‘Alba’- white flowers and dark green leaves/bronze veining.

Ligularias (ligs) are big leafy perennials whose roots must be kept constantly moist so that leaves don’t wilt or “faint”. Even after a summer shower, ligs may still go through a brief spell fainting in the mid-afternoon due to summer heat and water loss from transpiration. By early evening the leaves recover fully hydrated.

L. stenocephala ‘The Rocket’

Bigleaf ligs (L. dentata) and narrow-spiked ligularias (L. stenocephala), aka “golden ray”, grow well in temperate climes (USDA hardiness zones 6 and 7). Tropical species are listed under the genus Farfugium (zones 7b -10).

Both ligularias (ligs) and rodgersia demand moist soils and in part day sun tor light shade. Site them nearby water features like within the splash-zone of a waterfall. They grow exceptionally well along woodland creeks.

When properly sited, the foliage remains blemish-free all season long. Disease and pest problems are rare if growing conditions are ideal. Deer and rabbits rarely trouble them.

Planting in containers: plant a single crown into a 3 to 5 gallon size container filled with humus-rich potting soil. To restrict most water loss, line the bottom of the container with plastic shopping bags. This reduces irrigation needs that saves on your monthly water bill.

New Weigelas Keep Coming

Posted by Hugh on April 16th, 2020

‘Burgundy Fire’ weigela

‘Wine and Roses’ weigela

Native to Japan, Korea, and China, flowering weigelas (Weigela florida) are reliable old-fashioned shrubs bearing pink or rose colored blooms in mid-spring. This deciduous shrub has an arching branch habit. New weigelas are now appearing at local garden centers. Older cultivars, typically 6 to 9 feet in height, are being replaced with compact 2 – 5 feet forms.

Pink and red color flower shades appear in late spring or early summer, some with stunning purple or variegated foliage. Flowers attract bees, butterflies, and an occasional hummingbird or two.

Plant weigela in full or partially sunny garden bed or a large container. This deciduous shrub prefers a compost-rich well-drained soil. Irrigate in summer if weekly rainfall amounts fall below one inch. Feed weigela in spring with a slow-release shrub fertilizer.

Prune away winter dieback in early spring or after flowering finishes. Any other pruning can wait until flowers fade. Don’t put off pruning much later as next spring’s flowers develop in summer and fall.

Dwarf weigelas make charming companions with many perennial and annual flowers. Cultivars with purple or variegated foliage offers an additional color splash to a landscape planting. Weigelas are low maintenance landscape alternatives and have very few disease and insect problems.

Cultivars to try:

Burgundy Fire® – compact growing habit (3-4 feet tall and wide); leaves start out green, turn bronze-red in summer, and fiery wine-red in fall; fragrant pink flowers are not plentiful in spring.

Crimson Kisses® – 3-feet tall rounded shape shrub covered with dark, lipstick-red flowers kissed with a white eye.

Electric Love™ – 1.5- to 2-foot-tall and wide with dark purple foliage; vibrant red bell-shaped flowers.

‘Minuet’ – under 3 feet tall with lavender pink blooms.

My Monet® (‘Verweig’) – cream, pink and green variegation on a dwarf (10-16″) tall plant; attractive pink flowers; best in partial shade.

Midnight Wine® (‘Elvera’) – purple leaves and pink flowers, a uniquely dwarf 8 to 10 inches tall and almost 1.5 feet wide shrub mound.

Polka® – compact 3-5 feet shrub with thick dark green foliage and rich velvety two-toned pink/ yellow throat blooms.

Loads Of Hybrid Baptisias Available

Posted by Hugh on April 11th, 2020

Wild indigo or Baptisia (Baptisia spp.) are a wonderful group of U.S. native perennials (USDA hardiness zones 4-9). A few species have remained outside the gardening scene until recent years. Breeders are creating several hybrids that offer a grand color palette and superior plant form.

Baptisia, belong to the Pea family, new growth emerges in spring, lupine-like flowers that give rise to blue-grey leaves followed by spikes of pea-like flowers. Want to start a collection of baptisias? – Blue false indigo (Baptisia australis) is native to the prairies of North America, is easy to grow and thrives with little maintenance. Top variety is ‘Purple Smoke’ (B. australis x B. alba) with vibrant purple flowers, charcoal stems and gray-green foliage.

Yellow baptisia (Baptisia sphaerocarpa) is native in Texas and Louisiana and north to Oklahoma and Missouri. ‘Carolina Moonlight’ (B. sphaerocarpa x B. alba,) with soft yellow floral spikes; ‘Screaming Yellow’ (zones 5-9) with brilliant yellow-gold flowers, deep green foliage, and compact 2-3 feet high rounded form; ‘Wayne’s World’ grows 4 feet tall with bright white flower spikes.

‘Lemon Meringue’ baptisia (Photo courtesy of Walters Gardens, MI)

Newer varieties include the Decadence®series ‘Cherries Jubilee’ (cinnamon colored flowers), ‘Dark Chocolate’ (black, charcoal purple flowers), ‘Lemon Meringue’ (cool lemon yellow flowers), and ‘Chocolate Chip’ (smoky purple flowers).

Plants are very long-lived. Most species have spikes of flowers some blooms appear in May (mid spring) followed by 2-3 in. long, black seed pods which hold on well into winter. Pods and stems can be dried for use in decorative arrangements. Most bloom in spring, but some species bloom in summer. Baptisias are an easy plant to grow, perform best in full sun, grows in poor, adequately drained soils. Varieties range in size from 12 inches tall and wide to 4 feet tall and 6 feet wide. They’re highly deer resistant.

Landscape and other uses: include meadow plantings and as a specimen. Wild indigo plants are used in medicines and dye manufacture.

Outstanding collection: Visit the Paul J. Ciener Botanical Gardens in Kernersville, North Carolina which displays 15 different varieties.

Yellow Flowering Magnolias

Posted by Hugh on April 6th, 2020

Deciduous magnolias (Magnolia spp.) are popular landscape plants because of their bright cheery spring flowers. Breeding efforts back in the 1970’s created a new class of deciduous yellow-flowering magnolias. In 1978, the Brooklyn Botanical Gardens introduced the first, Magnolia ‘Elizabeth’ (creamy white). Yellow magnolias are hybrid crosses between M. acuminata, M. subcordata, M. denudata, among species. Several are designated Magnolia x brooklynensis.

The thick fleshy petals on magnolias are called “tepals”. Depending on the cultivar, flower colors range from oft white, light pink, and yellow color shades of creamy to dark yellow blooms. Growth rate, bloom time, tree growth rate, and disease resistance also differ. The greatest concern is that many varieties bloom in very early spring and are susceptible to frost injury in U.S. hardiness zones 6 and 7.

‘Gold Star’, ‘Golden Gala’, ‘Stellar Acclaim’, ‘Sun Spire’ and ‘Sundance’ have light yellow tepals. ‘Goldfinch’, ‘Butterflies’ and ‘Elizabeth’ are among the earliest to bloom; ‘Elizabeth’ has one of the longest flowering periods. ‘Judy Zuk’ and ‘Yellow Bird’ exhibit dark yellow tepals and usually are among the last to bloom. ‘Woodsman’ exhibit unique multicolored pink, white and green tepals.

In an evaluation of 30 cultivars by Dr. Donna Fare, at the USDA Research Station in McMinnville, Tennessee, the now retired ARS plant scientist found ‘Carlos’ and ‘Gold Star’ grew the tallest selections at 23 feet (7 m) each after ten years. ‘Golden Gala’, ‘Gold Star’, ‘Carlos’, ‘Lois’, and ‘Yellow Lantern’ had the largest trunk diameters averaging 1 inch (2.5 cm) per year. ‘Sun Spire’ had one of the smallest trunk diameters and showed an annual increase of about 1.5 cm per year.

Yellow magnolias generally grow 30 to 40 feet tall and 20 to 25 feet wide at maturity. Plant a single tree as a specimen, or several in groupings along a drive or walkway. These magnolias make wonderful shade trees planted near patios, low decks and other outdoor living areas. Trees can also be grown in large pots, planters and containers of 18 inches or more in diameter.

Yellow magnolias are easy to grow in moist, well-drained, acidic, fertile soil and full to partial sun. Magnolias prefers full sun for best flowering in northern climes (Zones 4-7), and in partially shaded understory in the South (Zone 8). Pruning usually isn’t necessary; remove stray and broken branches after spring flowering. Fertilize in early spring with a slow release balanced product like Osmocote® or Nutricote®.

Double Take® Flowering Quince

Posted by Hugh on April 2nd, 2020

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Flowering quince (Chaenomeles spp) is an early spring flowering shrub treasured for its brightly colored blooms (USDA hardiness zones 5-9). Old fashioned quince shrubs produced small amounts of fruits (quince) which were gathered and made into yummy jelly in the autumn kitchen. Old fashioned varieties often grew 10-12 feet tall shrubs and produced small sharp thorns which made picking the fruits a challenge.

Now appearing in local garden centers are three new compact cultivars in the Double Take® series called ‘Orange Storm’, ‘Scarlet Storm’ and ‘Pink Storm’. They were developed by Dr. Thomas Ranney at North Carolina State University Extension Center in Mills River, NC. Plants grow 4-5 feet in height and about the same in width (120-150 cm).

Their large vibrant double flowers are stunning in the early spring landscape. Blossoms measure almost 2 inches across and are visited in abundance by bees. Leaves emerge after blooms drop off. Once shrubs are established, usually within 1-2 years, plants are very heat and drought tolerant. Branches are thornless and deer resistant. Double-Take flowered quinces do not produce fruits (quinces) and are easy to care for.

‘Orange Storm flowering quince (J.E.C. photo)

Double Take quinces are easily grown in average, moist, well-drained soil in full sun to partial shade. Best flowering occurs in full sun. They adapt to a wide range of soil conditions, but prefer well-drained loam soil. Plants bloom on old growth. Avoid heavy pruning. After flowering, quinces may be pruned as specimen shrubs, espaliers or hedges. Promptly remove root suckers to control possible spread. Feed with a slow release fertilizer such as Osmocote® or Nutricote® at package directions.

Mostly disease and insect free, quinces are fireblight and scab susceptible in some parts of the U.S. Double Take quinces are more disease resistant than the species. Aphids, mites and scale can cause significant damage to the new spring growth. Chlorosis (yellowing of foliage) can occur in high pH soils. Flower buds are susceptible to significant damage from early spring frosts.

Personal favorite: ‘Scarlet Storm’ with abundant double scarlet red flowers are real standouts.

Landscape uses: Spring flowering specimen or group in shrub border or cottage garden. Branches may be clipped into a low hedge. Collect winter wood to force winter blooming indoors. Branches make gorgeous cut flowers.

Siberian Wallflowers – Tough Winter Annuals

Posted by Hugh on March 26th, 2020

‘Citrona Yellow’ wallflower in Dallas Botanical Gardens

‘Bowles Mauve’ wallflower

In areas of the U.S. where winters are mild, Siberian Wallflower (Erysimum cheiri), (formerly Cheiranthus cheiri), is an early flowering favorite in the late winter garden. The species hails from Southern Europe (USDA hardiness zones 7-9). Many books list them as biennials and a few as “tempermental perennials”.

Wallflower is a woody-based herbaceous perennial subshrub in the mustard family (Brassicaceae). They produce clusters (racemes) of fragrant 4-petaled flowers in a showy floral display bloom in the early spring cool weather followed by narrow pendant dehiscent seed pods.

Wallflowers, depending on variety, grow to 6-24 inches tall and slightly less in width. Flowers (each to 3/4 inches wide) are mostly bright yellow or yellow-orange to brown, but sometimes appear reddish purple to burgundy. Bright green leaves (to 2-8 inches long by 3/4 inches wide) are narrow and pointed.

Wallflowers are easy to grow, adapting to most types of well-drained soil and in full to partial sun. Full morning sun is preferred in cool northern areas. Plant them in rock gardens. border fronts or in raised beds in late winter. Fertilize lightly after planting and when late winter/spring flowering begins. No serious insect or disease problems trouble wallflowers.

This biennial plant will self-seed; you may want to cultivate seedlings for next winter’s garden. Otherwise, sow seeds in spring for bloom early next year.

Wallflowers have naturalized in British Columbia, Washington and California. In the southern U.S. they’re just catching on.